A Prolonged He+ Enhancement Within a Coronal Mass Ejection in the Solar Wind

R. M. Skoug, S. J. Bame, W. C. Feldman, J. T. Gosling, D. J. McComas, J. T. Steinberg, R. L. Tokar, P. Riley, L. F. Burlaga, N. F. Ness and C. W. Smith

Geophysical Research Letters, 26, 161--164, 1999.

Abstract:

A coronal mass ejection and magnetic cloud containing an unusually large enhancement of He+ was observed in the solar wind by the plasma and magnetic field instruments on the Advanced Composition Explorer (ACE) spacecraft on Maya 2--4, 1998. The He+/He++ ratio during this event exceeded 0.5% for a period of more than 24 hours, and reached values as high as 100%. The high He+/He++ ratio indicates the presence of prominence material, and in fact a disappearing filament and prominence were observed at the Sun in association with this event. The prolonged observation of He+ indicates that prominence material extended through much of this CME, the first such observation in a CME in the solar wind.