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VLBI data processing on coronal radio-sounding experiments of Mars Express


Ma, M and Molera Calves, G and Cimo, G and Zhang, P and Ming, X and Li, P and Kummamuru, P and Chu, Z and Jiang, T and Xia, B and Tetsuro, K and Tong, F and de Vicente, P and Quick, J and Zhang, H and Chen, Z, VLBI data processing on coronal radio-sounding experiments of Mars Express (In Press) [Refereed Article]


The ESA’s Mars Express solar corona experiments were performed at two solar conjunctions in the years 2015 and 2017 by a number of radio telescopes in the European VLBI Network. This paper presents the methods to measure the frequency and phase fluctuations of the spacecraft radio signal, and the applications to study the characteristics of the plasma turbulence effects on the signal at a single station and at multiple stations via cross-correlation. The power spectra of the frequency fluctuations observed between 4.9 and 76.3 Rs have a power-law shape close to a Kolmogorov spectrum over the frequency interval νlo < ν < νup, where the nominal value of νlo is set to 3 mHz and νup is in the range of 0.03 ∼ 0.15 Hz. The RMS of the frequency fluctuations is presented as a function of the heliocentric distance. Furthermore, we analyse the variations of the electron column density fluctuations at solar offsets 4.9 Rs and 9.9 Rs and the cross-correlation products between the VLBI stations. The power density of the differential fluctuations between different stations decreases at ν < 0.01 Hz. Finally, the fast flow speeds of solar wind > 700 km s-1 are derived from the cross-correlation of frequency fluctuations at ν < 0.01 Hz. The fast flow speeds of solar wind correspond to the high heliolatitude of the coronal region that the radio rays passed. The VLBI observations and analysis methods can be used to study the electron column density fluctuations and the turbulence at multiple spatial points in the inner solar wind by providing multiple lines of sight between the Earth and the spacecraft.

Item Details

Item Type:Refereed Article
Keywords:VLBI, space craft, radio telescopes, Mars Express
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Solar physics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Molera Calves, G (Dr Guifre Molera Calves)
UTAS Author:Kummamuru, P (Mr Pradyumna Kummamuru)
ID Code:145765
Year Published:In Press
Deposited By:Physics
Deposited On:2021-08-05
Last Modified:2021-09-07

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