Abundances of Suprathermal Heavy Ions in CIRs During the Minimum of Solar Cycle 23

作者：Bucik R^*; Mall U; Korth A; Mason G M

来源：Solar Physics, 2012, 281(1): 411-422.

DOI：10.1007/s11207-012-0094-6

• Corotating interaction regions
• Energetic ions
• Abundances

In this paper we examine the elemental composition of the 0.1 -aEuro parts per thousand 1 MeV nucleon(-1) interplanetary heavy ions from H to Fe in corotating interaction regions (CIRs) measured by the SIT (Suprathermal Ion Telescope) instrument. We use observations taken on board the STEREO spacecraft from January 2007 through December 2010, which included the unusually long solar minimum following Solar Cycle 23. During this period instruments on STEREO observed more than 50 CIR events making it possible to investigate CIR ion abundances during solar minimum conditions with unprecedented high statistics. The observations reveal annual variations of relative ion abundances in the CIRs during the 2007 -aEuro parts per thousand 2008 period as indicated by the He/H, He/O and Fe/O elemental ratios. We discuss possible causes of the variability in terms of the helium focusing cone passage and heliolatitude dependence. The year 2009 was very quiet in CIR-event activity. In 2010 the elemental composition in CIRs were influenced by sporadic solar energetic particle (SEP) events. The 2010 He/H and He/O abundance ratios in CIRs show large event-to-event variations with values resembling the SEP-like composition. This finding suggests that the suprathermal SEPs could be the source population for CIR acceleration.

• 出版日期2012-11