Issue |
A&A
Volume 507, Number 1, November III 2009
|
|
---|---|---|
Page(s) | 433 - 439 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361/200912028 | |
Published online | 27 August 2009 |
Submillimeter and X-ray observations of an X class flare
1
Centro de Rádio Astronomia e Astrofísica Mackenzie, R. da Consolação 896, 01302-907, São Paulo, SP, Brazil e-mail: guigue@craam.mackenzie.br, e-mail: guillermo.gimenez.de.castro@gmail.com
2
LESIA, Observatoire de Paris, Section de Meudon, 92195 Meudon, France
3
Space Sciences Laboratory, University of California, Berkeley, USA
4
Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil
5
Centro de Componentes Semicondutores, Universidade Estadual de Campinas, Campinas, Brazil
6
Complejo Astronómico El Leoncito, CONICET, San Juan, Argentina
Received:
10
March
2009
Accepted:
7
July
2009
The GOES X1.5 class flare that occurred on August 30, 2002 at 1327:30 UT is one of the few events detected so far at submillimeter wavelengths. We present a detailed analysis of this flare combining radio observations from 1.5 to 212 GHz (an upper limit of the flux is also provided at 405 GHz) and X-ray. Although the observations of radio emission up to 212 GHz indicates that relativistic electrons with energies of a few MeV were
accelerated, no significant hard X-ray emission was detected by RHESSI above ~250 keV. Images at 12–20 and 50–100 keV reveal a very compact, but resolved, source of about ~10″10″. EUV TRACE images show a multi-kernel structure suggesting a complex (multipolar) magnetic
topology. During the peak time the radio spectrum shows an extended
flatness from ~7 to 35 GHz. Modeling the optically thin part of the
radio spectrum as gyrosynchrotron emission we obtained the electron
spectrum (spectral index δ, instantaneous number of emitting
electrons). It is shown that in order to keep the expected X-ray emission from the same emitting electrons below the RHESSI background at 250 keV, a magnetic field above 500 G is necessary. On the other hand, the electron spectrum deduced from radio observations ≥50 GHz is harder than that deduced from ~70–250 keV X-ray data, meaning that there must exist a breaking energy around a few hundred keV. During the decay of the
impulsive phase, a hardening of the X-ray spectrum is observed which is
interpreted as a hardening of the electron distribution spectrum produced by the diffusion due to Coulomb collisions of the trapped electrons in a medium
with an electron density of ne ~ 3-5
1010 cm-3.
Key words: Sun: activity / Sun: flares / Sun: radio radiation / Sun: X-rays, gamma rays / Sun: particle emission
© ESO, 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.