ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes
We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Åles...
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ftdoajarticles:oai:doaj.org/article:28f203c139b147f59137fde21a5b7c03 2023-05-15T16:04:32+02:00 ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes I. W. McCrea M. Lockwood J. Moen F. Pitout P. Eglitis A. D. Aylward J.-C. Cerisier A. Thorolfssen S. E. Milan 2000-09-01T00:00:00Z https://doi.org/10.1007/s00585-000-1009-7 https://doaj.org/article/28f203c139b147f59137fde21a5b7c03 EN eng Copernicus Publications https://www.ann-geophys.net/18/1009/2000/angeo-18-1009-2000.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.1007/s00585-000-1009-7 0992-7689 1432-0576 https://doaj.org/article/28f203c139b147f59137fde21a5b7c03 Annales Geophysicae, Vol 18, Pp 1009-1026 (2000) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2000 ftdoajarticles https://doi.org/10.1007/s00585-000-1009-7 2022-12-31T12:19:40Z We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Ålesund and of HF radar backscatter, as observed by the CUTLASS radar. We study the response to an interval of about one hour when the interplanetary magnetic field (IMF), monitored by the WIND and ACE spacecraft, was southward. The cusp/cleft aurora is shown to correspond to a spatially extended region of elevated electron temperatures in the VHF radar data. Initial conditions were characterised by a northward-directed IMF and cusp/cleft aurora poleward of the ESR. A strong southward turning then occurred, causing an equatorward motion of the cusp/cleft aurora. Within the equatorward expanding, southward-IMF cusp/cleft, the ESR observed structured and elevated plasma densities and ion and electron temperatures. Cleft ion fountain upflows were seen in association with elevated ion temperatures and rapid eastward convection, consistent with the magnetic curvature force on newly opened field lines for the observed negative IMF B y . Subsequently, the ESR beam remained immediately poleward of the main cusp/cleft and a sequence of poleward-moving auroral transients passed over it. After the last of these, the ESR was in the polar cap and the radar observations were characterised by extremely low ionospheric densities and downward field-aligned flows. The IMF then turned northward again and the auroral oval contracted such that the ESR moved back into the cusp/cleft region. For the poleward-retreating, northward-IMF cusp/cleft, the convection flows were slower, upflows were weaker and the electron density and temperature enhancements were less structured. Following the northward turning, the bands of high electron temperature and cusp/cleft aurora bifurcated, consistent with both subsolar and lobe reconnection taking place ... Article in Journal/Newspaper EISCAT Ny Ålesund Ny-Ålesund Svalbard Tromsø Directory of Open Access Journals: DOAJ Articles Ny-Ålesund Svalbard Tromsø Annales Geophysicae 18 9 1009 1026 |
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Open Polar |
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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 I. W. McCrea M. Lockwood J. Moen F. Pitout P. Eglitis A. D. Aylward J.-C. Cerisier A. Thorolfssen S. E. Milan ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Ålesund and of HF radar backscatter, as observed by the CUTLASS radar. We study the response to an interval of about one hour when the interplanetary magnetic field (IMF), monitored by the WIND and ACE spacecraft, was southward. The cusp/cleft aurora is shown to correspond to a spatially extended region of elevated electron temperatures in the VHF radar data. Initial conditions were characterised by a northward-directed IMF and cusp/cleft aurora poleward of the ESR. A strong southward turning then occurred, causing an equatorward motion of the cusp/cleft aurora. Within the equatorward expanding, southward-IMF cusp/cleft, the ESR observed structured and elevated plasma densities and ion and electron temperatures. Cleft ion fountain upflows were seen in association with elevated ion temperatures and rapid eastward convection, consistent with the magnetic curvature force on newly opened field lines for the observed negative IMF B y . Subsequently, the ESR beam remained immediately poleward of the main cusp/cleft and a sequence of poleward-moving auroral transients passed over it. After the last of these, the ESR was in the polar cap and the radar observations were characterised by extremely low ionospheric densities and downward field-aligned flows. The IMF then turned northward again and the auroral oval contracted such that the ESR moved back into the cusp/cleft region. For the poleward-retreating, northward-IMF cusp/cleft, the convection flows were slower, upflows were weaker and the electron density and temperature enhancements were less structured. Following the northward turning, the bands of high electron temperature and cusp/cleft aurora bifurcated, consistent with both subsolar and lobe reconnection taking place ... |
format |
Article in Journal/Newspaper |
author |
I. W. McCrea M. Lockwood J. Moen F. Pitout P. Eglitis A. D. Aylward J.-C. Cerisier A. Thorolfssen S. E. Milan |
author_facet |
I. W. McCrea M. Lockwood J. Moen F. Pitout P. Eglitis A. D. Aylward J.-C. Cerisier A. Thorolfssen S. E. Milan |
author_sort |
I. W. McCrea |
title |
ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes |
title_short |
ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes |
title_full |
ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes |
title_fullStr |
ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes |
title_full_unstemmed |
ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes |
title_sort |
esr and eiscat observations of the response of the cusp and cleft to imf orientation changes |
publisher |
Copernicus Publications |
publishDate |
2000 |
url |
https://doi.org/10.1007/s00585-000-1009-7 https://doaj.org/article/28f203c139b147f59137fde21a5b7c03 |
geographic |
Ny-Ålesund Svalbard Tromsø |
geographic_facet |
Ny-Ålesund Svalbard Tromsø |
genre |
EISCAT Ny Ålesund Ny-Ålesund Svalbard Tromsø |
genre_facet |
EISCAT Ny Ålesund Ny-Ålesund Svalbard Tromsø |
op_source |
Annales Geophysicae, Vol 18, Pp 1009-1026 (2000) |
op_relation |
https://www.ann-geophys.net/18/1009/2000/angeo-18-1009-2000.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.1007/s00585-000-1009-7 0992-7689 1432-0576 https://doaj.org/article/28f203c139b147f59137fde21a5b7c03 |
op_doi |
https://doi.org/10.1007/s00585-000-1009-7 |
container_title |
Annales Geophysicae |
container_volume |
18 |
container_issue |
9 |
container_start_page |
1009 |
op_container_end_page |
1026 |
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1766400125757816832 |