Evidence from Hard X-Rays for Two-Stage Particle Acceleration in a Solar Flare

Frost, K. J.; Dennis, B. R.

doi:10.1086/150932

Cited by 204 publications

(84 citation statements)

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“…On the other hand, Chupp (1982) than the <100 keV continuum (Bai and Ramaty 1976;Bai 1982). These results, together with earlier X-ray observations (Frost and Dennis 1971) and gamma-ray measurements , Willet et al 1982 demonstrate that not all energetic particle populations in flares are accelerated at the same time,…”

Section: Implications Of Gamma Ray Observatioassupporting

confidence: 61%

Nuclear Processes in Solar Flares

Ramaty

1985

Physics of the Sun

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Section: Implications Of Gamma Ray Observatioassupporting

confidence: 61%

Nuclear Processes in Solar Flares

Ramaty

1985

Physics of the Sun

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“…Hard X-ray sources at altitudes of several 10 4 km in the corona have been suspected to be possible sites of particle acceleration. Their existence was first proposed by Frost & Dennis (1971) and confirmed by the discovery of a hard X-ray source above the top of a magnetic loop by Masuda et al (1994). Statistical studies using Yohkoh data (Tomczak 2001) and RHESSI (Krucker & Lin 2008) confirmed the existence of a hard X-ray component in 90% of the analyzed coronal sources.…”

Section: Introductionmentioning

confidence: 80%

Do solar decimetric spikes originate in coronal X-ray sources?

Battaglia¹,

Benz²

2009

A&A

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Context. In the standard solar flare scenario, a large number of particles are accelerated in the corona. Nonthermal electrons emit both X-rays and radio waves. Thus, correlated signatures of the acceleration process are predicted at both wavelengths, coinciding either close to the footpoints of a magnetic loop or near the coronal X-ray source. Aims. We attempt to study the spatial connection between coronal X-ray emission and decimetric radio spikes to determine the site and geometry of the acceleration process. Methods. The positions of radio-spike sources and coronal X-ray sources are determined and analyzed in a well-observed limb event. Radio spikes are identified in observations from the Phoenix-2 spectrometer. Data from the Nançay radioheliograph are used to determine the position of the radio spikes. RHESSI images in soft and hard X-ray wavelengths are used to determine the X-ray flare geometry. Those observations are complemented by images from GOES/SXI. Results. We find that the radio emission originates at altitudes much higher than the coronal X-ray source, having an offset from the coronal X-ray source amounting to 90 and to 113 and 131 from the two footpoints, averaged over time and frequency. Conclusions. Decimetric spikes do not originate from coronal X-ray flare sources contrary to previous expectations. However, the observations suggest a causal link between the coronal X-ray source, related to the major energy release site, and simultaneous activity in the higher corona.

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“…Hudson (1979) has reviewed the evidence for this component. It can be four.1 in hard X-ray observations from flares located behind the limb of the Sun (Hudson, Lin and Stewart 1981) and from flares on the visible solar hemisphere which produce extended X-ray bursts (Frost andDennis 1971, Hoyng, Brown andVan Beek 1976). These X-rays are produced in the corona and their spectrum is generally harder-than that of the impulsive X-rays.…”

Section: Of Poor Qualitymentioning

confidence: 99%

“…, Ramaty et al 1980. It has been known for sometime (Wild, Smer •d and Weiss 1963, Frost and Dennis 1971, Lin 1974, Ramaty et al 1980) that at least two phases of particle acceleration can occur in solar flares. The first phase is characterized by impulsive bursts of hard X-rays and microwaves and by Type iii radio emission, while the second phase is manifest in Type II bursts, microwave and metric Type IV emission, flare continuum radio emission and gradual hard X-rays.…”

Section: A Electromagnetic Radiationsmentioning

confidence: 99%