Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude
Interhemispheric conjugacy of auroral poleward expansion was studied using conjugate imaging riometers at ~67° inv. (invariant latitude) (Syowa Station, Antarctica, and Tjomes, Iceland) and at 75-77° inv. (Zhongshan Station, Antarctica; Longyearbyen, Svalbard and Danmarkshavn, Eastern Greenland). Ni...
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National Institute of Polar Research/Nagano JRC Co./National Institute of Polar Research/Solar-Terrestrial Environment Laboratory, Nagoya University/Danish Meteorological Institute/Polar Research Institute of China/Science Institute, University of Iceland
2000
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ftnipr:oai:nipr.repo.nii.ac.jp:00006300 2023-05-15T13:52:21+02:00 Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude Hisao Yamagishi Yuiti Fujita Natsuo Sato Masanori Nishino Peter Stauning Ruiyuan Liu Th. Saemundsson 2000-08 https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6300 http://id.nii.ac.jp/1291/00006300/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6300&item_no=1&attribute_id=18&file_no=1 en eng National Institute of Polar Research/Nagano JRC Co./National Institute of Polar Research/Solar-Terrestrial Environment Laboratory, Nagoya University/Danish Meteorological Institute/Polar Research Institute of China/Science Institute, University of Iceland National Institute of Polar Research https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6300 http://id.nii.ac.jp/1291/00006300/ AA11397422 Advances in polar upper atmosphere research, 14, 12-33(2000-08) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6300&item_no=1&attribute_id=18&file_no=1 Departmental Bulletin Paper P(論文) 2000 ftnipr 2023-03-18T20:23:29Z Interhemispheric conjugacy of auroral poleward expansion was studied using conjugate imaging riometers at ~67° inv. (invariant latitude) (Syowa Station, Antarctica, and Tjomes, Iceland) and at 75-77° inv. (Zhongshan Station, Antarctica; Longyearbyen, Svalbard and Danmarkshavn, Eastern Greenland). Ninety poleward expansion events at ~67° inv. observed in 1992-1993 were analyzed. The expansion at this latitude was characterized by a continuous poleward motion of cosmic noise absorption (CNA) bands with a velocity distribution that peaked at 1-1.5 km/s at a polar ionospheric altitude of ~90 km. The velocity distribution has another apparent peak at 3-5 km/s when measurements are made along the meridian. However, ~60% of the events forming this peak are overestimated because the motion of the CNA region's front was observed while the front was tilted away from the east-west direction. The difference in expansion velocities between conjugate stations remained within ±30% for half of the events. The time lag between the passage of a CNA band over conjugate stations was typically between 30-60 s. The product of this time lag and the poleward expanding velocity provides the location of the actual conjugate point. For 87% of the total number of events, the conjugate point for Syowa was located within ±200 km of Tjornes. The poleward expansion observed at 75°-77° inv. was characterized by a stepwise progression of CNA bands to higher latitudes. In other words, new CNA bands formed 50-180 km poleward of the preceding CNA band. The appearance of a new CNA band was often associated with an equatorward motion of the preceding CNA band. Equatorward moving CNA bands are thought to be located in a closed fieldline. The persistence of this band for several minutes was explained by pitch angle scattering of the trapped electrons as a result of a very stretched fieldline configuration in which the fieldline curvature was comparable to the Larmor radius of the trapped electrons. Although the conjugate pair used at these latitudes ... Report Antarc* Antarctica Danmarkshavn Greenland Iceland Longyearbyen Svalbard Advances in polar upper atmosphere research National Institute of Polar Research Repository, Japan Danmarkshavn ENVELOPE(-18.667,-18.667,76.767,76.767) Greenland Longyearbyen Svalbard Syowa Station Zhongshan ENVELOPE(76.371,76.371,-69.373,-69.373) Zhongshan Station ENVELOPE(76.371,76.371,-69.373,-69.373) |
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Open Polar |
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National Institute of Polar Research Repository, Japan |
op_collection_id |
ftnipr |
