SeminarsAndTalks
From Space Weather Lab
Contents |
[edit] 1 Space Sciences Seminar
Part of the CSI 991 seminar series. (Usually) Meets Wednesday at 3:00 pm in Research I, Room 301. Announcements are sent via one of the email lists shown at http://aurora.gmu.edu/spaceweather/.
Directions
- Weigel's office phone: 703-993-1361. Cell: 571-230-3233.
- Weigel's office is Research I, room 350.
- Google map showing the turns you need to take on campus from route 123: html
- GMU campus map showing the Research I building swf. On this map there is a parking deck that looks almost connected to Research I. You should park in the visitor's section of that parking deck (Sandy Creek).
- Metro Shuttle html. The shuttle drops you off at the Sandy Creek parking deck which is the blue building on this map html
[edit] 1.1 Fall, 2009
[edit] 1.1.1 November 18th
Real-time Updating of IRI in the Auroral Zone
Yongliang Zhang
APL
[edit] 1.1.2 November 11th
Larry Kepko
NASA/GSFC
Flow, aurora and Pi2 associations observed by THEMIS
It has been known for decades that auroral substorm onset occurs on (or at least near) the most equatorward auroral arc, which is thought to map to the near geosynchronous region. The lack of auroral signatures poleward of this arc prior to onset has been a major criticism of flow-burst driven models of substorm onset. The combined THEMIS 5 spacecraft in-situ and ground array measurements provide an unprecedented opportunity to examine the causal relationship between midtail plasma flows, aurora, and ground magnetic signatures. I first present an event from 2008 using multi-spectral all sky imager data from Gillam and in-situ data from THEMIS. The multispectral data indicate an equatorward moving auroral form prior to substorm onset. When this forms reaches the most equatorward arc, the arc brightens and an auroral substorm begins. The THEMIS data show fast Earthward flows prior to onset as well. I suggest that the results strongly support flow-burst driven models of magnetospheric activity. I discuss further the association of flow bursts and Pi2 pulsations, and discuss the possibility of using Pi2 waveforms to infer midtail reconnection dynamics.
[edit] 1.2 November 2nd
Note special day, time, and location: Monday in room 306 of Science and Tech I at 1pm.
Combining Observations and Simulations to Advance our Understanding of Solar Eruptions
Noé Lugaz (Institute for Astronomy – University of Hawaii)
As solar cycle 24 slowly begins, thanks to the always-expanding float of satellites observing the Sun and the heliosphere, immense progresses can be expected in the forecasting and understanding of space weather, in particular regarding the initiation and propagation of coronal mass ejections (CMEs). To make a full use of the new observation capabilities, numerical simulations are often required, in particular to separate instrumental effects from the observed physical phenomena. This is particularly true for line-of-sight observations, such as coronagraphic and heliospheric images, as well as for in-situ measurements for complex series of CMEs. In this talk, I will discuss recent progresses in determining CME physical properties from white-light images, both in the corona (LASCO) and in the heliosphere (SECCHI) with the help of numerical magneto-hydrodynamics models. I will also discuss new geometrical models, which can give information about the azimuthal properties of CMEs from stereoscopic heliospheric observations, and, which could greatly improve the forecasting of CME hit/miss at Earth. Finally, I will also explore how MHD models can help explaining in situ measurements at 1 AU, from isolated and multiple CMEs.
[edit] 1.2.1 October 28th
Christopher J. Mertens
NASA Langley Research Center, Hampton, Virginia, USA
Models of Atmospheric Response to Low- and High-Energy Particle Precipitation
Enhanced low-energy particle precipitation during solar-geomagnetic storms increases the ion concentrations in the ionosphere. The state of the ionospheric E-region, in particular, is governed by ion-neutral chemistry. During geomagnetic storms, auroral particle precipitation increases the ionization of the neutral atmosphere, producing vibrationally excited NO+ (i.e., NO+(v)) through fast exothermic ion-neutral chemical reactions, which emits in the 4.3 um spectral region. Since NO+ is the terminal E-region ion, by charge neutrality, NO+(v) 4.3 um emission is an excellent proxy suitable for characterizing storm-time enhancements to the E-region electron densities. Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region electron densities. The empirical model is called STORM-E and will be incorporated into the International Reference Ionosphere (IRI). In the first half of the talk, STORM-E development is discussed and results during the Halloween 2003 storm period are presented.
The second half of the talk is focused on radiation exposure from high-energy particle precipitation on the atmosphere. Galactic cosmic rays (GCR) and solar energetic particles (SEP) are the primary sources of human exposure to high linear energy transfer (LET) radiation in the atmosphere. A prototype operational nowcast model of air-crew radiation exposure is currently under development. The model predicts air-crew radiation exposure levels from both GCR and SEP that may accompany solar storms. The new air-crew radiation exposure model is called the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model. NAIRAS will provide global, data-driven, real-time exposure predictions of biologically harmful radiation at aviation altitudes. Observations are utilized from the ground (neutron monitors), from the atmosphere (the NCEP Global Forecast System), and from space (NASA/ACE and NOAA/GOES). Radiation exposure rates are calculated using the NASA physics-based HZETRN (High Charge (Z) and Energy TRaNsport) code. An overview of the NAIRAS model is given and results during the Halloween 2003 storms are presented.
[edit] 1.2.2 October 6th
(Note that this is a Tuesday)
Philip Judge
HAO/NCAR
Look what's under the magnetic carpet! Solar physics' key to open the corona: the chromosphere.
I will attempt to show why we can no longer just "brush the chromosphere under the carpet", magnetic or otherwise, and ignore its importance either in a solar or plasma pnysics context. I hope to convince you that the chromosphere deserves to be studied by more than an interesting group of souls who have, like myself, long since lost their way, and become hopelessly entangled in one of the most awkward parts of the Sun.
[edit] 1.2.3 September 30th
Antti Pulkkinen
Automatic determination of the conic coronal mass ejection model parameters
NASA/GSFC
Characterization of the three-dimensional structure of solar transients using incomplete plane of sky data is a difficult problem whose solutions have potential for societal benefit in terms of space weather applications. In this paper transients are characterized in three dimensions by means of conic coronal mass ejection (CME) approximation. A novel method for the automatic determination of cone model parameters from observed halo CMEs is introduced. The method uses both standard image processing techniques to extract the CME mass from white-light coronagraph images and a novel inversion routine providing the final cone parameters. A Bootstrap technique is used to provide model parameter distributions. When combined with heliospheric modeling, the cone model parameter distributions will provide direct means for ensemble predictions of transient propagation in the heliosphere.
An initial validation of the automatic method is carried by comparison to manually determined cone model parameters. It is shown using 14 halo CME events that there is reasonable agreement, especially between the heliocentric locations of the cones derived with the two methods. It is argued that both the heliocentric locations and the opening half-angles of the automatically determined cones may be more realistic than those obtained from the manual analysis.
[edit] 1.2.4 September 9th
Modeling Solar Coronal Flux Tubes in 2-D with Non-Isotropic Conduction
Art Poland
George Mason University
[edit] 1.3 Spring, 2009
[edit] 1.3.1 May 12
"Temporal and Spatial Distribution of Metal Species in the Upper Atmosphere"
John Correira
Catholic University of America
ABSTRACT: Every day the Earth is bombarded by approximately 100 tons of meteoric material. Most of this material is completely ablated on atmospheric entry, resulting in a layer of atomic metals in the upper atmosphere between 70 km and 150 km. These neutral atoms are ionized by solar radiation and charge exchange with ambient ions. UV radiances from the Global Ozone Monitoring Experiment (GOME) spectrometer on the ERS-2 satellite are used to determine long-term dayside temporal and spatial variations of the total vertical column density below 795 km of the meteoric metal species Mg Iand Mg II in the upper atmosphere. A retrieval algorithm developed to determine magnesium column densities was applied to all available data from the years 1996-2001. Long term results show the middle latitude dayside Mg II peaks in total vertical content during the summer, while neutral Mg demonstrates a much more subtle maximum in summer. An analysis of spatial variations shows geospatial distributions are patchy, with local regions of increased column density. To study short term variations and the role of meteors showers a time dependent mass flux rate is calculated using published estimates of meteor stream mass densities and activity profiles. There appears to be little correlation between modeled meteor shower mass flux rates and changes in the observed Mg I and Mg II metal column densities.
