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What is the Solar Wind Frame of Reference?

Němeček, Z; Ďurovcová, T; Šafránková, J; Němec, F; Matteini, L; Stansby, D; Janitzek, N; ... Wimmer-Schweingruber, RF; + view all (2020) What is the Solar Wind Frame of Reference? The Astrophysical Journal , 889 (2) , Article 163. 10.3847/1538-4357/ab65f7. Green open access

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Abstract

Various solar wind ion species move with different speeds and theoretical considerations as well as limited observations in a region close to the Sun show that heavy solar wind ions tend to flow faster than protons, at least in less-aged fast solar wind streams. The solar wind flow carries the frozen-in interplanetary magnetic field (IMF) and this situation evokes three related questions: (i) what is the proper solar wind speed, (ii) is this speed equal to the speed of the dominant component, whatever that may be, and (iii) what is the speed of the magnetic field? We show that simple theoretical considerations based on the MHD approximation as well as on the dynamics of charged particles in electric and magnetic fields suggest that the IMF velocity of motion (de Hoffmann–Teller (HT) velocity) would be deliberated as the velocity appropriate for solar wind studies. Our analysis based on the Wind, Helios, ACE, and SOHO observations of differential streaming of solar wind populations shows that their energy is conserved in the HT frame. On the other hand, the noise and temporal resolution of the data do not allow us to decide whether the total momentum is also conserved in this frame.

Type: Article
Title: What is the Solar Wind Frame of Reference?
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/ab65f7
Publisher version: http://dx.doi.org/10.3847/1538-4357/ab65f7
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10092712
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