At the ISTP Science Workshop of Jan 7-9, 1997, during a session to foster correlative studies between the solar and magnetospheric elements of ISTP, the SOHO/LASCO team showed a movie of the 6-7 Jan C2/C3 coronal sequence, because it was an excellent illustration of a 'halo' event.
Don Michels indicated that in his opinion, there was little doubt that a line-of-sight CME had occurred. It was skewed toward the southwest and there were at least two disk features that would be reasonable candidate sources, should the disk data ever materialize.
On January 10, the SOHO/CELIAS (XGSM ~230 Re) instrument observed the in-situ changes in the solar wind parameters. The solar wind speed and density both show a sudden rise at about 0010 UT (wind speed from 350 km/s to 430, rho from 7 to 13 /cc) Then there is a second jump at 0430 UT, when the speed again rises, to 520 km/s, and rho drops to about 2/cc for a couple of hours, then slowly returns to its pre-event value.
A few minutes later, the WIND suite of instruments (XGSM ~85 Re) also experience the effect of the event. Shortly before 0100 UT, a shock front is observed, followed by a magnetic cloud identified in the SWE and MFI data around 0430 UT. The Bz component of the IMF turns strongly southward (-15 nT) and slowly rotates back to Bz~0 over a period of some 12 hours. Preliminary analyses are underway (as of 1/14/97) in order to determine the geometry of the cloud, and will be reported in these pages as soon as they are available.
The event was followed through the magnetosphere, to the ionosphere and to the ground. The GEOTAIL spacecraft happened to be skimming the dayside magnetopause, and observed a large number of magnetopause crossings in response to the active upstream condi tions. The magnetospheric response quickly followed, resulting in wonderful auroral activity captured by the POLAR imagers, and well-correlated with ground-based magnetometer observations. Preliminary evidence further suggests increased levels in the radiation environment, and possibly a connection to the malfunction of an AT&T satellite.
Additional ground-based data from riometers, radars, all-sky imagers and others greatly complements the spaceborne measurements in this effort to understand the end-to-end tracking of an event from the surface of the Sun to the Earth's ionosphere.
If you are really interested in the geomagnetic impact of these events, the Minnesota Power Electric Company has a site called "Geomagnetic Storms and Impacts on Power Systems: Lessons Learned from Solar Cycle 22 and Outlook for Solar Cycle 23" which has detailed explanations and several examples of how geomagnetic activity can affect power systems.
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Last Updated: 03/28/97