Tracing the topology of the October 18-20, 1995, magnetic cloud with ~0.1 - 102 keV electrons

D. E. Larson, R. P. Lin, J. M. McTiernan, J. P. McFadden, R. E. Ergun, M. McCarthy, H. Reme, T. R. Sanderson, M. Kaiser, R. P. Lepping, and J. Mazur

Space Sciences Laboratory, University of California, Berkeley, California


Five solar impulsive ~1-102 keV electron events were detected while the WIND spacecraft was inside the magnetic cloud observed upstream of the Earth on October 18-20, 1995. The solar type III radio bursts produced by these electrons can be directly traced from ~1 AU back to X-ray flares in solar active region AR 7912, implying that at least one leg of the cloud was magnetically connected to that region. Analysis of the electron arrival times shows that the lengths of magnetic field lines in that leg vary from ~3 AU near the cloud exterior to ~1.2 AU near the cloud center, consistent with a model force-free helical flux rope. Although the cloud magnetic field exhibits the smooth, continuous rotation signature of a helical flux rope, the ~0.1-102 keV energetic electrons show numerous simultaneous abrupt changes from bidirectional streaming to unidirectional streaming to complete flux dropouts. We interpret these as evidence for patchy disconnection of one end or both ends of cloud magnetic field lines from the Sun.

Geophys. Res. Lett., 24, 1911-1914, 1997