Firehose constraints of the bi-Kappa-distributed electrons: a zero-order approach for the suprathermal electrons in the solar wind

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F17%3A00479267" target="_blank" >RIV/67985815:_____/17:00479267 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/68378289:_____/17:00477289

Výsledek na webu

<a href="http://dx.doi.org/10.1093/mnras/stw2336" target="_blank" >http://dx.doi.org/10.1093/mnras/stw2336</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1093/mnras/stw2336" target="_blank" >10.1093/mnras/stw2336</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Firehose constraints of the bi-Kappa-distributed electrons: a zero-order approach for the suprathermal electrons in the solar wind

Popis výsledku v původním jazyce

The increase of temperature predicted by the solar wind expansion in the direction parallel to the interplanetary magnetic field is already notorious for not being confirmed by the observations. In hot and dilute plasmas from space, particle-particle collisions are not efficient in constraining large deviations from isotropy, but the resulting firehose instability provides itself plausible limitations for the temperature anisotropy of both the electron and proton species. This paper takes into discussion the suprathermal (halo) electrons, which are ubiquitous in the solar wind, and may be highly anisotropic and susceptible to the firehose instability. Suprathermals enhance the high-energy tails of the velocity distributions making them well described by the Kappa distribution functions, with the advantage that these are power laws suitable to reproduce either the entire distribution or only the suprathermal halo tails. New features of the instability are captured from a linear stability analysis of bi-Kappa-distributed electrons with the temperature depending on the power-index.. This approach enables a realistic interpretation of non-thermal electrons and their effects on the instability: growth rates are systematically stimulated and thresholds are lowered with decreasing the power-index.. In a zero-order limiting approach of the halo component (minimizing the effects of a cooler and less anisotropic core population), the instability thresholds align to the limits of the temperature anisotropy reported by the observations. These results provide new and valuable support for an extended implication of the firehose instability in the relaxation of temperature anisotropy in collisionless plasmas from space.

Název v anglickém jazyce

Firehose constraints of the bi-Kappa-distributed electrons: a zero-order approach for the suprathermal electrons in the solar wind

Popis výsledku anglicky

The increase of temperature predicted by the solar wind expansion in the direction parallel to the interplanetary magnetic field is already notorious for not being confirmed by the observations. In hot and dilute plasmas from space, particle-particle collisions are not efficient in constraining large deviations from isotropy, but the resulting firehose instability provides itself plausible limitations for the temperature anisotropy of both the electron and proton species. This paper takes into discussion the suprathermal (halo) electrons, which are ubiquitous in the solar wind, and may be highly anisotropic and susceptible to the firehose instability. Suprathermals enhance the high-energy tails of the velocity distributions making them well described by the Kappa distribution functions, with the advantage that these are power laws suitable to reproduce either the entire distribution or only the suprathermal halo tails. New features of the instability are captured from a linear stability analysis of bi-Kappa-distributed electrons with the temperature depending on the power-index.. This approach enables a realistic interpretation of non-thermal electrons and their effects on the instability: growth rates are systematically stimulated and thresholds are lowered with decreasing the power-index.. In a zero-order limiting approach of the halo component (minimizing the effects of a cooler and less anisotropic core population), the instability thresholds align to the limits of the temperature anisotropy reported by the observations. These results provide new and valuable support for an extended implication of the firehose instability in the relaxation of temperature anisotropy in collisionless plasmas from space.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10308 - Astronomy (including astrophysics,space science)

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2017

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

e-ISSN

—

Svazek periodika

464

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

8

Strana od-do

564-571

Kód UT WoS článku

000393646300041

EID výsledku v databázi Scopus

2-s2.0-85010775873