scholarly journals A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar

2000 ◽  
Vol 18 (4) ◽  
pp. 445-453 ◽  
Author(s):  
K. A. McWilliams ◽  
T. K. Yeoman ◽  
G. Provan
Keyword(s):  
Radar Data ◽  
Hf Radar ◽  
Optical Measurements ◽  
Occurrence Rate ◽  
Related Phenomenon ◽  
Plasma Convection ◽  
Flux Transfer ◽  
Statistical Survey ◽  
Spacecraft Data ◽  
Resolution Data

Abstract. Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed ionospheric flow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic field lines, which occur during episodes of magnetic flux transfer to the terrestrial magnetosphere - flux transfer events or FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetary magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in different regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)

scholarly journals The dayside ultraviolet aurora and convection responses to a southward turning of the interplanetary magnetic field

2001 ◽  
Vol 19 (7) ◽  
pp. 707-721 ◽  
Author(s):  
K. A. McWilliams ◽  
T. K. Yeoman ◽  
J. B. Sigwarth ◽  
L. A. Frank ◽  
M. Brittnacher
Keyword(s):  
Large Scale ◽  
Small Region ◽  
Radar Data ◽  
Hf Radar ◽  
Current Response ◽  
Plasma Convection ◽  
Flux Transfer Events ◽  
Field Aligned Current ◽  
Flux Transfer ◽  
The Imf

Abstract. We examine the large-scale ultraviolet aurora and convection responses to a series of flux transfer events that immediately followed a sharp and isolated southward turning of the IMF. During the interval of interest, SuperDARN was monitoring the plasma convection in the dayside northern ionosphere, while the VIS Earth Camera and the Far Ul-traviolet Imager (UVI) were monitoring the northern hemisphere’s ultraviolet aurora. Reconnection signatures were seen in the SuperDARN HF radar data in the postnoon sector following a sharp southward turning of the IMF. The presence of flux transfer events is supported by measurements of a classic dispersed ion signature in the low-altitude cusp from the DMSP spacecraft. Subsequent to the onset of reconnection, the postnoon convection and ultraviolet aurora expanded in concert, reaching 18 MLT in half an hour. The auroral oval was found to move equatorward at the convection speed in the 16–18 MLT sector, implying that it was related directly to an adiaroic magnetospheric boundary. In the present study, we have estimated the field-aligned current response to magnetic reconnection in terms of the vorticity of the ionospheric plasma convection velocity. The convection velocities were obtained using two methods: (a) direct reconstruction of the full vector velocities from bistatic measurements of the convection by the SuperDARN HF radars in a relatively small region of the auroral zone, and (b) from global-scale spherical harmonic fits to the SuperDARN velocities deduced from the map potential model. Regions of high vorticity, which were predicted to be an estimate of a component of the total field-aligned current, agree extremely well with the images of the dayside UV aurora, indicating that, in this case, the plasma vorticity is an excellent estimator of the morphology of dayside field-aligned currents (FACs). The morphology of the aurora and ionospheric electric field in the postnoon sector supports the existence of a dayside current wedge induced in response to dayside reconnection.Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions; solar wind magne-tosphere interactions)

scholarly journals Statistical observations of the MLT, latitude and size of pulsed ionospheric flows with the CUTLASS Finland radar

1999 ◽  
Vol 17 (7) ◽  
pp. 855-867 ◽  
Author(s):  
G. Provan ◽  
T. K. Yeoman
Keyword(s):  
Hf Radar ◽  
High Time Resolution ◽  
Plasma Convection ◽  
Unified Framework ◽  
Coherent Scatter ◽  
Radar Observations ◽  
Scatter Radar ◽  
Precipitation Regimes ◽  
Low Altitude ◽  
Flux Transfer