[edit] 1.3.2 May 5
"The Lunar Data Project - Resurrecting Data From the Apollo Program"
David Williams
NASA, Goddard Space Flight Center
ABSTRACT: Every NASA mission must have a detailed plan to archive the scientific data collected in a standard format before it ever leaves the launch pad, but this was not always the case. Back in the Apollo era, there was no systematic requirement to archive the data at all, and no guidelines as to what constituted a standard archive product or what formats were acceptable. As a result, the Apollo data received at the National Space Science Data Center, NASA's archive located at Goddard Space Flight Center, were in many cases incomplete, not well documented, and on different media in various formats. The current collection of Apollo data at the NSSDC is housed on microfilm, microfiche, hard-copy documents and magnetic tape in UNIVAC, CDC 6600, EBSIDC and other obsolete formats. With the recent interest in returning ot the Moon we have undertaken the Lunar Data Project to restore these old Apollo data sets, some from instruments which operated on the Moon for 7 years, into standard digital formats for online distribution, as well as look for data that were never archived with NSSDC originally. We have had some success on both fronts, but as we get farther from the Apollo days, the data and the people with direct experience are becoming harder to find. We will discuss the history of the Apollo science program and our efforts to resurrect these old data for use in the current lunar exploration program.
[edit] 1.3.3 April 28
"Probing Dark Matter Properties through Dynamics of the Galaxy and the Local Group"
Ed Shaya
University of Maryland
ABSTRACT: Some key parameters of Dark Matter (DM) can most accurately be measured in the very nearby universe because DM dominates the mass in the outer Milky Way (MW) and in the other galaxies of the Local Group. Soon, the distribution of DM will be quantified by study of dynamical processes observable in fine detail within these entities. Precise measurements of 3-D velocities for stars, coherent star streams, and stars in satellite stellar systems out to the edge of the Galaxy can reveal the detailed shape of the dark matter halo as well as the total mass of the Galaxy. Similarly, 3-D velocities of galaxies in the Local Group can reveal the masses of individual dominant galaxies, the mass of the Local Group in total, and the density of the more smoothly distributed warm and hot DM. NASA's Space Interferometry Mission (SIM) will make measurements at the level of 2-3 microarcsec/yr per star and will provide us with the 2nd and 3rd dimensions of the velocity vectors of stars as faint as 20th mag. The specifics of these mass distributions, total mass-to-light ratios, clumpiness of the Galaxy potential, flatness of the halo, and cuspiness of galaxy cores provide the mass and nature of the dark matter particle(s), and test the standard model of cosmology on small scales.
[edit] 1.3.4 April 21
"Whither the thermosphere? Climate change at the edge of space"
John T. Emmert
Naval Research Laboratory
ABSTRACT: The Earth's thermosphere is the hot, thin, and partially ionized part of the atmosphere situated between altitudes of 90 and 800 km. Its high temperature is primarily due to absorption of solar extreme ultraviolet (EUV) radiation, which is balanced by radiative infrared cooling by carbon dioxide and other agents. The thermosphere exerts significant drag on orbiting spacecraft, which causes their orbits to decay at a rate proportional to the mass density of the ambient gas. Satellite tracking data thereby provide an extensive historical record of the thermosphere back to the dawn of the space age. Recent studies indicate that, after taking into account the strong influence of solar EUV variations, the thermosphere is slowly cooling and contracting, a trend that has important implications for orbit prediction and orbital debris management. In this presentation we review the structure and physics of the thermosphere and briefly describe how density is extracted from orbital tracking data. We then examine trends in thermospheric density, as well trends in other upper atmospheric properties, and discuss their interpretation.
[edit] 1.3.5 April 14
"Connecting Stars (their planets), Galaxies, and the Universe in the Decade of Astrometry"
Rob Olling
University of Maryland
ABSTRACT: In the coming era of precision astrophysics, new telescopes on the ground and in space will provide many, many Terabytes of highly precise photometric and astrometric (positional) measurements. The job of astrophysicists is to turn those precise measurements into "highly accurate facts," i.e. inferences with small systematic errors.
The accuracy of many astronomical inferences have been improving steadily over the last few decades: from factors of several to tens of percent. In the near-field, GAIA and SIM-Lite (hopefully) will push the accuracies to the sub-percent level, while the Planck mission will measure the Cosmic Microwave Background with similar accuracy. Many experiments aim to achieve similar accuracies in the intervening parts of the Universe.
I will briefly touch on several subjects:
- Briefly introduce the proposed SIM-Lite mission
- how to use millimag (0.1%) photometry to find transiting extra-solar planets with GAIA-like spacecraft and with my own LEAVITT design
- how to find solar-system analogs with astrometry
- how to perform cosmology in our own backyard with double stars
- how to obtain 1% geometric distances for galaxies in the Local Group (H_0)
[edit] 1.3.6 April 7
"Numerical Simulation of Interplanetary Coronal Mass Ejections for Space Weather Prediction"
Dusan Odstrcil
University of Colorado, Boulder
ABSTRACT: Coronal mass ejections (CMEs) have been identified as a prime causal link between solar activity and large, non-recurrent, geomagnetic storms. Modeling of the origin of CMEs is still in the research phases and it is not expected that real events can be routinely simulated in near future. Therefore, we have developed an intermediate modeling system which uses fitted coronagraph observations, specifies 3D ejecta, and drives the 3D numerical magnetohydrodynamic code ENLIL which uses the WSA coronal maps for background solar wind. We simulated a number of heliospheric events selected by community campaigns which enabled us to analyze the match between different parameters predicted by the model and observed by spacecraft. Attention is given to development of tools facilitating prediction of solar wind parameters at planets and spacecraft.
[edit] 1.3.7 March 24th
"The Solar Dynamics Observatory and the Wait for Solar Cycle 24"
W. Dean Pesnell
Goddard Space Flight Center
ABSTRACT: The Sun hiccups and satellites die. That is what NASA's Living With a Star Program is all about. The Solar Dynamics Observatory (SDO) is the first Space Weather Mission in LWS. SDO's main goal is to understand, driving towards a predictive capability, those solar variations that influence life on Earth and humanity's technological systems. The SDO science investigations will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. The SDO mission consists of three scientific investigations (AIA, EVE, and HMI), a spacecraft bus, and a dedicated Ka-band ground station to handle the 150 Mbps data flow. The science teams at LMSAL, LASP, and Stanford are responsible for processing, analyzing, distributing, and archiving the science data. We will talk about the building of SDO and the data and science it will provide to NASA. The late start of Solar Cycle 24 will allow SDO to measure a very interesting solar minimum period. In particular, helioseismic studies of the solar interior will benefit from the low activity that should still be present at the launch of SDO later this year.
[edit] 1.3.8 March 17th
"Chasing Lightning: Sferics, Tweeks and Whistlers"
Phillip A. Webb (GSFC and UMBC/GEST)
Kathleen Franzen (INSPIRE)
Abstract: The visible flash that we see from lightning is only part of the story. Lightning generates electromagnetic emissions at other frequencies that can propagate hundreds or thousands of kilometers across the surface of the Earth in the form of special signals called "tweeks" and "sferics". Some of these emissions can even travel tens of thousands of kilometers out into space before returning to the Earth as "whistlers". The INSPIRE Project, Inc is a non-profit scientific and educational corporation whose original mission was to bring the excitement of observing these very low frequency (VLF) natural radio emissions to high school students and interested individuals. Since 1989, INSPIRE has provided specially designed VLF radio receiver kits to over 2,600 participants around the world. A number of these participants use the VLF data they collect in very creative projects that include fiction, music and art exhibitions. This presentation will provide an overview of lightning and the resulting VLF emissions, the INSPIRE program and the VLF receiver, and discuss experiences gained from using the INSPIRE VLF kits as the basis of an undergraduate course that was taught for the first time in the Fall 2008 semester at University of Maryland Baltimore County (UMBC).
[edit] 1.3.9 February 24th
"A reinterpretation of the energy balance in EUV loops due to new results from Hinode-EIS"
Stephen Bradshaw (NASA/GSFC and GMU)
Abstract:
New observations made by the Hinode EUV Imaging Spectrometer have revealed persistent redshifts in solar active region loops in the temperature range $10^{5.6} \leq T \leq 10^{6.4}$~K. The presence of redshifts, interpreted as bulk downflows, indicates that the loops are undergoing radiative cooling rather than continuous heating. This has significant consequences for current ideas regarding the physics of the ubiquitous 1~MK loops observed by instruments such as TRACE and SoHO-EIT.
