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| Paper: |
The Interplanetary Population of Suprathermal Ions from Impulsive
Solar Energetic Particle Events: Solar Cycle Variations |
| Volume: |
484, Outstanding Problems in Heliophysics: From Coronal Heating to the Edge of the Heliosphere |
| Page: |
234 |
| Authors: |
Wiedenbeck, M. E.; Mason, G. M. |
| Abstract: |
Suprathermal ions in the solar corona or interplanetary medium play an
important role in the determining the accelerated particle population
produced by CME-driven shocks. Impulsive solar energetic particle
events provide one of the sources of interplanetary suprathermals, and
the presence of this material is detectable based on its unique
composition in which the ion 3He is normally enhanced by several
orders of magnitude over its typical solar wind abundance. Using
composition measurements made with instruments on NASA's Advanced
Composition Explorer between 1997 and 2013 we have investigated the
solar cycle variation of suprathermals from impulsive events over more
than a full solar cycle. We find that the fraction of time with
energetic 3He detectable in the interplanetary medium near 1 AU
dropped by more than a factor of 100 between the cycle 23 solar
maximum and the following minimum. Comparison between the rising
portions of cycles 23 and 24 shows that the fraction of time with
3He present is significantly lower in the present solar cycle. |
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