Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence
The analysis investigates the base heights of the ionosphere (h′F) when spread-F is recorded at Brisbane, Australia, for 2 separate periods, namely July and August 1966 when spread-F occurs frequently and September and October 1966 when the activity is much lower. It is found that for July and Augus...
Published in: | Journal of Atmospheric and Terrestrial Physics |
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Language: | English |
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1984
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Online Access: | https://espace.library.uq.edu.au/view/UQ:404865 |
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ftunivqespace:oai:espace.library.uq.edu.au:UQ:404865 2023-05-15T17:09:58+02:00 Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence Bowman G.G. 1984-01-01 https://espace.library.uq.edu.au/view/UQ:404865 eng eng Elsevier BV doi:10.1016/0021-9169(84)90044-8 issn:0021-9169 General Engineering Atmospheric Science General Earth and Planetary Sciences Geophysics General Environmental Science 1902 Film Television and Digital Media 1908 Geophysics Journal Article 1984 ftunivqespace https://doi.org/10.1016/0021-9169(84)90044-8 2020-08-05T21:42:54Z The analysis investigates the base heights of the ionosphere (h′F) when spread-F is recorded at Brisbane, Australia, for 2 separate periods, namely July and August 1966 when spread-F occurs frequently and September and October 1966 when the activity is much lower. It is found that for July and August there is little tendency for spread-F to occur preferentially when the base height is above the average for the period. However, for the September-October period, spread-F occurs more often (by a factor of 2 or 3 depending on the geomagnetic activity) when the base height is above rather than below the average height. Also, this analysis shows that the overall spread-F occurrence (for both periods investigated) decreased to some extent following increased geomagnetic activity. This suppressed activity in the hours following geomagnetic activity is confirmed by superposed-epoch analyses using K indices (for Macquarie Island) as controls. It is suggested that the results of all the analyses might be explained by invoking a transition height in the ionosphere (controlled by the neutral-particle density of the upper atmosphere). Ionospheric off-vertical reflections from above this height would be recorded as spread-F traces in this model. This transition height would be low in July and August when the neutral-particle density is low and higher in September and October. It is further proposed that changes in the neutral-particle density could also be associated with reduced spread-F activity following increased geomagnetic activity, as well as influencing the diurnal, annual and sunspot-cycle variations of spread-F occurrence in mid-latitudes. Article in Journal/Newspaper Macquarie Island The University of Queensland: UQ eSpace Brisbane ENVELOPE(-45.633,-45.633,-60.600,-60.600) Journal of Atmospheric and Terrestrial Physics 46 1 55 64 |
institution |
Open Polar |
collection |
The University of Queensland: UQ eSpace |
op_collection_id |
ftunivqespace |
language |
English |
topic |
General Engineering Atmospheric Science General Earth and Planetary Sciences Geophysics General Environmental Science 1902 Film Television and Digital Media 1908 Geophysics |
spellingShingle |
General Engineering Atmospheric Science General Earth and Planetary Sciences Geophysics General Environmental Science 1902 Film Television and Digital Media 1908 Geophysics Bowman G.G. Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence |
topic_facet |
General Engineering Atmospheric Science General Earth and Planetary Sciences Geophysics General Environmental Science 1902 Film Television and Digital Media 1908 Geophysics |
description |
The analysis investigates the base heights of the ionosphere (h′F) when spread-F is recorded at Brisbane, Australia, for 2 separate periods, namely July and August 1966 when spread-F occurs frequently and September and October 1966 when the activity is much lower. It is found that for July and August there is little tendency for spread-F to occur preferentially when the base height is above the average for the period. However, for the September-October period, spread-F occurs more often (by a factor of 2 or 3 depending on the geomagnetic activity) when the base height is above rather than below the average height. Also, this analysis shows that the overall spread-F occurrence (for both periods investigated) decreased to some extent following increased geomagnetic activity. This suppressed activity in the hours following geomagnetic activity is confirmed by superposed-epoch analyses using K indices (for Macquarie Island) as controls. It is suggested that the results of all the analyses might be explained by invoking a transition height in the ionosphere (controlled by the neutral-particle density of the upper atmosphere). Ionospheric off-vertical reflections from above this height would be recorded as spread-F traces in this model. This transition height would be low in July and August when the neutral-particle density is low and higher in September and October. It is further proposed that changes in the neutral-particle density could also be associated with reduced spread-F activity following increased geomagnetic activity, as well as influencing the diurnal, annual and sunspot-cycle variations of spread-F occurrence in mid-latitudes. |
format |
Article in Journal/Newspaper |
author |
Bowman G.G. |
author_facet |
Bowman G.G. |
author_sort |
Bowman G.G. |
title |
Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence |
title_short |
Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence |
title_full |
Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence |
title_fullStr |
Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence |
title_full_unstemmed |
Some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-F occurrence |
title_sort |
some effects of geomagnetic activity and ionospheric height rises on mid-latitude spread-f occurrence |
publisher |
Elsevier BV |
publishDate |
1984 |
url |
https://espace.library.uq.edu.au/view/UQ:404865 |
long_lat |
ENVELOPE(-45.633,-45.633,-60.600,-60.600) |
geographic |
Brisbane |
geographic_facet |
Brisbane |
genre |
Macquarie Island |
genre_facet |
Macquarie Island |
op_relation |
doi:10.1016/0021-9169(84)90044-8 issn:0021-9169 |
op_doi |
https://doi.org/10.1016/0021-9169(84)90044-8 |
container_title |
Journal of Atmospheric and Terrestrial Physics |
container_volume |
46 |
container_issue |
1 |
container_start_page |
55 |
op_container_end_page |
64 |
_version_ |
1766066356701102080 |