Convection measurements by incoherent scatter radars and SuperDARN:

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Convection measurements by incoherent scatter
radars and SuperDARN Toward resolving
occasional discrepancies A. V. Koustov, U of
Saskatchewan, Saskatoon, CANADA D.W. Danskin,
NRCan Geom Lab, Ottawa, CANADA
Despite the fact that both incoherent and
coherent scatter radars monitor plasma convection
at the F region heights, all conducted so far
comparisons show occasional significant
differences between measured velocities. It is
generally believed that these discrepancies are
caused by different spatial and temporal
resolutions of the instruments. In this
presentation, a review of previous comparisons is
given and new more recent EISCAT/SuperDARN data
on plasma convection are presented to illustrate
the need for more systematic and comprehensive
joint studies. This topic might be of interest to
observations of the AMISR radar (both at Poker
Flat and Resolute Bay) and the existing SuperDARN
radars
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Sondrestrom-Goose Bay HF Ruohoniemi et al. (1987)
HF velocities agree with Sondrestrom
measurements. At large ExB, HF velocity is larger
that ExB component.
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3
EISCAT-Hankasalmi HF Davies et al., 1999
Agreement is good. The slope of the linear fit
line is 0.7, HF velocities are smaller than ISR
velocities
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Sondrestrom-GooseBay (HF) Stokkseyri (HF)Xu et
al. (2001), line-of-sight comparison
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Velocity, m/s
HF velocity is comparable with ExB l-o-s
component
Range, km
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Sondrestrom-GooseBay (HF) Stokkseyri (HF) Xu
et al. (2001), projection comparison
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Agreement is reasonable with a few exceptions
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Sondrestrom-2-D SuperDARN Xu et al.(2001),
vector comparison
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Agreement is reasonable but data spread is
significant. Tendency for HF vectors to be
somewhat smaller at large ExBs.
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EISCAT-CUTLASS Danskin (2003), projection
comparison
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Agreement is astonishingly good for Feb 12, 1999
event and not so for the previous day of Feb
11, 1999.
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EISCAT-Pikkvibaer Danskin (2003), large-range
projection comparison
At larger ranges, data spread increases still
there are a lot of points of reasonable agreement.
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Other comparisons (Danskin)
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Convection derived by FIT technique with only one
HF radar agrees reasonably with EISCAT
measurements
For scanning mode and patchy ionosphere, the
agreement is not very good
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Potential geometry of the PolarDARN-AMISR
(Resolute) work
For Rankin, scans roughly along geographic
meridian are needed
For Inuvik, scans at -45 deg from geomagnetic
meridian are needed not feasible?
Information on Ne(h, MLAT) and ExB (h, MLAT) is
desired
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Summary and potential work
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• 1. Previous ISR-SuperDARN comparisons show that
  there is reasonable agreement between HF radar
  velocity and ExB as measured by incoherent
  scatter radars. However, there are periods when
  HF shows quite different velocities. Also, a
  tendency has been noticed that at large ExB, the
  HF velocities are somewhat smaller, statistically
  speaking.
• 2. Possible extension of previous work is joint
  observations of PolarDARN radars with Resolute
  AMISR. Some Resolute beam orientations seem to be
  suitable. The goals of the investigation could
  be
• Reasons for differences in velocity measurements
  between HF and ISR
• Validation work on performance of the SD map
  technique at very high latitudes
• c. Estimates of the heights of HF echoes by using
  information on Ne profiles
• d. Modes of HF signals. Are Pedersen rays fairly
  frequent?

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Relevant publications
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Danskin, D.W., Auroral HF backscatter from
the F and E regions, PhD Thesis, U of
Saskatchewan, Saskatoon, Canada, 2003.
Davies, J.A., M. Lester, S. E. Milan, and T. K.
Yeoman, A comparison of velocity measurements
from the CUTLASS Finland radar and the EISCAT UHF
system, Ann. Geophys., 17, 892-902, 1999.
Davies, J.A., Yeoman, T.K., Lester, M. and Milan,
S.E. A comparison of F-region ion velocity
observations from the EISCAT Svalbard and VHF
radars with irregularity drift velocity
measurements from the CUTLASS Finland HF radar,
Ann. Geophys, 18, 589594, 2000. Milan,
S.E., Davies, J.A., and Lester, M. Coherent HF
radar backscatter characteristics associated with
auroral forms identified by incoherent radar
techniques A comparison of CUTLASS and EISCAT
observations, J. Geophys. Res., 104,
22,591-22,604, 1999. Ruohoniemi, J. M., R.
A. Greenwald, K. B. Baker, J.-P. Villain, and M.
A. McCready, Drift motions of small-scale
irregularities in the high-latitude F region
An experimental comparison with plasma drift
Geophys. Res., 92, N5, 4553-4564, 1987.
Villain, J.-P., Caudal, G., and Hanuise, C., A
SAFARI-EISCAT comparison of F region small-scale
irregularities and the ion drift, Ann.
Geophysicae, 90, 84338443, 1985. Yeoman,
T.K., Wright, D. M., Stocker, A. J., and Jones,
T. B. An evaluation of range accuracy in the
SuperDARN over-the-horizon HF radar systems,
Radio Sci., 36, 801-813, 2001. Xu, L., A.
V. Koustov, J. Thayer and M. McCready, SuperDARN
convection and Sondrestrom plasma drift, Ann.
Geophys., 19, 749-759, 2001.