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تسجيل مستخدم جديدAbundances of Suprathermal Heavy Ions in CIRs on STEREO during the Minimum of Solar Cycle 23
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We examine the composition of the 0.1 - 1 MeV/n 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 two STEREO spacecraft during the unusually long minimum of Solar Cycle 23 from January 2007 through December 2010. 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 unprecedentedly high statistics. The observations reveal annual variations of relative ion abundances in the CIRs during the 2007 - 2008 period. In 2010 the elemental composition in CIRs were influenced by solar energetic particle events.
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In this paper we examine the elemental composition of the 0.1-1 MeV/nucleon 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 boar
d 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 2007-2008 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 points out that the suprathermal SEPs could be the source population for CIR acceleration.
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