Probing the Evolution of Solar Wind Temperature Anisotropies in the Inner Heliosphere

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F25%3A10510636" target="_blank" >RIV/00216208:11320/25:10510636 - isvavai.cz</a>

Result on the web

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=xHcz4AGnOj" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=xHcz4AGnOj</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.3847/2041-8213/ae2792" target="_blank" >10.3847/2041-8213/ae2792</a>

Result language

angličtina

Original language name

Probing the Evolution of Solar Wind Temperature Anisotropies in the Inner Heliosphere

Original language description

Using solar wind measurements from Solar Orbiter, we investigated the distribution and evolution of the temperature anisotropy of alpha-particles (the ratio of perpendicular to parallel temperatures) in the inner heliosphere, between 0.29 and approximately 1 au. We also compared these observations with the corresponding proton temperature anisotropy to better understand the evolution of ion thermal properties in the expanding solar wind. We found that the slow wind (&lt;= 400 km s-1) exhibits higher alpha-particle anisotropy compared to the fast wind (&gt;= 600 km s-1), where the anisotropy values are mostly below one. The alpha-particle anisotropy increases as solar wind speed decreases, in contrast to protons, where anisotropy increases with solar wind speed. Additionally, we find that, regardless of the distance from the Sun, alpha-particle anisotropy is greater than proton anisotropy when the normalized differential speed between alpha-particles and protons (Delta V/VA) is less than 0.3. However, when Delta V/VA exceeds 0.4, the trend reverses, and proton anisotropy becomes larger. The radial evolution also shows distinct differences between fast and slow wind. In the fast wind, proton anisotropy decreases with distance from 0.29 to 1 au, while alpha-particle anisotropy shows no clear radial trend and remains nearly constant. In the slow wind, both proton and alpha anisotropies decrease with distance from the Sun. These results reveal distinct behaviors of alpha-particles and protons in the expanding solar wind, highlighting the dependence of ion heating on solar wind speed and differential flow.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10305 - Fluids and plasma physics (including surface physics)

Project

<a href="/en/project/LUAUS25060" target="_blank" >LUAUS25060: How and where is the solar wind accelerated and heated and how do these processes influence its propagation through the heliosphere?</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

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

Name of the periodical

Astrophysical Journal Letters

ISSN

2041-8205

e-ISSN

2041-8213

Volume of the periodical

995

Issue of the periodical within the volume

2

Country of publishing house

US - UNITED STATES

Number of pages

7

Pages from-to

L68

UT code for WoS article

001641266300001

EID of the result in the Scopus database

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