A new interpretation of the energy balance in such loops is presented with model results that are found to agree well with the observed redshifts.
[edit] 1.3.10 February 10th
AGN jet interaction with ICM plasma: Kinetic effects and Thermal conduction
Fathalah Alouani Bibi (Physics and Astronomy Department, GMU)
Abstract: I will talk about some of my work prior to joining George Mason University. In particular, I will be talking about the importance of kinetic effects in electron transport and thermal conduction during the interaction of an AGN jet with inhomogeneous intra-cluster plasma. I will show some of the dynamics of cooling flow cluster and the role of AGN jets as a main heating source. I will also discuss the limitations of the classical Spitzer theory in cases of steep temperature gradients and in non-Maxwellian plasmas, and give some alternatives/corrections
[edit] 1.3.11 February 3rd
Forward Modeling of Coronal Mass Ejections using STEREO-SECCHI Data
Abstract: I will present a forward modeling technique to reconstruct coronal mass ejections observed with the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instruments package aboard the Solar Terrestrial Relations Observatory (STEREO). First, I will review the different techniques that can be used to reconstruct the 3D electron density of coronal structures such as CMEs. I will describe in more details the forward modeling method, which consists in fitting a geometric model of a flux rope to the observed images. Finally, I will present a survey of more than 30 CMEs studied with this technique.
[edit] 1.4 Fall, 2008
[edit] 1.4.1 November 18th
Flux Rope Instabilities at the Onset of CMEs
Bernhard Kliem
Mullard Space Science Lab, University College London, UK and Institute of Physics, University of Potsdam, Germany
Images of erupting prominences typically suggest the magnetic topology
of a single line tied flux rope. Many prominence eruptions and CMEs
begin with an approximately exponential rise, suggesting that an
instability of a flux rope may occur at the onset of the eruptions. I
will present numerical simulations of two relevant instabilities, the
well-known helical kink instability and the torus instability, using
the force-free line tied flux rope equilibrium by Titov and Demoulin as
initial condition. The properties of these instabilities indicate which
parameters of the initial configuration control whether the eruption
stays confined or becomes ejective, evolves into a fast or a slow CME,
shows strong or weak writhing. Exponential as well as power-law rise
profiles can be modeled. Supporting quantitative comparison of the
simulations with several well observed eruptions will be included.
[edit] 1.4.2 October 21st
Interstellar neutrals in the heliospheric interface
Vladsilav Izmodenov
Univ of Moscow
Abstract
The heliospheric interface is the region where the solar wind meets the local interstellar cloud. The cloud is partly ionized and neutral component of the cloud penetrates into the heliosphere where it can be observed. New observational information as crossing of the heliospheric termination shock (TS) by both Voyagers, new SOHO/SWAN and Ulysses data as well as maps of the heliospheric ENA spectra that are expected from the Interstellar Boundary Explorer (IBEX) mission after its launch on October 19 2008 create new requirements and new challenges for modelling of the heliospheric interface. Modern kinetic-gasdynamic models of the SW/LIC interaction takes into account multi-component nature of both the solar wind and the interstellar medium. New results that include dynamic effects of the interstellar H atoms, the 11-year and latitudinal variations of the solar wind, interstellar and heliospheric magnetic fields will be discussed. Analysis of the constraints on the models, which follow from the TS crossing by Voyagers and other observational data, will be given in the paper. Theoretical predictions of the ENA fluxes that will be measured by IBEX will be provided.
[edit] 1.4.3 September 30th
Physics of Solar and Stellar Coronal Heating
Vladimir Airapetian
GMU at NASA Goddard Space Flight Center
Since the discovery of the enigmatically hot layer in the Sun, the solar corona, the problem of its heating had remained elusive. Over the last 53 years we learned that the solar corona is not just hot "quiet" plasma, but a highly "emotional" place for the most violent eruptions in the solar system, occurring on scales from hundreds to hundreds of thousands of kilometers. The recent solar missions, SOHO, TRACE and Hinode provided crucial clues for resolving the long-standing problem of the solar coronal heating. Meanwhile the space missions, HST, Chandra, FUSE, XMM-Newton, have confirmed that hot and X-ray bright coronae exist not only in the Sun, but in stars ranging from young pre-main sequence stars to evolved giants. These new data raise one fundamental question in astrophysics: can the solar analogy be directly applied to other stars, and how do the underlying physical processes differ? In this review I will discuss recent observations of the solar and stellar coronae and the physical mechanisms involved in their heating.
[edit] 1.4.4 September 23rd
Ulysses Observations of Periodic Structures in the Solar Wind Velocity
Christina Henderson
Christina Henderson will present a surface-level talk about her research. The talk is aimed at an undergraduate level with no prior knowledge of the Sun/Earth system. The talk is open to discussion.
George Mason University
As we bask in the warm glow of a summer day, we become intimately familiar with the constant output of solar photons. Thanks to deflection by the Earth's magnetic field (called the magnetosphere), we are less intimately familiar with the constant outflow of solar plasma known as the solar wind. Spacecraft sitting outside the magnetosphere, however, can constantly measure properties of the solar wind such as the bulk velocity, magnetic field, and density. Ulysses is one such spacecraft. In this research, we use data gathered by Ulysses in its polar solar orbit over a span of 18 years from 1990 to 2008. We compute the power spectrum of the velocity, searching for periods in the range of 5- to 40-days, as these have the largest impact on predicting processes, like aurora, that occur in the Earth's magnetosphere. We develop methods to see the periods as they change in time by computing many power spectra while stepping through the data; we call this the spectrogram. We are able to compare the spectrogram with calculations of the fundamental period and harmonics of a idealized sawtooth type solar wind. We conclude that many periods in the spectrogram of the Ulysses data are due to real physical processes and not artifacts of the numerical calculations, such as harmonics. 3-D solar wind simulation results can be compared with Ulysses data; we hope to learn what physical processes could be missing in the simulations.
[edit] 1.4.5 September 16th
SECCHI View of CME Dynamics: Observations and Theory
Valbona Kunkel
George Mason University and NRL
The propagation of CMEs through the field of view of LASCO (2--30 Rs) has been extensively studied in the past 10 years. Based on theory-data comparison, it has been established that most, if not all, CMEs can be understood as erupting magnetic flux ropes and that the observed dynamics in this regime can be correctly described by the erupting flux rope model (Chen 1996). Until STEREO became available, CME dynamics were not observed and the EFR model has not been directly compared with data beyond 30 Rs. In this talk, I will discuss new SECCHI observations of CMEs and their dynamaics and extend the modeling of CME propagation to Hi 1 field of view (out to about 100 Rs projected). Four CMEs are discussed. It is shown that the erupting flux rope model is able to fit the observed height-time and velocity-time data throughout the EUVI-COR1-COR2-HI1 field of view. This suggests that the model correctly captures the main acceleration phase and the residual acceleration phase of CME dynamics, i.e., the forces acting on CMEs. It is found that significantly larger values of the drag coefficient in the model than previously used are required to fit both the COR1-COR2 data and HI1 data. This means that the extended field of view imposes stronger constraints on model parameters than previously thought, such as the drag coefficient and therefore the magnetic energy required to power the eruption and subsequent propagation.
[edit] 1.4.6 September 9th
An analytical model unscrambling the inner state of CMEs based on the scale measurements in coronagraphs
Yuming WANG
George Mason University
An analytical model is proposed to unscramble two physical parameters, polytropic index $\Gamma$ and the non-force-free index $I_{nff}$, defined by $|f_{em}/f_{th}|$ where $f_{em}$ and $f_{th}$ are the Lorentz force and thermal pressure force respectively, of flux-rope CMEs based only on the scale measurements in coronagraphs. By applying this model to the 2007 October 8 CME, we find that (1) $\Gamma$ of the CME plasma decreased quickly from 1.35 at the beginning to 1.05 before it went beyond 15 Rs and then continuously approached to 1.0, and (2) $I_{nff}$ kept decreasing from nearly 1.0 to below 0.1 when the CME leading edge arived at about 70 Rs. The first result implies taht the plasma in this CME was heated throughout the interplanetary space, and the CME underwent a nearly isothermal process. The second result suggests that the CME was not force-free at the early phase, but it tended to approach the force-free state when it ran away from the Sun. Besides, the model predicts that, for an initially non-force-free flux rope, $\Gamma$ will be less than 4/3 if it reaches force-free state at infinite distance, and particularly, $\Gamma=1$ and the density at the flux rope axis must be larger than that at the boundary if the flux rope finally goes to a steady propagating and expanding state. We expect that this model has potential application to other researches where a flux rope is employed.
