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Article: Imaging spectroscopy of solar microwave radiation. I. Flaring emission

TitleImaging spectroscopy of solar microwave radiation. I. Flaring emission
Authors
KeywordsSun: Corona
Sun: Flares
Sun: Radio Radiation
Sun: X-Rays, Gamma Rays
Issue Date1994
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205
Citation
Astrophysical Journal Letters, 1994, v. 430 n. 1, p. 425-434 How to Cite?
AbstractWe present observations of an impulsive microwave burst on the Sun with both high spatial and spectral resolution, made with the Solar Array at the Owens Valley Radio Observatory. The burst was imaged in total intensity, as well as both right and left circular polarization, at 24 frequencies distributed logarithmically over the range 2.4-14.0 GHz, with spatial resolution ranging from ∼5″-29″. This powerful new technique for studying microwave bursts shows that: (1) even a relatively weak burst with a simple temporal and spectral morphology in total power can have a complex spatial structure, comprising three distinct sources; (2) the burst structure changes with frequency so that images at widely spaced frequencies show a different number and/or location of sources, whereas images at closely spaced frequencies reveal the relationship between sources at different frequencies; and (3) the brightness temperature spectrum of each source is different, so that the composite total-power spectrum is not representative of the spectrum of any individual source. We used the measured brightness temperature spectrum to infer the emission process responsible for each microwave source, and to derive physical conditions in the source region. We confirmed our predictions using soft X-ray measurements from GOES, soft X-ray images from Yohkoh, and Ha flare images together with sunspot and magnetogram images from the Big Bear Solar Observatory. The primary microwave source, located close to but not coincident with either the lone flaring soft X-ray kernel or primary Ha kernel, had a peak brightness temperature of only ∼ 10 7 K, but nevertheless was produced by nonthermal gyrosynchrotron emission. The two secondary sources, both without any soft X-ray or Hα counterparts, had lower turnover frequencies but also were produced by nonthermal gyrosynchrotron emission. These sources were connected to the primary flare site by magnetic loops visible in soft X-rays, suggesting that their nonthermal electrons escaped from the primary microwave source.
Persistent Identifierhttp://hdl.handle.net/10722/174914
ISSN
2015 Impact Factor: 5.487
2015 SCImago Journal Rankings: 3.369

 

DC FieldValueLanguage
dc.contributor.authorLim, Jen_US
dc.contributor.authorGary, DEen_US
dc.contributor.authorHurford, GJen_US
dc.contributor.authorLemen, JRen_US
dc.date.accessioned2012-11-26T08:48:05Z-
dc.date.available2012-11-26T08:48:05Z-
dc.date.issued1994en_US
dc.identifier.citationAstrophysical Journal Letters, 1994, v. 430 n. 1, p. 425-434en_US
dc.identifier.issn2041-8205en_US
dc.identifier.urihttp://hdl.handle.net/10722/174914-
dc.description.abstractWe present observations of an impulsive microwave burst on the Sun with both high spatial and spectral resolution, made with the Solar Array at the Owens Valley Radio Observatory. The burst was imaged in total intensity, as well as both right and left circular polarization, at 24 frequencies distributed logarithmically over the range 2.4-14.0 GHz, with spatial resolution ranging from ∼5″-29″. This powerful new technique for studying microwave bursts shows that: (1) even a relatively weak burst with a simple temporal and spectral morphology in total power can have a complex spatial structure, comprising three distinct sources; (2) the burst structure changes with frequency so that images at widely spaced frequencies show a different number and/or location of sources, whereas images at closely spaced frequencies reveal the relationship between sources at different frequencies; and (3) the brightness temperature spectrum of each source is different, so that the composite total-power spectrum is not representative of the spectrum of any individual source. We used the measured brightness temperature spectrum to infer the emission process responsible for each microwave source, and to derive physical conditions in the source region. We confirmed our predictions using soft X-ray measurements from GOES, soft X-ray images from Yohkoh, and Ha flare images together with sunspot and magnetogram images from the Big Bear Solar Observatory. The primary microwave source, located close to but not coincident with either the lone flaring soft X-ray kernel or primary Ha kernel, had a peak brightness temperature of only ∼ 10 7 K, but nevertheless was produced by nonthermal gyrosynchrotron emission. The two secondary sources, both without any soft X-ray or Hα counterparts, had lower turnover frequencies but also were produced by nonthermal gyrosynchrotron emission. These sources were connected to the primary flare site by magnetic loops visible in soft X-rays, suggesting that their nonthermal electrons escaped from the primary microwave source.en_US
dc.languageengen_US
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205en_US
dc.relation.ispartofAstrophysical Journal Lettersen_US
dc.subjectSun: Coronaen_US
dc.subjectSun: Flaresen_US
dc.subjectSun: Radio Radiationen_US
dc.subjectSun: X-Rays, Gamma Raysen_US
dc.titleImaging spectroscopy of solar microwave radiation. I. Flaring emissionen_US
dc.typeArticleen_US
dc.identifier.emailLim, J: jjlim@hku.hken_US
dc.identifier.authorityLim, J=rp00745en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-12044255908en_US
dc.identifier.volume430en_US
dc.identifier.issue1en_US
dc.identifier.spage425en_US
dc.identifier.epage434en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridLim, J=7403453870en_US
dc.identifier.scopusauthoridGary, DE=7005231589en_US
dc.identifier.scopusauthoridHurford, GJ=7003316944en_US
dc.identifier.scopusauthoridLemen, JR=7003810570en_US

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