Davin E LarsonBR>
R P Lin; J McTiernan; R E Ergun; J Mazur; M. Kaiser; R. P. Lepping; J. L. Bougeret; G. K. Parks; T. R. Sanderson
We present a compilation of plasma observations from multiple experiments on the WIND spacecraft during the passage of a large magnetic cloud on October 18-20, 1995. The classic signatures of a magnetic cloud are observed: Smooth continuous rotation of field direction, bidirectional electron streaming and enhancement in He/H ratio. At least 10 solar type III radio events occurred during this interval and impulsive solar electrons were observed by the 3D Plasma instrument for at least 5 of these events. From the dispersive arrival time of these electrons, we calculate the magnetic field line length as a function of position within the cloud. We find the field line length is longest near the outer edges of the cloud and shortest in the middle of the cloud as would be expected for a nearly constant alpha force-free flux rope. The Yohkoh soft x-ray imager observed these flares within active region 7912, suggesting that at least one end of this magnetic cloud extends back to this region. In addition, electron fluxes show numerous abrupt discontinuities; periods for which the flux at all energies simultaneously decreases. Similar decreases are also observed in the energetic (100 KeV/N) ion fluxes observed by the EPACT/STEP instrument. We interpret these flux depletions as periods during which the WIND spacecraft is moving from field lines that are alternately disconnected and connected to the sun; presumably the result of magnetic reconnection within the corona. During the six day period starting with the initial eruption of the CME to the final passage of the cloud, the WAVES instrument observed a substantial increase in 1 Mhz wave activity, suggesting a continual restructuring of the coronal magnetic field. Of particular importance is when the reconnection occurs; either during the eruption process or subsequent to it. To further investigate this topic we present Yohkoh images of the eruption event.
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