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ISTP Event Study: May 19-20, 1996
Key Data Sets
Wind (Various Instruments), LANL Geosynchronous
Energetic Particles, Polar Auroral Imagers, SuperDarn, IMP-8, and Ground
Magnetometers
Key Results
Energy transport from solar wind to magnetosphere
to ionosphere: Observations and comparisons with MHD models.
Contacts
Kyle Baker, Johns Hopkins APL, 301-953-5923,
kile_baker@jhuapl.edu
Steve Curtis NASA/GSFC, u5sac@lepvax.gsfc.nasa.gov
More Information
Baker, K. B., et al., Overview of the May
19-20, 1996 ISTP event, AGU Spring Meeting, Baltimore, MD, May 27-30, 1997.
http://sd-www.jhuapl.edu/RADAR/96May19/
Abstract
The period from 1100 UT on May 19 to 0300
UT on May 20, 1996 was chosen as an ISTP event to study the transport of
energy from the solar wind to the Earth's magnetosphere and then to the
ionosphere. This study was designed to use MHD modeling techniques to model
the response of the magnetosphere/ionosphere system to solar wind inputs
and then compare the modeled results with directly observed data from as
many satellites and instruments as possible.
The first three hours of the study period were characterized by relatively steady IMF conditions, Bz near zero but slightly positive (in GSM coordinates), By negative, and Bx positive. This provided a good baseline for the MHD modeling. Starting at 1400 UT there was an a slow rotation of the IMF in the y-z plan, with the z-component becoming progressively more positive. At 1500 UT there was a sharp change in the IMF with the orientation returning approximately to the conditions prior to 1400 UT. There were several subsequent sharp changes in the IMF which took place from 1500 to 2200 UT. These slow changes in IMF orientation followed by sudden, sharp changes provide excellent conditions for comparing MHD models with observed ionospheric convection as observed by the SuperDARN radars and magnetic perturbations observed by a variety of magnetometers.
Optical activity as observed by the POLAR UVI imager was very low until approximately 1730 UT, when there was a rapid increase in auroral activity. Although the imaging data indicates a significant change in activity, very little activity was observed from ground magnetometers or at geosynchronous orbit. At approximately 20:20 UT a new burst of auroral activity was associated with a substorm which was clearly observed at geosynchronous orbit and in ground magnetic data. A subsequent substorm occurred at 00:35 UT on May 20. This second substorm produced a much more substantial increase in the auroral activity observed by the POLAR imagers.
The period of this study thus contains times of relatively steady solar wind conditions, periods of slow variations in the IMF, periods of sudden changes in the IMF, as well as two fairly isolated substorms. It is therefore a rich period for comparisons between MHD models and observations.
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