Quiet-time 0.04-2 MeV/nucleon Ions at 1 AU in Solar Cycles 23 and 24статья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 10 апреля 2018 г.
Аннотация:The fluxes of 3He, 4He, C, O, and Fe ions at low energies (about 0.04 –2 MeV/nucleon) are studied during quiet periods in Solar Cycles (SC) 23 and 24 using datafrom the ULEIS/ACE instrument. In selecting quiet periods (the definition is given in Section2.1), additional data from EPHIN/SOHO and EPAM/ACE were also used. The analysisof the ion energy spectra and their relative abundances shows that their behavior is governedby their first-ionization potential. Substantial differences in the ion energy spectra in twoconsecutive solar cycles are observed during the quiet periods selected. Quiet-time fluxesare divided into three distinct types according to the ∼80 – 320 keV/nucleon Fe/O ratio.Our results confirm the earlier observation that these types of suprathermal particles havedifferent origins, that is, they represent different seed populations that are accelerated bydifferent processes. Except for the solar activity minimum, the Fe/O ratio during quiet-timeperiods correspond either to the abundances of ions in particle fluxes accelerated in impulsivesolar flares or to the mean abundances of elements in the solar corona. At the activityminimum, this ratio takes on values that are characteristic for the solar wind. These resultsindicate that the background fluxes of low-energy particles in the ascending, maximum, anddecay phases of the solar cycle include significant contributions from both coronal particlesaccelerated to suprathermal energies and ions accelerated in small impulsive solar flares richin Fe, while the contribution of remnants from earlier SEP events cannot be excluded. Thecomparison of suprathermal ion abundances during the first five years of SC 23 and SC 24suggests that the quiet-time and non-quiet fluxes of Fe and 3He were lower in SC 24.