[edit] 1.4.7 August 28th
Multi-dimensional representation of the ionosphere from GNSS, altimetry and COSMIC
M. Schmidt (1), C. Zeilhofer (1), D. Bilitza (2), C.K. Shum (3), J. Zhang (1), L.-C. Tsai (4)
(1) Deutsches Geodaetisches Forschungsinstitut (DGFI), Alfons-Goppel-Strasse 11, 80539 Muenchen, Germany (2) Heliospheric Physics Laboratory/GMU, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA (3) Geodetic Science, School of Earth Sciences, The Ohio State University, 275 Mendenhall, 125 S Oval Mall, Columbus OH 43210, USA (4) Center for Space and Remote Sensing Research, National Central University, Taiwan
(schmidt@dgfi.badw.de, zeilhofer@dgfi.badw.de)
During the last decade various satellite missions have turned out to be promising tools for monitoring ionospheric parameters. Dual-frequency GNSS observations, e.g., can be used to determine the slant total electron content (STEC), i.e. the integral of the electron density along the ray-path of the signal between the transmitting satellite and a receiver. Furthermore, dual-frequency altimetry satellites allow measuring the vertical total electron content (VTEC).
In this contribution we present a multi-dimensional ionospheric model calculated from GNSS, altimetry and COSMIC measurements. To be more specific our model consists of a given reference part, computed from the International Reference Ionosphere (IRI), and an unknown correction term. Since the latter is represented as a series expansion in terms of multi-dimensional base functions, e.g., constructed from polynomial B-splines, trigonometric B-splines or spherical harmonics, our approach can be applied to global, regional and local data sets. The unknown series coefficients are calculable by applying parameter estimation procedures. Since the input data are heterogeneously sampled in space and in time due to the specific orbit and instrumental characteristics, finer structures of the target function are modelable just in regions with a sufficient number of observation sites.
[edit] 1.5 Summer, 2008
[edit] 1.5.1 Tuesday August 5th at 11 am in room 301
Space Weather research in South Africa
Lee-Anne McKinnell
[edit] 1.6 Spring, 2008
[edit] 1.6.1 Friday May 23rd at 11 am in room 302
Note special day, time, and room
Theoretical and Observational Constraints on Accretion Flows on Black Hole: The Case of sub-Keplerian Motion
Sandip K. Chakrabarti (1)
Senior Professor, S.N. Bose National Centre for Basic Sciences
Theoretically, matter enters into a black hole with velocity of light and thus every flow, independent of its past history, must be supersonic on the horizon. Not surprisingly, the transonic flow solutions respect such a boundary condition, even when it allows very exciting possibility that flows should pass through shocks and slow the matter down at a few Schwarzschild radii before the horizon. It is thus no surprise that ALL the observations (ranging from spectral state transition, Quasi-periodic oscillations, jets and outflows and non-thermal spectra from black holes) agree to the fact that such a Centrifugal Pressure Dominated Boundary Layer (CENBOL) should exist. There are several post-facto cartoon models in the literature which apparently have no knowledge of such beautiful behaviour of the flow and surprisingly come up with cartoon diagrams having the same behaviour. In our advective disk paradigm, jets are produced when CENBOL is present. Thus it no surprise that some post-facto models include the base of the jet (which is nothing but CENBOL in our picture) in explaining outgoing spectrum from disk surface and thereby creating a confusion that X-rays from the jets are also serious contestants. We show that for every observation that has been a pre-facto prediction of our paradigm of two component advective flow (TCAF). These are re-discovered by many in the literature under new names, pictures and models. What is more important, however, is that the theoretical solutions and the cartoons from fitting observational data are finally converging. This paves the way of further progress in the subject.
(1) Also, In Charge, Academic Affairs, Indian Centre for Space Physics, Kolkata
[edit] 1.6.2 May 7th
Robert Duffin
George Mason University
Type III-L Solar Radio Bursts and their Correlations with Solar Energetic Proton Events
Abstract
Type III-L bursts are a sub-class of type III solar radio bursts that tend to occur after the impulsive phase of flares; are longer in duration than individual type IIIs and tend to be low-frequency. There has been a proposal that type III-Ls are connected to solar energetic proton (SEP) events. Most work on this connection has started from samples of SEP events, but if type III-Ls are to be useful for prediction of SEP events, then we need to understand the properties of samples of type III-L bursts. This talk reports preliminary results from such a study. An operating definition based on previous work is used to identify type III-L events amongst M- and X-class flares from 2001; and then correlations with other properties of these events are investigated, including association with SEP events. If there is a correlation with SEP events, one important factor that these bursts allow us to address is the question of whether acceleration takes place at an associated CME, or closer to the flare site well below the CME.
[edit] 1.6.3 April 30th
Joseph Lazio
Naval Research Laboratory
The Dark Ages Lunar Interferometer (DALI)
The Dark Ages represent the last frontier in cosmology, the era between the genesis of the cosmic microwave background (CMB) at recombination and the formation of the first stars. During the Dark Ages, when the Universe was unlit by any star, the only detectable signal is likely to be that from neutral hydrogen (HI), which will appear in absorption against the CMB. The HI absorption represents potentially the richest of all data sets in cosmology—not only is the underlying physics relatively simple so that the Hi absorption can be used to constrain fundamental cosmological parameters in a manner similar to that of CMB observations, but the spectral nature of the signal allows the evolution of the Universe as a function of redshift (z) to be followed. The Hi absorption occurs in dark matter-dominated overdensities, locations that will later become the birthplaces of the first stars, so tracing this evolution will provide crucial insights into the properties of dark matter and potentially reveal aspects of cosmic inflation. Moreover, given the relatively simple physics—the Universal expansion, Compton scattering between CMB photons and residual electrons, and gravity—any deviation from the expected evolution would be a “clean” signature of fundamentally new physics.
The Dark Ages Lunar Interferometer (DALI) is a mission proposed for study to NASA for a telescope located on the far side of the Moon, the only site in the solar system shielded from human-generated interference and, at night, from solar radio emissions. The DALI array will observe at 3–30 m wavelengths (10–100 MHz; redshifts 15 \le z \le 150), and the DALI baseline concept builds on ground-based telescopes operating at similar wavelengths, e.g., the Long Wavelength Array (LWA) and Murchison Widefield Array (MWA). Specifically, the fundamental collecting element will be dipoles. The dipoles will be grouped into “stations,” deployed via rovers over an area of approximately 50 km in diameter to obtain the requisite angular resolution. The desired three-dimensional imaging requires approximately 1000 stations, each containing 100 dipoles (i.e., ~ 10^5 dipoles); alternate processing approaches may produce useful results with significantly fewer dipoles (factor ~ 3–10). Each station would be deployed by one rover, which would also serve as a “transmission hub” for sending the signals for correlation to a central processing facility. After sending the correlator output to Earth, analysis would then proceed via standard methods being developed for ground-based arrays.
[edit] 1.6.4 Friday May 23rd at 11 am
Note special day and time
Theoretical and Observational Constraints on Accretion Flows on Black Hole: The Case of sub-Keplerian Motion
Sandip K. Chakrabarti (1)
Senior Professor, S.N. Bose National Centre for Basic Sciences
Theoretically, matter enters into a black hole with velocity of light and thus every flow, independent of its past history, must be supersonic on the horizon. Not surprisingly, the transonic flow solutions respect such a boundary condition, even when it allows very exciting possibility that flows should pass through shocks and slow the matter down at a few Schwarzschild radii before the horizon. It is thus no surprise that ALL the observations (ranging from spectral state transition, Quasi-periodic oscillations, jets and outflows and non-thermal spectra from black holes) agree to the fact that such a Centrifugal Pressure Dominated Boundary Layer (CENBOL) should exist. There are several post-facto cartoon models in the literature which apparently have no knowledge of such beautiful behaviour of the flow and surprisingly come up with cartoon diagrams having the same behaviour. In our advective disk paradigm, jets are produced when CENBOL is present. Thus it no surprise that some post-facto models include the base of the jet (which is nothing but CENBOL in our picture) in explaining outgoing spectrum from disk surface and thereby creating a confusion that X-rays from the jets are also serious contestants. We show that for every observation that has been a pre-facto prediction of our paradigm of two component advective flow (TCAF). These are re-discovered by many in the literature under new names, pictures and models. What is more important, however, is that the theoretical solutions and the cartoons from fitting observational data are finally converging. This paves the way of further progress in the subject.