Abstract. A study has been performed on the occurrence of pulsed ionospheric flows as detected by the CUTLASS Finland HF radar. These flows have been suggested as being created at the ionospheric footprint of newly-reconnected field lines, during episodes of magnetic flux transfer into the terrestrial magnetosphere (flux transfer events or FTEs). Two years of both high-time resolution and normal scan data from the CUTLASS Finland radar have been analysed in order to perform a statistical study of the extent and location of the pulsed ionospheric flows. We note a great similarity between the statistical pattern of the coherent radar observations of pulsed ionospheric flows and the traditional low-altitude satellite identification of the particle signature associated with the cusp/cleft region. However, the coherent scatter radar observations suggest that the merging gap is far wider than that proposed by the Newell and Meng model. The new model for cusp low-altitude particle signatures, proposed by Lockwood and Onsager and Lockwood provides a unified framework to explain the dayside precipitation regimes observed both by the low-altitude satellites and by coherent scatter radar detection.Key words. Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)

scholarly journals On determining the noon polar cap boundary from SuperDARN HF radar backscatter characteristics

2000 ◽  
Vol 18 (12) ◽  
pp. 1523-1530 ◽  
Author(s):  
M. Pinnock ◽  
A. S. Rodger
Keyword(s):  
Local Time ◽  
Time Of Flight ◽  
Radar Data ◽  
Accurate Estimate ◽  
Hf Radar ◽  
Closed Field ◽  
Plasma Convection ◽  
Polar Cap ◽  
Radar Backscatter ◽  
Magnetospheric Cusp

Abstract. Previous work has shown that ionospheric HF radar backscatter in the noon sector can be used to locate the footprint of the magnetospheric cusp particle precipitation. This has enabled the radar data to be used as a proxy for the location of the polar cap boundary, and hence measure the flow of plasma across it to derive the reconnection electric field in the ionosphere. This work used only single radar data sets with a field of view limited to ~2 h of local time. In this case study using four of the SuperDARN radars, we examine the boundary determined over 6 h of magnetic local time around the noon sector and its relationship to the convection pattern. The variation with longitude of the latitude of the radar scatter with cusp characteristics shows a bay-like feature. It is shown that this feature is shaped by the variation with longitude of the poleward flow component of the ionospheric plasma and may be understood in terms of cusp ion time-of-flight effects. Using this interpretation, we derive the time-of-flight of the cusp ions and find that it is consistent with approximately 1 keV ions injected from a subsolar reconnection site. A method for deriving a more accurate estimate of the location of the open-closed field line boundary from HF radar data is described.Key words: Ionosphere (ionosphere–magnetosphere interactions; plasma convection) · Magnetospheric physics (magnetopause · cusp · and boundary layers)

scholarly journals Two-dimensional electric field measurements in the ionospheric footprint of a flux transfer event

2000 ◽  
Vol 18 (12) ◽  
pp. 1584-1598 ◽  
Author(s):  
K. A. McWilliams ◽  
T. K. Yeoman ◽  
S. W. H. Cowley
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Flux Tube ◽  
Convection Velocity ◽  
Hf Radar ◽  
Two Dimensional ◽  
Plasma Convection ◽  
Transfer Event ◽  
Ionospheric Convection ◽  
Flux Transfer

Abstract. Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the ionospheric footprint of a flux transfer event (a pulsed ionospheric flow, or PIF). Very stable and moderate interplanetary magnetic field conditions, along with a preceding prolonged period of northward interplanetary magnetic field, allow a detailed study of the spatial and the temporal evolution of the ionospheric response to magnetic reconnection. The flux tube footprint is tracked for half an hour across six hours of local time in the auroral zone, from magnetic local noon to dusk. The motion of the footprint of the newly reconnected flux tube is compared with the ionospheric convection velocity. Two primary intervals in the PIF's evolution have been determined. For the first half of its lifetime in the radar field of view the phase speed of the PIF is highly variable and the mean speed is nearly twice the ionospheric convection speed. For the final half of its lifetime the phase velocity becomes much less variable and slows down to the ionospheric convection velocity. The evolution of the flux tube in the magnetosphere has been studied using magnetic field, magnetopause and magnetosheath models. The data are consistent with an interval of azimuthally propagating magnetopause reconnection, in a manner consonant with a peeling of magnetic flux from the magnetopause, followed by an interval of anti-sunward convection of reconnected flux tubes.Key words: Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind · magnetosphere interactions)

scholarly journals Ionospheric response to variable electric fields in small-scale auroral structures

