A frequency-agile interferometer for solar microwave spectroscopy

Hurford, G. J.; Read, R. B.; Zirin, H.

doi:10.1007/bf00151327

Cited by 51 publications

(23 citation statements)

References 9 publications

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“…For comparison, the time profile of emission at 15.6 GHz, due to the well-known gyrosynchrotron mechanism, is also shown with data from the Owens Valley Solar Array (OVSA; Hurford, Read, & Zirin 1984). At the bottom is a 10 s period during peak P1, at 5 ms time resolution, showing the superposed rapid pulses with the main bulk emission subtracted.…”

Section: Introductionmentioning

confidence: 91%

A New Solar Burst Spectral Component Emitting Only in the Terahertz Range

Kaufmann

Raulin

Castro

et al. 2004

ApJ

117

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Solar flare energy manifestations were believed to be the result of the same kind of particle acceleration. It is generally accepted that a population of relativistic electrons accelerated during the impulsive phase of solar flares produces microwaves by synchrotron losses in the solar magnetic field and X-rays by collisions in denser regions of the solar atmosphere. We report the discovery of a new intense solar flare spectral radiation component, peaking somewhere in the shorter submillimeter to far-infrared range, identified during the 2003 November 4 large flare. The new solar submillimeter telescope, designed to extend the frequency range to above 100 GHz, detected this new component with increasing fluxes between 212 and 405 GHz. It appears along with, but is separated from, the well-known gyrosynchrotron emission component seen at microwave frequencies. The novel emission component had three major peaks with time, originated in a compact source whose position remained remarkably steady within 15Љ. Intense subsecond pulses are superposed with excess fluxes also increasing with frequency and amplitude increasing with the pulse repetition rate. The origin of the terahertz emission component during the flare impulsive phase is not known. It might be representative of emission due to electrons with energies considerably larger than the energies assumed to explain emission at microwaves. This component can attain considerably larger intensities in the far-infrared, with a spectrum extending to the white-light emission observed for that flare.

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Section: Introductionmentioning

confidence: 91%

A New Solar Burst Spectral Component Emitting Only in the Terahertz Range

Kaufmann

Raulin

Castro

et al. 2004

ApJ

117

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“…In the White event, the immeasurably low heating may perhaps not be unexpected due to the weakness of the nonthermal emission, whose radio flux did not exceed a couple of sfu even at the flare peak time. However, a comparably cold, dense flare with a radio flux more than two orders of magnitude larger has been reported by Bastian et al (2007) based on the combination of the microwave data jointly obtained with the Owens Valley Solar Array (OVSA, Hurford et al 1984;Gary & Hurford 1994), Nobeyama Radio Polarimeters (Torii et al 1979), and the Nobeyama RadioHeliograph (Nakajima et al 1994). From the detailed analysis of the radio spectral evolution and timing in the event, along with quantitative estimates of the fast electron acceleration efficiency, loss, and energy partitions, Bastian et al (2007) concluded in favor of the stochastic acceleration of electrons in this flare, waveturbulence-mediated transport of the electrons, and acceleratedelectron-driven moderate heating of the originally cold, dense plasma of the flaring loop, which was identified as the very site where the energy release and electron acceleration happened.…”

Section: Introductionmentioning

confidence: 92%

Validation of the Coronal Thick Target Source Model

Fleishman

Nita

et al. 2016

ApJ

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We present detailed 3D modeling of a dense, coronal thick-target X-ray flare using the GX Simulator tool, photospheric magnetic measurements, and microwave imaging and spectroscopy data. The developed model offers a remarkable agreement between the synthesized and observed spectra and images in both X-ray and microwave domains, which validates the entire model. The flaring loop parameters are chosen to reproduce the emission measure, temperature, and the nonthermal electron distribution at low energies derived from the X-ray spectral fit, while the remaining parameters, unconstrained by the X-ray data, are selected such as to match the microwave images and total power spectra. The modeling suggests that the accelerated electrons are trapped in the coronal part of the flaring loop, but away from where the magnetic field is minimal, and, thus, demonstrates that the data are clearly inconsistent with electron magnetic trapping in the weak diffusion regime mediated by the Coulomb collisions. Thus, the modeling supports the interpretation of the coronal thick-target sources as sites of electron acceleration in flares and supplies us with a realistic 3D model with physical parameters of the acceleration region and flaring loop.

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“…This is accompanied by a non-imaging radio polarimeter operating at nine fixed frequencies between 1 and 80 GHz. The Owens Valley Solar Array (OVSA) (Hurford et al 1984;Gary & Hurford 1999) has a smaller number of dishes but superior frequency coverage, operating at 86 fixed frequencies from 1 to 18 GHz. This allows the use of "frequency synthesis" (i.e., the interpretation of the measured (u,v)-plane 1 in terms of a model source spectrum) to augment the coverage in the (u,v)-plane to a certain extent.…”

Section: Radiomentioning

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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A frequency-agile interferometer for solar microwave spectroscopy

Cited by 51 publications

References 9 publications

A New Solar Burst Spectral Component Emitting Only in the Terahertz Range

A New Solar Burst Spectral Component Emitting Only in the Terahertz Range

Validation of the Coronal Thick Target Source Model

An Observational Overview of Solar Flares

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