Journal ArticleDOI
HF radar signatures of the cusp and low-latitude boundary layer
K. B. Baker,J. R. Dudeney,R. A. Greenwald,Michael Pinnock,Patrick T. Newell,Alan S. Rodger,N. Mattin,C.-I. Meng +7 more
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TLDR
In this article, an intercalibration study made using the Polar Anglo-American Conjugate Radar Experiment radars located at Goose Bay, Labrador, and Halley Station, Antarctica, and the Defense Meteorological Satellite Program (DMSP) satellites is used to provide clear identifications of the ionospheric cusp and the low-latitude boundary layer (LLBL).Abstract:
Continuous ground-based observations of ionospheric and magnetospheric regions are critical to the Geospace Environment Modeling (GEM) program. It is therefore important to establish clear intercalibrations between different ground-based instruments and satellites in order to clearly place the ground-based observations in context with the corresponding in situ satellite measurements. HF-radars operating at high latitudes are capable of observing very large spatial regions of the ionosphere on a nearly continuous basis. In this paper we report on an intercalibration study made using the Polar Anglo-American Conjugate Radar Experiment radars located at Goose Bay, Labrador, and Halley Station, Antarctica, and the Defense Meteorological Satellite Program (DMSP) satellites. The DMSP satellite data are used to provide clear identifications of the ionospheric cusp and the low-latitude boundary layer (LLBL). The radar data for eight cusp events and eight LLBL events have been examined in order to determine a radar signature of these ionospheric regions. This intercalibration indicates that the cusp is always characterized by wide, complex Doppler power spectra, whereas the LLBL is usually found to have spectra dominated by a single component. The distribution of spectral widths in the cusp is of a generally Gaussian form with a peak at about 220 m/s. The distribution of spectral widths in the LLBL is more like an exponential distribution, with the peak of the distribution occurring at about 50 m/s. There are a few cases in the LLBL where the Doppler power spectra are strikingly similar to those observed in the cusp.read more
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Dissertation
Radar Observations of Artificial Ionospheric Modification Effects
Abstract: Artificial ionospheric modification experiments by means of high power, high frequency radio waves using the EISCAT (European Incoherent SCATter) heater at Tromsø, northern Norway have been carried out for nearly three decades. These experiments are associated with large-scale increases in the electron temperature and density and generation of small-scale plasma irregularities, which are diagnosed by the EISCAT UHF and CUTLASS (Cooperative UK Twin Located Auroral Sounding System) HF radars. Experimental results from the EISCAT UHF radar, obtained from heating campaigns at Tromsø between 1996 and 1999, are used to study the effects of heater-induced instabilities on the analyses of EISCAT spectra. Plasma turbulence induced by high power heater waves produces unphysical estimates of ionospheric plasma parameters during the initial phase of heating, and a method is developed to correct for these problems. It is shown that these estimates are nevertheless, reliable over longer timescales of heating In the second study, relaxation characteristics of small-scale density perturbations measured using the CUTLASS Finland radar are modelled theoretically and shown to be largely consistent with large-scale temperatures measured using the EISCAT UHF radar. Certain cases are identified where alternative models of irregularity decay are required to describe the temporal behaviour in radar backscatter. These models consider influences such as electron temperature reductions, wave-wave coupling and background flow. The final study concentrates on a heating experiment in October 2000, where unusually broadened spectral widths of artificial HF backscatter measured with the CUTLASS Finland and Iceland radars was observed. The results were incompatible with previous explanations of similar observations. The Burg maximum entropy analysis was implemented to formulate a tentative explanation for the observations, involving simultaneous detection of artificial and natural irregularity echoes by the Iceland radar. This required the heater amplification of non co-located natural irregularities, already above the noise threshold of the radar.
Multiple time delays between IMF-driven convection changes at cross polar locations in the high-latitude ionosphere
TL;DR: In this paper, two SuperDARN radars were used to measure time delays between the arrival of interplanetary magnetic field (IMF)-driven convection changes at various locations in the high- latitude ionosphere situated diametrically across the geomagnetic pole from each other.
Journal ArticleDOI
A multi-instrument approach to mapping the global dayside merging rate
TL;DR: CUTLASS is supported by the Particle and Astronomy Research Council (PPARC grant PPA/G/O/1999/00 181) and the Finnish Meteorological Institute.
Journal ArticleDOI
Simultaneous Polar and Cluster Observations in the Northern and Southern Middle‐Altitude Polar Cusps Around Equinox
Journal ArticleDOI
Observations of the relationship between ionospheric central polar cap and dayside throat convection velocities, and solar wind/IMF driving
TL;DR: In this paper, the authors examined the relationship between solar wind and interplanetary magnetic field (IMF) conditions, restricted to periods of steady IMF, and found that on average the flow velocity depends on the square root of the rate of flux entry to the polar cap.
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Journal ArticleDOI
DARN/SUPERDARN : A global view of the dynamics of high-latitude convection
R. A. Greenwald,K. B. Baker,J. R. Dudeney,Michael Pinnock,T. B. Jones,E. C. Thomas,Jean-Paul Villain,Jean-Claude Cerisier,C. Senior,C. Hanuise,R. D. Hunsucker,George J. Sofko,James A. Koehler,Erling Nielsen,R. J. Pellinen,Anthony Walker,N. Saot,H. Yamagishi +17 more
TL;DR: The Dual Auroral Radar Network (DARN) is a global-scale network of HF and VHF radars capable of sensing backscatter from ionospheric irregularities in the E and F-regions of the high-latitude ionosphere as mentioned in this paper.
Journal ArticleDOI
A new magnetic coordinate system for conjugate studies at high latitudes
K. B. Baker,Simon Wing +1 more
TL;DR: In this article, the authors presented a variation on the corrected geomagnetic coordinate system that is well defined and smooth over the entire globe, and provided an analytic expression relating geographic coordinates, including altitude, to the magnetic coordinates.
Journal ArticleDOI
The frontside boundary layer of the magnetosphere and the problem of reconnection
TL;DR: In this article, Heos 2 plasma and magnetic field data obtained in the frontside boundary layers of the magnetosphere are presented, revealing that the low-latitude extension of the entry layer is of a somewhat different nature.
Journal ArticleDOI
The cusp and the cleft/boundary layer: Low-altitude identification and statistical local time variation
Patrick T. Newell,Ching-I. Meng +1 more
TL;DR: In this paper, the authors investigated the distinction between the low-altitude cusp and the cleft (with the latter identified as the ionospheric signature of low-latitude boundary layer (LLBL)) on both a statistical and a case study basis.
Journal ArticleDOI
Mapping the dayside ionosphere to the magnetosphere according to particle precipitation characteristics
Patrick T. Newell,Ching-I. Meng +1 more
TL;DR: In this article, a complementary approach is tried: regions are identified based on the plasma characteristics as observed by low-altitude satellites using an automated identification scheme applied to approximately 60,000 individual satellite passes through the dayside oval, probability maps are computed for observing various types of plasma precipitating into the ionosphere.
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