A multi-diagnostic approach to understanding high-latitude plasma transport during the Halloween 2003 storm

Abstract. During the Halloween 2003 storm event, significant electron density enhancements at elevated F-layer altitudes were recorded by the EISCAT and ESR radars in northern Europe between 20:00 and 24:00 UT on 30 October. At the same time, a sequence of optical images from Qaanaaq in northern Greenland captured a series of eastward-propagating polar cap patches. In this paper, an advanced 4-D tomographic method based on the assimilation of global GPS data, coupled to a predictive Kalman filtering technique, has been used to reveal the linkage between these ionospheric structures. The combination of the various data sources has clearly established the time history of this extreme event, in which high-density plasma was uplifted in the dayside ionosphere and convected anti-sunward across the polar cap to European high latitudes at an elevated F-layer. Using this multi instrument approach, we can differentiate between those density structures observed at the ESR which occurred as a result of cross-polar transport and those more likely to have been produced by in-situ soft particle precipitation, a distinction which is supported by the ESR and EISCAT data. The multi-diagnostic approach reported here has the potential significantly to extend our current understanding of high latitude plasma transport and the origin of electron density enhancements.

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Polar patches observed by ESR and their possible origin in the cusp region

Annales Geophysicae ◽

10.1007/s00585-000-1043-5 ◽

2000 ◽

Vol 18 (9) ◽

pp. 1043-1053 ◽

Cited By ~ 12

Author(s):

A. M. Smith ◽

S. E. Pryse ◽

L. Kersley

Keyword(s):

Energy Distribution ◽

Electron Density ◽

Plasma Flow ◽

Plasma Temperature ◽

Soft Particle ◽

Polar Ionosphere ◽

Polar Cap ◽

Particle Precipitation ◽

Cusp Region ◽

Reconnection Site

Abstract. Observations by the EISCAT Svalbard radar in summer have revealed electron density enhancements in the magnetic noon sector under conditions of IMF Bz southward. The features were identified as possible candidates for polar-cap patches drifting anti-Sunward with the plasma flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar and DMSP satellites, in a multi-instrument study, suggested that the origin of the structures lay upstream at lower latitudes, with the modulation in density being attributed to variability in soft-particle precipitation in the cusp region. It is proposed that the variations in precipitation may be linked to changes in the location of the reconnection site at the magnetopause, which in turn results in changes in the energy distribution of the precipitating particles.Key words: Ionosphere (ionosphere-magnetosphere interactions; plasma temperature and density; polar ionosphere)

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

Annales Geophysicae ◽

10.5194/angeo-22-1093-2004 ◽

2004 ◽

Vol 22 (4) ◽

pp. 1093-1102 ◽

Cited By ~ 10

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)

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On the possible role of cusp/cleft precipitation in the formation of polar-cap patches

Annales Geophysicae ◽

10.1007/s00585-999-1298-4 ◽

1999 ◽

Vol 17 (10) ◽

pp. 1298-1305 ◽

Cited By ~ 40

Author(s):

I. K. Walker ◽

J. Moen ◽

L. Kersley ◽

D. A. Lorentzen

Keyword(s):

Electron Density ◽

Source Region ◽

Convection Flow ◽

Substantial Part ◽

Soft Particle ◽

Polar Cap ◽

Particle Precipitation ◽

Flow Measurements ◽

F Region

Abstract. The work describes experimental observations of enhancements in the electron density of the ionospheric F-region created by cusp/cleft particle precipitation at the dayside entry to the polar-cap convection flow. Measurements by meridian scanning photometer and all-sky camera of optical red-line emissions from aurora are used to identify latitudinally narrow bands of soft-particle precipitation responsible for structured enhancements in electron density determined from images obtained by radio tomography. Two examples are discussed in which the electron density features with size scales and magnitudes commensurate with those of patches are shown to be formed by precipitation at the entry region to the anti-sunward flow. In one case the spectrum of the incoming particles results in ionisation being created, for the most part below 250 km, so that the patch will persist only for minutes after convecting away from the auroral source region. However in a second example, at a time when the plasma density of the solar wind was particularly high, a substantial part of the particle-induced enhancement formed above 250 km. It is suggested that, with the reduced recombination loss in the upper F-region, this structure will retain form as a patch during passage in the anti-sunward flow across the polar cap.Key words. Ionosphere (ionospheric irregularities; particle precipitation; polar ionosphere)

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Spatial structure of summertime ionospheric plasma near magnetic noon

Annales Geophysicae ◽

10.5194/angeo-23-25-2005 ◽

2005 ◽

Vol 23 (1) ◽

pp. 25-37 ◽

Cited By ~ 5

Author(s):

R. W. Sims ◽

S. E. Pryse ◽

W. F. Denig

Keyword(s):

High Latitude ◽

Ionospheric Plasma ◽

Local Times ◽

Soft Particle ◽

Supporting Evidence ◽

Plasma Convection ◽

Polar Cap ◽

Ionospheric Electron Density ◽

Plasma Distribution

Abstract. Results are presented from a multi-instrument study of the spatial distribution of the summertime, polar ionospheric electron density under conditions of relatively stable IMF Bz<0. The EISCAT Svalbard radar revealed a region of enhanced densities near magnetic noon that, when comparing radar scans from different local times, appeared to be spatially confined in longitude. This was identified as the tongue-of-ionisation (TOI) that comprised photoionisation of sub-auroral origin that is drawn poleward into the polar cap by the anti-sunward flow of the high-latitude convection. The TOI was bounded in longitude by high-latitude troughs; the pre-noon trough on the morning side with a minimum near 78° N and the post-noon trough on the afternoon side with a minimum at 80° N. Complementary measurements by radio tomography, the SuperDARN radars, and a DMSP satellite, together with comparisons with earlier modelling work, provided supporting evidence for the interpretation of the density structuring, and highlighted the role of plasma convection in the formation of summertime plasma distribution. Soft particle precipitation played only a secondary role in the modulation of the large summertime densities entering the polar cap.

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