Abundances of Suprathermal Heavy Ions in CIRs on STEREO during the Minimum of Solar Cycle 23

TL;DR

This study analyzes the composition of suprathermal heavy ions in corotating interaction regions during Solar Cycle 23's minimum, revealing annual variations and influences from solar energetic particles, based on STEREO spacecraft data.

Contribution

It provides the first high-statistics analysis of CIR ion abundances during solar minimum, highlighting temporal variations and solar event influences.

Findings

Annual variations in ion abundances during 2007-2008.

Influence of solar energetic particle events on 2010 CIR composition.

Over 50 CIR events analyzed during the solar minimum.

Abstract

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.