Cluster boundary layer measurements and optical observations at magnetically conjugate sites

• Main Authors: Moen, J., Holtet, J. A., Pedersen, A., Lybekk, B., Svenes, K., Oksavik, K., Denig, W. F., Lucek, E., Søraas, F., André, M.
• Other Authors: Department of Physics Oslo, Faculty of Mathematics and Natural Sciences Oslo, University of Oslo (UiO)-University of Oslo (UiO), Norwegian Defence Research Establishment (FFI), Department of Physics, Okayama University, Air Force Research Laboratory (AFRL), United States Air Force (USAF), Space and Atmospheric Physics Group London, Blackett Laboratory, Imperial College London-Imperial College London, Swedish Institute of Space Physics Kiruna (IRF)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2001
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Greenland; Svalbard
• Online Access: https://hal.science/hal-00316954; https://hal.science/hal-00316954/document; https://hal.science/hal-00316954/file/angeo-19-1655-2001.pdf

International audience The Cluster spacecraft experienced several boundary layer encounters when flying outbound from the magnetosphere to the magnetosheath in the dusk sector on 14 January 2001. The dayside boundary layer was populated by magnetosheath electrons, but not with quite as high densities as in the magnetosheath itself. The Cluster ground track was calculated using the Tsyganenko-96 model which appears to be a strong tool for combining high-altitude satellite and ground observations, given that the solar wind conditions are known. This paper focuses on identifying auroral responses corresponding to boundary layer dynamics observed by Cluster. The first boundary layer encounter studied was a brief visit into a closed LLBL, most likely due to a boundary wave that travelled tailward over the spacecraft. A corresponding equatorward and eastward movement was seen in the post-noon aurora between Greenland and Svalbard. The second boundary encounter was in a high-latitude cusp, and occurred as a consequence of a transient reconfiguration of the cusp. The cusp expanded duskward over the spacecraft into the late post-noon sector. NOAA-12 probed the 16:30 MLT sector of this auroral activity, and measured a 1.4 keV electron beam located poleward of the 30 keV electron-trapping boundary. A sequence of three moving auroral forms emanating from this active region are likely candidates for flux transfer events. The auroral signatures are discussed in relation to earlier observations, and appear to be an example of accelerated electrons/discrete post-noon aurora on open magnetic field lines.