Solar flares as proxy for the young Sun: satellite observed thermosphere response to an X17.2 flare of Earth's upper atmosphere

Author(s)

Sandro Krauss, B. Fichtinger, H. Lammer, W. Hausleitner, Yu. N. Kulikov, I. Ribas, V. I. Shematovich, D. Bisikalo, H. I. M. Lichtenegger, T. V. Zaqarashvili, M. L. Khodachenko, A. Hanslmeier

Abstract

We analyzed the measured thermospheric response of an extreme solar

X17.2 flare that irradiated the Earth's upper atmosphere during the

so-called Halloween events in late October/early November 2003. We

suggest that such events can serve as proxies for the intense

electromagnetic and corpuscular radiation environment of the Sun or

other stars during their early phases of evolution. We applied and

compared empirical thermosphere models with satellite drag measurements

from the GRACE satellites and found that the Jacchia-Bowman 2008 model

can reproduce the drag measurements very well during undisturbed solar

conditions but gets worse during extreme solar events. By analyzing the

peak of the X17.2 flare spectra and comparing it with spectra of young

solar proxies, our results indicate that the peak flare radiation flux

corresponds to a hypothetical Sun-like star or the Sun at the age of

approximately 2.3 Gyr. This implies that the peak extreme ultraviolet

(EUV) radiation is enhanced by a factor of about 2.5 times compared to

today's Sun. On the assumption that the Sun emitted an EUV flux of that

magnitude and by modifying the activity indices in the Jacchia-Bowman

2008 model, we obtain an average exobase temperature of 1950 K, which

corresponds with previous theoretical studies related to thermospheric

heating and expansion caused by the solar EUV flux.

Organisation(s)

Department of Astrophysics

External organisation(s)

Österreichische Akademie der Wissenschaften (ÖAW), Russian Academy of Sciences, Universitat Autònoma de Barcelona

Journal

Annales Geophysicae

Volume

30

Pages

1129-1141

Publication date

08-2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics, 103003 Astronomy

Portal url

https://ucrisportal.univie.ac.at/en/publications/c6fc6598-bc89-4392-9432-17944d0bbbae