Coronal Electron Density Fluctuations Inferred from Akatsuki Spacecraft Radio Observations
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Author(s)
Wexler, D.
Imamura, T.
Efimov, A.
Song, P.
Lukanina, L.
Ando, H.
Jensen, E.
Vierinen, J.
Coster, A.
Date Issued
August 11, 2020
Publisher
Springer Netherlands
Citation
Solar Physics. 2020 Aug 11;295(8):111
Version
Author's final manuscript
Abstract
Abstract
Trans-coronal radio observations were taken during the 2011 observing campaign of the Akatsuki spacecraft through superior conjunction. The observed X-band (8.4 GHz) signals exhibit frequency fluctuations (FF) that are produced by temporal variations in electron density along the radio ray path. A two-component model for interpretation of the FF is proposed: FF scales largely with acoustic wave amplitude through the inner coronal regions where the sound speed dwarfs the solar wind outflow speed, while FF in the region of solar wind acceleration is dominated by the increased density oscillation frequency on the sensing path that results from bulk advection of the plasma inhomogeneities. An estimate of fractional electron density fluctuation is obtained from the mid-corona. A radial profile of slow solar wind speed is determined in the extended corona using mass-flux continuity principles. The coronal sonic point for slow solar wind is estimated to range from 4 to 5 solar radii from the heliocenter.
MIT Department
Haystack Observatory
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1007/s11207-020-01677-1
