Počet záznamů: 1
Over-expansion of a coronal mass ejection generates sub-Alfvénic plasma conditions in the solar wind at Earth
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SYSNO ASEP 0552241 Druh ASEP J - Článek v odborném periodiku Zařazení RIV J - Článek v odborném periodiku Poddruh J Článek ve WOS Název Over-expansion of a coronal mass ejection generates sub-Alfvénic plasma conditions in the solar wind at Earth Tvůrce(i) Chané, E. (BE)
Schmieder, B. (FR)
Dasso, S. (AR)
Verbeke, C. (BE)
Grison, Benjamin (UFA-U) RID, ORCID
Démoulin, P. (FR)
Poedts, S. (BE)Celkový počet autorů 7 Číslo článku A149 Zdroj.dok. Astronomy & Astrophysics. - : EDP Sciences - ISSN 0004-6361
Roč. 647, Mar 26 (2021)Poč.str. 12 s. Jazyk dok. eng - angličtina Země vyd. FR - Francie Klíč. slova coronal mass ejections (CMEs) ; infrared ; solar wind ; magnetohydrodynamics (MHD) Vědní obor RIV BL - Fyzika plazmatu a výboje v plynech Obor OECD Fluids and plasma physics (including surface physics) CEP GA18-05285S GA ČR - Grantová agentura ČR Způsob publikování Open access Institucionální podpora UFA-U - RVO:68378289 UT WOS 000636920700001 EID SCOPUS 85103480384 DOI 10.1051/0004-6361/202039867 Anotace Context. From May 24–25, 2002, four spacecraft located in the solar wind at about 1 astronomical unit (au) measured plasma densities
one to two orders of magnitude lower than usual. The density was so low that the flow became sub-Alfvénic for four hours, and the
Alfvén Mach number was as low as 0.4. Consequently, the Earth lost its bow shock, and two long Alfvén wings were generated.
Aims. This is one of the lowest density events ever recorded in the solar wind at 1 au, and the least documented one. Our goal is to
understand what caused the very low density.
Methods. Large Angle and Spectrometric Coronagraph (LASCO) and in situ data were used to identify whether something unusual
occurred that could have generated such low densities
Results. The very low density was recorded inside a large interplanetary coronal mass ejection (ICME), which displayed a long,
linearly declining velocity profile, typical of expanding ICMEs. We deduce a normalised radial expansion rate of 1.6. Such a strong
expansion, occurring over a long period of time, implies a radial size expansion growing with the distance from the Sun to the power
1.6. This can explain a two-orders-of-magnitude drop in plasma density. Data from LASCO and the Advanced Composition Explorer
show that this over-expanding ICME was travelling in the wake of a previous ICME.
Conclusions. The very low densities measured in the solar wind in May 2002 were caused by the over-expansion of a large ICME.
This over-expansion was made possible because the ICME was travelling in a low-density and high-velocity environment present in
the wake of another ICME coming from a nearby region on the Sun and ejected only three hours previously. Such conditions are very
unusual, which explains why such very low densities are almost never observed.Pracoviště Ústav fyziky atmosféry Kontakt Kateřina Adamovičová, adamovicova@ufa.cas.cz, Tel.: 272 016 012 ; Kateřina Potužníková, kaca@ufa.cas.cz, Tel.: 272 016 019 Rok sběru 2022 Elektronická adresa https://hal-obspm.ccsd.cnrs.fr/obspm-03368166/file/chane21_overexpansion_CME_23May02_final.pdf
Počet záznamů: 1