EISCAT observations of plasma convection and the high-latitude, winter F-region during substorm activity

1984 ◽  
Vol 46 (6-7) ◽  
pp. 489-499 ◽  
Author(s):  
M Lockwood ◽  
A.D Farmer ◽  
H.J Opgenoorth ◽  
S.R Crothers
Keyword(s):  
High Latitude ◽  
Plasma Convection ◽  
F Region ◽  
Substorm Activity

scholarly journals Modulation of nightside polar patches by substorm activity

2009 ◽  
Vol 27 (10) ◽  
pp. 3923-3932 ◽  
Author(s):  
A. G. Wood ◽  
S. E. Pryse ◽  
J. Moen
Keyword(s):  
Spatial Distribution ◽  
High Latitude ◽  
Ionospheric Plasma ◽  
Plasma Convection ◽  
Convection Pattern ◽  
Polar Cap ◽  
Incoherent Scatter ◽  
Repetition Time ◽  
Substorm Activity ◽  
European Sector

Abstract. Results are presented from a multi-instrument study showing the influence of geomagnetic substorm activity on the spatial distribution of the high-latitude ionospheric plasma. Incoherent scatter radar and radio tomography measurements on 12 December 2001 were used to directly observe the remnants of polar patches in the nightside ionosphere and to investigate their characteristics. The patches occurred under conditions of IMF Bz negative and IMF By negative. They were attributed to dayside photoionisation transported by the high-latitude convection pattern across the polar cap and into the nighttime European sector. The patches on the nightside were separated by some 5° latitude during substorm expansion, but this was reduced to some 2° when the activity had subsided. The different patch separations resulted from the expansion and contraction of the high-latitude plasma convection pattern on the nightside in response to the substorm activity. The patches of larger separation occurred in the antisunward cross-polar flow as it entered the nightside sector. Those of smaller separation were also in antisunward flow, but close to the equatorward edge of the convection pattern, in the slower, diverging flow at the Harang discontinuity. A patch repetition time of some 10 to 30 min was estimated depending on the phase of the substorm.

scholarly journals Evidence for solar-production as a source of polar-cap plasma

2004 ◽  
Vol 22 (4) ◽  
pp. 1093-1102 ◽  
Author(s):  
S. E. Pryse ◽  
R. W. Sims ◽  
J. Moen ◽  
L. Kersley ◽  
D. Lorentzen ◽  
...  
Keyword(s):  
High Latitude ◽  
Extended Period ◽  
Soft Particle ◽  
Plasma Convection ◽  
Polar Cap ◽  
Ionosphere Plasma ◽  
F Region ◽  
Modelling Studies ◽  
Restricted Region ◽  
Radio Tomographic Imaging

Abstract. The focus of the study is a region of enhanced ionospheric densities observed by the EISCAT Svalbard radar in the polar F-region near local magnetic noon under conditions of IMF Bz<0. Multi-instrument observations, using optical, spacecraft and radar instrumentation, together with radio tomographic imaging, have been used to identify the source of the enhancement and establish the background ionospheric conditions. Soft-particle precipitation was ruled out as a candidate for the production. Tomographic observations identified a latitudinally restricted region of enhanced densities at sub-auroral latitudes, distinct from the normal mid-latitude ionosphere, which was likely to be the source. The evidence suggested that the increased sub-auroral densities were photoionisation produced at the equatorward edge of the afternoon high-latitude cell, where the plasma is exposed to sunlight for an extended period as it flows slowly sunward toward magnetic noon. It is proposed that this plasma, once in the noon sector, was drawn antisunward by the high-latitude convection toward polar latitudes where it was identified by the EISCAT Svalbard radar. The observations are discussed in terms of earlier modelling studies of polar patch densities. Key words. Ionosphere (polar ionosphere; plasma temerature; plasma convection)

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 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 Simultaneous high- and low-latitude reconnection: ESR and DMSP observations

2002 ◽  
Vol 20 (9) ◽  
pp. 1311-1320 ◽  
Author(s):  
F. Pitout ◽  
P. T. Newell ◽  
S. C. Buchert
Keyword(s):  
High Latitude ◽  
Time Interval ◽  
High Latitudes ◽  
Polar Ionosphere ◽  
Plasma Convection ◽  
Low Latitude ◽  
Svalbard Archipelago ◽  
Cusp Region ◽  
Ionosphere Plasma ◽  
Particle Measurement

Abstract. We present EISCAT Svalbard Radar and DMSP observations of a double cusp during an interval of predominantly northward IMF on 26 November 2000. In the cusp region, the ESR dish, pointing northward, recorded sun-ward ionospheric flow at high latitudes (above 82° GL), indicating reconnection occuring in the magnetospheric lobe. Meanwhile, the same dish also recorded bursts of poleward flow, indicative of bursty reconnection at the subsolar magnetopause. Within this time interval, the DMSP F13 satellite passed in the close vicinity of the Svalbard archipelago. The particle measurement on board exhibited a double cusp structure in which two oppositely oriented ion dispersions are recorded. We interpret this set of data in terms of simultaneous merging at low- and high-latitude magnetopause. We discuss the conditions for which such simultaneous high-latitude and low-latitude reconnection can be anticipated. We also discuss the consequences of the presence of two X-lines in the dayside polar ionosphere.Key words. Magnetospheric physics (solar wind-magnetosphere interactions) – Ionosphere (polar ionosphere; plasma convection)

scholarly journals Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet

1998 ◽  
Vol 16 (1) ◽  
pp. 55-68 ◽  
Author(s):  
S. E. Milan ◽  
M. Lester
Keyword(s):  
Spectral Characteristics ◽  
Temporal Variations ◽  
Approximate Determination ◽  
Spectral Signature ◽  
Plasma Convection ◽  
Flow Angle ◽  
F Region ◽  
Ion Acoustic ◽  
E Region ◽  
Acoustic Speed

Abstract. A common feature of evening near-range ionospheric backscatter in the CUTLASS Iceland radar field of view is two parallel, approximately L-shell-aligned regions of westward flow which are attributed to irregularities in the auroral eastward electrojet region of the ionosphere. These backscatter channels are separated by approximately 100–200 km in range. The orientation of the CUTLASS Iceland radar beams and the zonally aligned nature of the flow allows an approximate determination of flow angle to be made without the necessity of bistatic measurements. The two flow channels have different azimuthal variations in flow velocity and spectral width. The nearer of the two regions has two distinct spectral signatures. The eastern beams detect spectra with velocities which saturate at or near the ion-acoustic speed, and have low spectral widths (less than 100 m s–1), while the western beams detect lower velocities and higher spectral widths (above 200 m s–1). The more distant of the two channels has only one spectral signature with velocities above the ion-acoustic speed and high spectral widths. The spectral characteristics of the backscatter are consistent with E-region scatter in the nearer channel and upper-E-region or F-region scatter in the further channel. Temporal variations in the characteristics of both channels support current theories of E-region turbulent heating and previous observations of velocity-dependent backscatter cross-section. In future, observations of this nature will provide a powerful tool for the investigation of simultaneous E- and F-region irregularity generation under similar (nearly co-located or magnetically conjugate) electric field conditions.Key words. Auroral ionosphere · Ionospheric irregularities · Plasma convection

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