Plasma waves observed by the Solar Orbiter spacecraft

Student: Mičko Ján
Supervisor: Dr. Jan Souček (UFA CAS), Dr. David Píša /UFA CAS), Prof. RNDr. Ondřej Santolík, Dr.
Status: Assigned


The Sun's expanding atmosphere, known as the solar wind, is a domain where fundamental processes common to solar and astrophysical plasma can be studied under conditions impossible to reproduce on Earth. The solar wind, a supersonic plasma flow emanating from Sun's corona, fills the overall heliosphere and plays an essential role in energy transport across the solar system. After decades of study and space exploration, there are still unresolved problems related to the solar wind's origin, its heating, and acceleration. It is generally believed that complex mechanisms that couple particles and electromagnetic fluctuations are at the origin of these processes.

In the solar wind, scientific spacecraft observe a variety of plasma waves. One relevant example are electrostatic Langmuir waves at the electron plasma frequency, associated with suprathermal electron beams produced by either solar flares [1] or accelerated by interplanetary shocks [2]. These waves are believed to undergo linear mode conversion and/or nonlinear wave-wave interactions that produce electromagnetic emissions at the local electron plasma frequency and its second harmonic. These electromagnetic waves the propagate through the heliosphere and are observed at a large distance from the source as Type II or Type III radio emissions. Solar wind plasmas also support a variety of lower frequency waves associated with the dynamics of solar wind ions.

The proposed project focuses on the Solar Orbiter mission [3], launched on 10 February 2020. Solar Orbiter carries scientific instruments for observing the Sun, the solar corona, and the solar wind. Among them, four in-situ instruments directly measure the properties of charged particles and electromagnetic fields in the solar wind along the spacecraft trajectory at a range of heliocentric distances. In particular, the RPW (Radio and Plasma Waves) instrument [4] measures electromagnetic field fluctuations and waves from under 1 Hz to 16 MHz, covering the full range of heliospheric electromagnetic phenomena. The team at the Institute of Atmospheric Physics of the Czech Academy of Sciences (IAP) is responsible for operations and data processing of data from the Time Domain Sampler (TDS) unit of RPW, designed and built at the institute.

An applicant will be a part of the RPW team analyzing in-situ solar wind measurements, addressing open scientific questions in the physics of plasma waves, studying the interaction of waves with charged particles of the solar wind. The applicant can also be involved in instrument operations and data calibration. The research shall be conducted in collaboration with other scientific institutes involved in the Solar Orbiter mission.

[1] Lin, R. P., Potter, D. W., Gurnett, D. A., and Scarf, F. L. (1981). Energetic electrons and plasma waves associated with a solar type III radio burst. ApJ, 251:364–373.
[2] Bale, S. D., Reiner, M. J., Bougeret, J.-L., Kaiser, M. L., Krucker, S., Larson, D. E., and Lin, R. P. (1999). The source region of an interplanetary type II radio burst. Geophys. Res. Lett., 26:1573–1576.
[3] D. Müller et al., The Solar Orbiter mission - Science overview, A&A 642 A1, 2020, DOI: 10.1051/0004-6361/202038467
[4] M. Maksimovic et al., The Solar Orbiter Radio and Plasma Waves (RPW) instrument, A&A 642 A12, 2020, DOI: 10.1051/0004-6361/201936214