We present an analysis of the alpha to proton solar wind abundance ratio (AHe) during a period characterized by significant large size scale density fluctuations, focusing on an event in which the proton and alpha enhancements are anti-correlated. In a recent study using 11 years (1995–2005) of solar wind observations from the Wind spacecraft, N. M. Viall et al.  showed that periodic proton density structures occurred at particular radial length-scales more often than others. The source of these periodic density structures is a significant and outstanding question. Are they generated in the interplanetary medium, or are they a relic of coronal activity as the solar wind was formed? We use AHe to answer this question, as solar wind elemental abundance ratios are not expected to change during transit. For this event, the anti-phase nature of the AHe variations strongly suggests that periodic solar wind density structures originate in the solar corona.
Geophysical Research Letters
American Geophysical Union
Digital Object Identifier (DOI)
Viall, N. M., H. E. Spence, and J. Kasper (2009), Are periodic solar wind number density structures formed in the solar corona? Geophys. Res. Lett., 36, L23102, doi:10.1029/2009GL041191.
Copyright 2009 by the American Geophysical Union.