Source and drift of ions during geomagnetic storms in 1932-2009
Abstract
A database of local and global Dxt and Dcx indices (corrected and extended Dst indices) from 1932 onwards has recently been constructed (dcx.oulu.fi). We have investigated the average properties of geomagnetic storms using the local Dxt indices at the four Dst stations in 1932-2009. Imposing the condition of complete data availability during storms, we found 1268/362/134/59 storms with Dxt minimum less than -50/-100/-150/-200 nT, respectively. The distribution of the largest storm-time disturbances was found to be strongly peaked at 18 local time, challenging local midnight as the dominant ion source. Relative timing of local minima at two stations verifies that stations at earlier LT hour observe their minimum a couple of hours after the deepest minimum, in agreement with westward drift of ions. Here we use this unique database to make the extensive analysis of the temporal development of storm time disturbances, e.g., ion injection and drift in the magnetosphere during geomagnetic storms. The large number of storms during the extended time interval of nearly 80 years allows sufficient statistics for such a study. Comparing the timing of storm minima at the neighboring stations, we can extract, e.g., the average drift speed of ions. We find interesting changes in the location and time difference of the minima with storm intensity, indicating that the ions are at lower L-shells and drift to earlier local times during intense storms. This also explains the relatively smaller local time asymmetry of strong storms.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMSM31C2341H
- Keywords:
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- 1500 GEOMAGNETISM AND PALEOMAGNETISM;
- 2778 MAGNETOSPHERIC PHYSICS / Ring current;
- 2788 MAGNETOSPHERIC PHYSICS / Magnetic storms and substorms