Berčič, L;
Landi, S;
Maksimović, M;
(2021)
The Interplay Between Ambipolar Electric Field and Coulomb Collisions in the Solar Wind Acceleration Region.
Journal of Geophysical Research: Space Physics
, 126
(3)
, Article e2020JA028864. 10.1029/2020ja028864.
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Abstract
The solar wind protons are accelerated to supersonic velocities within the distance of 10 solar radii from the Sun, as a consequence of a complex physical mechanism including particle kinetic effects as well as the field‐particle energy and momentum exchange. We use a numerical kinetic model of the solar wind, accounting for Coulomb collisions (BiCoP), and model a solar wind accelerated only by the ambipolar electrostatic filed (E) arising due to the difference in mass between electron and proton, and assuring quasi‐neutrality and zero current. We study the effect E, which was found to be on the order of Dreicer electric field (ED) (Dreicer, 1959), has on the resulting electron velocity distribution functions (VDF). The strahl electron radial evolution is represented by means of its pitch‐angle width (PAW), and the strahl parallel temperature (Ts,‖). A continuous transition between collisional and weakly collisional regime results in broader PAW, compared to the single‐exobase prediction imposed by the exospheric models. Collisions were found to scatter strahl electrons below 250 eV, which in turn has an effect on the measured Ts,‖. A slight increase was found in Ts,‖ with radial distance, and was stronger for the more collisional run. We estimate that the coronal electron temperature inferred from the observations of Ts,‖ in the solar wind, would be overestimated for between 8 and 15%.
| Type: | Article |
|---|---|
| Title: | The Interplay Between Ambipolar Electric Field and Coulomb Collisions in the Solar Wind Acceleration Region |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2020ja028864 |
| Publisher version: | https://doi.org/10.1029/2020ja028864 |
| 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. |
| Keywords: | ambipolar, electric field, electron distribution function, kinetic model, solar wind |
| 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/10123408 |
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