Impulsive (Flash) Phase of Solar Flares: Hard X-Ray, Microwave, EUV and Optical Observations

Kane, S. R.

doi:10.1007/978-94-010-2257-6_9

Cited by 86 publications

(15 citation statements)

References 93 publications

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“…All of the RS type III group or blips appear in the impulsive phase of X-ray flares, which is consistent with statistical studies in the metric wavelength (e.g. Kane 1974). According to the Solar Geophysical Data (SGD), one RS type III on 2002 April 14 and two pulsation groups on 1999 September 11 and December 16 occurred without any flares detected in Hα and X-ray.…”

Section: Observationssupporting

confidence: 88%

Microwave type III bursts and pulsation groups

Ning

Ding²,

et al. 2005

A&A

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Abstract. We analyse 22 continuous microwave reverse slope (RS) type III and 21 microwave pulsation groups observed by the Purple Mountain Observatory (PMO) spectrometer over the frequency range of 4.5−7.5 GHz from 1999−2003. The RS type III groups have an average of 12 bursts per group, a mean duration of 0.1−2 s around 6 GHz, a mean quasi-period of 2.0 ± 0.6 s and a mean drift rate of 7.0 GHz s −1 . The shortest quasi-period is measurable down to 0.05 s thanks to the high time resolution of this instrument. The microwave pulsation groups have an average of 22 events per group, a mean duration of 3−4 s and a mean quasi-period of 3.7 ± 1.1 s. The RS type III bursts have the same quasi-period as the upward type III bursts documented before. We discuss two possible origins of the quasi-periodicity of type III bursts. One is the quasi-periodic process in magnetic reconnection at the same site, and the other is spatially unresolved stochastic processes in solar flares.

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Section: Observationssupporting

confidence: 88%

Microwave type III bursts and pulsation groups

Ning

Ding²,

et al. 2005

A&A

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“…Impulsive behavior is commonly seen in both HXR and microwave light curves ( Kane 1974), but the two emissions do not necessarily behave identically. Temporally, higher energy HXR and microwave emissions tend to be delayed from lower energy HXRs (e.g., Crannell et al 1978;Nakajima et al 1983;Bai & Dennis 1985;Aschwanden et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Comparative Analysis of Nonthermal Emissions and Electron Transport in a Solar Flare

Minoshima¹,

Yokoyama²,

Mitani³

2008

ApJ

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We study nonthermal emission in a solar flare occurring on 2003 May 29 using RHESSI hard X-ray ( HXR) and Nobeyama microwave observations. This flare shows several typical behaviors of HXR and microwave emission: time delay of microwave peaks relative to HXR peaks, loop-top microwave and footpoint HXR sources, and a harder electron energy distribution from the microwave spectrum than from the HXR spectrum. In addition, we found that the time profile of the spectral index of the higher energy (k100 keV ) HXRs is similar to that of the microwaves, and is delayed relative to that of the lower energy (P100 keV ) HXRs. We interpret these observations in terms of an electron transport model called trap-plus-precipitation. We numerically solved the spatially homogeneous FokkerPlanck equation to determine electron evolution in energy and pitch-angle space. By comparing observations with the behavior of HXR and microwave emission predicted by the model, we examine the pitch-angle distribution of the electrons injected into the flare site. We find that the observed spectral variations can be qualitatively explained if the injected electrons have a pitch-angle distribution concentrated perpendicular to the magnetic field lines rather than an isotropic distribution.

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“…By presumed identification of these bursts with active regions behind theo cculting limb, their longitude 0 and hence their minimum height for visibility Zmi . = =R(cosec0-1) are found (Kane, 1974a;Datlowe et al, 1974;Royand Datlowe, 1975). Aside from the uncertainty and inaccuracy of such position identification, this problem suffers from two severe limitations.…”

Section: X-rays From Flares Behind the Limbmentioning

confidence: 99%

“…Firstly it depends on the burst source being localised in longitude. This requirement is almost certainly not met for very large events such as that instanced by Kane (1974a) (viz., the March 30, 1969 which was seen directly from radio heliograms (Wild and Smerd, 1972) to involve energetic electrons over a huge area of the Sun. Even in small events (Roy and Datlowe, 1975) the assumption is seen to be very doubtful when it is observed how much soft X-ray emission extends onto the disc in OSO-5 heliograms taken near the time of a typical event (cf.…”

Section: X-rays From Flares Behind the Limbmentioning

confidence: 99%

“…Kane, 1974a;Takakura, 1973) that a solar hard X-ray burst probably emanates from a considerable range of heights in the solar atmosphere, much of the controversy in the literature has been concerned with whether the bulk of the emission is generated high or low in the atmosphere. This state of affairs exists partly because of the lack of spatially resolved hard X-ray observations at present, and partly due to insufficient theoretical analysis of geometric characteristics of source models.…”

Section: Introductionmentioning

confidence: 99%

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The height distribution of flare hard X-rays in thick and thin target models

Brown

McClymont

1975

Sol Phys

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The current controversy between thick and thin target models of hard X-ray flares is reviewed and it is concluded that the most promising method of distinguishing them is in terms of the differences in the distribution of the source with height in the solar atmosphere.Quantitative predictions are made of this height distribution for both models and the results discussed in relation to observations of hard X-ray emission from flares behind the limb. It is concluded that the thick target model is as compatible with such events as the thin target whereas the latter is in general much less satisfactory in terms of energy requirements and of flare observations at other wavelengths. Other source models are also briefly considered.

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Impulsive (Flash) Phase of Solar Flares: Hard X-Ray, Microwave, EUV and Optical Observations

Cited by 86 publications

References 93 publications

Microwave type III bursts and pulsation groups

Microwave type III bursts and pulsation groups

Comparative Analysis of Nonthermal Emissions and Electron Transport in a Solar Flare

The height distribution of flare hard X-rays in thick and thin target models

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