Gamma-Ray Imaging of the 2003 October/November Solar Flares

Hurford, G. J.; Krucker, S.; Lin, R. P.; Schwartz, R. A.; Share, G. H.; Smith, David M.

doi:10.1086/505329

Cited by 146 publications

(133 citation statements)

References 22 publications

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“…If the extended source observed in interval A is still present in interval B, although at a low level, the size of the impulsive component alone should be even smaller than values given above. The source location is again near the southern ribbon but shifted by $15 00 relative to the last position of the radio source in interval A, and it roughly coincides with the flare-averaged 2.2 MeV footpoint position observed on the southern ribbon ( Hurford et al 2006). Although radio emission from the other 2.2 MeV footpoint on the northern ribbon is clearly outside the optimum imaging field of view, it is within one of the multibeams.…”

Section: Imagingsupporting

confidence: 70%

“…It arises from an apparently extended source with average size of 57 00 AE 4 00 located between the ribbons, which shows a slow apparent motion of about 25 km s À1 . RHESSI hard X-ray imaging observations in the 250Y450 keV range show two hard X-ray footpoints and a fainter third source in between the footpoints ( Hurford et al 2006). This third source is unlikely a footpoint source but is rather emission from the corona (Krucker et al 2008), although projection effects do not allow us to unambiguously identify the origin of this source.…”

Section: Imagingmentioning

confidence: 91%

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Radio Submillimeter and γ‐Ray Observations of the 2003 October 28 Solar Flare

Trottet

Krucker

Lüthi

et al. 2008

ApJ

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Radio observations at 210 GHz taken by the Bernese Multibeam Radiometer for KOSMA ( BEMRAK ) are combined with hard X-ray and -ray observations from the SONG instrument on board CORONA-F and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI ) to investigate high-energy particle acceleration during the energetic solar flare of 2003 October 28. Two distinct components at submillimeter wavelengths are found. The first is a gradual, long-lasting (>30 minutes) component with large apparent source sizes ($60 00 ). Its spectrum below $200 GHz is consistent with synchrotron emission from flare-accelerated electrons producing hard X-ray and -ray bremsstrahlung assuming a magnetic field strength of !200 G in the radio source and a confinement time of the radioemitting electrons in the source of less than 30 s. The other component is impulsive and starts simultaneously with high-energy (>200 MeV nucleon À1 ) proton acceleration and the production of pions. The derived radio source size is compact ( 10 00 ), and the emission is cospatial with the location of precipitating flare-accelerated >30 MeV protons as seen in -ray imaging. The close correlation in time and space of radio emission with the production of pions suggests that synchrotron emission of positrons produced in charged-pion decay might be responsible for the observed compact radio source. However, order-of-magnitude approximations rather suggest that the derived numbers of positrons from charged-pion decay are probably too small to account for the observed radio emission. Synchrotron emission from energetic electrons therefore appears as the most likely emission mechanism for the compact radio source seen in the impulsive phase, although it does not account for its close correlation, in time and space, with pion production.

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Section: Imagingsupporting

confidence: 70%

Section: Imagingmentioning

confidence: 91%

Radio Submillimeter and γ‐Ray Observations of the 2003 October 28 Solar Flare

Trottet

Krucker

Lüthi

et al. 2008

ApJ

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“…Flareintegrated RHESSI imaging results of this event are published by Hurford et al (2006) showing that the 2.2 MeV emission produced by energetic protons comes from two sources, one on each of the flare ribbons, but displaced by ∼15Љ from the 200-300 keV footpoints. Next to the two electron bremsstrahlung footpoints, a fainter third source from in between the footpoints is also observed in the 200-300 keV image (Hurford et al 2006, Fig.…”

Section: The 2003 October 28 Flarementioning

confidence: 98%

“…RHESSI imaging (Hurford et al 2002) uses nine bigrid rotating modulation collimators (RMCs). Behind each RMC is a cryogenically cooled germanium detector that provides high spectral resolution (∼1-10 keV FWHM) over the 3 keV-17 MeV energy range (Smith et al 2002).…”

Section: Observations and Data Analysismentioning

confidence: 99%

“…Together with the RHESSI imaging capability, this provides for the first time imaging spectroscopy in the g-ray range. The images taken above 200 keV presented in this Letter are all reconstructed from rear-segment data with the help of the CLEAN algorithm (Hurford et al 2002) using subcollimators 4-9 (the grids in front of subcollimators 1-3 are not thick enough to efficiently modulate incoming counts above 300 keV). Subcollimators 4-9 generally show clear modulation, although subcollimator 4, which provides the finest spatial resolution (∼12Љ FWHM), often provides only noisy images with a very limited dynamic range of ∼2.…”

Section: Observations and Data Analysismentioning

confidence: 99%

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Coronal γ-Ray Bremsstrahlung from Solar Flare-accelerated Electrons

Krucker

Hurford

MacKinnon

et al. 2008

ApJ

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The Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) provides for the first time imaging spectroscopy of solar flares up to the g-ray range. The three RHESSI flares with best counting statistics are analyzed in the 200-800 keV range revealing g-ray emission produced by electron bremsstrahlung from footpoints of flare loops, but also from the corona. Footpoint emission dominates during the g-ray peak, but as the g-ray emission decreases the coronal source becomes more and more prominent. Furthermore, the coronal source shows a much harder spectrum (with power-law indices g between 1.5 and 2) than the footpoints (with g between 3 and 4). These observations suggest that flareaccelerated high-energy (∼MeV) electrons stay long enough in the corona to lose their energy by collisions producing g-ray emission, while lower energetic electrons precipitate more rapidly to the footpoints.

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Scientific considerations for future spectroscopic measurements from space of activity on the Sun

Holman

2016

JGR Space Physics

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High‐resolution UV and X‐ray spectroscopy are important to understanding the origin and evolution of magnetic energy release in the solar atmosphere, as well as the subsequent evolution of heated plasma and accelerated particles. Electromagnetic radiation is observed from plasma heated to temperatures ranging from about 10 kK to above 10 MK, from accelerated electrons emitting photons primarily at X‐ray energies, and from ions emitting in γ rays. These observations require space‐based instruments sensitive to emissions at wavelengths shorter than the near UV. This article reviews some recent observations with emphasis on solar eruptive events, the models that describe them, and the measurements they indicate are needed for substantial progress in the future. Specific examples are discussed demonstrating that imaging spectroscopy with a cadence of seconds or better is needed to follow, understand, and predict the evolution of solar activity. Critical to substantial progress is the combination of a judicious choice of UV, EUV, and soft X‐ray imaging spectroscopy sensitive to the evolution of this thermal plasma combined with hard X‐ray imaging spectroscopy sensitive to suprathermal electrons. The major challenge will be to conceive instruments that, within the bounds of possible technologies and funding, have the flexibility and field of view to obtain spectroscopic observations where and when events occur while providing an optimum balance of dynamic range, spectral resolution and range, and spatial resolution.

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Gamma-Ray Imaging of the 2003 October/November Solar Flares

Cited by 146 publications

References 22 publications

Radio Submillimeter and γ‐Ray Observations of the 2003 October 28 Solar Flare

Radio Submillimeter and γ‐Ray Observations of the 2003 October 28 Solar Flare

Coronal γ-Ray Bremsstrahlung from Solar Flare-accelerated Electrons

Scientific considerations for future spectroscopic measurements from space of activity on the Sun

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