SeminarsAndTalks
From Space Weather Lab
Contents |
[edit] 1 Space Sciences Seminar
Part of the CSI 991 seminar series. Meets Wednesday at 3:00pm in Research I, Room 301. Directions
- Google map showing the turns you need to take on campus from route 123: html
- GMU campus map showing the Research I building html. 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, 2008
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] 1.2 Summer, 2008
[edit] 1.2.1 Tuesday August 5th at 11 am in room 301
Space Weather research in South Africa
Lee-Anne McKinnell
[edit] 1.3 Spring, 2008
[edit] 1.3.1 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] 1.3.2 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] 1.3.3 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] 1.3.4 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] 1.3.5 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] 1.3.6 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] 1.3.7 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] 1.3.8 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] 1.3.9 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] 1.3.10 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] 1.4 Fall, 2007
[edit] 1.4.1 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] 1.4.2 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] 1.4.3 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] 1.4.4 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] 1.4.5 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] 1.4.6 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] 1.4.7 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] 1.4.8 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] 1.4.9 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] 1.4.10 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] 1.5 Spring, 2007
[edit] 1.5.1 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] 1.5.2 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] 1.5.3 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] 1.5.4 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] 1.5.5 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, 2008
- New Meeting Time TBD (Slot agreed so far 3:00-4:00PM Tuesdays)
- Still room 302
[edit] 2.1.1 Sep 2
Multiscale modeling of magnetospheric reconnection
- Kuznetsova et. al., 2007 | DIRECT DOWNLOAD:PDF Document
- HOST: Rebekah Evans
[edit] 2.2 Summer, 2008
[edit] 2.2.1 Aug 12
Solar excursion phases during the last 14 solar cycles
- Mursula and Zieger, 1998 | DIRECT DOWNLOAD: PDF Document
- HOST: Christy Henderson
[edit] 2.2.2 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] 2.2.3 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] 2.2.4 July 1
- Saito et al., 2007 NASA/ADS Page | DIRECT DOWNLOAD:PDF Document
- HOST: Brian Curtis
[edit] 2.3 Spring, 2008
[edit] 2.3.1 June 3rd
- Lin et al., 2007 NASA/ADS Page
[edit] 2.3.2 May 12th
- Gonzalez et al., 1994 NASA/ADS page.
[edit] 2.3.3 April 28th
- Schmeltz et al., 2007 NASA/ADS page.
[edit] 2.4 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] 2.5 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
