Introduction and Motivation

Fichtner, H.; Lazar, M.

doi:10.1007/978-3-030-82623-9_1

Cited by 1 publication

(2 citation statements)

References 34 publications

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“…In [47], the core was fitted by a bi-Maxwellian, while the suprathermal tails were fitted by a modified bi-Kappa VDF. As shown in [30], the expression of a modified Kappa differs from that of the Olbertian Kappa by a factor (κ-3/2) and leads to a temperature independent of κ in the modified Kappa. The fitting parameters are thus not only dependent on the considered velocity range of the data but also on the distributions used for the fits, as already mentioned in [49].…”

Section: Angle N [10mentioning

confidence: 99%

“…In the present work, we improve the Kappa exospheric model by considering regularized Kappa distributions [29] so that the power law is no longer limited to kappa values κ > 2 to calculate the heat flux, contrary to what is imposed when using Olbertian Kappa or modified Kappa [30]. The fits of the observed velocity distributions of the particles by Kappa functions in the solar wind can give kappa indices close and even sometimes lower than 2 (e.g., [10,31] for a review).…”

Section: Introductionmentioning

confidence: 99%

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Exospheric Solar Wind Model Based on Regularized Kappa Distributions for the Electrons Constrained by Parker Solar Probe Observations

Pierrard,

Péters de Bonhome,

Halekas

et al. 2023

Plasma

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In the present work, the kinetic exospheric model of the solar wind is improved by considering regularized Kappa distributions that have no diverging moments through consideration of a cut-off at relativistic velocities. The model becomes valid even for kappa indices lower than 2, which is important since low values of kappa are observed in the fast solar wind. The exospheric model shows that the electric potential accelerates the wind to supersonic velocities. The presence of suprathermal Strahl electrons at the exobase can further increase the velocity to higher values, leading to profiles comparable to the observations in the fast and slow wind at all radial distances. The kappa index is not the only parameter that influences the acceleration of the wind: the difference in the altitude of the exobase also makes a significant difference between the fast and slow wind. The exobase is located at lower altitudes in the coronal holes where the density is smaller than in the other regions of the corona, allowing the wind originating from the holes to be accelerated to higher velocities. The new observations of Parker Solar Probe are used to constrain the model. The observations at low radial distances show suprathermal electrons already well present in the Strahl in the antisunward direction and a deficit in the sunward direction, confirming the exospheric feature of almost no incoming particles. For proton distributions, we observe that the proton tail parallel to the magnetic field is already present at 17.2 Rs.

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Section: Angle N [10mentioning

confidence: 99%