1998 ◽  
Vol 16 (10) ◽  
pp. 1343-1354 ◽  
Author(s):  
B. S. Lanchester ◽  
M. H. Rees ◽  
K. J. F. Sedgemore ◽  
J. R. Palmer ◽  
H. U. Frey ◽  
...  
Keyword(s):  
Electric Fields ◽  
Radar Data ◽  
Optical Measurements ◽  
Small Scale ◽  
Plasma Convection ◽  
Density Profiles ◽  
Space Resolution ◽  
E Region ◽  
Radar Measurements ◽  
Electron Density Profiles

Abstract. High time and space resolution optical and radar measurements have revealed the influence of electric fields on E-region electron density profiles in small-scale auroral structures. Large electric fields are present adjacent to auroral filaments produced by monoenergetic electron fluxes. The ionisation profiles measured within and beside the auroral filaments show the effects of plasma convection due to electric fields as well as the consequences of the response time to large and dynamic fluxes of energetic electrons. Without high-resolution optical measurements, the interpretation of the radar data is limited.Key words. Auroral ionosphere · Ionosphere-magnetosphere interactions · EISCAT

scholarly journals Gap Filling of the CALYPSO HF Radar Sea Surface Current Data through Past Measurements and Satellite Wind Observations

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Adam Gauci ◽  
Aldo Drago ◽  
John Abela
Keyword(s):  
Oil Spills ◽  
Surface Current ◽  
Radar Data ◽  
Current Data ◽  
Hf Radar ◽  
Sea Surface ◽  
Machine Learning Techniques ◽  
Learning Techniques ◽  
Spatial Coverage ◽  
Essential Components

High frequency (HF) radar installations are becoming essential components of operational real-time marine monitoring systems. The underlying technology is being further enhanced to fully exploit the potential of mapping sea surface currents and wave fields over wide areas with high spatial and temporal resolution, even in adverse meteo-marine conditions. Data applications are opening to many different sectors, reaching out beyond research and monitoring, targeting downstream services in support to key national and regional stakeholders. In the CALYPSO project, the HF radar system composed of CODAR SeaSonde stations installed in the Malta Channel is specifically serving to assist in the response against marine oil spills and to support search and rescue at sea. One key drawback concerns the sporadic inconsistency in the spatial coverage of radar data which is dictated by the sea state as well as by interference from unknown sources that may be competing with transmissions in the same frequency band. This work investigates the use of Machine Learning techniques to fill in missing data in a high resolution grid. Past radar data and wind vectors obtained from satellites are used to predict missing information and provide a more consistent dataset.

Spatio-Temporal Deep Learning for Ocean Current Prediction Based on HF Radar Data

2019 ◽  
Author(s):  
Nathachai Thongniran ◽  
Peerapon Vateekul ◽  
Kulsawasd Jitkajornwanich ◽  
Siam Lawawirojwong ◽  
Panu Srestasathiern
Keyword(s):  
Deep Learning ◽  
Radar Data ◽  
Hf Radar ◽  
Ocean Current ◽  
Spatio Temporal

The Effect of Solar Wind Mach Numbers on the Occurrence Rate of Flux Transfer Events at the Dayside Magnetopause

2019 ◽  
Vol 46 (8) ◽  
pp. 4106-4113 ◽  
Author(s):  
C. Chen ◽  
T. R. Sun ◽  
C. Wang ◽  
Z. H. Huang ◽  
B. B. Tang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Occurrence Rate ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Mach Numbers ◽  
Flux Transfer

Surface circulation and Lagrangian transport in the SE Bay of Biscay from HF radar data

2013 ◽  
Author(s):  
Anna Rubio ◽  
Lohitzune Solabarrieta ◽  
Manuel Gonzalez ◽  
Julien Mader ◽  
Sonia Castanedo ◽  
...  
Keyword(s):  
Radar Data ◽  
Hf Radar ◽  
Bay Of Biscay ◽  
Lagrangian Transport ◽  
Surface Circulation
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