Telescopic/Microscopic View of a Substorm
1 October 2002A powerful solar eruption occurred on 29 March 2001, which then released a coronal mass ejection toward the Earth. Early on 31 March 2001, since it is taking about 2 days for the CME to reach the Earth, a strong interplanetary shock struck the Earth, initiating one of the largest geomagnetic storms of this solar cycle.
The magnetopause, and very probably even the Earth's bow shock, were pushed inside the geostationary orbit (6.6 Earth Radii [RE] geocentric distance). Such an extreme magnetospheric global compression is very rare. In a paper in the Geophysical Research Letters, D.N. Baker et al. report on the findings of the four Cluster spacecraft and the IMAGE satellite that witnessed the rare event.
At the time of the event, the Cluster constellation was near local midnight and at 4 RE geocentric distance. Cluster sensors observed an energetic electron injection event associated with a strong magnetospheric substorm. The energetic neutral atom imaging experiments onboard the IMAGE spacecraft detected an injection of ions in the pre-midnight sector commencing at 06:30 UT. Electron injection signatures at the four separate Cluster locations allowed for infering the location, speed, and direction of the substorm injection boundary. Hence, the Cluster (and IMAGE) telescope-microscope combination is a long-sought realization of a major magnetospheric research objective and shows the power of localized multipoint measurements from Cluster.
D.N. Baker et al., A telescopic and microscopic view of a magnetospheric substorm on 31 March 2001, Geophys. Res. Lett., 29 (18), 1862, doi:10.1029/2001GL014491, 2002