Kinetic Properties of Solar Wind Minor Ions and Protons Measured With SOHO/CELIAS}

author: S.~Hefti H.~Gr\"{u}nwaldt F.~M.~Ipavich P.~Bochsler D.~Hovestadt M.~R.~Aellig M.~Hilchenbach A.~B.~Galvin J.~Geiss F.~Gliem G.~Gloeckler B.~Klecker E.~Marsch E.~M\"{o}bius M.~Neugebauer P.~Wurz

J. Geophys. Res. -Space Physics-

Using observations of the charge and mass spectrometer CELIAS/CTOF and CELIAS/Proton Monitor on board the SOHO spacecraft we present an overview of speeds and kinetic temperatures of minor ions and protons in the solar wind near solar minimum, covering the Carrington Rotations 1908 to 1912. In the case of a collision dominated solar wind, the speed of minor ions is expected to be lower or equal to the speed of the protons, and all species are expected to have equal temperatures. On the other hand, minor ions can be accelerated and heated by wave-particle interaction. In this case, equal thermal speeds of all species are expected. CTOF data allow the determination of the kinetic parameters of various ions with high accuracy and with high time resolution. The mean $\ion{O}{6+}$ speed of the observed period is $390\,\mbox{km}\,\mbox{s}^{-1}$. The speeds of $\ion{Si}{7+}$ and $\ion{Fe}{9+}$ correlate well with $\ion{O}{6+}$, the linear correlation coefficient being 0.96 or higher. Our results also indicate that silicon and iron tend to lag behind oxygen with a speed difference of $\approx 20\,\mbox{km}\,\mbox{s}^{-1}$ at $500\,\mbox{km}\,\mbox{s}^{-1}$. At the same time the kinetic temperature of the ions under investigation exhibit the well-known mass proportionality, which is attributed to wave-particle interactions. During the period of low solar activity in consideration, many cases are observed where the kinetic temperature is extraordinarily low ($10^4\,\mbox{K}$ for $\ion{O}{6+}$).

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Last Update: August 20, 1998, James Weygand