posted on 2017-02-06, 14:34authored byT. Ogawa, N. F. Arnold, S. Kirkwood, N. Nishitani, M. Lester
Peculiar near range echoes observed in summer
with the SuperDARN HF radar in Finland are presented. The
echoes were detected at four frequencies of 9, 11, 13 and 15
MHz at slant ranges of 105–250 km for about 100 min. Interferometer
measurements indicate that the echoes are returned
from 80–100 km altitudes with elevation angles of 20◦–60◦
.
Echo power (≤ 16 dB), Doppler velocity (between –30 and
+ 30 m s^−1
) and spectral width (≤ 60 m s^−1
) fluctuate with
periods of several to 20 min, perhaps due to short–period atmospheric
gravity waves. When the HF radar detected the
echoes, a vertical incidence MST radar, located at Esrange
in Sweden (650 km north of the HF radar site), observed polar
mesosphere summer echoes (PMSE) at altitudes of 80–
90 km. This fact suggests that the near range HF echoes
are PMSE at HF band, although both radars did not probe a
common volume. With increasing radar frequency, HF echo
ranges are closer to the radar site and echo power becomes
weaker. Possible mechanisms to explain these features are
discussed.
Funding
The authors wish to thank the team of the Radio
and Space Plasma Physics group at the University of Leicester
who constructed, deployed and operated the CUTLASS HF radars.
The ESRAD radar is jointly funded by the Swedish Space Corporation
and the Swedish Research Council. N. F. Arnold was supported
by an advanced fellowship from the UK Particle Physics and Astronomy
Research Council and CUTLASS operations were funded
by PPARC grant RP16021.
History
Citation
Annales Geophysicae, 2003, 21 (4), pp. 1047-1055 (9)
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)