What is the Solar Wind Frame of Reference?

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 froze...

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Published inThe Astrophysical journal Vol. 889; no. 2; pp. 163 - 176
Main Authors N me ek, Zden k, urovcová, Tereza, Šafránková, Jana, N mec, František, Matteini, Lorenzo, Stansby, David, Janitzek, Nils, Berger, Lars, Wimmer-Schweingruber, Robert F.
Format Journal Article
LanguageEnglish
Published Philadelphia The American Astronomical Society 01.02.2020
IOP Publishing
American Astronomical Society
Subjects
Alfven waves
Astrophysics
Charged particles
Charging
Energy conservation
Fast solar wind
Interplanetary magnetic field
Interplanetary magnetic fields
Magnetic fields
Magnetohydrodynamics
Physics
Slow solar wind
Solar wind
Solar wind flow
Solar wind ions
Solar wind velocity
Temporal resolution
Velocity
Wind flow
Wind speed
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Summary: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.
Bibliography:AAS19472
The Sun and the Heliosphere
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab65f7