The occurrence of intense solar flares represents, usually, an
inconvenience for satellites in space. The radiation of these flares in
the hard-X and gamma-ray band are orders of magnitude stronger than that
of other high-energy objects. They are often followed by a strong
increase of energetic particles thrown into interplanetary space,
thereby posing a threat to satellite operations. The Sun is currently in
an active phase, and, for example, active region AR11748 (top left)
produced recently a series of intense solar flares.
Although INTEGRAL was not built for studying solar flare, it detects
photons of solar origin. Especially the Anti-Coincidence Shield (ACS) of
the SPI instrument, with its large effective area, is very suitable for
solar flare studies. Lately, within the FP7 SEPServer Project, the
capabilities of SPI/ACS for solar studies by means of Monte-Carlo
simulations have been explored [5,6] (top right). Light curves of 23
solar flares of the last solar cycle (up to 2008) were evaluated and
some 50 more light curves of the present cycle are currently in study.
For the most intense flares, the Ge matrix of SPI can provide spectra in
the 0.5-10 MeV range (bottom right). Light curves and spectra of four
X-class solar flares have been extracted and analyzed [see 1,2,3,4], so
far. The collage shows images/figures, illustrating the kind of solar
study that can be done by INTEGRAL.
- Top left: Proba 2/SWAP 174 Å image of the Sun on May 14, 2013 at 14:04
UT. AR 11748 (east limb) produced a series of four X-class solar flares
between May 13 and 15, 2013 (image taken from http://www.SolarMonitor.org).
- Bottom left: SPI/ACS count rate data of the recent, May 13, 2013 solar
flare that took place around 16:05 UT (V. Beckmann, private communication).
- Top right: Monte-Carlo simulation for the configuration corresponding
to the October 28, 2003 solar flare. Blue lines: photon tracks; red
lines: secondary particles created by photon interactions in the spacecraft.
- Bottom right: gamma-ray spectrum of the October 28, 2003 solar flare
as measured by the SPI Ge array. This plot, generated by SEPServer [7],
shows the temporal evolution of the gammay-ray spectrum (intensity of
the photons in [counts/(s MeV)] as a function of time).
References:
5th INTEGRAL Workshop, ESA Special Publication, 552, 669, 2004
Gros et al.
Properties of the energetic particle distributions during the October 28,
2003 solar flare from INTEGRAL/SPI observations
Kiener et al.
A&A, 445, 725, 2006
High resolution γ-ray spectroscopy of flares on the east and west limbs of the Sun
Harris et al. A&A, 461, 723, 2007
Proceedings of Science (INTEGRAL 2012), 2013
Zhang et al.
Credits: R. Rodríguez-Gasén, J. Kiener, V. Tatischeff, C. Hamadache,
K.-L. Klein, N. Vilmer, and the SEPServer Consortium. V. Beckmann
provided the ACS data shown here.
