On the Acceleration of Helium in the Heliosphere

Details On the Acceleration of Helium in the Heliosphere On the Acceleration of Helium in the Heliosphere

May 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agusmsh33b..06k&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #SH33B-06

Other

2102 Corotating Streams, 2114 Energetic Particles (7514), 2134 Interplanetary Magnetic Fields, 2139 Interplanetary Shocks, 2152 Pickup Ions

Scientific paper

ACE/SEPICA and SOHO/CELIAS/STOF observations have revealed the surprising result that on average energetic He+ is after H+ and He2+ the third most abundant energetic particle population in the heliosphere. Depending on the type of the source population the energetic He+/He2+ ratio in the energetic particle population can reach unusually high values; in the energy range of 250keV/n - 800keV/n ratios close to unity. Interplanetary pickup ions have been identified to be the major source of the energetic He+ that are preferentially accelerated at co-rotating interaction regions (CIRs), transient interaction regions (TIRs), and interplanetary traveling shocks. Furthermore, the ACE/ULEIS, ACE/SEPICA, and Wind/STICS measurements showed that 3He and He+ ions are accelerated at CME-driven IP shocks. More recently, enhanced He+/He2+ ratios have been observed in association with current sheet crossings, flows, and enhanced magnetic turbulence. The abundance ratio appears to be very variable which indicates that either the source or the acceleration efficiency of the accelerator may be different. Numerical simulations and theoretical considerations provide evidence that there maybe other critical parameters that govern acceleration such as the shock normal direction. In this presentation we will concentrate on the acceleration properties of the above- mentioned structures by using energetic helium data and compared these results with numerical simulations, and theoretical models.

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