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 (E-D) (Dreicer, 1959), has on the resulting electron velocity distribution functions. The strahl electron radial evolution is represented by means of its pitch-angle width (PAW), and the strahl parallel temperature (T-s,T-||). 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 T-s,T-||. A slight increase was found in T-s,T-|| with radial distance, and was stronger for the more collisional run. We estimate that the coronal electron temperature inferred from the observations of T-s,T-|| in the solar wind, would be overestimated for between 8% and 15%.

The Interplay Between Ambipolar Electric Field and Coulomb Collisions in the Solar Wind Acceleration Region / L. Bercic; S. Landi; M. Maksimovic. - In: JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS. - ISSN 2169-9380. - ELETTRONICO. - 126:(2021), pp. 0-0. [10.1029/2020ja028864]

The Interplay Between Ambipolar Electric Field and Coulomb Collisions in the Solar Wind Acceleration Region

L. Bercic
Conceptualization
;
S. Landi
Conceptualization
;
2021

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 (E-D) (Dreicer, 1959), has on the resulting electron velocity distribution functions. The strahl electron radial evolution is represented by means of its pitch-angle width (PAW), and the strahl parallel temperature (T-s,T-||). 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 T-s,T-||. A slight increase was found in T-s,T-|| with radial distance, and was stronger for the more collisional run. We estimate that the coronal electron temperature inferred from the observations of T-s,T-|| in the solar wind, would be overestimated for between 8% and 15%.
2021
126
0
0
L. Bercic; S. Landi; M. Maksimovic
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1329992
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