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

• Main Authors: Pryse, S. E., Sims, R. W., Moen, J., Kersley, L., Lorentzen, D., Denig, W. F.
• Other Authors: Department of Physics, University of Wales, Department of Physics Oslo, Faculty of Mathematics and Natural Sciences Oslo, University of Oslo (UiO)-University of Oslo (UiO), Arctic Geophysics Research, The University Centre in Svalbard (UNIS), AFRL Space Vehicles Directorate, Air Force Research Laboratory (AFRL), United States Air Force (USAF)-United States Air Force (USAF)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2004
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Svalbard; EISCAT
• Online Access: https://hal.science/hal-00317286; https://hal.science/hal-00317286/document; https://hal.science/hal-00317286/file/angeo-22-1093-2004.pdf

International audience 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 B z <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)