Telescopic/Microscopic View of a Substorm
1 October 2002
A 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.
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The Solar storm viewed by the IMAGE (the telescope) and by Cluster (the microscope). From D.N. Baker et al., Geophys. Res. Lett, 2002. |
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.
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A schematic summary of the substorm onset events at 06:30 UT on 31 March, 2001 (from D.N. Baker et al., Geophys. Res. Lett, 2002). |
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