Very high latitude F-region irregularities observed by HF-radar backscatter

1983 ◽  
Vol 10 (9) ◽  
pp. 904-907 ◽  
Author(s):  
K. B. Baker ◽  
R. A. Greenwald ◽  
R. T. Tsunoda
Keyword(s):  
High Latitude ◽  
Hf Radar ◽  
Radar Backscatter ◽  
F Region ◽  
Very High

scholarly journals A comparison of satellite scintillation measurements with HF radar backscatter characteristics

2005 ◽  
Vol 23 (11) ◽  
pp. 3451-3455 ◽  
Author(s):  
S. E. Milan ◽  
S. Basu ◽  
T. K. Yeoman ◽  
R. E. Sheehan
Keyword(s):  
Broad Spectrum ◽  
High Latitude ◽  
Auroral Zone ◽  
Intersection Point ◽  
Density Fluctuations ◽  
Hf Radar ◽  
Ionospheric Scintillation ◽  
Radar Backscatter ◽  
Density Perturbations ◽  
Coherent Radar

Abstract. We examine the correspondence between high latitude ionospheric scintillation measurements made at 250MHz with the occurrence of 10MHz HF coherent radar backscatter, on 13 and 14 December 2002. We demonstrate that when the ionospheric intersection point of the scintillation measurements is co-located with significant HF radar backscatter, the observed scintillation, quantified by the S4 index, is elevated. Conversely, when the radar indicates that backscatter is observed away from the intersection point due to movements of the auroral zone, the observed scintillation is low. This suggests that scintillation is highly location-dependent, being enhanced in the auroral zone and being lower at sub-auroral latitudes. The coexistence of scintillation and HF radar backscatter, produced by ionospheric density perturbations with scale sizes of 100s of metres and ~15 m, respectively, suggests that a broad spectrum of density fluctuations is found in the auroral zone.

scholarly journals Climatology of GPS phase scintillation and HF radar backscatter for the high-latitude ionosphere under solar minimum conditions

2011 ◽  
Vol 29 (2) ◽  
pp. 377-392 ◽  
Author(s):  
P. Prikryl ◽  
P. T. Jayachandran ◽  
S. C. Mushini ◽  
R. Chadwick
Keyword(s):  
High Latitude ◽  
Solar Minimum ◽  
Auroral Oval ◽  
Hf Radar ◽  
Small Scale ◽  
Electron Content ◽  
Radar Backscatter ◽  
Total Electron ◽  
Network Chain ◽  
Field Aligned Irregularities

Abstract. Maps of GPS phase scintillation at high latitudes have been constructed after the first two years of operation of the Canadian High Arctic Ionospheric Network (CHAIN) during the 2008–2009 solar minimum. CHAIN consists of ten dual-frequency receivers, configured to measure amplitude and phase scintillation from L1 GPS signals and ionospheric total electron content (TEC) from L1 and L2 GPS signals. Those ionospheric data have been mapped as a function of magnetic local time and geomagnetic latitude assuming ionospheric pierce points (IPPs) at 350 km. The mean TEC depletions are identified with the statistical high-latitude and mid-latitude troughs. Phase scintillation occurs predominantly in the nightside auroral oval and the ionospheric footprint of the cusp. The strongest phase scintillation is associated with auroral arc brightening and substorms or with perturbed cusp ionosphere. Auroral phase scintillation tends to be intermittent, localized and of short duration, while the dayside scintillation observed for individual satellites can stay continuously above a given threshold for several minutes and such scintillation patches persist over a large area of the cusp/cleft region sampled by different satellites for several hours. The seasonal variation of the phase scintillation occurrence also differs between the nightside auroral oval and the cusp. The auroral phase scintillation shows an expected semiannual oscillation with equinoctial maxima known to be associated with aurorae, while the cusp scintillation is dominated by an annual cycle maximizing in autumn-winter. These differences point to different irregularity production mechanisms: energetic electron precipitation into dynamic auroral arcs versus cusp ionospheric convection dynamics. Observations suggest anisotropy of scintillation-causing irregularities with stronger L-shell alignment of irregularities in the cusp while a significant component of field-aligned irregularities is found in the nightside auroral oval. Scintillation-causing irregularities can coexist with small-scale field-aligned irregularities resulting in HF radar backscatter. The statistical cusp and auroral oval are characterized by the occurrence of HF radar ionospheric backscatter and mean ground magnetic perturbations due to ionospheric currents.

High Latitude F-Region Drift Studies.

