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SuperDARN radar HF propagation and absorption response to the substorm expansion phase

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journal contribution
posted on 24.01.2017, 11:36 by J. K. Gauld, T. K. Yeoman, J. A. Davies, S. E. Milan, F. Honary
Coherent scatter HF ionospheric radar systems such as SuperDARN offer a powerful experimental technique for the investigation of the magnetospheric substorm. However, a common signature in the early expansion phase is a loss of HF backscatter, which has limited the utility of the radar systems in substorm research. Such data loss has generally been attributed to either HF absorption in the D-region ionosphere, or the consequence of regions of very low ionospheric electric field. Here observations from a well-instrumented isolated substorm which resulted in such a characteristic HF radar data loss are examined to explore the impact of the substorm expansion phase on the HF radar system. The radar response from the SuperDARN Hankasalmi system is interpreted in the context of data from the EIS-CAT incoherent scatter radar systems and the IRIS Riometer at Kilpisjarvi, along with calculations of HF absorption for both IRIS and Hankasalmi and ray-tracing simulations. Such a study offers an explanation of the physical mechanisms behind the HF radar data loss phenomenon. It is found that, at least for the case study presented, the major cause of data loss is not HF absorption, but changes in HF propagation conditions. These result in the loss of many propagation paths for radar backscatter, but also the creation of some new, viable propagation paths. The implications for the use of the characteristics of the data loss as a diagnostic of the substorm process, HF communications channels, and possible radar operational strategies which might mitigate the level of HF radar data loss, are discussed.

Funding

The CUTLASS HF radars are deployed and operated by the University of Leicester, and are jointly funded by the UK Particle Physics and Astronomy Research Council (Grant no. PPA/R/R/1997/00256), the Finnish Meteorological Institute, and the Swedish Institute for Space Physics. The authors thank the director and staff of EISCAT for the operation of the facility and dissemination of the data. EISCAT is an international facility funded collaboratively by the research councils of Finland (SA), France (CNRS), the Federal Republic of Germany (MPG), Japan (NIPR), Norway (NAVF), Sweden (NFR) and the United Kingdom (PPARC). IMAGE data were kindly supplied by the Finnish Meteorological Institute. JKG was supported by a PPARC studentship. JAD is supported on PPARC Grant number PPA/G/O/1997/000254. The riometer data originated from the Imaging Riometer for Ionospheric Studies (IRIS), operated by the Department of Communications Systems at Lancaster University (UK), funded by the Particle Physics and Astronomy Research Council (PPARC) in collaboration with the Sodankyla Geophysical Observatory.

History

Citation

Annales Geophysicae, 2002, 20 (10), pp. 1631-1645 (15)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Annales Geophysicae

Publisher

European Geosciences Union (EGU), Copernicus Publications, Springer Verlag (Germany)

issn

0992-7689

eissn

1432-0576

Acceptance date

27/03/2002

Copyright date

2002

Available date

24/01/2017

Publisher version

http://www.ann-geophys.net/20/1631/2002/angeo-20-1631-2002.html

Language

en