Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study
A period (08:10–14:40 MLT, 11 February 1997) of enhanced electron density in the D- and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift ea...
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ftdoajarticles:oai:doaj.org/article:4f07ecffa5644bd3adaa3cc2320c6aa8 2023-05-15T16:04:39+02:00 Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study A. J. Kavanagh F. Honary I. W. McCrea E. Donovan E. E. Woodfield J. Manninen P. C. Anderson 2002-09-01T00:00:00Z https://doi.org/10.5194/angeo-20-1321-2002 https://doaj.org/article/4f07ecffa5644bd3adaa3cc2320c6aa8 EN eng Copernicus Publications https://www.ann-geophys.net/20/1321/2002/angeo-20-1321-2002.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-20-1321-2002 0992-7689 1432-0576 https://doaj.org/article/4f07ecffa5644bd3adaa3cc2320c6aa8 Annales Geophysicae, Vol 20, Pp 1321-1334 (2002) Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 article 2002 ftdoajarticles https://doi.org/10.5194/angeo-20-1321-2002 2022-12-31T15:55:46Z A period (08:10–14:40 MLT, 11 February 1997) of enhanced electron density in the D- and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift eastward after substorm injection and precipitate in the morning sector. The precipitation is triggered by small pulses in the solar wind pressure, which drive wave particle interactions. The characteristic energy of precipitation is inferred from drift timing on different L-shells and apparently verified by EISCAT measurements. The IMF influence on the precipitation in the auroral zone is also briefly discussed. A large change in the precipitation spectrum is attributed to increased numbers of ions and much reduced electron fluxes. These are detected by a close passing DMSP satellite. The possibility that these ions are from the low latitude boundary layer (LLBL) is discussed with reference to structured narrow band Pc1 waves observed by a search coil magnetometer, co-located with IRIS. The intensity of the waves grows with increased distance equatorward of the cusp position (determined by both satellite and HF radar), contrary to expectations if the precipitation is linked to the LLBL. It is suggested that the ion precipitation is, instead, due to the recovery phase of a small geomagnetic storm, following on from very active conditions. The movement of absorption in the later stages of the event is compared with observations of the ionospheric convection velocities. A good agreement is found to exist in this time interval suggesting that E × B drift has become the dominant drift mechanism over the gradient-curvature drift separation of the moving absorption patches observed at the beginning of the morning precipitation event. Key words. Ionosphere (auroral ionosphere; particle precipitation) Magnetospheric physics (storms and substorms) Article in Journal/Newspaper EISCAT Directory of Open Access Journals: DOAJ Articles Annales Geophysicae 20 9 1321 1334 |
institution |
Open Polar |
collection |
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 A. J. Kavanagh F. Honary I. W. McCrea E. Donovan E. E. Woodfield J. Manninen P. C. Anderson Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
topic_facet |
Science Q Physics QC1-999 Geophysics. Cosmic physics QC801-809 |
description |
A period (08:10–14:40 MLT, 11 February 1997) of enhanced electron density in the D- and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift eastward after substorm injection and precipitate in the morning sector. The precipitation is triggered by small pulses in the solar wind pressure, which drive wave particle interactions. The characteristic energy of precipitation is inferred from drift timing on different L-shells and apparently verified by EISCAT measurements. The IMF influence on the precipitation in the auroral zone is also briefly discussed. A large change in the precipitation spectrum is attributed to increased numbers of ions and much reduced electron fluxes. These are detected by a close passing DMSP satellite. The possibility that these ions are from the low latitude boundary layer (LLBL) is discussed with reference to structured narrow band Pc1 waves observed by a search coil magnetometer, co-located with IRIS. The intensity of the waves grows with increased distance equatorward of the cusp position (determined by both satellite and HF radar), contrary to expectations if the precipitation is linked to the LLBL. It is suggested that the ion precipitation is, instead, due to the recovery phase of a small geomagnetic storm, following on from very active conditions. The movement of absorption in the later stages of the event is compared with observations of the ionospheric convection velocities. A good agreement is found to exist in this time interval suggesting that E × B drift has become the dominant drift mechanism over the gradient-curvature drift separation of the moving absorption patches observed at the beginning of the morning precipitation event. Key words. Ionosphere (auroral ionosphere; particle precipitation) Magnetospheric physics (storms and substorms) |
format |
Article in Journal/Newspaper |
author |
A. J. Kavanagh F. Honary I. W. McCrea E. Donovan E. E. Woodfield J. Manninen P. C. Anderson |
author_facet |
A. J. Kavanagh F. Honary I. W. McCrea E. Donovan E. E. Woodfield J. Manninen P. C. Anderson |
author_sort |
A. J. Kavanagh |
title |
Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
title_short |
Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
title_full |
Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
title_fullStr |
Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
title_full_unstemmed |
Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
title_sort |
substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study |
publisher |
Copernicus Publications |
publishDate |
2002 |
url |
https://doi.org/10.5194/angeo-20-1321-2002 https://doaj.org/article/4f07ecffa5644bd3adaa3cc2320c6aa8 |
genre |
EISCAT |
genre_facet |
EISCAT |
op_source |
Annales Geophysicae, Vol 20, Pp 1321-1334 (2002) |
op_relation |
https://www.ann-geophys.net/20/1321/2002/angeo-20-1321-2002.pdf https://doaj.org/toc/0992-7689 https://doaj.org/toc/1432-0576 doi:10.5194/angeo-20-1321-2002 0992-7689 1432-0576 https://doaj.org/article/4f07ecffa5644bd3adaa3cc2320c6aa8 |
op_doi |
https://doi.org/10.5194/angeo-20-1321-2002 |
container_title |
Annales Geophysicae |
container_volume |
20 |
container_issue |
9 |
container_start_page |
1321 |
op_container_end_page |
1334 |
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1766400259935698944 |