Analysis of the first coronagraphic multi-band observations of a sungrazing comet

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F23%3A00604486" target="_blank" >RIV/67985815:_____/23:00604486 - isvavai.cz</a>

Result on the web

<a href="https://hdl.handle.net/11104/0361902" target="_blank" >https://hdl.handle.net/11104/0361902</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202346881" target="_blank" >10.1051/0004-6361/202346881</a>

Result language

angličtina

Original language name

Analysis of the first coronagraphic multi-band observations of a sungrazing comet

Original language description

Context. Between 24 and 25 December 2021 a sungrazing comet (SOHO-4341) approached the Sun, being observed by “classical” visible light (VL) coronagraphs on board the SOHO and STEREO missions, and also by the innovative Metis coronagraph on board the ESA-NASA Solar Orbiter mission in the VL and ultraviolet (UV H i Lyman-α) band. Aims. We show how VL data acquired by the Metis coronagraph can be combined with those provided by other space-based coronagraphs to reconstruct the comet orbit, but also to provide information on the dust composition from the polarized VL emission. Moreover, we show how the UVemission can be employed to measure local plasma parameters of the ambient solar wind. Methods. By using the comet positions tracked with VL Metis images (with spatial resolution that is four times better than UV), the UV images (with a time cadence that is five times faster than VL) have been coaligned to maximize the signal-to-noise ratio in the UV band. The local electron density ne was measured from the observed exponential decay of the UV Lyman-α intensity along the tail, while the solar wind speed vwind was measured from the UV Lyman-α tail inclination with respect to the cometary orbital path deprojected in 3D. Moreover, the proton kinetic temperature Tk was also obtained by the aperture angle of the UV Lyman-α tail. Results. When the comet was at an average heliocentric distance of 14.3R , the comet had a radial speed of 155kms−1 and a tangential speed of 59kms−1. The comet had a UV Lyman-α tail extending in the anti-solar direction over more than 1.5R . From the analysis of the tail shape in UV we obtained the local solar wind speed (vwind = 190kms−1), electron density (ne = 1.5 × 104 cm−3), and proton temperature (Tk = 1.2 × 106 K). Moreover, theoretical analysis of the measured UV Lyman-α intensity allowed us to estimate the radius of the cometary nucleus (Rcom = 65m) and the water outgassing rate (QH2O = 4.8 × 1028 molecs−1). Conclusions. These results show that sungrazing comets are unique “local probes” for the ambient coronal plasma, providing measurements that are not as affected by the line-of-sight integration effects as those provided by remote sensing instruments, in regions of the Heliosphere that are not explored in situ by the ongoing space missions.

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

10308 - Astronomy (including astrophysics,space science)

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2023

Confidentiality

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

Name of the periodical

Astronomy & Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Volume of the periodical

680

Issue of the periodical within the volume

Dec.

Country of publishing house

FR - FRANCE

Number of pages

18

Pages from-to

A90

UT code for WoS article

001125494400020

EID of the result in the Scopus database

2-s2.0-85180737977