The influence of suprathermal electrons on the derivation of coronal electron temperatures from solar wind motor ion charge states

The CELIAS/CTOF (Charge Time Of Flight) mass spectrometer on board the SOHO mission measures the ionic and elemental composition of minor ions in the solar wind. From density ratios of adjacent charge states of minor ions we derive, consistent with previous measurements of the same type, mean freeze -in temperatures in the slow solar wind in the range between about 1.1 x 10 (6) K and 1.6 x 10(6) K depending upon the charge states and elements consi dered. These values are obtained assuming a Maxwellian distribution of the electrons in the inner corona. We assess the influence of suprathermal elec trons in the corona upon the density ratios and, subsequently, on the tempe rature estimates that are drawn from minor ion charge spectra. It was found that only limited amounts of suprathermal electrons are compatible with th e charge state observations in the slow solar wind. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.