Diurnal and seasonal occurrence of polar patches
Analysis of the diurnal and seasonal variation of polar patches, as identified in two years of HF-radar data from Halley, Antarctica during a period near sunspot maximum, shows that there is a broad maximum in occurrence centred about magnetic noon, not local noon. There are minima in occurrence nea...
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ftnerc:oai:nora.nerc.ac.uk:515272 2023-05-15T13:49:33+02:00 Diurnal and seasonal occurrence of polar patches Rodger, A. S. Graham, A. C. 1996 http://nora.nerc.ac.uk/id/eprint/515272/ https://doi.org/10.1007/s00585-996-0533-5 unknown Springer Rodger, A. S.; Graham, A. C. 1996 Diurnal and seasonal occurrence of polar patches. Annales Geophysicae, 14 (5). 533-537. https://doi.org/10.1007/s00585-996-0533-5 <https://doi.org/10.1007/s00585-996-0533-5> Publication - Article PeerReviewed 1996 ftnerc https://doi.org/10.1007/s00585-996-0533-5 2023-02-04T19:43:58Z Analysis of the diurnal and seasonal variation of polar patches, as identified in two years of HF-radar data from Halley, Antarctica during a period near sunspot maximum, shows that there is a broad maximum in occurrence centred about magnetic noon, not local noon. There are minima in occurrence near midsummer and midwinter, with maxima in occurrence between equinox and winter. There are no significant correlations between the occurrence of polar patches and the corresponding hourly averages of the solar wind and IMF parameters, except that patches usually occur when the interplanetary magnetic field has a southward component. The results can be understood in terms of UT and seasonal differences in the plasma concentration being convected from the dayside ionosphere into the polar cap. In summer and winter the electron concentrations in the polar cap are high and low, respectively, but relatively unstructured. About equinox, a tongue of enhanced ionisation is convected into the polar cap; this tongue is then structured by the effects of the interplanetary magnetic field, but these Halley data cannot be used to separate the various competing mechanisms for patch formation. The observed diurnal and seasonal variation in the occurrence of polar patches are largely consistent with predictions of Sojka et al. (1994) when their results are translated into the southern hemisphere. However, the ionospheric effects of flux transfer events are still considered essential in their formation, a feature not yet included in the Sojka et al. model. Article in Journal/Newspaper Antarc* Antarctica Natural Environment Research Council: NERC Open Research Archive Midwinter ENVELOPE(139.931,139.931,-66.690,-66.690) Annales Geophysicae 14 5 533 537 |
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Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
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ftnerc |
language |
unknown |
description |
Analysis of the diurnal and seasonal variation of polar patches, as identified in two years of HF-radar data from Halley, Antarctica during a period near sunspot maximum, shows that there is a broad maximum in occurrence centred about magnetic noon, not local noon. There are minima in occurrence near midsummer and midwinter, with maxima in occurrence between equinox and winter. There are no significant correlations between the occurrence of polar patches and the corresponding hourly averages of the solar wind and IMF parameters, except that patches usually occur when the interplanetary magnetic field has a southward component. The results can be understood in terms of UT and seasonal differences in the plasma concentration being convected from the dayside ionosphere into the polar cap. In summer and winter the electron concentrations in the polar cap are high and low, respectively, but relatively unstructured. About equinox, a tongue of enhanced ionisation is convected into the polar cap; this tongue is then structured by the effects of the interplanetary magnetic field, but these Halley data cannot be used to separate the various competing mechanisms for patch formation. The observed diurnal and seasonal variation in the occurrence of polar patches are largely consistent with predictions of Sojka et al. (1994) when their results are translated into the southern hemisphere. However, the ionospheric effects of flux transfer events are still considered essential in their formation, a feature not yet included in the Sojka et al. model. |
format |
Article in Journal/Newspaper |
author |
Rodger, A. S. Graham, A. C. |
spellingShingle |
Rodger, A. S. Graham, A. C. Diurnal and seasonal occurrence of polar patches |
author_facet |
Rodger, A. S. Graham, A. C. |
author_sort |
Rodger, A. S. |
title |
Diurnal and seasonal occurrence of polar patches |
title_short |
Diurnal and seasonal occurrence of polar patches |
title_full |
Diurnal and seasonal occurrence of polar patches |
title_fullStr |
Diurnal and seasonal occurrence of polar patches |
title_full_unstemmed |
Diurnal and seasonal occurrence of polar patches |
title_sort |
diurnal and seasonal occurrence of polar patches |
publisher |
Springer |
publishDate |
1996 |
url |
http://nora.nerc.ac.uk/id/eprint/515272/ https://doi.org/10.1007/s00585-996-0533-5 |
long_lat |
ENVELOPE(139.931,139.931,-66.690,-66.690) |
geographic |
Midwinter |
geographic_facet |
Midwinter |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_relation |
Rodger, A. S.; Graham, A. C. 1996 Diurnal and seasonal occurrence of polar patches. Annales Geophysicae, 14 (5). 533-537. https://doi.org/10.1007/s00585-996-0533-5 <https://doi.org/10.1007/s00585-996-0533-5> |
op_doi |
https://doi.org/10.1007/s00585-996-0533-5 |
container_title |
Annales Geophysicae |
container_volume |
14 |
container_issue |
5 |
container_start_page |
533 |
op_container_end_page |
537 |
_version_ |
1766251597241778176 |