(1) Also, In Charge, Academic Affairs, Indian Centre for Space Physics, Kolkata
[edit] 1.6.5 May 7th
Robert Duffin
George Mason University
Type III-L Solar Radio Bursts and their Correlations with Solar Energetic Proton Events
Abstract
Type III-L bursts are a sub-class of type III solar radio bursts that tend to occur after the impulsive phase of flares; are longer in duration than individual type IIIs and tend to be low-frequency. There has been a proposal that type III-Ls are connected to solar energetic proton (SEP) events. Most work on this connection has started from samples of SEP events, but if type III-Ls are to be useful for prediction of SEP events, then we need to understand the properties of samples of type III-L bursts. This talk reports preliminary results from such a study. An operating definition based on previous work is used to identify type III-L events amongst M- and X-class flares from 2001; and then correlations with other properties of these events are investigated, including association with SEP events. If there is a correlation with SEP events, one important factor that these bursts allow us to address is the question of whether acceleration takes place at an associated CME, or closer to the flare site well below the CME.
[edit] 1.6.6 April 30th
Joseph Lazio
Naval Research Laboratory
The Dark Ages Lunar Interferometer (DALI)
The Dark Ages represent the last frontier in cosmology, the era between the genesis of the cosmic microwave background (CMB) at recombination and the formation of the first stars. During the Dark Ages, when the Universe was unlit by any star, the only detectable signal is likely to be that from neutral hydrogen (HI), which will appear in absorption against the CMB. The HI absorption represents potentially the richest of all data sets in cosmology—not only is the underlying physics relatively simple so that the Hi absorption can be used to constrain fundamental cosmological parameters in a manner similar to that of CMB observations, but the spectral nature of the signal allows the evolution of the Universe as a function of redshift (z) to be followed. The Hi absorption occurs in dark matter-dominated overdensities, locations that will later become the birthplaces of the first stars, so tracing this evolution will provide crucial insights into the properties of dark matter and potentially reveal aspects of cosmic inflation. Moreover, given the relatively simple physics—the Universal expansion, Compton scattering between CMB photons and residual electrons, and gravity—any deviation from the expected evolution would be a “clean” signature of fundamentally new physics.
The Dark Ages Lunar Interferometer (DALI) is a mission proposed for study to NASA for a telescope located on the far side of the Moon, the only site in the solar system shielded from human-generated interference and, at night, from solar radio emissions. The DALI array will observe at 3–30 m wavelengths (10–100 MHz; redshifts 15 \le z \le 150), and the DALI baseline concept builds on ground-based telescopes operating at similar wavelengths, e.g., the Long Wavelength Array (LWA) and Murchison Widefield Array (MWA). Specifically, the fundamental collecting element will be dipoles. The dipoles will be grouped into “stations,” deployed via rovers over an area of approximately 50 km in diameter to obtain the requisite angular resolution. The desired three-dimensional imaging requires approximately 1000 stations, each containing 100 dipoles (i.e., ~ 10^5 dipoles); alternate processing approaches may produce useful results with significantly fewer dipoles (factor ~ 3–10). Each station would be deployed by one rover, which would also serve as a “transmission hub” for sending the signals for correlation to a central processing facility. After sending the correlator output to Earth, analysis would then proceed via standard methods being developed for ground-based arrays.
[edit] 1.6.7 March 26th
Juan C Luna
George Mason University
The role of bulk and thermal Comptonization in producing the time lags observed in X-ray pulsars
Fourier analysis of X-ray pulsar data reveals the presence of time lags between hard and soft channels in millisecond pulsars. There is currently no consistent theoretical explanation for this effect based on a fundamental physical model for pulsar sources. In the proposed research, a new theoretical model is developed from first principles based on the bulk and thermal Comptonization occurring in the gas inside the accretion column above one (or both) of the magnetic poles on a rotating neutron star. The model utilizes a combination of Fourier and Laplace transformation in order to obtain quantitative predictions for the time lags. This approach will be used to make predictions about the possible presence of time lags in the spectra of bright pulsars such as Her X-1. Theoretical interpretation of the time lags can provide detailed information about the size and properties of the scattering plasma and also the spatial density profile of the scattering electrons.
[edit] 1.6.8 March 19th
V. Truhlik
Institute of Atmospheric Physics, Prague, Czech Republic
Studying of solar activity variation of the electron temperature in the topside ionosphere
Electron temperature (Te) in the topside ionosphere and plasmasphere is an important parameter because thermal electrons play a key role in the energy balance of these regions. The IRI (International Reference ionosphere) model includes an empirical representation of Te in the topside ionosphere depending on altitude, latitude, local time, and season. But due to a lack of data and sometimes conflicting measurements, the solar activity variation of Te has not been reliably modeled so far.
We have made good progress in modeling the Te behavior with the help of a large database of satellite electron temperature measurements, and of Incoherent Scatter Radars observations, and with the assistance of simulations with the theoretical FLIP model. The presentation will focus in particular on (1) comparison of calculation of the FLIP model with data (2) latitudinal and altitudinal variation of Te and the heat flux (3) discussion prevailing cooling and heating terms influencing Te balance and causing its changing with solar activity. We will also discuss development of a new global Te model with the Te solar activity variation as a correction term which can help to improve current Te model in IRI.
[edit] 1.6.9 February 20th
Phil Richards
George Mason University
Controversies in Solar EUV Irradiance and Ionospheric Photoelectron fluxes
For many years, there has been controversy over the magnitude of both the solar EUV (0-100 nm) irradiance and 0-1 keV photoelectron flux. The solar EUV irradiance is the primary driver of the energetics and dynamics of the Earth's upper atmosphere above 100 km. There are uncertainties in theoretical photoelectron fluxes because of uncertainties in cross sections and solar EUV irradiance. Accurate solar EUV irradiance measurements are difficult to make because they must be made at high altitudes and because the energetic photons degrade the instruments that measure them. The ionization of oxygen and nitrogen in the upper atmosphere produces energetic photoelectrons as well as ions. Photoelectrons take approximately half the incident photon energy in the creation of secondary ions and electrons and airglow emissions. In recent years, the photoelectron flux has become important because the airglow emissions are heavily used in diagnosing variations in the upper atmosphere. This paper reexamines the consistency of solar EUV irradiance and ionospheric photoelectron fluxes using recent measurements.
[edit] 1.6.10 February 13th
Geospace Imaging: The Big Picture
Bob Meier
George Mason University
Various regions of the geospace environment have been named and are often studied as if they exist in isolation. Yet emerging high quality multidisciplinary global datasets clearly demonstrate the complex and highly variable synergy among traditional space physics regimes. As a result, interdisciplinary endeavors, such as for example, magnetospheric-ionospheric coupling studies, are growing rapidly but face difficult challenges in understanding just how the various geospace regions interact. The recent progression of global imaging missions and the encouraging efforts to interface models of the various geospace regions give hope that one day we may actually be able to literally see “the big picture” that is crucial for understanding the space environment as a whole system. Ultimately we may be able to trace the paths of radiation and plasma eruptions from their origins at the Sun through to the responsive interactions among the magnetosphere, plasmasphere, ionosphere, and thermosphere. This lecture will trace the evolution of global imaging, from the initial measurements, to what we are learning now, to innovative prospects for developing new understanding from big pictures of the neutral and ionized components of geospace.
