Modulation of the auroral proton spectrum in the upper atmosphere |
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| Institution: | 1. Geophysical Institute, University of Alaska, Fairbanks, Alaska USA;2. The Auroral Observatory, University of Tromsø, 9000 Tromsø, Norway;1. Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Palo Alto, CA 94304, USA;2. Finnish Meteorological Institute, FI-00560, Helsinki, Finland;3. University College London, Dept. of Physics and Astronomy, Gower Street, London WC1E 6BT, UK;4. Instituto Nacional de Pesquisas Espaciais, S. J. Campos, SP, Brazil;5. HAO/NCAR, P.O. Box 3000, Boulder, CO 80307-3000, USA;6. RHEA System and ESA SSA Programme Office, 64293 Darmstadt, Germany;7. NASA Goddard Space Flight Center, Greenbelt, MD, USA;8. Univ. of Aberystwyth, Penglais STY23 3B, UK;9. RAL Space and STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, UK;10. DH Consultancy BVBA, Diestsestraat 133/3, 3000 Leuven, Belgium;11. German Aerospace Center, Kalkhorstweg 53, 17235 Neustrelitz, Germany;12. Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991, Russian Federation;13. KU Leuven, Celestijnenlaan 200B, Leuven 3001, Belgium;14. Predictive Science Inc., San Diego, CA 92121, USA;15. National Space Science Center, Chinese Academy of Sciences, Haidian District, Beijing 100190, China;p. Instituto de Astronomia y Fisica del Espacio, C1428ZAA Buenos Aires, Argentina;q. Dept. of Physics, Univ. Alberta, Edmonton, AB T6G 2J1, Canada;r. Space Weather and Environment Informatics Lab., National Inst. of Information and Communications Techn., Tokyo 184-8795, Japan;s. Center for Excellence in Space Sciences and Indian Institute of Science, Education and Research, Kolkata, Mohanpur 74125, India;t. Planetary Plasma and Atmospheric Research Center, Tohoku University, 6-3 Aoba, Aramaki, Aoba, Sendai 980-8578, Japan;u. Space Science Department/Chantilly, Aerospace Corporation, Chantilly, VA 20151, USA;v. NOAA Space Weather Prediction Center, Boulder CO 80305, USA;w. Swedish Institute of Space Physics, 75121 Uppsala, Sweden;x. Space Weather Services, Bureau of Meteorology, Surry Hills NSW, Australia;y. Institute for Scientific Research, Boston College, Newton, MA 02459, USA;z. LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon, France;1. Astronomy, Space Science and Meteorology Department, Faculty of Science, Cairo University, Giza, Egypt;2. Basic Science Department, Canadian International College, Cairo, Egypt;3. Sorbonne Université, Ecole polytechnique, Institut Polytechnique de Paris, Université Paris Saclay, Observatoire de Paris, CNRS, Laboratoire de Physique des Plasmas (LPP), 75005, Paris, France;4. Department of ECE, KL Deemed to be University, Koneru Lakshmaiah Education Foundation, Vaddeswaram, Guntur, Andhra Pradesh, 522303, India;5. Faculty of Navigation Science and Space Technology, Beni-Suef University, Egypt;6. Institue of Basic and Applied Science, Egypt Japan University of Science and Technology, Alexandria, Egypt;1. Institue of Basic and Applied Science, Egypt Japan University of Science and Technology, Alexandria, Egypt;2. Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Nagoya, Aichi, Japan;3. Space Weather Monitoring Center, Helwan University, Cairo, Egypt;4. Mathematics & Engineering Physics Department, Faculty of Engineering, Mansoura University, Egypt |
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| Abstract: | An energetic auroral proton entering the atmosphere will alternate between being a proton and a neutral hydrogen atom by charge-exchange collisions with atmospheric constituents. This study uses a simple procedure to evaluate the energy degradation of the penetrating protons/hydrogen atoms by using semi-empirical range relations in air, and derives the particle energy variation as a function of altitude, starting from proton spectra observed from rockets above the main collision region. The main assumptions are that the geomagnetic field is homogeneous and vertical and that the pitch angle of the proton/hydrogen atom is preserved in collisions with atmospheric constituents before being thermalized. The calculations show that the incoming particle flux first loses the low energy particles at the highest pitch angles, even if the beam itself widens as it penetrates the atmosphere. The largest energy loss for particles with initial energy between 10 and 1000 keV occurs in the height interval between 100 and 125 km. |
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