A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies
A polar cap absorption (PCA) event, beginning on 19 October 1989, is examined using the Imaging Riometer for Ionospheric Studies (IRIS) developed at the Univ. of Maryland. IRIS is a 49-beam (7 x 7) phased-array 38.2 MHz radiowave imaging system and operating at Amundsen-Scott South Pole Station, Ant...
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ftdtic:ADA227764 2023-05-15T13:24:28+02:00 A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies Davis, Timothy C. AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH 1990 text/html http://www.dtic.mil/docs/citations/ADA227764 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA227764 en eng http://www.dtic.mil/docs/citations/ADA227764 Approved for public release; distribution is unlimited. DTIC AND NTIS Atmospheric Physics *POLAR CAP ABSORPTION *RIOMETERS DELAY DAY ENERGETIC PROPERTIES PHASED ARRAYS CROSS CORRELATION PARTICLE FLUX THESES STATIONS VERY HIGH FREQUENCY IRIS(IMAGING RIOMETER FOR IONOSPHERIC STUDIES) POLAR CAP ABSORPTION EVENT 1989 IMAGING RIOMETERS SOUTH POLE STATION ENERGETIC PARTICLE FLUX ANTARCTICA Text 1990 ftdtic 2016-02-23T00:11:35Z A polar cap absorption (PCA) event, beginning on 19 October 1989, is examined using the Imaging Riometer for Ionospheric Studies (IRIS) developed at the Univ. of Maryland. IRIS is a 49-beam (7 x 7) phased-array 38.2 MHz radiowave imaging system and operating at Amundsen-Scott South Pole Station, Antarctica. After applying a low-pass (>10 minute) filter, we perform a cross-correlation between the central beam and the other beams in the array. From the cross- correlation analysis, we attempt to determine whether there is any delay of effects during event onset and early main phase (plateau) within the array. For most of the period studied, no delay was detected; i.e. features of each beam's absorption time series were essentially simultaneous. However, significant delays (approx. 2 minutes) occurred at the equatorward edge during a local absorption peak occurring just prior to magnetic local noon. The peak is coincident with short-term energetic particle flux enhancements detected by GOES-7. Two possible mechanisms are proposed: a local time variation of cutoff rigidities possibly associated with the relative position of the dayside cusp, and a short-term change in energetic particle rigidity spectrum. Text Amundsen-Scott Antarc* Antarctica South pole South pole Defense Technical Information Center: DTIC Technical Reports database South Pole Amundsen-Scott ENVELOPE(0.000,0.000,-90.000,-90.000) Amundsen Scott South Pole Station ENVELOPE(0.000,0.000,-90.000,-90.000) Amundsen-Scott South Pole Station ENVELOPE(139.273,139.273,-89.998,-89.998) |
institution |
Open Polar |
collection |
Defense Technical Information Center: DTIC Technical Reports database |
op_collection_id |
ftdtic |
language |
English |
topic |
Atmospheric Physics *POLAR CAP ABSORPTION *RIOMETERS DELAY DAY ENERGETIC PROPERTIES PHASED ARRAYS CROSS CORRELATION PARTICLE FLUX THESES STATIONS VERY HIGH FREQUENCY IRIS(IMAGING RIOMETER FOR IONOSPHERIC STUDIES) POLAR CAP ABSORPTION EVENT 1989 IMAGING RIOMETERS SOUTH POLE STATION ENERGETIC PARTICLE FLUX ANTARCTICA |
spellingShingle |
Atmospheric Physics *POLAR CAP ABSORPTION *RIOMETERS DELAY DAY ENERGETIC PROPERTIES PHASED ARRAYS CROSS CORRELATION PARTICLE FLUX THESES STATIONS VERY HIGH FREQUENCY IRIS(IMAGING RIOMETER FOR IONOSPHERIC STUDIES) POLAR CAP ABSORPTION EVENT 1989 IMAGING RIOMETERS SOUTH POLE STATION ENERGETIC PARTICLE FLUX ANTARCTICA Davis, Timothy C. A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies |
topic_facet |
Atmospheric Physics *POLAR CAP ABSORPTION *RIOMETERS DELAY DAY ENERGETIC PROPERTIES PHASED ARRAYS CROSS CORRELATION PARTICLE FLUX THESES STATIONS VERY HIGH FREQUENCY IRIS(IMAGING RIOMETER FOR IONOSPHERIC STUDIES) POLAR CAP ABSORPTION EVENT 1989 IMAGING RIOMETERS SOUTH POLE STATION ENERGETIC PARTICLE FLUX ANTARCTICA |
description |
A polar cap absorption (PCA) event, beginning on 19 October 1989, is examined using the Imaging Riometer for Ionospheric Studies (IRIS) developed at the Univ. of Maryland. IRIS is a 49-beam (7 x 7) phased-array 38.2 MHz radiowave imaging system and operating at Amundsen-Scott South Pole Station, Antarctica. After applying a low-pass (>10 minute) filter, we perform a cross-correlation between the central beam and the other beams in the array. From the cross- correlation analysis, we attempt to determine whether there is any delay of effects during event onset and early main phase (plateau) within the array. For most of the period studied, no delay was detected; i.e. features of each beam's absorption time series were essentially simultaneous. However, significant delays (approx. 2 minutes) occurred at the equatorward edge during a local absorption peak occurring just prior to magnetic local noon. The peak is coincident with short-term energetic particle flux enhancements detected by GOES-7. Two possible mechanisms are proposed: a local time variation of cutoff rigidities possibly associated with the relative position of the dayside cusp, and a short-term change in energetic particle rigidity spectrum. |
author2 |
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH |
format |
Text |
author |
Davis, Timothy C. |
author_facet |
Davis, Timothy C. |
author_sort |
Davis, Timothy C. |
title |
A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies |
title_short |
A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies |
title_full |
A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies |
title_fullStr |
A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies |
title_full_unstemmed |
A Case Study of the 19 October 1989 Polar Cap Absorption Event Using the Imaging Riometer for Ionospheric Studies |
title_sort |
case study of the 19 october 1989 polar cap absorption event using the imaging riometer for ionospheric studies |
publishDate |
1990 |
url |
http://www.dtic.mil/docs/citations/ADA227764 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA227764 |
long_lat |
ENVELOPE(0.000,0.000,-90.000,-90.000) ENVELOPE(0.000,0.000,-90.000,-90.000) ENVELOPE(139.273,139.273,-89.998,-89.998) |
geographic |
South Pole Amundsen-Scott Amundsen Scott South Pole Station Amundsen-Scott South Pole Station |
geographic_facet |
South Pole Amundsen-Scott Amundsen Scott South Pole Station Amundsen-Scott South Pole Station |
genre |
Amundsen-Scott Antarc* Antarctica South pole South pole |
genre_facet |
Amundsen-Scott Antarc* Antarctica South pole South pole |
op_source |
DTIC AND NTIS |
op_relation |
http://www.dtic.mil/docs/citations/ADA227764 |
op_rights |
Approved for public release; distribution is unlimited. |
_version_ |
1766379823616229376 |