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The radio signal transmitted by the Mars Express (MEX) spacecraft was observed regularly between the years 2013-2020 at X-band (8.42 GHz) using the European Very Long Baseline Interferometry (EVN) network and University of Tasmania's…

Aims. The phase scintillation of the European Space Agency's (ESA) Venus Express (VEX) spacecraft telemetry signal was observed at X-band (\lambda = 3.6 cm) with a number of radio telescopes of the European VLBI Network (EVN) in the period…

This work devotes to investigations of solar corona and solar wind plasma by the method of radio probing with using of very long baseline interferometry (VLBI). We performed the theoretical calculation of power spectrum of interferometric…

Probing the solar corona is crucial to study the coronal heating and solar wind acceleration. However, the transient and inhomogeneous solar wind flows carry large-amplitude inherent Alfven waves and turbulence, which make detection more…

We present a unified method to derive both solar wind velocities and coronal electron densities in the near-Sun corona using Doppler spectral broadening of spacecraft radio signals. The method is generalized to be frequency independent…

Solar and Stellar Astrophysics · Physics 2026-03-26 Keshav Aggarwal , R. K. Choudhary , Abhirup Datta , Roopa M. V. , Takeshi Imamura , Hiroki Ando

Radio signals propagating via the solar corona and solar wind are significantly affected by compressive waves, impacting properties of solar bursts as well as sources viewed through the turbulent solar atmosphere. While static fluctuations…

Solar and Stellar Astrophysics · Physics 2024-04-23 Francesco Azzollini , A. Gordon Emslie , Daniel L. Clarkson , Nicolina Chrysaphi , Eduard P. Kontar

Waves are thought to play a significant role in the heating of the solar atmosphere and the acceleration of the wind. Among the many types of waves observed in the Sun, the so-called p-modes with a 3 mHz frequency peak dominate the lower…

Modern radio telescopes are extremely sensitive to plasma on the line of sight from a radio source to the antenna. Plasmas in the corona and solar wind produce measurable changes in the radio wave amplitude and phase, and the phase…

Astrophysics · Physics 2009-11-13 Steven R. Spangler , Catherine A. Whiting

We use the plasma density based on measurements of the probe-to-spacecraft potential in combination with magnetic field measurements by MAG to study fields and density fluctuations in the solar wind observed by Solar Orbiter during the…

Fluctuations of solar wind magnetic field and plasma parameters exhibit a typical turbulence power spectrum with a spectral index ranging between $\sim -5/3$ and $\sim -3/2$. In particular, at $1$ AU, the magnetic field spectrum, observed…

Space Physics · Physics 2019-07-10 R. Bruno , D. Telloni , L. Sorriso-Valvo , R. Marino , R. De Marco , R. DAmicis

Solar wind fluctuations, such as magnetic field or velocity, show power law power spectra suggestive both of an inertial range of intermittent turbulence (with $\sim -5/3$ exponent) and at lower frequencies, of fluctuations of coronal…

Astrophysics · Physics 2009-11-13 R. M. Nicol , S. C. Chapman , R. O. Dendy

Fluctuations and structure across a wide range of spatial and temporal scales are frequently studied in the solar wind. The properties of the low-frequency fluctuations are of relevance to turbulent energy injection into the plasma and the…

Solar and Stellar Astrophysics · Physics 2026-01-06 Jiaming Wang , Francesco Pecora , Rohit Chhiber , Sohom Roy , William H. Matthaeus

The Mars Global Surveyor (MGS), Mars Express (MEX), and Venus Express (VEX) experienced several superior solar conjunctions. These conjunctions cause severe degradations of radio signals when the line of sight between the Earth and the…

Space Physics · Physics 2013-01-08 A. K. Verma , A. Fienga , J. Laskar , K. Issautier , H. Manche , M. Gastineau

The recently released spacecraft potential measured by the RPW instrument on-board Solar Orbiter has been used to estimate the solar wind electron density in the inner heliosphere. Solar-wind electron density measured during June 2020 has…

Plasma turbulence is thought to be associated with various physical processes involved in solar flares, including magnetic reconnection, particle acceleration and transport. Using Ramaty High Energy Solar Spectroscopic Imager ({\it RHESSI})…

Solar and Stellar Astrophysics · Physics 2015-05-27 E. P. Kontar , I. G. Hannah , N. H. Bian

We present a turbulence index independent framework for simultaneously deriving solar wind velocity and coronal electron density in the near-Sun region using the spectral broadening of spacecraft radio signals. The formulation accommodates…

Solar and Stellar Astrophysics · Physics 2026-03-25 Keshav Aggarwal , R. K. Choudhary , Abhirup Datta , Soumyaneal Banerjee , Takeshi Imamura , Hiroki Ando

Solar Orbiter will observe the Sun and the inner heliosphere to study the connections between solar activity, coronal structure, and the origin of the solar wind. The plasma instruments on board Solar Orbiter will determine the…

Space Physics · Physics 2020-01-08 Georgios Nicolaou , Daniel Verscharen , Robert T. Wicks , Christopher J. Owen

The solar inner corona is a region that plays a critical role in energizing the solar wind and propelling it to supersonic and supra-Alfvenic velocities. Despite its importance, this region remains poorly understood because of being least…

Solar and Stellar Astrophysics · Physics 2023-08-25 Richa N. Jain , R. K. Choudhary , Anil Bhardwaj , T. Imamura , Anshuman Sharma , Umang M. Parikh

Electric field measurements of the Time Domain Sampler (TDS) receiver, part of the Radio and Plasma Waves (RPW) instrument on board Solar Orbiter, often exhibit very intense broadband wave emissions at frequencies below 20~kHz in the…

Using data collected by the Indian Mars Orbiter Mission in October 2021, we investigated coronal regions of the Sun by analyzing the Doppler spectral width of radio signals to estimate solar wind velocity. A simplified equation is…

Solar and Stellar Astrophysics · Physics 2025-04-02 Keshav Aggarwal , R. K. Choudhary , Abhirup Datta , Roopa M. V. , Bijoy K. Dai
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