Observation of Disturbed Plasma Structures in the Environment of the Sun and Near-Earth Space with Radio Sounding and Local Measurements

Abstract

An experiment on radio sounding of the circumsolar plasma by signals from the Mars Express spacecraft in 2013 was carried out in the period from March 4 through May 31. The investigated characteristics were the frequency of signals in the centimeter and decimeter ranges and the differential frequency. A number of events were recorded in which the intensity of the frequency fluctuations of the signals probing the plasma was several times higher than the background values. As shown by the analysis of observations of solar activity, such as an increase in the flux of X-rays and SOHO LASCO coronagraph data, this is explained by the passage of disturbed plasma streams generated in the solar corona through the spacecraft radio communication path with the Earth. The comparison of the radio transmission data with the results of measurements of the parameters of the near-Earth plasma using the Wind spacecraft in adjacent periods of time. As a result of the analysis of the data on the proton concentration, it became clear that sharp increases in both the average values and fluctuations of this characteristic were also observed near the Earth. The time lag between the events observed in the circumsolar and near-Earth plasma shows that the cause of the disturbances is the increased activity of the same coronal region rotating with the Sun.