Multiscale views of an Alfvenic slow solar wind: 3D velocity distribution functions observed by the Proton-Alpha Sensor of Solar Orbiter
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F21%3A10439898" target="_blank" >RIV/00216208:11320/21:10439898 - isvavai.cz</a>
Result on the web
<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=sUsI0Vph8-" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=sUsI0Vph8-</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1051/0004-6361/202141095" target="_blank" >10.1051/0004-6361/202141095</a>
Alternative languages
Result language
angličtina
Original language name
Multiscale views of an Alfvenic slow solar wind: 3D velocity distribution functions observed by the Proton-Alpha Sensor of Solar Orbiter
Original language description
Context. The Alfvenic slow solar wind is of particular interest, as it is often characterized by intense magnetic turbulence, complex proton 3D velocity distribution functions (VDF), and an ensuing richness of kinetic and dynamic processes. Aims. We take advantage of the fast time cadence of measurements taken by the Proton-Alpha Sensor (PAS) on board Solar Orbiter to analyze the kinetic properties of the proton population, the variability of their VDFs, and the possible link with propagating magnetic structures. We also study the magnetic (B) and velocity (V) correlation that characterizes this type of wind down to the ion gyroperiod. Methods. We analyzed the VDFs measured by PAS, a novelty that take advantages of the capability of 3D measurements at a 4 Hz cadence. In addition, we considered MAG observations. Results. We first show that there is a remarkable correlation between the B and V components observed down to timescales approaching the ion gyrofrequency. This concerns a wide variety of fluctuations, such as waves, isolated peaks, and discontinuities. The great variability of the proton VDFs is also documented. The juxtaposition of a core and a field-aligned beam is the norm but the relative density of the beam, drift speed, and temperatures can considerably change on scales as short as as a few seconds. The characteristics of the core are comparatively more stable. These variations in the beam characteristics mostly explain the variations in the total parallel temperature and, therefore, in the total anisotropy of the proton VDFs. Two magnetic structures that are associated with significant changes in the shape of VDFs, one corresponding to relaxation of total anisotropy and the other to its strong increase, are analyzed here. Our statistical analysis shows a clear link between total anisotropy (and, thus, beam characteristics) and the direction of B with respect to the Parker spiral. In the present case, flux tubes aligned with Parker spiral contain an average proton VDF with a much more developed beam (thus, with larger total anisotropy) than those that are inclined, perpendicular, or even reverse with regard to the outward direction. Conclusions. These observations document the variability of the proton VDF shape in relation to the propagation of magnetic structures. This is a key area of interest for understanding of the effect of turbulence on solar wind dynamics.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - 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)
Result continuities
Project
<a href="/en/project/GA19-18993S" target="_blank" >GA19-18993S: Transport of energy of solar wind variations from larger to smaller scales</a><br>
Continuities
P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)
Others
Publication year
2021
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Astronomy & Astrophysics
ISSN
0004-6361
e-ISSN
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Volume of the periodical
656
Issue of the periodical within the volume
Dec
Country of publishing house
FR - FRANCE
Number of pages
10
Pages from-to
A36
UT code for WoS article
000730246400047
EID of the result in the Scopus database
2-s2.0-85121586724