1986 ◽  
Author(s):  
Bodo W. Reinisch ◽  
Jurgen Buchau ◽  
Edward J. Weber ◽  
Claude G. Dozois ◽  
Klaus Bibl
Keyword(s):  
High Latitude ◽  
F Region

scholarly journals High resolution observations of spectral width features associatedwith ULF wave signatures in artificial HF radar backscatter

2004 ◽  
Vol 22 (1) ◽  
pp. 169-182 ◽  
Author(s):  
D. M. Wright ◽  
T. K. Yeoman ◽  
L. J. Baddeley ◽  
J. A. Davies ◽  
R. S. Dhillon ◽  
...  
Keyword(s):  
High Resolution ◽  
Plasma Source ◽  
Spectral Width ◽  
Hf Radar ◽  
Mhd Waves ◽  
Small Scale ◽  
Ulf Waves ◽  
Source Population ◽  
Radar Backscatter ◽  
Field Lines

Abstract. The EISCAT high power heating facility at Tromsø, northern Norway, has been utilised to generate artificial radar backscatter in the fields of view of the CUTLASS HF radars. It has been demonstrated that this technique offers a means of making very accurate and high resolution observations of naturally occurring ULF waves. During such experiments, the usually narrow radar spectral widths associated with artificial irregularities increase at times when small scale-sized (high m-number) ULF waves are observed. Possible mechanisms by which these particle-driven high-m waves may modify the observed spectral widths have been investigated. The results are found to be consistent with Pc1 (ion-cyclotron) wave activity, causing aliasing of the radar spectra, in agreement with previous modelling work. The observations also support recent suggestions that Pc1 waves may be modulated by the action of longer period ULF standing waves, which are simultaneously detected on the magnetospheric field lines. Drifting ring current protons with energies of ∼ 10keV are indicated as a common plasma source population for both wave types. Key words. Magnetospheric physics (MHD waves and instabilities) – Space plasma physics (wave-particle interactions) – Ionosphere (active experiments)

scholarly journals Very high electron temperatures in the daytime F region at Sondrestrom

1984 ◽  
Vol 11 (9) ◽  
pp. 919-922 ◽  
Author(s):  
Wlodek Kofman ◽  
Vincent B. Wickwar
Keyword(s):  
High Electron ◽  
F Region ◽  
Very High

scholarly journals A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

2002 ◽  
Vol 20 (11) ◽  
pp. 1769-1781 ◽  
Author(s):  
J.-P. Villain ◽  
R. André ◽  
M. Pinnock ◽  
R. A. Greenwald ◽  
C. Hanuise
Keyword(s):  
High Latitude ◽  
Statistical Study ◽  
Spectral Width ◽  
Auroral Oval ◽  
F Region ◽  
Radar Network ◽  
Period 2 ◽  
Time Period ◽  
High Latitude Ionosphere ◽  
Data Points

Abstract. The HF radars of the Super Dual Auroral Radar Network (SuperDARN) provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities)

scholarly journals Mapping ionospheric backscatter measured by the SuperDARN HF radars – Part 2: Assessing SuperDARN virtual height models

2008 ◽  
Vol 26 (4) ◽  
pp. 843-852 ◽  
Author(s):  
T. K. Yeoman ◽  
G. Chisham ◽  
L. J. Baddeley ◽  
R. S. Dhillon ◽  
T. J. T. Karhunen ◽  
...  
Keyword(s):  
Large Scale ◽  
Elevation Angle ◽  
Field Measurements ◽  
Companion Paper ◽  
Hf Radar ◽  
Propagation Path ◽  
Angle Of Arrival ◽  
Virtual Height ◽  
F Region ◽  
Propagation Paths

Abstract. The Super Dual Auroral Radar Network (SuperDARN) network of HF coherent backscatter radars form a unique global diagnostic of large-scale ionospheric and magnetospheric dynamics in the Northern and Southern Hemispheres. Currently the ground projections of the HF radar returns are routinely determined by a simple rangefinding algorithm, which takes no account of the prevailing, or indeed the average, HF propagation conditions. This is in spite of the fact that both direct E- and F-region backscatter and 1½-hop E- and F-region backscatter are commonly used in geophysical interpretation of the data. In a companion paper, Chisham et al. (2008) have suggested a new virtual height model for SuperDARN, based on average measured propagation paths. Over shorter propagation paths the existing rangefinding algorithm is adequate, but mapping errors become significant for longer paths where the roundness of the Earth becomes important, and a correct assumption of virtual height becomes more difficult. The SuperDARN radar at Hankasalmi has a propagation path to high power HF ionospheric modification facilities at both Tromsø on a ½-hop path and SPEAR on a 1½-hop path. The SuperDARN radar at Þykkvibǽr has propagation paths to both facilities over 1½-hop paths. These paths provide an opportunity to quantitatively test the available SuperDARN virtual height models. It is also possible to use HF radar backscatter which has been artificially induced by the ionospheric heaters as an accurate calibration point for the Hankasalmi elevation angle of arrival data, providing a range correction algorithm for the SuperDARN radars which directly uses elevation angle. These developments enable the accurate mappings of the SuperDARN electric field measurements which are required for the growing number of multi-instrument studies of the Earth's ionosphere and magnetosphere.

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