In the → solar wind, the temperature derived from the
mean → thermal agitation of the electrons. More specifically,
electric field receivers on board space probes carry out the spectroscopy of the
→ thermal noise due to the potential fluctuations produced by
the thermal agitation of the electrons, yielding the electron temperature in certain conditions
(N. Meyer-Vernet, 2007, Basics of the Solar Wind, Cambridge Univ. Press).
See also → proton temperature.