Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images
We demonstrate that high-resolution 557.7-nm all-sky images are useful tools for investigating the spatial and temporal evolution of merging on the dayside magnetopause. Analysis of ground and satellite measurements leads us to conclude that high-latitude merging events can occur at multiple sites s...
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ftdoajarticles:oai:doaj.org/article:0972cecd16f94e358b5163fd34099d92 2023-05-15T17:48:28+02:00 Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images N. C. Maynard J. Moen W. J. Burke M. Lester D. M. Ober J. D. Scudder K. D. Siebert D. R. Weimer C. T. Russell A. Balogh 2004-09-01T00:00:00Z https://doi.org/10.5194/angeo-22-2917-2004 https://doaj.org/article/0972cecd16f94e358b5163fd34099d92 EN eng Copernicus Publications https://www.ann-geophys.net/22/2917/2004/angeo-22-2917-2004.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-22-2917-2004 0992-7689 1432-0576 https://doaj.org/article/0972cecd16f94e358b5163fd34099d92 Annales Geophysicae, Vol 22, Pp 2917-2942 (2004) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2004 ftdoajarticles https://doi.org/10.5194/angeo-22-2917-2004 2022-12-31T14:27:12Z We demonstrate that high-resolution 557.7-nm all-sky images are useful tools for investigating the spatial and temporal evolution of merging on the dayside magnetopause. Analysis of ground and satellite measurements leads us to conclude that high-latitude merging events can occur at multiple sites simultaneously and vary asynchronously on time scales of 30s to 3min. Variations of 557.7nm emissions were observed at a 10s cadence at Ny-Ålesund on 19 December 2001, while significant changes in the IMF clock angle were reaching the magnetopause. The optical patterns are consistent with a scenario in which merging occurs around the rim of the high-latitude cusp at positions dictated by the IMF clock angle. Electrons energized at merging sites represent plausible sources for 557.7nm emissions in the cusp. Polar observations at the magnetopause have directly linked enhanced fluxes of ≥0.5keV electrons with merging. Spectra of electrons responsible for some of the emissions, measured during a DMSP F15 overflight, exhibit "inverted-V" features, indicating further acceleration above the ionosphere. SuperDARN spectral width boundaries, characteristic of open-closed field line transitions, are located at the equatorward edge of the 557.7nm emissions. Optical data suggest that with IMF B Y >0, the Northern Hemisphere cusp divides into three source regions. When the IMF clock angle was ~150° structured 557.7-nm emissions came from east of the 13:00MLT meridian. At larger clock angles the emissions appeared between 12:00 and 13:00MLT. No significant 557.7-nm emissions were detected in the prenoon MLT sector. MHD simulations corroborate our scenario, showing that with the observed large dipole-tilt and IMF clock angles, merging sites develop near the front and eastern portions of the high-altitude cusp rim in the Northern Hemisphere and near the western part of the cusp rim in the Southern Hemisphere. Article in Journal/Newspaper Ny Ålesund Ny-Ålesund Directory of Open Access Journals: DOAJ Articles Ny-Ålesund Annales Geophysicae 22 8 2917 2942 |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
spellingShingle |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 N. C. Maynard J. Moen W. J. Burke M. Lester D. M. Ober J. D. Scudder K. D. Siebert D. R. Weimer C. T. Russell A. Balogh Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
We demonstrate that high-resolution 557.7-nm all-sky images are useful tools for investigating the spatial and temporal evolution of merging on the dayside magnetopause. Analysis of ground and satellite measurements leads us to conclude that high-latitude merging events can occur at multiple sites simultaneously and vary asynchronously on time scales of 30s to 3min. Variations of 557.7nm emissions were observed at a 10s cadence at Ny-Ålesund on 19 December 2001, while significant changes in the IMF clock angle were reaching the magnetopause. The optical patterns are consistent with a scenario in which merging occurs around the rim of the high-latitude cusp at positions dictated by the IMF clock angle. Electrons energized at merging sites represent plausible sources for 557.7nm emissions in the cusp. Polar observations at the magnetopause have directly linked enhanced fluxes of ≥0.5keV electrons with merging. Spectra of electrons responsible for some of the emissions, measured during a DMSP F15 overflight, exhibit "inverted-V" features, indicating further acceleration above the ionosphere. SuperDARN spectral width boundaries, characteristic of open-closed field line transitions, are located at the equatorward edge of the 557.7nm emissions. Optical data suggest that with IMF B Y >0, the Northern Hemisphere cusp divides into three source regions. When the IMF clock angle was ~150° structured 557.7-nm emissions came from east of the 13:00MLT meridian. At larger clock angles the emissions appeared between 12:00 and 13:00MLT. No significant 557.7-nm emissions were detected in the prenoon MLT sector. MHD simulations corroborate our scenario, showing that with the observed large dipole-tilt and IMF clock angles, merging sites develop near the front and eastern portions of the high-altitude cusp rim in the Northern Hemisphere and near the western part of the cusp rim in the Southern Hemisphere. |
format |
Article in Journal/Newspaper |
author |
N. C. Maynard J. Moen W. J. Burke M. Lester D. M. Ober J. D. Scudder K. D. Siebert D. R. Weimer C. T. Russell A. Balogh |
author_facet |
N. C. Maynard J. Moen W. J. Burke M. Lester D. M. Ober J. D. Scudder K. D. Siebert D. R. Weimer C. T. Russell A. Balogh |
author_sort |
N. C. Maynard |
title |
Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
title_short |
Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
title_full |
Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
title_fullStr |
Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
title_full_unstemmed |
Temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
title_sort |
temporal-spatial structure of magnetic merging at the magnetopause inferred from 557.7-nm all-sky images |
publisher |
Copernicus Publications |
publishDate |
2004 |
url |
https://doi.org/10.5194/angeo-22-2917-2004 https://doaj.org/article/0972cecd16f94e358b5163fd34099d92 |
geographic |
Ny-Ålesund |
geographic_facet |
Ny-Ålesund |
genre |
Ny Ålesund Ny-Ålesund |
genre_facet |
Ny Ålesund Ny-Ålesund |
op_source |
Annales Geophysicae, Vol 22, Pp 2917-2942 (2004) |
op_relation |
https://www.ann-geophys.net/22/2917/2004/angeo-22-2917-2004.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-22-2917-2004 0992-7689 1432-0576 https://doaj.org/article/0972cecd16f94e358b5163fd34099d92 |
op_doi |
https://doi.org/10.5194/angeo-22-2917-2004 |
container_title |
Annales Geophysicae |
container_volume |
22 |
container_issue |
8 |
container_start_page |
2917 |
op_container_end_page |
2942 |
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1766154553925828608 |