On the thermal noise “temperature” in an anisotropic plasma

Electrostatic waves are often detected with wire dipoles longer than the wave‐lengths. The electrostatic directivity pattern of such antennas has lobes roughly perpendicular to those of short dipoles. As a consequence, in a plasma where the electron temperatures are different along (T║) and across (T⟂) the magnetic field, the thermal noise “temperature” is T⟂ if the antenna is parallel to B and (T║+T⟂)/2 if it is perpendicular. Practical applications for space plasma and wave polarization measurements are given.