Brian Curtis/Model Analysis
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[edit] 1 Model Analysis Page
[edit] 1.1 Look at the Results
[edit] 1.1.1 Comparisons (to be moved after intro)
- somes of the field lines appear to cross, but this is a 2-D plot. why?
- The BATSRUS Model has a dipolar look in the magnetosphere low density run, with the high density run appearing to stretch more tailward. The OpenGGCM model run does not show any dipolar look to the magnetosphere, it is very stretched tailward and compressed sunward.
- There is a line at around 02:10 in the OpenGGCM models, the following is the calculation made to find its speed. 600 seconds, ~30Re (6400Km/Re) would make the solar wind around 320 Km/s.
- This line has a thickness, and in each model run and each density there is a difference between them. I decided to keep them on the same scale as the free scale made it hard to see in the BATSRUS runs. 6Re with the low density and basing on the width of the IMF field lines drawn would give the high density a 2.5-3 Re thickness.
- Estimate of magnetopause location: Equation from Kivelson and Russell
so using a constant velocity (-360 Km/s) and plugging in densities of 7 and 3, you get magnetopause locations of 10.91 and 12.57 respectively. A visual study shows that the standoff location is around 17Re for Density 3 and about 13 Re for Density 7.
- both OpenGGCM Den 3 and 7 compress after Bz shift
- The OpenGGCM has a distinguished line of higher density material in the solar wind as it passes by earth here, the BATSRUS isn't as defined here. should there be one?
- It appears that after the Bz shift the nose of the magnetosphere in the OpenGGCM gets a bottlenosed look here, while the BATSRUS does not here.
- Comparing BATSRUS and OpenGGCM density 7, It appears as if the BATSRUS image creation run had stopped working towards the end of the time. But could it be possible that the BATSRUS model just kept it stabilized after the Bz Shift came through?
- there is a buildup of high density particles in the cusps within the first few segments of the run, i believe this is typical, but to this magnitude, i don't know.
- at 2:40 into the BATSRUS+RCM run, there is a giant black blob that shoots off towards the magnetotail, but its black, which according to the legend is a polar cap line, yet this isn't possible, since it detached itself (reconnection).
- there appears to be an earthward flow from the tailward side of the magnetosphere in the BATSRUS+RCM/BATSRUS
- after the Bz shift passes both BATSRUS models move ejecta tailward, but in the openGGCM this is hard to tell
[edit] 1.2 Intro Info
Dr. Weigel and myself are looking at the impacts of a solar wind density of 3 and 7 on the response of the magnetosphere. It's known that the initial density shock causes a certain response, but we are interested in how the different densities effect reconnection later on after the initial shock.
- Plots:
- Magnetosphere
- x-axis [-30 - 20 Re]
- y-axis [constant]
- z-axis [-48 - 48 Re]
- Density [color bar] (Max-of-data #/cc) & (0 - 30 #/cc)
- Current [Arrows] micro-amperes/meter
- Field Lines [colored lines]
- Ionosphere
- x-axis [-.643 - .643 Re]
- y-axis [.643 - -.643 Re]
- z-axis [constant]
- Current [color bar] (Max-of-data micro-amperes/meter) & (0 - 3000000 micro-amperes/meter)
- Conductivity [black lines] (kV)
The following are the models we are looking to compare results with.
We are giving each model the same inputs
[edit] 1.3 OpenGGCM
- Uses MHD in the outer magnetosphere
- Semi-conservative because the conservative has instabilities in low /beta regions where the pressure is computed as the difference between two large quantities.
- Time-stepping is an explicit second order predictor-corrector finite difference method
- The region within 3 Re uses a coupled thermosphere-ionosphere model
- Because there are super-magnetospheric flows and shocks, a flux-limited scheme is used
- OpenGGCM uses a hybrid (Harten, 1972). A 4th order scheme is combined with a minimal diffusion error. This switch ensures a high-order accuracy where there are no discontinuties.
- @ discontinuities - the solution degrades to a low-order (such as shocks and ?contacts?)
- The high-order scheme fails due to numerical dispersion
- Grid: Stretched Cartesian
[edit] 1.4 BATSRUS
This model contains many different domains. The ones we were specifically interested in were the Global Magnetosphere and Inner Magnetosphere (talked about in RCM section) and a small section of the inner heliosphere.
- Inner Heliosphere (IH)
- This domain extends from about 20 solar radii all the way to the planet.
- The physics of this domain are approximated by the ideal MHD equations
- The IH contains information for the boundary conditions for the GM
- Global Magnetosphere (GM)
- The upstream boundary of the GM is typically at about 30Re (this is inside the IH domain)
- This domain contains the bow shock, magnetopause, and magnetotail of the planet
- Downstream boundary in the hundreds of Re, with 50-100Re orthogonal to the sun-earth line
- resistive MHD equations are used, except near the planet where it overlaps with the IM
- coordinate systems are Geocentric Solar magnetic (GSM), Geocentric Solar Ecliptic (GSE), and sometimes Solar Magnetic (SM)
- inner boundary around 1-3 Re
[edit] 1.5 BATSRUS-RCM
The RCM is just an addition to the BATSRUS model, that includes the two domains above plus the following
- Inner Magnetosphere (IM)
- consists of the closed field line region around the planet.
- this solves equations that describe the motion of the keV-energy ions and electrons.
- Kinetic effects are important for these particles as well as several types of theoretical models that have been developed to describe them
- The Rice Convection Model (RCM) computes the field aligned currentsm abd ionospheric potentials, but still required an input og the magnetic field, and assumes that the paticles have an isotropic pitch angle distribution.
- the IM obtains the geometrical and plasma information from the GM.
