Bremen 2000 – scientific programme
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EP: Extraterrestrische Physik
EP 5: Planeten und Monde II
EP 5.9: Talk
Wednesday, March 22, 2000, 12:30–12:45, H3
On the relation between relativistic electron enhancements in the outer radiation belt, magnetic storms, and substorm activity — •P. Bühler1 and L. Desorgher2 — 1Paul Scherrer Institut, Laboratorium für Astrophysik, CH-5232 Villigen PSI — 2Physikalisches Institut der Universität Bern, Sidlerstrasse 5, CH-3012 Bern
The relativistic electron fluxes of the outer radiation belt are subject to strong temporal variations. The most prominent changes are initiated by fast solar wind streams impinging upon the magnetosphere, which often also cause enhanced substorm activity and magnetic storms. Using over 4 years of data from the particle detector REM aboard the UK satellite Strv-1b in a GTO, we investigated the relation between these different appearances of geomagnetic activity. A typical sequence is that there is a drop in the relativistic electron intensity during the main phase of the magnetic storm and a succesive enhancement during the recovery phase which sometimes leads to much higher than pre-storm fluxes. Whereas the flux drop is well correlated with the magnetic storm intensity, measured by Dst, and is mainly due to the deceleration of the particles caused by the ring current induced magnetic field decrease, there is only a bad correlation between the post-storm electron fluxes and Dst. It is much more the level of substorm activity during the recovery phase, which is driven by the solar wind and IMF conditions, which determines the size of the flux enhancements. It can therefor happen that great magnetic storms are followed by small electron flux levels but also that small magnetic storms are associated with large electron enhancements.