DOI: 10.48322/jdj2-1912
title: Parker Solar Probe/FIELDS Simplified Quasi-Thermal Noise data

description: Parker Solar Probe/FIELDS Simplified Quasi-Thermal Noise data (SQTN).
The SQTN spectroscopy is a method which allows to deduce the electron density and the core temperature of the plasma surrounding a s/c, by using the power spectra acquired from an electric dipole antenna (see [1] for the PSP case, and references therein).
There are two dipoles on the PSP/FIELDS experiment [2] exploitable for the SQTN, named V1V2 and V3V4, which are both connected to the FIELDS Radio Frequency Spectrometer (RFS), see [3].
The density is deduced from the plasma frequency (fp) detection algorithm, applied to RFS available spectra, with elimination of questionable detection (or false positive) using QTN theory (see [1]). No fp detection results in filling the data by -1e31 (for all variables provided here). In particular, since we are using 2x2m dipoles on PSP, the fp detection is impossible when the local Debye length is larger than about 5m. On a daily basis, the typical rate of validated detection of fp is more than 90% of the available spectra when PSP is within 0.25 AU of the Sun, but this rate may drop to only 20% at larger distances (0.5 AU being the upper limit used to product this CDF file, which corresponds at most to +/- 15 days around the exact date of the PSP perihelion).
When the fp detection is validated, fp errors bars are defined taking into account the RFS_LFR spectral resolution (64 pseudo-logarithmically spaced frequencies in the range of 10 kHz-1.7 MHz), then refined by using QTN theory, and this finally provides the error bars for the density (electron_density_delta). The electron density is then deduced as the most probable value within the error bars, using again QTN theory.
Note the electron density provided here is fully independant of antennas calibrations and floating potential, but not the electron core temperature which is deduced from the QTN level below fp (see [1]), so the core temperature will be certainly more subject to future improvments of this CDF file (see version and mods, v00 corresponding to the method exactly as published for the two first encounters/perihelions by PSP in [1]).
All variables provided here were not subject to post-processing noise filtering nor any interpolation/smoothing of data.
The time resolution of the RFS varies with instrument mode, so does these electron data derived from RFS data.  During encounter (when PSP is within 0.25 AU of the Sun), cadence for RFS HFR and LFR spectra is typically about 7 seconds (and about 3.5 seconds during +/- 3 days around the perihelion date from encounter 06). During cruise mode, which is the default mode for operations outside of 0.25 AU, cadence for HFR and LFR spectra is about 56 seconds.
References:
1. Moncuquet, M., Meyer-Vernet, N., Issautier, K. et al. (2020), Astrophysical Journal Supplement Series, 246:44. https://doi.org/10.3847/1538-4365/ab5a84
2. Bale, S.D., Goetz, K., Harvey, P.R. et al. Space Sci Rev (2016) 204: 49. https://doi.org/10.1007/s11214-016-0244-5
3. Pulupa, M., Bale, S. D., Bonnell, J.W. et al. (2017) JGR Space Physics, 122, 2836-2854. https://doi.org/10.1002/2016JA023345