Horizontal electrojet associated with the sun-aligned arcs |
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| Institution: | 1. Department of Physics, University of Saskatchewan, Saskatoon, Canada, S7N 5E2;2. Center for Atmospheric and Space Sciences, Utah State University, Logan, USA;1. Department of Pulmonary and critical care medicine and West China Biomedical Big Data Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China;2. Med-X Center for Informatics Sichuan University, Chengdu, Sichuan, China;3. SenseTime Research, Beijing, China;4. West China Hospital- SenseTime Joint Lab, Chengdu, Sichuan, China;1. The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA;2. National Center for Atmospheric Research, Boulder, CO, USA;1. National Space Science Center NSSC, Chinese Academy of Sciences, Beijing, China;2. University of Chinese Academy of Sciences, Beijing, China;3. Beijing Key Laboratory of Space Environment Exploration, Beijing, China;4. German Research Centre for Geosciences GFZ, Potsdam, Germany;5. Institute of Geodesy and Geoinformation Science, Technische Universität Berlin, Berlin, Germany;1. JHU/APL, United States;2. NCAR, HAO, United States |
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| Abstract: | Analysis of two strong sun-aligned arcs over the Canadian Eureka Observatory (89° CGM) near the north magnetic pole and accompanying related ground magnetometer measurements has identified an electrojet current of ∼1×104 A flowing within the arcs in a sunward direction. The electrojet current was carried by low energy electrons created by impacting precipitation drifting at E×B/B2 velocity within the arcs, where E is the dawn-to-dusk electric field. One of the arcs moved rapidly in a dawn to dusk direction. The measured arc velocity was 365 m/s. This agrees well with the velocity of 380 m/s inferred from the magnetic field signature of the electrojet current. This study suggests that such an electrojet is present whenever a polar arc is set up. However, a few conditions are required to observe clear ground magnetic signatures of the electrojet: (1) quiet local magnetic conditions; (2) a single sun aligned arc near or moving across zenith; and (3) arc excitation by ≥1 keV electrons. |
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