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 Signatures of moving polar cap arcs in the F-region PolarDARN echoes

2012 ◽  
Vol 30 (3) ◽  
pp. 441-455 ◽  
Author(s):  
A. V. Koustov ◽  
K. Hosokawa ◽  
N. Nishitani ◽  
K. Shiokawa ◽  
H. Liu
Keyword(s):  
Spectral Width ◽  
Global Scale ◽  
Auroral Oval ◽  
Polar Cap ◽  
Common Features ◽  
F Region ◽  
Radar Network ◽  
Radar Measurements ◽  
Resolute Bay ◽  
Region Plasma

Abstract. Joint observations of the all-sky camera at Resolute Bay (Nunavut, Canada) and the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Rankin Inlet and Inuvik (Canada) are considered to establish radar signatures of poleward moving polar cap arcs "detaching" from the auroral oval. Common features of the events considered are enhanced power or echo occurrence in the wake of the arcs and enhanced spectral width of these echoes. When the arcs were oriented along some of the radar beams, velocity reversals at the arc location were observed with the directions of the arc-associated flows corresponding to a converging electric field. For the event of 9 December 2007, two arcs were poleward progressing almost along the central beams of the Inuvik radar at the speed close to the E × B drift of the bulk of the F-region plasma as inferred from HF Doppler velocities and from independent measurements by the Resolute Bay ionosonde. In global-scale convection maps inferred from all Super Dual Auroral Radar Network (SuperDARN) radar measurements, the polar cap arcs were often seen close to the reversal line of additional mesoscale convection cells located poleward of the normal cells related to the auroral oval.

scholarly journals Effects of Abrupt Variations of Solar Wind Dynamic Pressure on the High-Latitude Ionosphere

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Igino Coco ◽  
Ermanno Amata ◽  
Maria Federica Marcucci ◽  
Danila Ambrosino ◽  
Simon G. Shepherd
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Statistical Study ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Polar Cap ◽  
Radar Backscatter ◽  
Preliminary Results ◽  
Radar Network ◽  
High Latitude Ionosphere

We show the results of a statistical study on the effects in the high-latitude ionosphere of abrupt variations of solar wind dynamic pressure, using Super Dual Auroral Radar Network (SuperDARN) data in both hemispheres. We find that, during periods of quiet ionospheric conditions, the amount of radar backscatter increases when a variation in the dynamic pressure occurs, both positive (increase of the pressure) and negative (decrease of the pressure). We also investigate the behaviour of the Cross-Polar Cap Potential (CPCP) during pressure variations and show preliminary results.

Effects of field line mapping on the gradient-drift instability in the coupled E and F region high-latitude ionosphere

Radio Science ◽  
1994 ◽  
Vol 29 (1) ◽  
pp. 317-335 ◽  
Author(s):  
P. K. Chaturvedi ◽  
M. J. Keskinen ◽  
S. L. Ossakow ◽  
J. A. Fedder
Keyword(s):  
Field Line ◽  
High Latitude ◽  
F Region ◽  
High Latitude Ionosphere ◽  
Gradient Drift ◽  
Drift Instability

RUSSIAN HIGH-LATITUDE NETWORK OF OBLIQUE IONOSPHERIC SOUNDING

2021 ◽  
pp. 5-13
Author(s):  
D. D. Rogov ◽  
◽  
V. M. Vystavnoi ◽  
N. F. Blagoveshchenskaya ◽  
P. E. Baryshev ◽  
...  
Keyword(s):  
High Latitude ◽  
Communication Systems ◽  
Arctic Region ◽  
Small Scale ◽  
Radio Waves ◽  
Radio Communication ◽  
Remote Diagnostics ◽  
F Region ◽  
High Latitude Ionosphere ◽  
Ionospheric Sounding

The network for monitoring the high-latitude ionosphere by the method of oblique ionospheric sounding deployed in the Russian Arctic region is considered. The study describes the main results of operational data processing for studying the high-latitude ionosphere and determining the conditions for the optimum operation of radio communication systems and over-the-horizon radars in this region. The study demonstrates the potential of the network as a tool for the remote diagnostics of parameters of small-scale artificial ionospheric irregularities induced by powerful HF radio waves in the mid-latitude ionospheric F-region.