[edit] 1.7 Fall, 2007
[edit] 1.7.1 November 14th, 2007
Merging Galaxies: A Nearby Laboratory for High-Redshift Star Formation and Supermassive Black Holes
David Rupke
University of Maryland
drupke@astro.umd.edu
The rates of star formation and black hole activity in the universe peaked 10 billion years ago. The majority of this star formation occurred in dusty, merging galaxies, which in turn evolved into galaxies containing luminous black holes. Many examples of these dusty mergers occur in the local universe. I will review some of the unique properties of these local mergers, including morphologies, masses, gas dynamics, and heavy element content. I will place them both in the context of other galaxies in the local universe and in the context of their high-redshift counterparts.
[edit] 1.7.2 November 7, 2007
Stephen Rinehart
NASA -- Goddard Space Flight Center
Stephen.A.Rinehart@nasa.gov
From Spitzer to SPECS: The Future of Far-Infrared Astronomy
The development of infrared astronomy in the 20th century led to the discovery that the universe appears fundamentally different at long wavelengths. Missions such as the Infrared Astronomical Satellite (IRAS), the Infrared Space Observatory (ISO), and the Kuiper Airborne Observatory (KAO) have led to new understanding of the origins of galaxies, stars, and planets. Spitzer, currently on-orbit, has continued breaking new ground, and upcoming facilities such as the Herschel Space Telescope and the Stratospheric Observatory for Infrared Astronomy (SOFIA) promise to continue the legacy of their predecessors. As these missions move forward, we will develop the next generation of far-infrared observatories, taking advantage of new technologies and new techniques to address some of the most compelling astrophysical questions of our time.
[edit] 1.7.3 October 31, 2007
Manolis K. Georgoulis
Johns Hopkins University/APL
http://sd-www.jhuapl.edu/FlareGenesis/Team/Manolis/
Progress and Challenges in the Analysis of Solar Vector Magnetograms: Why do we need these measurements, anyway?
Despite decades of ground-breaking advances in solar vector magnetography, vector magnetograms with a potential for meaningful science are routinely produced only within the last fifteen years or so. However, serious limitations in the acquisition of such pristine data result in an inherently incomplete physical understanding of the solar magnetized atmosphere. We are in urgent need of even this partial information because nearly every aspect of the long- or short-term evolution in the Sun stems from the emergence and evolution of solar magnetic fields. I will briefly review the current status of the analysis and the challenges pertaining to solar vector magnetograms. My main focus, however, will be on the new insight of the magnetic Sun that these measurements can help us gain. I will try to show that fitting even some pieces of the inextricable puzzle of solar magnetism can lead to substantial developments in the physical understanding of our magnetic star.
[edit] 1.7.4 October 17th, 2007
The Angry Sun: Explosions in the Corona
James Klimchuk
james.klimchuk@nrl.navy.mil
Space Science Division, Naval Research Lab
Although the Sun is a benevolent provider of warmth and comfort, it also has a very angry side. Solar outbursts cause inclement space weather that sometimes wrecks havoc on technological systems on which our society is progressively more dependent. These outbursts involve the sudden release of energy that is stored in stressed coronal magnetic fields. They occur on a wide variety of scales. In this talk, I will discuss the smallest and largest events: nanoflares, which collectively heat the corona to multi-million degree temperatures and are responsible for the variable X-ray and UV radiation that modifies the Earth’s upper atmosphere; and coronal mass ejections (CMEs), which are spectacular eruptions responsible for the largest geomagnetic storms. I will present new observations from the recently launched Hinode and STEREO missions, and I will review the current state of theoretical understanding.
[edit] 1.7.5 October 10, 2007
Seeing the Heliosphere with New Eyes: First Results from the SECCHI Experiment on STEREO
Angelos Vourlidas
SECCHI Project Scientist, Naval Research Laboratory
The STEREO mission was launched on October, 2006 with the main objective to study Coronal Mass Ejections (CMEs) from their initiation in the solar corona to their arrival at Earth using a suite of remote sensing and in-situ instruments on two, almost identical, spacecraft. The mission objectives are mainly addressed by the imaging experiment, named Sun-Earth Connection Coronal & Heliospheric Investigation (SECCHI), which comprises a suite of five telescopes; an EUVI full disk imager, two coronagraphs covering the range from 1.5 to 15 solar radii, and two heliospheric imagers observing along the Sun-Earth LINE from 15 solar radii to the Earth's orbit and beyond. It is the first time that such imaging capabilities are available and they will certainly lead to important advances in our understanding of the CME initiation, propagation, and its three-dimensional configuration. In this talk, we will showcase the observations and initial results from the first months of operations of the SECCHI telescopes. We will also discuss the instrument performance and synergies with existing observatories (e.g., SOHO). SECCHI was built by a consortium of US and European institutions under the direction of the Solar Physics Branch at the U.S. Naval Research Laboratory.
[edit] 1.7.6 October 3, 2007
New perspective on CME rates and their distributions: Lessons from CACTus (Computer Aided CME Tracking)
Eva Robbrecht
Eva.Robbrecht@oma.be
SIDC/Royal Observatory of Belgium
We present the first 'objective' LASCO CME catalog, a result of the application of the CACTus software on the LASCO archive during the interval September 1997 - January 2007. We have studied the CME characteristics over solar cycle 23 and have compared them with similar results obtained by manual detection (CDAW catalog).
The main results that I will discuss during my talk are:
I. There is a great discrepancy between CACTus and CDAW CME rates, both in shape and in amplitude. The CACTus statistics are dominated by narrow events that are mostly not included in the CDAW catalog.
II. While the classical CME picture is a white light structure having a typical angular width of 45° in the coronagraphic field of view, our catalog suggests that the CME process is scale invariant, i.e. that no typical CME size exists.
III. Are narrow CMEs witnessing the continuous renewal of the magnetic field? Are all plasma outflows an indication of the same physical mechanism?
IV. Our different CME statistics shed new light on the composition of CME (and other) catalogs and highlights the need for caution in the usage of catalogs. Perhaps the most revealing conclusion of this paper is that at present, no 'ground truth' CME catalog exists, since no consensus exists about the nature and origin of marginal coronal eruptions.
[edit] 1.7.7 September 26, 2007
Reducing Parameter Estimation Bias in Empirical Models:�A Case for Data Assimilation in Radiation Belt Science
Josh Rigler, NCAR/HAO
jrigler@hao.ncar.edu
Leaving relevant variables out of a model will almost invariably lead to biased estimates of any empirical parameters required by the model, assuming that these parameters are optimized to somehow minimize the�discrepancy between model output and real data. Since this is quite often the case, the previous statement acknowledges formally what many modelers already understand intuitively: parameterized models that�ignore relevant physics tend to compensate by over- or under-stating the influence of whatever physics were actually included in the model.��
This raises the question of how one mitigates bias error so that the physics being modeled are most accurately portrayed? I present results from an ongoing study using data-derived radiation belt electron flux models, combined with a relatively simple data assimilation�technique. By simultaneously estimating its parameters, and correcting the model to better match observations, much correlated structure in the model residuals that causes bias error is removed, thereby providing more realistic parameter estimates. This a very general result, so similar results should be possible using any formal data assimilation scheme and empirical or semi-empirical model.
[edit] 1.7.8 September 19, 2007
Global Hybrid Modeling of Magnetic and Energetic Particle Storms on the Magnetosphere
Farzad Kazeminezhad
West Virginia High Tech Consortium Foundation
farzad@wvhtf.org
A 2.5 dimensional hybrid model of massless fluid electrons and kinetic ions which also includes a simple ionosphere-magnetosphere coupling is used to investigate the impacts of interplanetary shocks and high energy particles presumably resulting from magnetic storms on the magnetosphere. The code is structured to model the magnetosphere dynamics of the Earth-Solar wind system by utilizing a finite element mesh specifically tailored to magnetosphere’s regions. It spans many hundred Earth radii in each direction (upstream, downstream, dawn and dusk). Realistic parameters characteristic of solar wind, its IMF and geomagnetic field are used. The code has been tested by its ability to predicting a magnetosphere by initializing a dipole at equilibrium with a flow subjected to an incoming solar wind with an IMF. The tests revealed generation of a steady state bow shock, as well as dayside reconnection (for southward IMF) as well as a tail sheet formation.
The interplanetary shock is generated by a sudden enhancement of the incoming IMF by an order of magnitude. This act introduced a fast MHD shock which propagated downstream and collided with the bow shock. This collision resulted not only in a steep rise in density and temperature of the bow shock, but also in the tail sheet region as the shock propagated downstream. The densities and temperatures, though, eventually relaxed to what are normal bow shock and tail values as the fast shock left the simulation domain. The sharp rise in the tail density which is insulated by geomagnetic field lines, can only be a result of kinetic effects. The results are analyzed and the role of different kinetic effects along with diagnostics discussed.
