A strong CME-related magnetic cloud interaction with the Earth's magnetosphere: ISTP observations of rapid relativistic electron acceleration on May 15, 1997

D. N. Baker, T. I. Pulkkinen, X. Li, S. G. Kanekal, K. W. Ogilvie, R. P. Lepping, J. B. Blake, L. B. Callis, G. Rostoker, H. J. Singer, and G. D. Reeves



A geoeffective magnetic cloud impacted the Earth early on 15 May 1997. The cloud exhibited strong initial southward interplanetary magnetic field (BZ~25 nT), which caused intense substorm activity and an intense geomagnetic storm (Dst ~170 nT). SAMPEX data showed that relativistic electrons (E ³ 1.0 MeV) appeared suddenly deep in the magnetosphere at L=3 to 4. These electrons were not directly "injected" from higher altitudes (i.e., from the magnetotail), nor did they come from an interplanetary source. The electron increase was preceded (for ~2 hours) by remarkably strong low-frequency wave activity as seen by CANOPUS ground stations and by the GOES-8 spacecraft at geostationary orbit. POLAR/CEPPAD measurements support the result that high-energy electrons suddenly appeared deep in the magnetosphere. Thus, these new multi-point data suggest that strong magnetospheric waves can quickly and efficiently accelerate electrons to multi-MeV energies deep in the radiation belts on timescales of tens of minutes.

Geophys. Res. Lett., 25, 2975-2978, 1998