Second harmonic emission during solar flares

Type III (type U) radio bursts are signatures of energetic electrons generated during solar flares, traveling along open (closed) magnetic coronal field lines. The burst photons correspond to the second harmonic of the plasma frequency and are generated by the coalescence of two Langmuir waves excit...

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Guardado en:
Detalles Bibliográficos
Publicado: 2002
Materias:
Sun: flares
Sun: radio radiation
Turbulence
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v564_n2I_p1035_Vasquez
http://hdl.handle.net/20.500.12110/paper_0004637X_v564_n2I_p1035_Vasquez
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_0004637X_v564_n2I_p1035_Vasquez
record_format dspace
spelling paper:paper_0004637X_v564_n2I_p1035_Vasquez2023-06-08T14:28:44Z Second harmonic emission during solar flares Sun: flares Sun: radio radiation Turbulence Type III (type U) radio bursts are signatures of energetic electrons generated during solar flares, traveling along open (closed) magnetic coronal field lines. The burst photons correspond to the second harmonic of the plasma frequency and are generated by the coalescence of two Langmuir waves excited by the beam. In the present paper we derive expressions for the emissivity and absorption in the second harmonic of the plasma frequency without assuming the so-called head-on approximation. Only plasma wave isotropy is assumed. The resulting expressions yield important reductions in the emissivity when compared to the head-on results, as well as to lower absorption coefficients. We calculate second harmonic emissivities for several electron beam intensities. The spectrum of Langmuir turbulence used to compute second harmonic emissivity is consistently derived from a model that includes collisional effects and quasilinear relaxation. We speculate that further reductions in the emissivity, down to levels compatible with observations, would be obtained if nonlinear scattering of Langmuir waves with ion-acoustic turbulence and background density inhomogeneities are considered. 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v564_n2I_p1035_Vasquez http://hdl.handle.net/20.500.12110/paper_0004637X_v564_n2I_p1035_Vasquez
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Sun: flares
Sun: radio radiation
Turbulence
spellingShingle Sun: flares
Sun: radio radiation
Turbulence
Second harmonic emission during solar flares
topic_facet Sun: flares
Sun: radio radiation
Turbulence
description Type III (type U) radio bursts are signatures of energetic electrons generated during solar flares, traveling along open (closed) magnetic coronal field lines. The burst photons correspond to the second harmonic of the plasma frequency and are generated by the coalescence of two Langmuir waves excited by the beam. In the present paper we derive expressions for the emissivity and absorption in the second harmonic of the plasma frequency without assuming the so-called head-on approximation. Only plasma wave isotropy is assumed. The resulting expressions yield important reductions in the emissivity when compared to the head-on results, as well as to lower absorption coefficients. We calculate second harmonic emissivities for several electron beam intensities. The spectrum of Langmuir turbulence used to compute second harmonic emissivity is consistently derived from a model that includes collisional effects and quasilinear relaxation. We speculate that further reductions in the emissivity, down to levels compatible with observations, would be obtained if nonlinear scattering of Langmuir waves with ion-acoustic turbulence and background density inhomogeneities are considered.
title Second harmonic emission during solar flares
title_short Second harmonic emission during solar flares
title_full Second harmonic emission during solar flares
title_fullStr Second harmonic emission during solar flares
title_full_unstemmed Second harmonic emission during solar flares
title_sort second harmonic emission during solar flares
publishDate 2002
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v564_n2I_p1035_Vasquez
http://hdl.handle.net/20.500.12110/paper_0004637X_v564_n2I_p1035_Vasquez
_version_ 1768541730917842944

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