scholarly journals ULF wave occurrence statistics in a high-latitude HF Doppler sounder

1999 ◽  
Vol 17 (6) ◽  
pp. 749-758 ◽  
Author(s):  
D. M. Wright ◽  
T. K. Yeoman ◽  
T. B. Jones
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
High Latitude ◽  
Statistical Study ◽  
Low Frequency ◽  
Occurrence Rate ◽  
Mhd Waves ◽  
Ulf Wave ◽  
High Latitude Ionosphere ◽  
Mhd Waves And Instabilities

Abstract. Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, Norway (69.7°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The findings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions affect such observations of ULF waves.Key words. Ionosphere (auroral ionosphere; ionosphere -magnetosphere interactions) · Magnetospheric physics (MHD waves and instabilities)

scholarly journals The relationship between electric fields, conductances and currents in the high-latitude ionosphere: a statistical study using EISCAT data

1999 ◽  
Vol 17 (1) ◽  
pp. 43-52 ◽  
Author(s):  
J. A. Davies ◽  
M. Lester
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
High Latitude ◽  
Statistical Study ◽  
Field Vector ◽  
Relative Contribution ◽  
High Latitude Ionosphere ◽  
The Times ◽  
The Relationship ◽  
Uhf Radar

Abstract. The relationship between electric fields, height-integrated conductivities and electric currents in the high-latitude nightside electrojet region is known to be complex. The tristatic nature of the EISCAT UHF radar facility provides an excellent means of exploring this interrelationship as it enables simultaneous estimates to be made of the full electric field vector and the ionospheric Hall and Pedersen conductances, further allowing the determination of both field-perpendicular electric current components. Over 1300 h of common programme observations by the UHF radar system provide the basis of a statistical study of electric fields, conductances and currents in the high-latitude ionosphere, from which preliminary results are presented. Times at which there is significant solar contribution to the ionospheric conductances have been excluded by limiting the observations according to solar zenith angle. Initial results indicate that, in general, the times of peak conductance, identified from the entire set of EISCAT observations, do not correspond to the times of the largest electric field values; the relative contribution of ionospheric conductance and electric field to the electrojet currents therefore depends critically on local time, a conclusion which corroborates work by previous authors. Simultaneous measurements confirm a tendency for a decrease in both Hall and Pedersen conductances to be accompanied by an increase in the electric field, at least for moderate and large electric field value, a tendency which is also identified to some extent in the ratio of the conductances, which acts as an indicator of the energy of precipitating particles.Key words. Ionosphere (auroral ionosphere; electric fields and currents)

scholarly journals Factors determining spectral width of HF echoes from high latitudes

2007 ◽  
Vol 25 (3) ◽  
pp. 675-687 ◽  
Author(s):  
P. V. Ponomarenko ◽  
C. L. Waters ◽  
F. W. Menk
Keyword(s):  
Ionospheric Plasma ◽  
Spectral Width ◽  
Closed Field ◽  
Data Types ◽  
Standard Data ◽  
F Region ◽  
Radar Network ◽  
Scale Size ◽  
Radar Echo ◽  
Closed Field Line

Abstract. Spectral width is one of the standard data types produced by the Super Dual Auroral Radar Network (SuperDARN). A pronounced latitudinal gradient in spectral width has been reported in the literature and is used as an empirical proxy for the ionospheric footprint of the open-closed field-line boundary. In this work we investigated the daytime radar echo properties near the spectral width boundary using a multi-frequency sounding regime. We have found that the relatively large spectral width values ≥150 m/s observed poleward of the boundary are produced by ionospheric irregularities with lifetime τl≃10–25 ms, which is essentially independent of the scale size. These irregularities are statistically co-located with low-energy (~100 eV) electron precipitation, which may play a major role in producing F-region turbulence above 75 MLAT via restructuring the ionospheric plasma on time scales ~τl.

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