The high energy flux of particles are simulated by injecting Kev to Mev range particles. These particles are traced as their trajectories are stored. The deflection angle of the incoming particles versus their incident energies and their incident latitudes are obtained for the cases in which the incident IMF points north versus southward. Both these investigations are aimed at better understanding of the transport of energy and momentum by geomagnetic storms through their resulting interplanetary shock waves and high energy particles into the inner magnetosphere. This work is supported by the NSF-ATM-0651690.
[edit] 1.7.9 September 12, 2007
Observations of Interplanetary Coronal Mass Ejections in the Inner Heliosphere Using Multiple Spacecraft
Ian Richardson
Astroparticle Physics Laboratory, NASA Goddard Space Flight Center
ianr@milkyway.gsfc.nasa.gov
Observations of interplanetary coronal mass ejections (ICMEs), the interplanetary counterparts of coronal mass ejections at the Sun, in the inner heliosphere during cycle 23 have largely been confined to the vicinity of Earth. However, in the mid-1970s to early 1980s, observations made by the Helios 1 and 2 spacecraft, in heliocentric orbits at 0.3-1 AU, together with observations near the Earth, provided a unique opportunity to investigate ICMEs and their associated shocks and energetic particle events at widely separated locations. With the recent launch of the STEREO spacecraft, and the SENTENELS mission under development, multi-point observations of interplanetary structures at <~ 1 AU will again be possible. The in-situ signatures of ICMEs will be reviewed, and results from earlier multi-point studies discussed, including their implications for these newer missions and space weather forecasting.
[edit] 1.7.10 September 5, 2007
Living in an Asymmetric Solar System: What are we learning from the solar system final frontier
Merav Opher
George Mason University, 4400 University Drive, Fairfax, VA 22030
mopher@physics.gmu.edu
In the last couple of years we are having a flurry of activity at the edge of the solar system. After more than 30 years the twin Voyager spacecrafts arrived at the edge of the solar system and are sending back new data that are putting in putting in check old paradigms and forcing us to reexamine old theories. The twin spacecraft are probing the northern and southern hemispheres of the heliosphere providing us a stereo view. We showed recently (Opher et al. Science 2007; Opher et al. ApJL 2006) that only an asymmetric Solar system can explain the current data (radio emissions and streaming of low energy particles). Furthermore we were able to constrain the direction of the local interstellar magnetic field as not being in the plane of the disk of the galaxy (as was thought previously). This could be the first constrain of turbulence in the local interstellar medium in small scales. In this presentation I will review this findings, our present knowledge of the solar system final frontier and the current puzzles and open questions.
[edit] 1.8 Spring, 2007
[edit] 1.8.1 February 21, 2007
The CFD center at GMU
Rainald Lohner
Head, CFD Center Dept. of Computational and Data Sciences College of Sciences M.S. 6A2, George Mason University, Fairfax, VA 22030-4444, USA
An overview of the activities of the CFD center at GMU will be presented. Both the strategic application areas covered by the Center, as well as the fundamental and technical questions associated with them will be discussed. Current open questions will be discussed, as well as possible ways of resolving them.
[edit] 1.8.2 Febrary 28, 2007
A Review of Atmospheric Flow and Dispersion Patterns
Fernando E. Camelli
Center for Computational Fluid Dynamics
Department of Computational Data Sciences
College of Sciences, George Mason University
fcamelli@gmu.edu
The application of Computational Fluid Dynamics (CFD) for transport and dispersion of pollutants in the urban scales has increased in the last decade. Improvement in computer performance is one of the pivotal reasons for this growing interest in using CFD with this type of application. In addition, the threat of an intentional chemical/biological/nuclear (CBN) release in a densely populated urban area has sparked research on dispersion patterns in urban scales for the past decade. The research of gas dispersion for scales larger than a city has been the focus of study for decades now, and Gaussian models have been the most successfully applied to these large scales. Unfortunately, the simpler models have been unable to reproduce and capture all the complex processes at an urban level. The reason for this failure is primarily the inability to represent the mechanical forces (i.e. building geometry, trees, traffic) and the thermal forces (i.e. surface heating, HAVC systems) that control dispersion at this scale level. Dispersion models that use first principle physics are available today as a direct result of the sustained increase of computational ability, thus allowing the performance of more operations in less time. This talk will review a Computational Fluid Dynamics (CFD) model called FEFLO-URBAN used to accurately calculate in time the flow field inside an urban layout. The transport and dispersion of a passive release is incorporated using an Eulerian framework. Five different scenarios will be presented: first, a realistic urban setting in Northern Virginia where the building geometry was obtained through blueprints (commercial development at Tysons Corner); second, the MUST experiment conducted in the U.S. Army Dugway Proving Ground Horizontal Grid test site in Utah; third, a scenario in New York City using FEFLO-URBAN as part of a collaborative effort supporting the design of the upcoming experiment in the Madison Square Garden area; fourth, the study of assessing maximum possible damage for contaminant release events in a generic subway station; and finally, the transport and dispersion problem around ship vessels, studying the flow patterns for the LPD17 and the concentration levels for the T-AKE 1. Discussion of last two seminars and handout
[edit] 1.8.3 March 21, 2007
Comparative studies of multi-scale convective transport through the Earth’s plasma sheet
Timothy B. Guild
The Aerospace Corporation
Space Sciences Department/Chantilly
In this talk we will explore multi-scale, convective transport through the Earth’s plasma sheet using in situ observations and global terrestrial magnetospheric simulations. We statistically test the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model with observations from the Geotail spacecraft at a variety of spatial and temporal scales within the plasma sheet. These comparisons illuminate model shortcomings and highlight the additional physics necessary to resolve data/model discrepancies. Specifically, we will describe comparisons of global-scale plasma moments, magnetic fields, and bulk flows within the plasma sheet. By characterizing the LFM plasma sheet velocity distribution as a function of simulation resolution, we find that increased resolution inherently changes the nature of the dynamics and transport within the LFM plasma sheet, bringing it into closer agreement with magnetotail observations containing fast, localized bulk flows. Due to the importance of these fast flows to mass, momentum, and energy transport in both the observed and simulated plasma sheets, we use the LFM to establish that locally-reconnecting magnetic lobe field lines initiate these simulated “flow channels”, explore the physical processes governing their subsequent evolution, and examine their similarity to observations of bursty bulk flows.
[edit] 1.8.4 March 28, 2007
Self-Organized Criticality in a Numerical MHD Current Sheet with Cross-Scale Coupling to a Current-Driven Kinetic Instability
Alex Klimas
NASA, Goddard Space Flight Center
alex.klimas@nasa.gov 301-286-3682
Through analyses due to Uritsky et al. [JGR, 2002; GRL, 2003, 2006] of Polar UVI auroral emissions data, it is now well established that regions of bright UV emissions in the night-side aurora exhibit the properties of avalanches in a system in SOC. Based on the observed relationship between localized reconnection in Earth’s magnetotail and consequent auroral UV emissions, on the large range of emissions scales plus the necessary excitation energy, neither of which can have their origins in the ionosphere, and on various analogies between the driving and dissipation of sandpile SOC models and the loading and unloading of magnetic flux/energy in the magnetotail, Uritsky et al. and Klimas et al. [JGR, 2004] have suggested that the auroral dynamics is a reflection of the reconnection dynamics of the magnetotail, which is in or near a self-organized critical state. A study of reconnection in a 2-D current-sheet model containing coupled resistive MHD and kinetic-micro turbulence components will be discussed. The current sheet supports a magnetic field reversal and is configured so that under steady loading at its boundaries an equilibrium state can be reached in which the rate at which magnetic flux is driven into the reversal is balanced by the rate at which it is dissipated through annihilation. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. It has been shown that the Poynting flux evolves through bursts of avalanching activity separated by quiet times during which the current sheet recovers. All of the analysis techniques (and more) that have been applied to the auroral image data have also been applied to this Poynting flux. New results will be presented showing that the Poynting flux exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. A strong correlation between these key properties of the model and those of the auroral UV emissions will be demonstrated. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.
