Changes in Geomagnetic Field Direction resulting from Corona Mass Ejection

Recorded at Marjan Research, Mountain View, California
Copyright © J-N Aubrun, 2003

On October 28,2003 at 3:00 am PST, a strong CME departed from the sun at an estimated speed of about 2125 Km/s (~5 million miles /hour). Time of travel to Earth was estimated at 19.63 Hours.

Typical variations in the magnetic field direction during a day are of 200 to 400 arcsecs (1 to 2 mrads ) (Figure 1). This CME induced variations up to 7 mrads which are seen for 30 hours after initial impact (Figures 2 to 5). Short period (~2 minutes) and longer period oscillations can be observed during this time.

 Figure 1: Typical geomagnetic field variation

Figure 2: Beginning of the CME impact and effect on geomagnetic field

Figure 3: Strong oscillations are created as more particles enter the field

Figure 4: Oscillations continue to occur and slowly damp out

Figure 5: Field returning to almost normal after 29 hours

The magnetic deviation data obtained in Mountain View, CA
is very similar to that published by the Fresno, CA Magnetic Observatory
(http://geomag.usgs.gov/obs_data.html) as seen in Figure 6 .

Figure 6: Comparison with Fresno Magnetic Observatory Data (bottom)