HR: 1330h
AN: SA22A-0095    [PDF]
TI: Determination of the Altitude of Cosmic Noise Absorption at Cusp Latitudes Using the Vertical Parallax Technique
AU: Terkildsen, M
EM: phmbt@alinga.newcastle.edu.au
AF: CRC for Satellite Systems, Physics Building University of Newcastle University Drive, CALLAGHAN, NSW 2308 Australia
AU: * Fraser, B
EM: brian.fraser@newcastle.edu.au
AF: CRC for Satellite Systems, Physics Building University of Newcastle University Drive, CALLAGHAN, NSW 2308 Australia
AU: Yamagishi, H
EM: yamagisi@nipr.ac.jp
AF: National Institute for Polar Research, 9-10 Kaga 1-chrome Itabashi-ku, TOKYO, 175-8515 Japan
AU: Morris, R
EM: ray.morris@aad.gov.au
AF: Australian Antarctic Division, Channel Hwy, KINGSTON, TAS 7050 Australia
AU: Liu, R Y
AF: Polar Research Institute of China, 451 Jinqiao Rd, SHANGHAI, 2001 29 China
AB: The overlapping beam patterns of two closely spaced imaging riometers have been used to make direct observations of the altitude of maximum ionospheric absorption of cosmic radio noise. The method employs the simple vertical parallax technique. One drawback of the riometry technique of observing density enhancements in the ionosphere has been its inability to retrieve direct height information regarding precipitation regions from absorption measurements. To obtain absorption height information requires either the application of a multifrequency technique, or coordination of riometer data and data from independent instruments such as iono-digisondes or incoherent scatter radar. The unique proximal location of the Southern Hemisphere Imaging Riometer Experiment \(SHIRE\), located at Davis, Antarctica and the NIPR/STELab imaging riometer at Zhongshan, Antarctica, just 109km away, presents an opportunity to use parallax methods as a means of determining the altitude of Cosmic Noise Absorption in the cusp region, on an event basis. The relative fields of view of the two instruments have near optimal overlap for the application of parallax methods of this kind, with overlapping beams at any altitude above 40km. Using this new technique, we confirm the altitude of maximum radiowave absorption at between 90 and 100km \(ionospheric D region\) for auroral zone precipitation on the nightside, indicating precipitation of magnetospheric electrons $>$10keV in energy. We also report on the observation of riometer absorption events occurring in the ionospheric E and F regions. Studies of auroral absorption events with multiple enhancements show that the altitude at which individual enhancements occur may vary significantly. This is reflected in the variation of the peak absorption level for each enhancement.
DE: 2407 Auroral ionosphere (2704)
DE: 2435 Ionospheric disturbances
DE: 2736 Magnetosphere/ionosphere interactions
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting