Midnight sector observations of auroral omega bands
We present observations of auroral omega bands on 28 September 2009. Although generally associated with the substorm recovery phase and typically observed in the morning sector, the features presented here occurred just after expansion phase onset and were observed in the midnight sector, dawnward o...
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ftucl:oai:eprints.ucl.ac.uk.OAI2:1303001 2023-05-15T16:51:55+02:00 Midnight sector observations of auroral omega bands Wild, JA Woodfield, EE Donovan, E Fear, RC Grocott, A Lester, M Fazakerley, AN Lucek, E Khotyaintsev, Y Andre, M Kadokura, A Hosokawa, K Carlson, C McFadden, JP Glassmeier, KH Angelopoulos, V Bjornsson, G 2011-03-18 http://discovery.ucl.ac.uk/1303001/ unknown AMER GEOPHYSICAL UNION J GEOPHYS RES-SPACE , 116 , Article A00I30. (2011) MULTI-INSTRUMENT OBSERVATIONS DAWN-DUSK ASYMMETRY PLASMA SHEET OPTICAL OBSERVATIONS CLUSTER MISSION ELECTRIC-FIELDS MORNING-SECTOR CURRENT SYSTEM POYNTING FLUX PULSATIONS Article 2011 ftucl 2013-11-10T04:05:50Z We present observations of auroral omega bands on 28 September 2009. Although generally associated with the substorm recovery phase and typically observed in the morning sector, the features presented here occurred just after expansion phase onset and were observed in the midnight sector, dawnward of the onset region. An all-sky imager located in northeastern Iceland revealed that the omega bands were similar to 150 x 200 km in size and propagated eastward at similar to 0.4 km s(-1) while a colocated ground magnetometer recorded the simultaneous occurrence of Ps6 pulsations. Although somewhat smaller and slower moving than the majority of previously reported omega bands, the observed structures are clear examples of this phenomenon, albeit in an atypical location and unusually early in the substorm cycle. The THEMIS C probe provided detailed measurements of the upstream interplanetary environment, while the Cluster satellites were located in the tail plasma sheet conjugate to the ground-based all-sky imager. The Cluster satellites observed bursts of 0.1-3 keV electrons moving parallel to the magnetic field toward the Northern Hemisphere auroral ionosphere; these bursts were associated with increased levels of field-aligned Poynting flux. The in situ measurements are consistent with electron acceleration via shear Alfven waves in the plasma sheet similar to 8 R-E tailward of the Earth. Although a one-to-one association between auroral and magnetospheric features was not found, our observations suggest that Alfven waves in the plasma sheet are responsible for field-aligned currents that cause Ps6 pulsations and auroral brightening in the ionosphere. Our findings agree with the conclusions of earlier studies that auroral omega bands have a source mechanism in the midtail plasma sheet. Article in Journal/Newspaper Iceland University College London: UCL Discovery |
institution |
Open Polar |
collection |
University College London: UCL Discovery |
op_collection_id |
ftucl |
language |
unknown |
topic |
MULTI-INSTRUMENT OBSERVATIONS DAWN-DUSK ASYMMETRY PLASMA SHEET OPTICAL OBSERVATIONS CLUSTER MISSION ELECTRIC-FIELDS MORNING-SECTOR CURRENT SYSTEM POYNTING FLUX PULSATIONS |
spellingShingle |
MULTI-INSTRUMENT OBSERVATIONS DAWN-DUSK ASYMMETRY PLASMA SHEET OPTICAL OBSERVATIONS CLUSTER MISSION ELECTRIC-FIELDS MORNING-SECTOR CURRENT SYSTEM POYNTING FLUX PULSATIONS Wild, JA Woodfield, EE Donovan, E Fear, RC Grocott, A Lester, M Fazakerley, AN Lucek, E Khotyaintsev, Y Andre, M Kadokura, A Hosokawa, K Carlson, C McFadden, JP Glassmeier, KH Angelopoulos, V Bjornsson, G Midnight sector observations of auroral omega bands |
topic_facet |
MULTI-INSTRUMENT OBSERVATIONS DAWN-DUSK ASYMMETRY PLASMA SHEET OPTICAL OBSERVATIONS CLUSTER MISSION ELECTRIC-FIELDS MORNING-SECTOR CURRENT SYSTEM POYNTING FLUX PULSATIONS |
description |
We present observations of auroral omega bands on 28 September 2009. Although generally associated with the substorm recovery phase and typically observed in the morning sector, the features presented here occurred just after expansion phase onset and were observed in the midnight sector, dawnward of the onset region. An all-sky imager located in northeastern Iceland revealed that the omega bands were similar to 150 x 200 km in size and propagated eastward at similar to 0.4 km s(-1) while a colocated ground magnetometer recorded the simultaneous occurrence of Ps6 pulsations. Although somewhat smaller and slower moving than the majority of previously reported omega bands, the observed structures are clear examples of this phenomenon, albeit in an atypical location and unusually early in the substorm cycle. The THEMIS C probe provided detailed measurements of the upstream interplanetary environment, while the Cluster satellites were located in the tail plasma sheet conjugate to the ground-based all-sky imager. The Cluster satellites observed bursts of 0.1-3 keV electrons moving parallel to the magnetic field toward the Northern Hemisphere auroral ionosphere; these bursts were associated with increased levels of field-aligned Poynting flux. The in situ measurements are consistent with electron acceleration via shear Alfven waves in the plasma sheet similar to 8 R-E tailward of the Earth. Although a one-to-one association between auroral and magnetospheric features was not found, our observations suggest that Alfven waves in the plasma sheet are responsible for field-aligned currents that cause Ps6 pulsations and auroral brightening in the ionosphere. Our findings agree with the conclusions of earlier studies that auroral omega bands have a source mechanism in the midtail plasma sheet. |
format |
Article in Journal/Newspaper |
author |
Wild, JA Woodfield, EE Donovan, E Fear, RC Grocott, A Lester, M Fazakerley, AN Lucek, E Khotyaintsev, Y Andre, M Kadokura, A Hosokawa, K Carlson, C McFadden, JP Glassmeier, KH Angelopoulos, V Bjornsson, G |
author_facet |
Wild, JA Woodfield, EE Donovan, E Fear, RC Grocott, A Lester, M Fazakerley, AN Lucek, E Khotyaintsev, Y Andre, M Kadokura, A Hosokawa, K Carlson, C McFadden, JP Glassmeier, KH Angelopoulos, V Bjornsson, G |
author_sort |
Wild, JA |
title |
Midnight sector observations of auroral omega bands |
title_short |
Midnight sector observations of auroral omega bands |
title_full |
Midnight sector observations of auroral omega bands |
title_fullStr |
Midnight sector observations of auroral omega bands |
title_full_unstemmed |
Midnight sector observations of auroral omega bands |
title_sort |
midnight sector observations of auroral omega bands |
publisher |
AMER GEOPHYSICAL UNION |
publishDate |
2011 |
url |
http://discovery.ucl.ac.uk/1303001/ |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
J GEOPHYS RES-SPACE , 116 , Article A00I30. (2011) |
_version_ |
1766042045819912192 |