This paper presents the highlights of joint observations of the inner magnetosphere by the Arase spacecraft, the Van Allen Probes spacecraft, and ground-based experiments integrated into spacecraft programs. The concurrent operation of the two missions in 2017-2019 facilitated the separation of the spatial and temporal structures of dynamic phenomena occurring in the inner magnetosphere. Because the orbital inclination angle of Arase is larger than that of Van Allen Probes, Arase collected observations at higher L -shells up to L ∼ 10 . After March 2017, similar variations in plasma and waves were detected by Van Allen Probes and Arase. We describe plasma wave observations at longitudinally separated locations in space and geomagnetically-conjugate locations in space and on the ground. The results of instrument intercalibrations between the two missions are also presented. Arase continued its normal operation after the scientific operation of Van Allen Probes completed in October 2019. The combined Van Allen Probes (2012-2019) and Arase (2017-present) observations will cover a full solar cycle. This will be the first comprehensive long-term observation of the inner magnetosphere and radiation belts.

Applied Physics Laboratory The Johns Hopkins University 11101 Johns Hopkins Rd Laurel MD 20723 USA

Department of Atmospheric and Oceanic Sciences University of California Los Angeles 7115 Math Sciences Bldg Los Angeles CA 90095 USA

Department of Physics and Astronomy University of Iowa Van Allen Hall Iowa City IA 52242 USA

Department of Physics New Jersey Institute of Technology Newark NJ 07102 USA

Dept of Space Physics Institute of Atmospheric Physics Czech Academy of Sciences Bocni 2 1401 14100 Prague Czechia

Faculty of Mathematics an Physics Charles University 5 Holesovickach 2 18000 Prague Czechia

Graduate School of Engineering Kyushu Institute of Technology Kitakyusyu 804 8550 Japan

Graduate School of Natural Science and Technology Kanazawa University Kanazawa 920 1192 Japan

Graduate School of Science Kyoto University Kyoto 606 8502 Japan

Graduate School of Science Osaka University Toyonaka 560 0043 Japan

Graduate School of Science Tohoku University Sendai 980 8578 Japan

Graduate School of Science University of Tokyo Tokyo 113 0033 Japan

Institute for Advanced Research Nagoya University Nagoya 464 8601 Japan

Institute for Space Earth Environmental Research Nagoya University Nagoya 464 8601 Japan

Institute for the Study of Earth Oceans and Space University of New Hampshire 8 College Road Durham NH 03824 USA

Institute of Astronomy and Astrophysics Academia Sinica No 1 Sec 4 Roosevelt Rd Taipei 10617 Taiwan

Institute of Space and Astronautical Science Japan Aerospace Exploration Agency Sagamihara 252 5210 Japan

Inteligence and Space Reserarch Division Los Alamos National Laboratory PO Box 1663 Los Alamos NM USA

Laboratory for Atmospheric and Space Physics University of Colorado 3665 Discovery Drive 600 UCB Boulder CO 80303 USA

Research Institute for Sustainable Humanosphere Kyoto University Uji 611 0011 Japan

School of Physics and Astronomy University of Minnesota 116 Church St SE Minneapolis MN 55455 USA

Strategic Planning and Management Department Japan Aerospace Exploration Agency Tokyo 101 8008 Japan

The Aerospace Corporation P O Box 92957 Los Angeles CA 90009 2957 USA

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