language |
English |
description |
Interhemispheric conjugacy of auroral poleward expansion was studied using conjugate imaging riometers at ~67° inv. (invariant latitude) (Syowa Station, Antarctica, and Tjomes, Iceland) and at 75-77° inv. (Zhongshan Station, Antarctica; Longyearbyen, Svalbard and Danmarkshavn, Eastern Greenland). Ninety poleward expansion events at ~67° inv. observed in 1992-1993 were analyzed. The expansion at this latitude was characterized by a continuous poleward motion of cosmic noise absorption (CNA) bands with a velocity distribution that peaked at 1-1.5 km/s at a polar ionospheric altitude of ~90 km. The velocity distribution has another apparent peak at 3-5 km/s when measurements are made along the meridian. However, ~60% of the events forming this peak are overestimated because the motion of the CNA region's front was observed while the front was tilted away from the east-west direction. The difference in expansion velocities between conjugate stations remained within ±30% for half of the events. The time lag between the passage of a CNA band over conjugate stations was typically between 30-60 s. The product of this time lag and the poleward expanding velocity provides the location of the actual conjugate point. For 87% of the total number of events, the conjugate point for Syowa was located within ±200 km of Tjornes. The poleward expansion observed at 75°-77° inv. was characterized by a stepwise progression of CNA bands to higher latitudes. In other words, new CNA bands formed 50-180 km poleward of the preceding CNA band. The appearance of a new CNA band was often associated with an equatorward motion of the preceding CNA band. Equatorward moving CNA bands are thought to be located in a closed fieldline. The persistence of this band for several minutes was explained by pitch angle scattering of the trapped electrons as a result of a very stretched fieldline configuration in which the fieldline curvature was comparable to the Larmor radius of the trapped electrons. Although the conjugate pair used at these latitudes ... |
format |
Report |
author |
Hisao Yamagishi Yuiti Fujita Natsuo Sato Masanori Nishino Peter Stauning Ruiyuan Liu Th. Saemundsson |
spellingShingle |
Hisao Yamagishi Yuiti Fujita Natsuo Sato Masanori Nishino Peter Stauning Ruiyuan Liu Th. Saemundsson Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
author_facet |
Hisao Yamagishi Yuiti Fujita Natsuo Sato Masanori Nishino Peter Stauning Ruiyuan Liu Th. Saemundsson |
author_sort |
Hisao Yamagishi |
title |
Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
title_short |
Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
title_full |
Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
title_fullStr |
Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
title_full_unstemmed |
Interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
title_sort |
interhemispheric conjugacy of auroral poleward expansion observed by conjugate imaging riometers at 67゜ and 75゜- 77゜ invariant latitude |
publisher |
National Institute of Polar Research/Nagano JRC Co./National Institute of Polar Research/Solar-Terrestrial Environment Laboratory, Nagoya University/Danish Meteorological Institute/Polar Research Institute of China/Science Institute, University of Iceland |
publishDate |
2000 |
url |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6300 http://id.nii.ac.jp/1291/00006300/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6300&item_no=1&attribute_id=18&file_no=1 |
long_lat |
ENVELOPE(-18.667,-18.667,76.767,76.767) ENVELOPE(76.371,76.371,-69.373,-69.373) ENVELOPE(76.371,76.371,-69.373,-69.373) |
geographic |
Danmarkshavn Greenland Longyearbyen Svalbard Syowa Station Zhongshan Zhongshan Station |
geographic_facet |
Danmarkshavn Greenland Longyearbyen Svalbard Syowa Station Zhongshan Zhongshan Station |
genre |
Antarc* Antarctica Danmarkshavn Greenland Iceland Longyearbyen Svalbard Advances in polar upper atmosphere research |
genre_facet |
Antarc* Antarctica Danmarkshavn Greenland Iceland Longyearbyen Svalbard Advances in polar upper atmosphere research |
op_relation |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=6300 http://id.nii.ac.jp/1291/00006300/ AA11397422 Advances in polar upper atmosphere research, 14, 12-33(2000-08) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=6300&item_no=1&attribute_id=18&file_no=1 |
_version_ |
1766256636000731136 |