Magnetospheric Model Performance During Conjugate Aurora
Reiff, Patricia H.
Master of Science
At 16:40 UT on August 17th, 2001, the IMAGE satellite was in position to view an auroral storm in the Northern Hemisphere, while the POLAR satellite was simultaneously in position to view the storm in the Southern Hemisphere. For many low-latitude auroras, the precipitation maps along field lines from the Southern Hemisphere to the Northern Hemisphere. However, in this case, the IMF had a very strong dawn-dusk component which has been shown to make the polar cap shift towards the dusk in one hemisphere and towards the dawn in the other, but this has not yet been confirmed by simultaneous auroral imaging. Using the satellite images in the 130 nm to 160 nm wavelength range, we have been able to identify the Polar Cap Boundary in both hemispheres throughout the event, and calculated the Dawn-Dusk Offset, ∆L, in both hemispheres. We then found correlations of 0.90 in the Northern Hemisphere and 0.83 in the Southern Hemisphere between ∆L, ranging from 4 to 12 degrees during the event, and By, ranging from 20 to 32 nT during the event. ∆L also correlated well against IMF Clock Angle (ϴC) and the Epsilon parameter (ϵ=vB2sin[ϴC/2]) when using specific time averages of these parameters. The same methods are then applied to the compute Polar Cap Boundaries in the BATSRUS, OpenGGCM, and LFM-MIX models that were run to simulate the event. We find that none of the models accurately describe the observed open-closed field line boundary during this event, with BATSRUS tending to produce boundaries that are too ideal and symmetric, OpenGGCM producing boundaries that are highly distorted and random, and the LFM-MIX model always yielding low correlations between ∆L and the various solar wind parameters.
Space physics; Physics; Aurora