F.: Evidence for solar-production as a source of polarcap plasma

• Main Authors: S. E. Pryse, R. W. Sims, J. Moen, L. Kersley, D. Lorentzen, W. F. Denig
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Svalbard; EISCAT
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.646.6284; http://www.ann-geophys.net/22/1093/2004/angeo-22-1093-2004.pdf

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, us-ing 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 observa-tions 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 densi-ties were photoionisation produced at the equatorward edge of the afternoon high-latitude cell, where the plasma is ex-posed 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 observa-tions are discussed in terms of earlier modelling studies of polar patch densities. Key words. Ionosphere (polar ionosphere; plasma temera-ture; plasma convection) 1