Quasi‐thermal noise measurements on STEREO: Kinetic temperature deduction using electron shot noise model

Abstract

Quasi‐thermal noise (QTN) spectroscopy is an accurate technique for in situ measurements of electron density and temperature in space plasmas. A QTN spectrum is determined by plasma and antenna properties. On STEREO/WAVES, since the antennas are relatively short and thick, the QTN spectrum is dominated by electron shot noise, especially at low frequencies, which reduces the accuracy of the method. Here we use the STEREO low‐frequency receiver, proton density measured by Plasma and Suprathermal Ion Composition instrument, and a QTN and shot noise models to provide electron temperature data from both STEREO A and B spacecraft. This derivation is important since no reliable measurements of electron temperature exist on board these spacecraft. We compare the results of our analysis with the electron temperature provided by the Wind spacecraft during the period when Wind and STEREO B were close to each other. The comparison shows that our technique is reliable when results are integrated on a time scale of the order of 50 to 60 min.

Anticorrelation between the Bulk Speed and the Electron Temperature in the Pristine Solar Wind: First Results from the Parker Solar Probe and Comparison with Helios

“…The so-called QTN spectroscopy has been applied successfully to several past missions operating in the solar wind such as ISSE 3 (Meyer-Vernet 1979;Couturier et al 1981), Ulysses (Maksimovic et al 1995;Issautier et al 1999), WIND (Maksimovic et al 1998) or STEREO (Martinović et al 2016). It has been implemented on the FIELDS instrument to provide accurate measurements of the electron density and temperature of the outer corona down to 10 Solar radii (Bale et al 2016).…”

The Solar Probe Plus Radio Frequency Spectrometer: Measurement requirements, analog design, and digital signal processing

“…When this condition does not hold, the amplitude and width of the plasma peak can be too small for the peak to be resolved. In this case, other sources such as shot noise can dominate the observations [ Zouganelis et al , 2010 , ], although it is still possible to extract some information from the spectrum [ Martinović et al , ].…”

Solar Wind Electron Parameters Determination on Wind Spacecraft Using Quasi‐Thermal Noise Spectroscopy

“…Usage of the method presented here on instruments equipped with short and thick antennas, such as PSP Fields (Bale et al., 2016) and Solar Orbiter Radio and Plasma Waves (Maksimović et al., 2020), is possible but requires implementation of the impact noise effects at lower frequencies. This task was previously successfully done for STEREO measurements (Martinović et al., 2016; Zouganelis et al., 2010), but a confident numerical model of impact noise at f ≈ f p (Meyer‐Vernet, 1983) is not developed and is a topic for future work.…”

“…Since then, the method has been improved to include the effects of suprathermal electrons (Couturier et al., 1981; Meyer‐Vernet & Perche, 1989), specific electron VDFs (Chateau & Meyer‐Vernet, 1989; 1991; Le Chat et al., 2009; Zouganelis, 2008), ions (Issautier et al., 1996, 1999; Meyer‐Vernet et al., 1986), strong magnetic field (Sentman, 1982; Meyer‐Vernet et al., 1993; Moncuquet et al., 1997), or electron‐neutral collisions (Balmain, 1969; Martinović et al., 2017). It was recognized that measurement quality can be affected due to instrumental limitations, such as dipole antenna arms separation (Meyer‐Vernet & Perche, 1989; Meyer‐Vernet et al., 2017) or geometry (Martinović et al., 2015) and the usage of short and/or thick antennas, which significantly enhance electron impact noise (Maksimović et al., 2005; Martinović et al., 2016; Le Chat et al., 2013).…”