Gamma-ray and microwave evidence for two phases of acceleration in solar flares

Bai, T.; Ramaty, R.

doi:10.1007/bf00162457

Cited by 37 publications

(16 citation statements)

References 20 publications

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“…(See article by Ramaty 1982, in this volume, for a detailed discussion on the delay of the emission of 2.22 MeV photons owing.to the finite capture time of the neutrons). This led Bai and Ramaty (1976) to conclude that the > 0.35 MeV electrons and > 10 MeV protons are acce l erated in the second phase. However, as can be seen in Figure 1, even though the build-up of the higher-energy emissions in the August 4, 1972 flare was slower than that nf the hard X-rays, the two emissions were not clearly separated in time.…”

Section: Gamma-raysmentioning

confidence: 99%

The Acceleration and Propagation of Solar Flare Energetic Particles

1985

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Section: Gamma-raysmentioning

confidence: 99%

The Acceleration and Propagation of Solar Flare Energetic Particles

1985

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“…(2) Energetic nuclei are accelerated with a time history that is consistent with the energetic photon continuum (> 100 keV) (Bai and Ramaty, 1976).…”

Section: Scientific Perspectivementioning

confidence: 99%

The gamma ray spectrometer for the Solar Maximum Mission

et al. 1980

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The Solar Maximum Mission Gamma Ray Experiment (SMM GRE) utilizes an actively shielded, multicrystal scintillation spectrometer to measure the flux of solar gamma rays. The instrument provides a 476-channel pulse height spectrum (with energy resolution of ~7% at 662 keV) every 16.38 s over the energy range 0.3-9 MeV. Higher time resolution (2 s) is available in three windows between 3.5 and 6.5 MeV to study prompt gamma ray line emission at 4.4 and 6.1 MeV. Gamma ray spectral analysis can be extended to -> 15 MeV on command. Photons in the energy band from 300-350 keV are recorded with a time resolution of 64 ms. A high energy configuration also gives the spectrum of photons in the energy range from 10-100 MeV and the flux of neutrons ~>20 MeV. Both have a time resolution of 2 s. Auxiliary X-ray detectors will provide spectra with 1-sec time resolution over the energy range of 10-140 keV. The instrument is designed to measure the intensity, energy, and Doppler shift of narrow gamma ray lines as well as the intensity of extremely broadened lines and the photon continuum. The main objective is to use this time and spectral information from both nuclear gamma ray lines and the photon continuum in a direct study of the dynamics of the solar flare/particle acceleration phenomena.

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“…They found that the electron energy distribution inferred from the microwave spectrum is systematically harder than that inferred from the HXR spectrum, and suggested that the electron energy distribution becomes harder toward higher energy. There are three probable explanations for such spectra: (1) two (or more) different electron populations with distinct physical characteristics, (2) ''secondstep acceleration'' (e.g., Bai & Ramaty 1976), and (3) ''trap-plusprecipitation'' (TPP; e.g., Melrose & Brown 1976). Melrose & Brown (1976) presented analytic solutions of the electron energy continuity equation under two conditions, strong and weak diffusion limits ( Kennel & Petscheck 1966).…”

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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Gamma-ray and microwave evidence for two phases of acceleration in solar flares

Cited by 37 publications

References 20 publications

The Acceleration and Propagation of Solar Flare Energetic Particles

The Acceleration and Propagation of Solar Flare Energetic Particles

The gamma ray spectrometer for the Solar Maximum Mission

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

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