scholarly journals Statistical Patterns of Ionospheric Convection Derived From Mid-latitude, High-Latitude, and Polar SuperDARN HF Radar Observations

2018 ◽  
Vol 123 (4) ◽  
pp. 3196-3216 ◽  
Author(s):  
E. G. Thomas ◽  
S. G. Shepherd
Keyword(s):  
High Latitude ◽  
Hf Radar ◽  
Radar Observations ◽  
Ionospheric Convection

scholarly journals Small-scale characteristics of extremely high latitude aurora

2009 ◽  
Vol 27 (9) ◽  
pp. 3335-3347 ◽  
Author(s):  
J. A. Cumnock ◽  
L. G. Blomberg ◽  
A. Kullen ◽  
T. Karlsson ◽  
Keyword(s):  
High Latitude ◽  
Large Scale ◽  
Small Scale ◽  
Strong Correlations ◽  
Polar Cap ◽  
Plasma Flows ◽  
Ionospheric Convection ◽  
Local Closure ◽  
Scale Characteristics

Abstract. We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF By. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

scholarly journals Blending Surface Currents from HF Radar Observations and Numerical Modeling: Tidal Hindcasts and Forecasts

2015 ◽  
Vol 32 (2) ◽  
pp. 256-281 ◽  
Author(s):  
E. V. Stanev ◽  
F. Ziemer ◽  
J. Schulz-Stellenfleth ◽  
J. Seemann ◽  
J. Staneva ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
German Bight ◽  
Spatial Scales ◽  
Surface Current ◽  
Hf Radar ◽  
Optimal Interpolation ◽  
Kelvin Wave ◽  
Arctic Seas ◽  
Current Estimate ◽  
Radar Observations

AbstractAn observation network operating three Wellen Radars (WERAs) in the German Bight, which are part of the Coastal Observing System for Northern and Arctic Seas (COSYNA), is presented in detail. Major consideration is given to expanding the patchy observations over the entire German Bight on a 1-km grid and producing state estimates at intratidal scales, and 6- and 12-h forecasts. This was achieved with the help of the proposed spatiotemporal optimal interpolation (STOI) method, which efficiently uses observations and simulations from a free model run within an analysis window of one or two tidal cycles. In this way the method maximizes the use of available observations and can be considered as a step toward the “best surface current estimate.” The performance of the analysis was investigated based on the achieved reduction of the misfit between model and observations. The complex dynamics of the study domain was illustrated based on the spatial and temporal changes of tidal ellipses for the M2 and M4 constituents from HF radar observations. It was demonstrated that blending observations and numerical modeling facilitates physical interpretation of processes such as the nonlinear distortion of the Kelvin wave in the coastal zone and in particular in front of the Elbe and Weser estuaries. Comparisons with in situ data acquired outside the area covered by the HF radar demonstrated that the analysis method is able to propagate the HF radar information to larger spatial scales.

scholarly journals Comparison of the magnetic equivalent convection direction and ionospheric convection observed by the SuperDARN radars

2006 ◽  
Vol 24 (11) ◽  
pp. 2981-2990 ◽  
Author(s):  
L. V. Benkevitch ◽  
A. V. Koustov ◽  
J. Liang ◽  
J. F. Watermann
Keyword(s):  
Local Time ◽  
High Latitude ◽  
Early Morning ◽  
Auroral Oval ◽  
Magnetic Local Time ◽  
Ionospheric Convection ◽  
Morning Sector ◽  
Magnetometer Data ◽  
Different Seasons

Abstract. SuperDARN radar and high-latitude magnetometer observations are used to statistically investigate quality of the convection direction estimates from magnetometer data if assumption is made that the magnetic equivalent convection vector (MEC) corresponds to the convection direction. The statistics includes five full days, ~75 000 of joint individual measurements for different seasons. It is demonstrated that the best (worst) agreement between the MEC and ionospheric convection occurs for the sunlit, summer (dark, winter) ionosphere. Overall, the MEC direction is reasonable (deviates less than 45° from the SuperDARN direction) in at least ~55% of points and it is better for the latitudes of the auroral oval. In terms of the magnetic local time, the agreement is the best (worst) in the dusk (early morning) sector. Possible reasons for differences between the MEC and ionospheric convection directions are discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document