Solar Wind Electron Parameters Determination on Wind Spacecraft Using Quasi-Thermal Noise Spectroscopy
Quasi-thermal noise (QTN) spectroscopy has been extensively used as an accurate tool to measure electron density and temperature in space plasmas. If the antenna length to radius ratio is sufficiently large, a typical measured spectrum clearly shows a resonance at the electron plasma frequency and a lower frequency plateau that quantify the electron distributions. The Wind spacecraft, with its long, thin antennas, is considered the mission par excellence for the implementation of the QTN method. However, a major issue in applying QTN spectroscopy is contamination from signals other than the ubiquitous plasma noise in the vicinity of plasma frequency, affecting the measured spectra and confusing their physical interpretation. In this work, we present a new method for selecting the observations of uncontaminated QTN, distinguishing it from other plasma and spacecraft effects. The selected measurements are used to obtain accurate values for both thermal and suprathermal electron parameters. Testing of the method on 1.5M observations under various conditions in the solar wind, including slow and fast wind and solar transients, confirms the reliability and accuracy of the method with no systematic flaws.