Lyman-alpha emission from nonthermal proton beams

Orrall, F. Q.; Zirker, J. B.

doi:10.1086/154642

Cited by 60 publications

(49 citation statements)

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“…The ion (or proton) component is also very poorly constrained, and improving this will require very much better γ-ray spectroscopy, with much improved signal-to-noise ratio. We also have no knowledge at all of lower energy protons (of a few tens or hundreds of keV), though diagnostics such as Doppler-shifted Lyman-α (emitted by charge-exchanging low-energy protons (Orrall & Zirker 1976) and the (disputed) observations of Hα impact polarization (Vogt & Hénoux 1999) might help us in this direction.…”

Section: Future Improvementsmentioning

confidence: 99%

An Observational Overview of Solar Flares

et al. 2011

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We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.

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Section: Future Improvementsmentioning

confidence: 99%

An Observational Overview of Solar Flares

et al. 2011

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“…T he Search for Proton Beams As Ðrst discussed by Orrall & Zirker (1976), protons accelerated toward the star during a solar or stellar Ñare may exchange charge with ambient hydrogen atoms and emit redshifted photons in the various hydrogen transitions, including Lya. Thus, an enhancement in the red wing of Lya that does not appear in the blue wing is a good indicator of the presence of proton beams.…”

Section: Flare Dynamicsmentioning

confidence: 99%

Far‐Ultraviolet Observations of Flares on the dM0e Star AU Microscopii

Robinson

Linsky

Woodgate

et al. 2001

ApJ

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We report on far-ultraviolet (FUV) observations of Ñares on the dM0e star AU Microscopii obtained on 1998 September 6 with the Space Telescope Imaging Spectrograph onboard the Hubble Space T elescope. The data consist of medium-resolution echelle spectra covering the wavelength region from 1170 to 1730 with a spectral resolution of j/*j \ 45,800. The observations were obtained using the A TIME-TAG observing mode in which the time and position of each detected photon is recorded. This allows a study of variability that is constrained only by counting statistics. During a total on-source time of 10,105 s, we observed numerous microÑare bursts as well as four well-deÐned Ñare events. These Ñares lasted between 10 s and 3 minutes and were most easily detected in the FUV continuum and the Si IV and C IV resonance lines. Variations in both the cooler (e.g., Lya, C II, O I) and hotter (O V, N V, Fe XXI) emission lines were much less pronounced. We examined the physical characteristics of the Ñare events, including the time history of the wavelength-integrated Ñuxes in the continuum and the various emission lines. In particular, we searched for, but did not Ðnd, evidence for increased emission in the red wing of the Lya line, which would indicate the presence of moderately energetic proton beams. We integrated the emission over the entire time of major Ñare activity to investigate the average line and continuum properties of the time-averaged spectrum, including Ñows and turbulence as a function of temperature. We also considered the shape of the FUV continuum, which may actually be caused by the enhancement of numerous weak emission lines. Unfortunately, none of the events were strong enough to allow a detailed examination of line proÐles as a function of time.

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“…The transport and collisional degradation of energetic charged particles through the solar atmosphere dbring flares has been studied by a number of authors, and energy deposition rates as a function of depth evaluated (see, e.g., Najita and Orrall, 1970;Brown, 1972Brown, , 1973Orrall and Zirker, 1976;Emslie, 1978Emslie, , 1980Hudson and Dwivedi, 1982).…”

Section: Variation Of Deposited Energy With Depthmentioning

confidence: 99%

Chromospheric heating by electron and proton bombardment in the solar flare of June 7, 1980

Emslie

1983

Sol Phys

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Lyman-alpha emission from nonthermal proton beams

Cited by 60 publications

References 0 publications

An Observational Overview of Solar Flares

An Observational Overview of Solar Flares

Far‐Ultraviolet Observations of Flares on the dM0e Star AU Microscopii

Chromospheric heating by electron and proton bombardment in the solar flare of June 7, 1980

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