The dependence of high-latitude dayside ionospheric flows on the North-South component of the IMF: A high time resolution correlation analysis using EISCAT “Polar” and AMPTE UKS and IRM data

Abstract. High-time resolution CUTLASS observations and ground-based magnetometers have been employed to study the occurrence of vortical flow structures propagating through the high-latitude ionosphere during magnetospheric substorms. Fast-moving flow vortices (~800 m s-1) associated with Hall currents flowing around upward directed field-aligned currents are frequently observed propagating at high speed (~1 km s-1) azimuthally away from the region of the ionosphere associated with the location of the substorm expansion phase onset. Furthermore, a statistical analysis drawn from over 1000 h of high-time resolution, nightside radar data has enabled the characterisation of the bulk properties of these vortical flow systems. Their occurrence with respect to substorm phase has been investigated and a possible generation mechanism has been suggested.Key words: Ionosphere (auroral ionosphere; electric fields and currents) · Magnetospheric physics (storms and substorms)

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CUTLASS/IMAGE observations of high-latitude convection features during substorms

Annales Geophysicae ◽

10.1007/s00585-997-0692-z ◽

1997 ◽

Vol 15 (6) ◽

pp. 692-702 ◽

Cited By ~ 25

Author(s):

T. K. Yeoman ◽

H. Lühr

Keyword(s):

Time Resolution ◽

High Latitude ◽

Geomagnetic Latitude ◽

Hf Radar ◽

High Time ◽

Spatial Extent ◽

Line Of Sight ◽

Return Flow ◽

High Time Resolution ◽

Substorm Activity

Abstract. The CUTLASS Finland HF radar has been operational since February 1995. The radar frequently observes backscatter during the midnight sector from a latitude range 70–75° geographic, latitudes often associated with the polar cap. These intervals of backscatter occur during intervals of substorm activity, predominantly in periods of relatively quiet magnetospheric activity, with Kp during the interval under study being 2- and ΣKp for the day being only 8-. During August 1995 the radar ran in a high time resolution mode, allowing measurements of line-of-sight convection velocities along a single beam with a temporal resolution of 14 s, and measurement of a full spatial scan of line-of-sight convection velocities every four minutes. Data from such scans reveal the radar to be measuring return flow convection during the interval of substorm activity. For three intervals during the period under study, a reduction in the spatial extent of radar backscatter occurred. This is a consequence of D region HF absorption and its limited extent in the present study is probably a consequence of the high latitude of the substorm activity, with the electrojet centre lying between 67° and 71° geomagnetic latitude. The high time resolution beam of the radar additionally demonstrates that the convection is highly time dependent. Pulses of equatorward flow exceeding ~600 m s–1 are observed with a duration of ~5 min and a repetition period of ~8 min. Their spatial extent in the CUTLASS field of view was 400–500 km in longitude, and 300–400 km in latitude. Each pulse of enhanced equatorward flow was preceded by an interval of suppressed flow and enhanced ionospheric Hall conductance. The transient features are interpreted as being due to ionospheric current vortices associated with field aligned current pairs. The relationship between these observations and substorm phenomena in the magnetotail is discussed.

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High time resolution measurement of multiple electron precipitations with energy-time dispersion in high-latitude part of the cusp region

Journal of Geophysical Research Atmospheres ◽

10.1029/2004ja010664 ◽

2005 ◽

Vol 110 (A7) ◽

Cited By ~ 5

Author(s):

H. Tanaka

Keyword(s):

Time Resolution ◽

High Latitude ◽

High Time ◽

High Time Resolution ◽

Cusp Region ◽

Resolution Measurement ◽

Time Dispersion

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High-time resolution conjugate SuperDARN radar observations of the dayside convection response to changes in IMF B<sub>y</sub>

Annales Geophysicae ◽

10.1007/s00585-000-0191-y ◽

2000 ◽

Vol 18 (2) ◽

pp. 191-201 ◽

Cited By ~ 13

Author(s):

G. Chisham ◽

M. Pinnock ◽

A. S. Rodger ◽

J. -P. Villain

Keyword(s):

Solar Wind ◽

Time Resolution ◽

Sampling Period ◽

High Time ◽

High Time Resolution ◽

Plasma Convection ◽

Ionosphere Plasma ◽

Full Scan ◽

Convection Patterns ◽

The Imf

Abstract. We present data from conjugate SuperDARN radars describing the high-latitude ionosphere's response to changes in the direction of IMF By during a period of steady IMF Bz southward and Bx positive. During this interval, the radars were operating in a special mode which gave high-time resolution data (30 s sampling period) on three adjacent beams with a full scan every 3 min. The location of the radars around magnetic local noon at the time of the event allowed detailed observations of the variations in the ionospheric convection patterns close to the cusp region as IMF By varied. A significant time delay was observed in the ionospheric response to the IMF By changes between the two hemispheres. This is explained as being partially a consequence of the location of the dominant merging region on the magnetopause, which is ~8-12RE closer to the northern ionosphere than to the southern ionosphere (along the magnetic field line) due to the dipole tilt of the magnetosphere and the orientation of the IMF. This interpretation supports the anti-parallel merging hypothesis and highlights the importance of the IMF Bx component in solar wind-magnetosphere coupling.Key words: Ionosphere (plasma convection) - Magnetospheric physics (magnetopause, cusp, and boundary layers; solar wind - magnetosphere interactions)

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Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak

International Astronomical Union Colloquium ◽

10.1017/s0252921100025744 ◽

1994 ◽

Vol 144 ◽

pp. 431-434

Author(s):

M. Minarovjech ◽

M. Rybanský

Keyword(s):

Solar Corona ◽

Time Resolution ◽

Active Regions ◽

High Time ◽

High Time Resolution ◽

List Type ◽

Type Number ◽

Coronal Line ◽

Global Cycle

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.

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