Large-scale coordinated observations of Pc5 pulsation events
HF (high-frequency) radars belonging to SuperDARN (Super Dual Auroral Radar Network) receive backscatter over substantial fields of view which, when combined, allow for simultaneous returns over extensive regions of the polar caps and midlatitudes. This makes them ideal instruments for the observ...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2016-09-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/34/857/2016/angeo-34-857-2016.pdf |
| _version_ | 1818985090669084672 |
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| author | Z. Mtumela A. D. M. Walker J. A. E. Stephenson M. J. Kosch M. J. Kosch M. J. Kosch |
| author_facet | Z. Mtumela A. D. M. Walker J. A. E. Stephenson M. J. Kosch M. J. Kosch M. J. Kosch |
| author_sort | Z. Mtumela |
| collection | DOAJ |
| description | HF (high-frequency) radars belonging to SuperDARN (Super Dual Auroral Radar Network) receive backscatter over
substantial fields of view which, when combined, allow for
simultaneous returns over extensive regions of the polar caps and midlatitudes.
This makes them ideal instruments for the observation of pulsations in the
Pc5 (1–5 mHz) frequency band. Relatively few pulsation
events observed by multiple radars have been reported in the literature. Here we
describe observations of three such events which extend over more than
120° of magnetic longitude in the Northern Hemisphere and one of which is also detected in the Southern Hemisphere. All three events show
characteristics of field line resonances. In one case the pulsation has also
been observed by magnetometers under or near the radar fields of view. The
extensive longitudinal coverage allows accurate determination of azimuthal wave
numbers. These are at the upper end of the lower values associated with
external sources such as those in the solar wind. Such sources imply
antisunward flow. However, the azimuthal wave number is negative, implying
westward propagation at magnetic local times on both sides of noon, as would be
expected from drift–bounce resonance with positive particles. Quiet conditions
and a very low ring current during the events argue against this. The
identification of the source of pulsations from a number of different
mechanisms remains a problem of interest. |
| first_indexed | 2024-12-20T18:29:22Z |
| format | Article |
| id | doaj.art-dd15b92018a64fa0919a2d6aaaefac0f |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-20T18:29:22Z |
| publishDate | 2016-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-dd15b92018a64fa0919a2d6aaaefac0f2022-12-21T19:30:06ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762016-09-013485787010.5194/angeo-34-857-2016Large-scale coordinated observations of Pc5 pulsation eventsZ. Mtumela0A. D. M. Walker1J. A. E. Stephenson2M. J. Kosch3M. J. Kosch4M. J. Kosch5South African National Space Agency (SANSA), Space Science, P.O. Box 32, Hermanus, 7200, South AfricaSchool of Chemistry and Physics, University of KwaZulu-Natal, P/Bag X54001, Durban, 4000, South AfricaSchool of Chemistry and Physics, University of KwaZulu-Natal, P/Bag X54001, Durban, 4000, South AfricaSouth African National Space Agency (SANSA), Space Science, P.O. Box 32, Hermanus, 7200, South AfricaLancaster University, Lancaster, LA1 4YB, UKUniversity of the Western Cape, Cape Town, 7535, South AfricaHF (high-frequency) radars belonging to SuperDARN (Super Dual Auroral Radar Network) receive backscatter over substantial fields of view which, when combined, allow for simultaneous returns over extensive regions of the polar caps and midlatitudes. This makes them ideal instruments for the observation of pulsations in the Pc5 (1–5 mHz) frequency band. Relatively few pulsation events observed by multiple radars have been reported in the literature. Here we describe observations of three such events which extend over more than 120° of magnetic longitude in the Northern Hemisphere and one of which is also detected in the Southern Hemisphere. All three events show characteristics of field line resonances. In one case the pulsation has also been observed by magnetometers under or near the radar fields of view. The extensive longitudinal coverage allows accurate determination of azimuthal wave numbers. These are at the upper end of the lower values associated with external sources such as those in the solar wind. Such sources imply antisunward flow. However, the azimuthal wave number is negative, implying westward propagation at magnetic local times on both sides of noon, as would be expected from drift–bounce resonance with positive particles. Quiet conditions and a very low ring current during the events argue against this. The identification of the source of pulsations from a number of different mechanisms remains a problem of interest.https://www.ann-geophys.net/34/857/2016/angeo-34-857-2016.pdf |
| spellingShingle | Z. Mtumela A. D. M. Walker J. A. E. Stephenson M. J. Kosch M. J. Kosch M. J. Kosch Large-scale coordinated observations of Pc5 pulsation events Annales Geophysicae |
| title | Large-scale coordinated observations of Pc5 pulsation
events |
| title_full | Large-scale coordinated observations of Pc5 pulsation
events |
| title_fullStr | Large-scale coordinated observations of Pc5 pulsation
events |
| title_full_unstemmed | Large-scale coordinated observations of Pc5 pulsation
events |
| title_short | Large-scale coordinated observations of Pc5 pulsation
events |
| title_sort | large scale coordinated observations of pc5 pulsation events |
| url | https://www.ann-geophys.net/34/857/2016/angeo-34-857-2016.pdf |
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