Abundances and charge states in quiet-time low-energy ion fluxes at 1 AU
Abstract
Abundances of C and Fe ions with energies 0.04-1.28 MeV/nuc in the 23rd solar activity cycle are examined in the quiet-time fluxes using ACE, SOHO and STEREO data. They are com-bined with charge state measurement data from SEPICA (ACE, 0.18-0.43 MeV/nuc). Quiet periods of solar activity were selected using the criteria a) Jp < 2x10-4 protons/(cm2 s sr MeV) for 4-8 MeV protons (from EPHIN/SOHO) and b) the ratio H/He < 10 at these energies. The values of C/O and Fe/O were determined over the solar cycle and the following was found. In about 50% of the time intervals during high activity they both were near the average values observed in the solar corona, whereas at solar minimum in more than 90% of the periods the ratios were around the solar wind values. Most of the quiet time periods around maximum, which have sufficient statistics show high average Fe charge states (>15), consistent with im-pulsive solar event origin. During the SC minima the abundances in almost all cases correspond to solar wind values. The results obtained suggest that the active structures on the Sun arising at low solar activity are mostly responsible for background particle fluxes at these energies. There may be microflares, disappearing of ribbons, soft X-ray bright points etc.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1631K