The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions
Recent work suggests that the quasi-periodic (QP) modulation ~10–50 s of naturally occurring ELF-VLF radio emissions (~0.5–5 kHz) is produced by the compressional action of Pc3 magnetic pulsations on the source of the emissions. Whilst it is generally accepted that these magnetic pulsations have an...
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ftdoajarticles:oai:doaj.org/article:17efb3f1c60f443cbbd4faf391a7cb00 2023-05-15T13:51:50+02:00 The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions K. Morrison M. P. Freeman 1995-11-01T00:00:00Z https://doi.org/10.1007/s00585-995-1127-3 https://doaj.org/article/17efb3f1c60f443cbbd4faf391a7cb00 EN eng Copernicus Publications https://www.ann-geophys.net/13/1127/1995/angeo-13-1127-1995.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.1007/s00585-995-1127-3 0992-7689 1432-0576 https://doaj.org/article/17efb3f1c60f443cbbd4faf391a7cb00 Annales Geophysicae, Vol 13, Pp 1127-1133 (1995) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 1995 ftdoajarticles https://doi.org/10.1007/s00585-995-1127-3 2022-12-31T07:02:23Z Recent work suggests that the quasi-periodic (QP) modulation ~10–50 s of naturally occurring ELF-VLF radio emissions (~0.5–5 kHz) is produced by the compressional action of Pc3 magnetic pulsations on the source of the emissions. Whilst it is generally accepted that these magnetic pulsations have an exogenic source, it is not clear what the mechanism of their generation is. A study of QP emissions observed during 1988 at Halley, Antarctica, in conjunction with IMP-8 satellite solar wind data, shows that the occurrence and modulation frequency of the emissions are strongly dependent upon the direction and strength of the IMF, respectively. The observed relationships are very similar to those previously reported for Pc3 pulsations associated with upstream ion-cyclotron resonance, involving proton beams reflected at the bowshock. In comparing the observed QP modulation frequencies with upstream wave theory, agreement was found by considering wave excitation exclusively associated with a proton beam reflected from a position on the bowshock at which the shock normal is parallel to the ambient IMF direction. Other geometries were found to be either impropitious or uncertain. The work indicates the useful diagnostic role QP emissions could play in the study of compressional ULF waves in the upstream solar wind and in monitoring the IMF conditions responsible for their generation. Article in Journal/Newspaper Antarc* Antarctica Directory of Open Access Journals: DOAJ Articles Annales Geophysicae 13 11 1127 1133 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
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ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
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Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 K. Morrison M. P. Freeman The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
Recent work suggests that the quasi-periodic (QP) modulation ~10–50 s of naturally occurring ELF-VLF radio emissions (~0.5–5 kHz) is produced by the compressional action of Pc3 magnetic pulsations on the source of the emissions. Whilst it is generally accepted that these magnetic pulsations have an exogenic source, it is not clear what the mechanism of their generation is. A study of QP emissions observed during 1988 at Halley, Antarctica, in conjunction with IMP-8 satellite solar wind data, shows that the occurrence and modulation frequency of the emissions are strongly dependent upon the direction and strength of the IMF, respectively. The observed relationships are very similar to those previously reported for Pc3 pulsations associated with upstream ion-cyclotron resonance, involving proton beams reflected at the bowshock. In comparing the observed QP modulation frequencies with upstream wave theory, agreement was found by considering wave excitation exclusively associated with a proton beam reflected from a position on the bowshock at which the shock normal is parallel to the ambient IMF direction. Other geometries were found to be either impropitious or uncertain. The work indicates the useful diagnostic role QP emissions could play in the study of compressional ULF waves in the upstream solar wind and in monitoring the IMF conditions responsible for their generation. |
format |
Article in Journal/Newspaper |
author |
K. Morrison M. P. Freeman |
author_facet |
K. Morrison M. P. Freeman |
author_sort |
K. Morrison |
title |
The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions |
title_short |
The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions |
title_full |
The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions |
title_fullStr |
The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions |
title_full_unstemmed |
The role of upstream ULF waves in the generation of quasi-periodic ELF-VLF emissions |
title_sort |
role of upstream ulf waves in the generation of quasi-periodic elf-vlf emissions |
publisher |
Copernicus Publications |
publishDate |
1995 |
url |
https://doi.org/10.1007/s00585-995-1127-3 https://doaj.org/article/17efb3f1c60f443cbbd4faf391a7cb00 |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_source |
Annales Geophysicae, Vol 13, Pp 1127-1133 (1995) |
op_relation |
https://www.ann-geophys.net/13/1127/1995/angeo-13-1127-1995.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.1007/s00585-995-1127-3 0992-7689 1432-0576 https://doaj.org/article/17efb3f1c60f443cbbd4faf391a7cb00 |
op_doi |
https://doi.org/10.1007/s00585-995-1127-3 |
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Annales Geophysicae |
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13 |
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11 |
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1127 |
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1133 |
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