http://arxiv.org/abs/1705.07471
We have studied the spatial and temporal distribution of element abundances of large “gradual” solar energetic-particle (SEP) events, and especially the source plasma temperatures, derived from those abundances, using measurements from the Wind and Solar Terrestrial Relations Observatory (STEREO) spacecraft, widely separated in solar longitude. A power-law relationship between abundance enhancements and mass-to- charge ratio A/Q of the ions can be used to determine Q values and source plasma temperatures at remote spacecraft with instruments that were not designed for charge-state measurements. We search for possible source variations along the accelerating shock wave, finding one clear case where the accelerating shock wave appears to dispatch ions from 3.2+-0.8 MK plasma toward one spacecraft and those from 1.6+-0.2 MK plasma to- ward the other, 116 deg away. The difference persists three days and then fades away. Three other SEP events show similar abundances and source temperatures at different spacecraft, in one case, over 222 deg in longitude. This initial study shows how the power- law relation between abundance enhancements and ion A/Q values provides a new technique to determine Q and plasma temperatures in the seed population of SEP ions over a broad region of space using remote spacecraft with instruments that were not originally designed for measurements of ionization states.
D. Reames
Tue, 23 May 17
18/68
Comments: 19 pages, 10 figures, submitted to Solar Physics