Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate
International audience Using data from the EISCAT (European Incoherent Scatter) VHF and CUTLASS (Co-operative UK Twin-Located Auroral Sounding System) HF radars, we study the formation of ionospheric polar cap patches and their relationship to the magnetopause reconnection pulses identified in the c...
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Online Access: | https://hal.science/hal-00318075 https://hal.science/hal-00318075/document https://hal.science/hal-00318075/file/angeo-23-3513-2005.pdf |
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ftinsu:oai:HAL:hal-00318075v1 2023-11-12T04:16:36+01:00 Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate Lockwood, M. Davies, J. A. Moen, J. van Eyken, A. P. Oksavik, K. Mccrea, I. W. Lester, M. STFC Rutherford Appleton Laboratory (RAL) Science and Technology Facilities Council (STFC) Department of Physics Oslo Faculty of Mathematics and Natural Sciences Oslo University of Oslo (UiO)-University of Oslo (UiO) EISCAT Headquarters Department of Physics and Astronomy Leicester University of Leicester 2005-12-21 https://hal.science/hal-00318075 https://hal.science/hal-00318075/document https://hal.science/hal-00318075/file/angeo-23-3513-2005.pdf en eng HAL CCSD European Geosciences Union hal-00318075 https://hal.science/hal-00318075 https://hal.science/hal-00318075/document https://hal.science/hal-00318075/file/angeo-23-3513-2005.pdf info:eu-repo/semantics/OpenAccess ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00318075 Annales Geophysicae, 2005, 23 (11), pp.3513-3532 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/article Journal articles 2005 ftinsu 2023-10-25T16:25:06Z International audience Using data from the EISCAT (European Incoherent Scatter) VHF and CUTLASS (Co-operative UK Twin-Located Auroral Sounding System) HF radars, we study the formation of ionospheric polar cap patches and their relationship to the magnetopause reconnection pulses identified in the companion paper by Lockwood et al. (2005). It is shown that the poleward-moving, high-concentration plasma patches observed in the ionosphere by EISCAT on 23 November 1999, as reported by Davies et al. (2002), were often associated with corresponding reconnection rate pulses. However, not all such pulses generated a patch and only within a limited MLT range (11:00-12:00 MLT) did a patch result from a reconnection pulse. Three proposed mechanisms for the production of patches, and of the concentration minima that separate them, are analysed and evaluated: (1) concentration enhancement within the patches by cusp/cleft precipitation; (2) plasma depletion in the minima between the patches by fast plasma flows; and (3) intermittent injection of photoionisation-enhanced plasma into the polar cap. We devise a test to distinguish between the effects of these mechanisms. Some of the events repeat too frequently to apply the test. Others have sufficiently long repeat periods and mechanism (3) is shown to be the only explanation of three of the longer-lived patches seen on this day. However, effect (2) also appears to contribute to some events. We conclude that plasma concentration gradients on the edges of the larger patches arise mainly from local time variations in the subauroral plasma, via the mechanism proposed by Lockwood et al. (2000). Article in Journal/Newspaper EISCAT Institut national des sciences de l'Univers: HAL-INSU Lockwood ENVELOPE(167.400,167.400,-84.150,-84.150) |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences Lockwood, M. Davies, J. A. Moen, J. van Eyken, A. P. Oksavik, K. Mccrea, I. W. Lester, M. Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience Using data from the EISCAT (European Incoherent Scatter) VHF and CUTLASS (Co-operative UK Twin-Located Auroral Sounding System) HF radars, we study the formation of ionospheric polar cap patches and their relationship to the magnetopause reconnection pulses identified in the companion paper by Lockwood et al. (2005). It is shown that the poleward-moving, high-concentration plasma patches observed in the ionosphere by EISCAT on 23 November 1999, as reported by Davies et al. (2002), were often associated with corresponding reconnection rate pulses. However, not all such pulses generated a patch and only within a limited MLT range (11:00-12:00 MLT) did a patch result from a reconnection pulse. Three proposed mechanisms for the production of patches, and of the concentration minima that separate them, are analysed and evaluated: (1) concentration enhancement within the patches by cusp/cleft precipitation; (2) plasma depletion in the minima between the patches by fast plasma flows; and (3) intermittent injection of photoionisation-enhanced plasma into the polar cap. We devise a test to distinguish between the effects of these mechanisms. Some of the events repeat too frequently to apply the test. Others have sufficiently long repeat periods and mechanism (3) is shown to be the only explanation of three of the longer-lived patches seen on this day. However, effect (2) also appears to contribute to some events. We conclude that plasma concentration gradients on the edges of the larger patches arise mainly from local time variations in the subauroral plasma, via the mechanism proposed by Lockwood et al. (2000). |
author2 |
STFC Rutherford Appleton Laboratory (RAL) Science and Technology Facilities Council (STFC) Department of Physics Oslo Faculty of Mathematics and Natural Sciences Oslo University of Oslo (UiO)-University of Oslo (UiO) EISCAT Headquarters Department of Physics and Astronomy Leicester University of Leicester |
format |
Article in Journal/Newspaper |
author |
Lockwood, M. Davies, J. A. Moen, J. van Eyken, A. P. Oksavik, K. Mccrea, I. W. Lester, M. |
author_facet |
Lockwood, M. Davies, J. A. Moen, J. van Eyken, A. P. Oksavik, K. Mccrea, I. W. Lester, M. |
author_sort |
Lockwood, M. |
title |
Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
title_short |
Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
title_full |
Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
title_fullStr |
Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
title_full_unstemmed |
Motion of the dayside polar cap boundary during substorm cycles: II. Generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
title_sort |
motion of the dayside polar cap boundary during substorm cycles: ii. generation of poleward-moving events and polar cap patches by pulses in the magnetopause reconnection rate |
publisher |
HAL CCSD |
publishDate |
2005 |
url |
https://hal.science/hal-00318075 https://hal.science/hal-00318075/document https://hal.science/hal-00318075/file/angeo-23-3513-2005.pdf |
long_lat |
ENVELOPE(167.400,167.400,-84.150,-84.150) |
geographic |
Lockwood |
geographic_facet |
Lockwood |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
ISSN: 0992-7689 EISSN: 1432-0576 Annales Geophysicae https://hal.science/hal-00318075 Annales Geophysicae, 2005, 23 (11), pp.3513-3532 |
op_relation |
hal-00318075 https://hal.science/hal-00318075 https://hal.science/hal-00318075/document https://hal.science/hal-00318075/file/angeo-23-3513-2005.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782333669082398720 |