Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles The Astrophysical Journal Supplement Year : 2020

Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe

Eduard Kontar
  • Function : Author
Laura Balmaceda
  • Function : Author
Stuart Bale
Marc Pulupa
David Malaspina
John Bonnell
Peter Harvey
Keith Goetz
Robert Macdowall
Justin Kasper
Anthony Case
Kelly Korreck
Davin Larson
Roberto Livi
Michael Stevens
Phyllis Whittlesey
Alexander Hegedus
  • Function : Author

Abstract

Radio waves are strongly scattered in the solar wind, so that their apparent sources seem to be considerably larger and shifted than the actual ones. Since the scattering depends on the spectrum of density turbulence, a better understanding of the radio wave propagation provides indirect information on the relative density fluctuations, epsilon = < n >, at the effective turbulence scale length. Here, we analyzed 30 type III bursts detected by Parker Solar Probe (PSP). For the first time, we retrieved type III burst decay times, tau(d), between 1 and 10 MHz thanks to an unparalleled temporal resolution of PSP. We observed a significant deviation in a power-law slope for frequencies above 1 MHz when compared to previous measurements below 1 MHz by the twin-spacecraft Solar TErrestrial RElations Observatory (STEREO) mission. We note that altitudes of radio bursts generated at 1 MHz roughly coincide with an expected location of the Alfven point, where the solar wind becomes super-Alfvenic. By comparing PSP observations and Monte Carlo simulations, we predict relative density fluctuations, epsilon, at the effective turbulence scale length at radial distances between 2.5 and 14 R-circle dot to range from 0.22 to 0.09. Finally, we calculated relative density fluctuations, o, measured in situ by PSP at a radial distance from the Sun of 35.7 R-circle dot during perihelion #1, and perihelion #2 to be 0.07 and 0.06, respectively. It is in a very good agreement with previous STEREO predictions (epsilon = 0.06-0.07) obtained by remote measurements of radio sources generated at this radial distance.
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insu-02937876 , version 1 (18-09-2020)

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Vratislav Krupar, Adam Szabo, Milan Maksimovic, Oksana Kruparova, Eduard Kontar, et al.. Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe. The Astrophysical Journal Supplement, 2020, Early Results from Parker Solar Probe: Ushering a New Frontier in Space Exploration, 246 (2), pp.57. ⟨10.3847/1538-4365/ab65bd⟩. ⟨insu-02937876⟩
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