Intercomparisons of Solar Wind Electron Temperature on Parker Solar Probe Using QTN and SPAN-E Measurements
Résumé
Electrons are expected to play an important role in the thermally driven solar wind expansion. Onboard Parker Solar Probe (PSP), Quasi-thermal noise (QTN) spectroscopy and the electron electrostatic analyzer (SPAN-E) are two independent techniques to measure the solar wind electrons, which provides possible cross-checking for each other. In this work, we give a detailed statistical comparison of the solar wind electron temperature (total electron temperature Te and core electron temperature Tc) obtained by the QTN technique and those derived by SPAN-E, combining 12-day observations around each perihelion from Encounter One (E01) to Ten (E10) of PSP. Our preliminary results show that Tc measured by QTN and SPAN-E are generally consistent with each other, and reach better agreement closer to the Sun. We note that there is a systematic discrepancy between the ratio of Te/Tc derived from QTN and the one from SPAN-E, especially near the perihelion (i.e., <0.2 AU). An in-depth comparison is also conducted for different solar wind populations (i.e., classified by the proton bulk speed Vp and the solar wind mass flux) to examine this discrepancy. Based on these results, possible biases on both methods to determine the solar wind electron parameters are discussed, which may provide some hints on the further calibration of SPAN-E and theoretical extensions of QTN method.
