Kinetic Physics with Solar Wind Heavy Ions Measured at 1 AU
One possibility to study kinetic processes such as particle acceleration, transport and thermalization in the solar wind are in-situ measurements of ion velocity distribution functions (VDFs). In particular the extension of the VDF analysis to the wide range of heavy ions allows to investigate the dependence of the underlying processes on the particles’ mass and charge in a systematical way. In this thesis we analyze nonthermal signatures in the velocity distribution functions of solarwind heavy ions, in particular differential speeds and thermal speed ratios between the heavy ions and the solar wind protons. For our investigation we utilize measurements that were conducted with the Charge Element Isotope Analysis System (CELIAS) experiment onboard the Solar and Heliospheric Observatory (SOHO) that is located at the Lagrange Point L1 at a distance of about one astronomical unit (1 AU) from the Sun. The measurement data is recorded during a relatively short period around solar minimum between DOY 174 and 220 in 1996. The SOHO/CELIAS experiment is one of only a few instrument suites located in the undisturbed solar wind, far away from planetary magnetospheres, that is able to measure a wide range of solar wind heavy ion species with relatively high counting statistics and fast measurement cadence. Our studies include both the investigation of long-term speed spectra in the form of accumulated count rates over the full measurement period and the analysis of short-term speed distributions, so-called 1D-reduced velocity distribution functions, that are recorded with the intrinsic cadence of the CELIAS/CTOF (Charge-Time-Of-Flight) sensor of about 5 minutes.
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