[edit] 1.8.5 May 2, 2007
The International Reference Ionosphere – Climatological standard for the ionosphere
Dieter Bilitza
Raytheon IIS, GSFC, Space Physics Data Facility, Code 672, Greenbelt, MD 20771
Dieter.Bilitza.1@gsfc.nasa.gov
The International Reference Ionosphere (IRI) a joint project of URSI and COSPAR is the defacto standard for a climatological specification of ionospheric parameters. IRI is based on a wide range of ground and space data and has been steadily improved since its inception in 1969 with the ever-increasing volume of ionospheric data and with better mathematical descriptions of the observed global and temporal variation patterns. The IRI model has been validated with a large amount of data including data from the most recent ionospheric satellites (KOMPSAT, ROCSAT and TIMED) and data from global network of ionosondes. This talk will give an overview over the IRI effort with special emphasis on the activities that are currently in progress. I will discuss the latest version of the IRI model, IRI-2007, highlighting the most recent changes and additions. Finally, the talk will review some of the applications of the IRI model.
[edit] 2 Journal Club
[edit] 2.1 Fall, 2009
[edit] 2.1.1 Sept. 29th
- Roundtable discussions of Graduate Work.
[edit] 2.1.2 Sept. 22nd
- Yod Poomvises will discuss his research
- Title: CME propagation and expansion in 3-D space in the heliosphere based on STEREO/SECCHI observations.
- Abstract: We report a study of kinematics and morphological evolution of CMEs by using STEREO/SECCHI observation to track in 3-D space a set of well observed events from the sun to a large distance in the heliosphere. The CME tracking is based on the Raytrace model (Thernisien et al 2006), which is able to represent a CME as a 3-D flux rope in the upper portion and two straight legs in the lower portion. The true 3-D location can be obtained. We are able to further calculate 3D velocity and 3D acceleration of CMEs free of project effect. In particular, the true cross-section of CMEs, and thus the expansion speed can be found. For the 5 events studied, we find that their bulk velocities eventually converge into a narrow range of 190 km/s – 430 km/s, while their initial velocities range from about 150 km/s to 1500 km/s. Their expansion velocities also converge into a narrow range between 140 km/s and 300 km/s. We find that the deceleration for fast events and acceleration for slow events mainly occur within 40 solar radii.
[edit] 2.1.3 Sept. 15th
- Ambient solar wind's effect on ICME transit times
- ADS Link: http://adsabs.harvard.edu/abs/2008GeoRL..3515105C
- http://aurora.gmu.edu/~bcurtis/files/Case_et_al_2008.pdf
- Host: Brian Curtis
[edit] 2.2 Spring, 2009
- Meeting Time: 10:30 - 11:30 AM Tuesdays
- Room 302
[edit] 2.2.1 Mar. 31, 2009
- Parallel Electric Fields Inferred During a Pulsating Aurora
- Authors: J.D. Williams, E. MacDonald, M. McCarthy, L. Peticolas, and G.K.Parks, Ann. Geophys., 24, 1829-1837, 2006
- Download: http://hal.archives-ouvertes.fr/docs/00/31/81/17/PDF/angeo-24-1829-2006.pdf
- Host: Randy Bell
[edit] 2.2.2 Mar. 3, 2009
- On Formation of a Shock Wave in Front of a Coronal Mass Ejection With Velocity Exceeding the Critical One
- Author: M.V. Eselevich and V.G. Eselevich, Geophysical Research Letter, Vol. 35, L22105, doi:10.1029/2008GRL035482, 2008
- Host: Indrajit Das
[edit] 2.2.3 Feb. 17, 2009
- Processes and Mechanisms Governing the Initiation and Propagation of CMEs
- B. Vrsnak. Annales Geophysicae,. 26, 3089-3101, 2008
- Download: [1]
- HOST: Oscar Olmedo
[edit] 2.3 Fall, 2008
- New Meeting Time 3:00-4:00PM Tuesdays
- Room 301
[edit] 2.3.1 Oct 14th
Particle Acceleration at Perpendicular Shocks
- Zank et al., 2005 | DIRECT DOWNLOAD:PDF Document
- HOST: Oscar Olmedo
[edit] 2.3.2 Sep 2
Multiscale modeling of magnetospheric reconnection
- Kuznetsova et. al., 2007 | DIRECT DOWNLOAD:PDF Document
- HOST: Rebekah Evans
[edit] 2.4 Summer, 2008
[edit] 2.4.1 Aug 12
Solar excursion phases during the last 14 solar cycles
- Mursula and Zieger, 1998 | DIRECT DOWNLOAD: PDF Document
- HOST: Christy Henderson
[edit] 2.4.2 July 29
Characteristic magnetic field and speed properties of interplanetary coronal mass ejections and their sheath regions
- Owens et al., 2005 | DIRECT DOWNLOAD:PDF Document
- HOST: Yod Poomvises
[edit] 2.4.3 July 15
NUMERICAL INVESTIGATION OF THE HOMOLOGOUS CORONAL MASS EJECTION EVENTS FROM ACTIVE REGION 9236
- Lugaz et al., 2007 NASA/ADS Page | DIRECT DOWNLOAD:PDF Document
- HOST: Indrajit Das
[edit] 2.4.4 July 1
- Saito et al., 2007 NASA/ADS Page | DIRECT DOWNLOAD:PDF Document
- HOST: Brian Curtis
[edit] 2.5 Spring, 2008
[edit] 2.5.1 June 3rd
- Lin et al., 2007 NASA/ADS Page
[edit] 2.5.2 May 12th
- Gonzalez et al., 1994 NASA/ADS page.
[edit] 2.5.3 April 28th
- Schmeltz et al., 2007 NASA/ADS page.
[edit] 2.6 Fall, 2007
There are two Journal Clubs this semester: A Joint Space Weather Journal Club and the Astrophysics Journal Club and a stand-alone Space Weather Journal Club. The joint journal club meets every other week (generally in SUB II). See http://physics.gmu.edu/~mjordan/AJC.html for links to papers. The stand-along club meets intermittenly in the off weeks (generally in Res. I, room 301).
- September 12 (Room: SUB II room 5)
- "Implications of Interstellar Dust and Interstellar Magnetic Field at the Heliosphere", P.C.Frisch,July 23, 2007 astro-ph arXiv:0707.2970v2
- "The radius and mass or the subgiant star beta Hyi from interferometry and asteroseismology", J. R. North, et al, MNRAS 380, L80-L83 (2007)
- "The Orientation of the Local Interstellar Magnetic Field", M. Opher, et al, Science 11 May 2007 316:875-878
- "NGC 4254: An act of harrassment uncovered by the Arecibo Legacy Fast ALFA survey", M.P. Haynes, et al, ApJ 665: L19-L22, 2007 August 10
- "Optically unseen H1 detections towards the Virgo Cluster detedted in the Arecibo Legacy Fast ALFA survey", B.R. Kent, et al, ApJ 665: L15-L18, 2007 August 10
- September 26 (Room: SUB II room 5)
- TBD
- October 10 (Room: SUB II room 4)
- TBD
- October 31 (Room: SUB II room 6)
- TBD
- November 14 (Room: SUB II room 4)
- TBD
- November 28 (Room: SUB II room 4)
- TBD
- December 5 (Room: SUB II room 4)
- TBD
[edit] 2.7 Spring, 2007
Space Weather Journal Club
- January 23: Yuming Wang : "Geomagnetic storms caused by compressed structures"
- January 30: Yong Liu: "Ion Thermalization and Wave Excitation Downstream of Earth's Quasiperpendicular and Marginally Supercritical Bow Shock"
- February 06: Yong Liu - second part
- February 13: Bob Weigel "Ring Currents"
- February 20: Ken Dere
- Feburary 27: Art Poland
- March 06: Merav Opher "Magnetic Effects in the Heliosphere"
- March 13: NOTE: Spring Break
- March 20: Bob Meier
- March 27: Dimitris Vassilliadis
- April 03: I will not be here - passover TBD
- April 10: Christy
- April 17: canceled
- April 24: Yod: "The Association of CME with their effects near Earth" by R. Schwenn et al (2005)
- May 01: Oscar Olmedo
- May 08: Rebekah Evans
- May 15: Jim Chen
- May 22: AGU-joint assembly
- May 29 - last seminar before the summer
