Issue |
A&A
Volume 632, December 2019
|
|
---|---|---|
Article Number | A92 | |
Number of page(s) | 8 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361/201936728 | |
Published online | 10 December 2019 |
Investigating the nature of the link between magnetic field orientation and proton temperature in the solar wind
1
Institute for National Astrophysics (INAF) – Institute for Space Astrophysics and Planetology (IAPS), Via Fosso del Cavaliere 100, 00133 Rome, Italy
e-mail: raffaella.damicis@inaf.it
2
Italian Space Agency (ASI), Via del Politecnico snc, 00133 Rome, Italy
Received:
18
September
2019
Accepted:
29
October
2019
Solar wind fluctuations are a mixture of propagating disturbances and advected structures that transfer into the interplanetary space the complicated magnetic topology present at the basis of the corona. The large-scale interplanetary magnetic field introduces a preferential direction in the solar wind, which is particularly relevant for both the propagation of the fluctuations and their anisotropy and for the topology of the structures advected by the wind. This paper focusses on a particular link observed between angular displacements of the local magnetic field orientation from the radial direction and values of the proton temperature. In particular, we find that observations by Helios and Wind show a positive correlation between proton temperature and magnetic field orientation. This is especially true within Alfvénic wind characterized by large-amplitude fluctuations of the background field orientation. Moreover, in the case of Wind, we found a robust dependence of the perpendicular component of the proton temperature on the magnetic field angular displacement. We interpret this signature as possibly due to a physical mechanism related to the proton cyclotron resonance. Finally, by simulating the sampling procedure of the proton velocity distribution function (VDF) of an electrostatic analyzer, we show that the observed temperature anisotropy is not due to instrumental effects.
Key words: solar wind / magnetic fields / methods: data analysis / turbulence / Sun: heliosphere / plasmas
© ESO 2019
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.