Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter

HF radar backscatter which has been artificially-induced by a high power RF facility has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data, induced by the SPEAR high power radar on Svalbard, are used to investigate ULF wave...

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Main Authors: Tim K. Yeoman, L. J. Baddeley, R. S. Dhillon, T. R. Robinson, D. M. Wright
Format: Other Non-Article Part of Journal/Newspaper
Language:unknown
Published: 2008
Subjects:
Online Access:https://figshare.com/articles/journal_contribution/Bistatic_observations_of_large_and_small_scale_ULF_waves_in_SPEAR-induced_HF_coherent_backscatter/10097294
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spelling ftleicesterunfig:oai:figshare.com:article/10097294 2023-05-15T18:29:46+02:00 Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter Tim K. Yeoman L. J. Baddeley R. S. Dhillon T. R. Robinson D. M. Wright 2008-08-05T00:00:00Z https://figshare.com/articles/journal_contribution/Bistatic_observations_of_large_and_small_scale_ULF_waves_in_SPEAR-induced_HF_coherent_backscatter/10097294 unknown 2381/8161 https://figshare.com/articles/journal_contribution/Bistatic_observations_of_large_and_small_scale_ULF_waves_in_SPEAR-induced_HF_coherent_backscatter/10097294 All Rights Reserved Uncategorized IR content Text Journal contribution 2008 ftleicesterunfig 2021-11-11T20:10:51Z HF radar backscatter which has been artificially-induced by a high power RF facility has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data, induced by the SPEAR high power radar on Svalbard, are used to investigate ULF wave processes observed by the CUTLASS HF radars. Observations are presented of both waves with a large-scale nature, driven externally to the magnetosphere and those with small azimuthal scale lengths, driven by wave-particle interactions. For ULF wave events with large azimuthal scale lengths an excellent agreement in the observed wave polarisation ellipse is found between the radar observations and ground-based magnetometer data. In contrast, for the small scale events, no ground-based magnetic counterpart is observed. Indeed the data from the two CUTLASS radars seem inconsistent, and each radar must be interpreted separately, as the spatial resolution of the radars is sufficient to resolve the wave characteristics along the radar beams, but insufficient to resolve the wave characteristics across the beams. A high azimuthal wave number (m) wave with a period of 300 s and m~−60 is observed to occur over Svalbard at ~14:00 magnetic local time. This confirms the existence of waves driven by wave-particle interactions with trapped particle populations in the outer magnetosphere. A comparison of the observed wave characteristics with previous, lower latitude, observations suggests that these high latitude waves have a similar azimuthal scale size to those generated in the inner magnetosphere; the azimuthal wave number of −60 observed in the present study is comparable to previous values of −20– −50, but suggests an increase of m with latitude. A similar energy source in drifting proton populations is also suggested, but with lower characteristic proton energies of 10 keV implicated at high latitude, compared to the 20–60 keV energies invoked for previous lower latitude observations. Other Non-Article Part of Journal/Newspaper Svalbard University of Leicester: Figshare Svalbard
institution Open Polar
collection University of Leicester: Figshare
op_collection_id ftleicesterunfig
language unknown
topic Uncategorized
IR content
spellingShingle Uncategorized
IR content
Tim K. Yeoman
L. J. Baddeley
R. S. Dhillon
T. R. Robinson
D. M. Wright
Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter
topic_facet Uncategorized
IR content
description HF radar backscatter which has been artificially-induced by a high power RF facility has been demonstrated to provide ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data, induced by the SPEAR high power radar on Svalbard, are used to investigate ULF wave processes observed by the CUTLASS HF radars. Observations are presented of both waves with a large-scale nature, driven externally to the magnetosphere and those with small azimuthal scale lengths, driven by wave-particle interactions. For ULF wave events with large azimuthal scale lengths an excellent agreement in the observed wave polarisation ellipse is found between the radar observations and ground-based magnetometer data. In contrast, for the small scale events, no ground-based magnetic counterpart is observed. Indeed the data from the two CUTLASS radars seem inconsistent, and each radar must be interpreted separately, as the spatial resolution of the radars is sufficient to resolve the wave characteristics along the radar beams, but insufficient to resolve the wave characteristics across the beams. A high azimuthal wave number (m) wave with a period of 300 s and m~−60 is observed to occur over Svalbard at ~14:00 magnetic local time. This confirms the existence of waves driven by wave-particle interactions with trapped particle populations in the outer magnetosphere. A comparison of the observed wave characteristics with previous, lower latitude, observations suggests that these high latitude waves have a similar azimuthal scale size to those generated in the inner magnetosphere; the azimuthal wave number of −60 observed in the present study is comparable to previous values of −20– −50, but suggests an increase of m with latitude. A similar energy source in drifting proton populations is also suggested, but with lower characteristic proton energies of 10 keV implicated at high latitude, compared to the 20–60 keV energies invoked for previous lower latitude observations.
format Other Non-Article Part of Journal/Newspaper
author Tim K. Yeoman
L. J. Baddeley
R. S. Dhillon
T. R. Robinson
D. M. Wright
author_facet Tim K. Yeoman
L. J. Baddeley
R. S. Dhillon
T. R. Robinson
D. M. Wright
author_sort Tim K. Yeoman
title Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter
title_short Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter
title_full Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter
title_fullStr Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter
title_full_unstemmed Bistatic observations of large and small scale ULF waves in SPEAR-induced HF coherent backscatter
title_sort bistatic observations of large and small scale ulf waves in spear-induced hf coherent backscatter
publishDate 2008
url https://figshare.com/articles/journal_contribution/Bistatic_observations_of_large_and_small_scale_ULF_waves_in_SPEAR-induced_HF_coherent_backscatter/10097294
geographic Svalbard
geographic_facet Svalbard
genre Svalbard
genre_facet Svalbard
op_relation 2381/8161
https://figshare.com/articles/journal_contribution/Bistatic_observations_of_large_and_small_scale_ULF_waves_in_SPEAR-induced_HF_coherent_backscatter/10097294
op_rights All Rights Reserved
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