Living Rev. Sol. Phys. (2017) 14:2
Arnold O. Benz
© The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract Solar ﬂares are observed at all wavelengths from decameter radio waves
to gamma-rays beyond 1 GeV. This review focuses on recent observations in EUV,
soft and hard X-rays, white light, and radio waves. Space missions such as RHESSI,
Yohkoh, TRACE, SOHO, and more recently Hinode and SDO have enlarged widely
the observational base. They have revealed a number of surprises: Coronal sources
appear before the hard X-ray emission in chromospheric footpoints, major ﬂare accel-
eration sites appear to be independent of coronal mass ejections, electrons, and ions
may be accelerated at different sites, there are at least 3 different magnetic topolo-
gies, and basic characteristics vary from small to large ﬂares. Recent progress also
includes improved insights into the ﬂare energy partition, on the location(s) of energy
release, tests of energy release scenarios and particle acceleration. The interplay of
observations with theory is important to deduce the geometry and to disentangle the
various processes involved. There is increasing evidence supporting magnetic recon-
This article is a revised version of http://dx.doi.org/10.12942/lrsp-2008-1.
Change summary Major revision, updated and expanded.
Change details Signiﬁcant new results from RHESSI and SDO are included. In particular, Sect. 3.4 on
“Emissions from above the coronal source” was added (including two new ﬁgures) and Sect. 3.2 on
“Coronal hard X-ray sources” was expanded. New observations of ﬂares in white light are reported
(replaced Fig. 25 with a movie), as well as recent multi-wavelength observations in radio waves and
gamma-rays combined with hard X-rays. Four references were removed and 49 new references added.
Electronic supplementary material The online version of this article (doi:10.1007/s41116-016-0004-3)
contains supplementary material, which is available to authorized users.
Arnold O. Benz
Institute for Astronomy, ETH, 8092 Zurich, Switzerland
Institute of 4D Technologies, FHNW, 5210 Windisch, Switzerland