Articles | Volume 43, issue 2
https://doi.org/10.5194/angeo-43-621-2025
https://doi.org/10.5194/angeo-43-621-2025
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20 Oct 2025
Regular paper | Highlight paper |  | 20 Oct 2025

Effects of geomagnetic mirror force and pitch angles of precipitating electrons on ionization of the polar upper atmosphere

Tomotaka M. Tanaka, Yasunobu Ogawa, Yuto Katoh, Mizuki Fukizawa, Anton Artemyev, Vassilis Angelopoulos, Xiao-Jia Zhang, Yoshimasa Tanaka, and Akira Kadokura

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Cited articles

Angelopoulos, V., Cruce, P., Drozdov, A., Grimes, E. W., Hatzigeorgiu, N., King, D. A., Larson, D., Lewis, J. W., McTiernan, J. M., Roberts, D. A., Russell, C. L., Hori, T., Kasahara, Y., Kumamoto, A., Matsuoka, A., Miyashita, Y., Miyoshi, Y., Shinohara, I., Teramoto, M., Faden, J. B., Halford, A. J., McCarthy, M., Millan, R. M., Sample, J. G., Smith, D. M., Woodger, L. A., Masson, A., Narock, A. A., Asamura, K., Chang, T. F., Chiang, C.-Y., Kazama, Y., Keika, K., Matsuda, S., Segawa, T., Seki, K., Shoji, M., Tam, S. W. Y., Umemura, N., Wang, B.-J., Wang, S.-Y., Redmon, R., Rodriguez, J. V., Singer, H. J., Vandegriff, J., Abe, S., Nose, M., Shinbori, A., Tanaka, Y.-M., UeNo, S., Andersson, L., Dunn, P., Fowler, C., Halekas, J. S., Hara, T., Harada, Y., Lee, C. O., Lillis, R., Mitchell, D. L., Argall, M. R., Bromund, K., Burch, J. L., Cohen, I. J., Galloy, M., Giles, B., Jaynes, A. N., Le Contel, O., Oka, M., Phan, T. D., Walsh, B. M., Westlake, J., Wilder, F. D., Bale, S. D., Livi, R., Pulupa, M., Whittlesey, P., DeWolfe, A., Harter, B., Lucas, E., Auster, U., Bonnell, J. W., Cully, C. M., Donovan, E., Ergun, R. E., Frey, H. U., Jackel, B., Keiling, A., Korth, H., McFadden, J. P., Nishimura, Y., Plaschke, F., Robert, P., Turner, D. L., Weygand, J. M., Candey, R. M., Johnson, R. C., Kovalick, T., Liu, M. H., McGuire, R. E., Breneman, A., Kersten, K., and Schroeder, P.: The Space Physics Environment Data Analysis System (SPEDAS), Space Sci. Rev., 215, 9, https://doi.org/10.1007/s11214-018-0576-4, 2019. 
Capannolo, L., Li, W., Ma, Q., Qin, M., Shen, X.-C., Angelopoulos, V., Artemyev, A., Zhang, X.-J., and Hanzelka, M.: Electron Precipitation Observed by ELFIN Using Proton Precipitation as a Proxy for Electromagnetic Ion Cyclotron (EMIC) Waves, Geophysical Research Letters, 50, e2023GL103519, https://doi.org/10.1029/2023GL103519, 2023. 
Emmert, J. T., Jones Jr., M., Siskind, D. E., Drob, D. P., Picone, J. M., Stevens, M. H., Bailey, S. M., Bender, S., Bernath, P. F., Funke, B., Hervig, M. E., and Pérot, K.: NRLMSIS 2.1: An Empirical Model of Nitric Oxide Incorporated Into MSIS, Journal of Geophysical Research: Space Physics, 127, e2022JA030896, https://doi.org/10.1029/2022JA030896, 2022. 
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Editor-in-chief
The authors studied the effects of the geomagnetic mirror force on electron density enhancements in the polar atmosphere due to energetic electron precipitation. Considering this phenomenon in simulations this substantially reduced electron density, which was veryfied by observations. This could have wide consequences for the improvement of atmospheric ionization models.
Short summary
The magnetic mirror force bends the orbits of electrons precipitating into the atmosphere. It has been suggested that relativistic electrons make much less ionization due to the force than if it did not exist, but the actual effectivity in the atmospheric electron density has not been revealed. We used conjugated observational data from the ELFIN (Electron Losses and Fields INvestigation) satellite and the EISCAT (European Incoherent SCATter scientific radar system) Tromsø radar to find that the electron density decreased by about 40 % at 80 km altitude because of the force.
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