ISTP Sun-Earth Connections Event: Solar Observations

January 6 - 11, 1997

Note: This web page is preliminary, not citable, and for discussion purposes only

SHINE's preliminary report on the origin of this event

During the January 6 - 10 ISTP workshop, Don Michels of the LASCO (Large Angle Spectrometric Coronagraph) team showed a movie of the halo CME observed by LASCO, a coronagraph on SOHO. It first appeared in the LASCO C2 field of view at about 16 UT on January 6, 1997 (the C2 field of view begins at 2 solar radii). The CME appeared to directed in the earthward or anti-earthward direction; there was a large amount of activity on the disk, so it was decided that the CME had a large chance of being earth-directed.

It was difficult to determine the speed of the CME because the relative angle of propagation was probably very close to the equatorial plane. However, Dr. Michels estimated that a typical CME speed of this class would travel somewhere between 400 and 500 km/sec. At a speed of 450 km/sec, the CME would reach L1 in 3 3/4 days, or around 10 UT on January 10. The following image is a projection of the halo onto an EIT image of the sun (during a previous rotation). By completing the circle formed by the halo (the green ring), one can see that the event encompasses disk center.

Unfortunately, the SOHO EIT (Extreme Ultraviolet Imaging Telescope) was undergoing instrument engineering during this period; the Yohkoh SXT (Soft X-ray Telescope) images are included in the following movie:

The GOES X-ray flux for that day was particularly quiet, with an LDE (long duration event) from 14:30 - 16:30 UT:

The SOHO MDI (Michaelson-Doppler Imager magnetograms indicate small concentrations of magnetic field during periods of suspected magnetic clouds (this analysis is very preliminary). A separate page shows a summary of magnetograms for several months observed by MDI as well as some combined images with SOHO/EIT. The following image is the magnetogram for 6 January 1997 at 9:19 UT:

On January 10, the Celias MTOF Proton Monitor (XGSM ~230 Re) 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, density from 7 to 13 /cc) There is a second jump at 0430 UT when the speed again rises to 520 km/s, and the density drops to about 2/cc for a couple of hours; it then slowly returns to its pre-event value.