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608 results on '"Sakai, Jun-ichi"'

2. Particle-In-Cell simulations of circularly polarised Alfv\'en wave phase mixing: a new mechanism for electron acceleration in collisionless plasmas

Author

Tsiklauri, David, Sakai, Jun-Ichi, and Saito, Shinji

Subjects
Astrophysics, Physics - Plasma Physics, Physics - Space Physics
Abstract

In this work we used Particle-In-Cell simulations to study the interaction of circularly polarised Alfv\'en waves with one dimensional plasma density inhomogeneities transverse to the uniform magnetic field (phase mixing) in collisionless plasmas. In our preliminary work we reported discovery of a new electron acceleration mechanism, in which progressive distortion of the Alfv\'en wave front, due to the differences in local Alfv\'en speed, generates an oblique (nearly parallel to the magnetic field) electrostatic field. The latter accelerates electrons through the Landau resonance. Here we report a detailed study of this novel mechanism, including: (i) analysis of broadening of the ion distribution function due to the presence of Alfv\'en waves and (ii) the generation of compressive perturbations due to both weak non-linearity and plasma density inhomogeneity. The amplitude decay law in the inhomogeneous regions, in the kinetic regime, is demonstrated to be the same as in the MHD approximation described by Heyvaerts and Priest (1983)., Comment: Final, accepted in Astron. Astrophys., version; Low resolution figures are included here; High resolution figure version is available from D. Tsiklauri upon request. Astron. Astrophys. (in press)

Published
2004
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3. Phase mixing of shear Alfven waves as a new mechanism for electron acceleration in collisionless, kinetic plasmas

Author

Tsiklauri, David, Sakai, Jun-Ichi, and Saito, Shinji

Subjects
Astrophysics
Abstract

Particle-In-Cell (kinetic) simulations of shear Alfv\'en wave interaction with one dimensional, across the uniform magnetic field, density inhomogeneity (phase mixing) in collisionless plasma were performed for the first time. As a result a new electron acceleration mechanism is discovered. Progressive distortion of Alfv\'en wave front, due to the differences in local Alfv\'en speed, generates nearly parallel to the magnetic field electrostatic fields, which accelerate electrons via Landau damping. Surprisingly, amplitude decay law in the inhomogeneous regions, in the kinetic regime, is the same as in the MHD approximation described by Heyvaerts and Priest (1983)., Comment: Final, accepted in New J. Phys., version, New IMPORTANT material added. Also can be downloaded from http://www.iop.org/EJ/abstract/1367-2630/7/1/079/

Published
2004
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23. Anti-TNF-α Therapy for Refractory Uveitis Associated with Behçet's Syndrome and Sarcoidosis: A Single Center Study of 131 Patients.

Author

Kunimi, Keiko, Usui, Yoshihiko, Asakage, Masakai, Maehara, Chihiro, Tsubota, Kinya, Mitsuhashi, Ryosuke, Umazume, Akihiko, Kezuka, Takeshi, Sakai, Jun-Ichi, and Goto, Hiroshi

Abstract

The efficacy of infliximab (IFX) and adalimumab (ADA) for treating Behçet's syndrome (BS) and sarcoidosis has not been compared adequately. We reviewed the medical records of patients with uveitis diagnosed at Tokyo Medical University Hospital and compared the efficacy of IFX and ADA for BS and the efficacy of ADA for sarcoidosis and BS. 68 patients in IFX group and 63 patients in ADA group were analyzed. In BS patients, IFX and ADA were both effective in improving uveitic macular edema (UME). ADA improved UME in BS but not in sarcoidosis patients. The efficacy of ADA in reducing doses of corticosteroids and glaucoma medications was better in sarcoidosis than in the BS group. Both IFX and ADA are efficacious in improving UME in BS patients. The reason that ADA improves UME better in BS than in sarcoidosis may be due to the difference in pathogenesis between these diseases. [ABSTRACT FROM AUTHOR]

Published
2022
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28. Book reviews

Author

Humphreys, R. M., Kemp, S., Savonije, G., van der Hucht, K. A., van der Kruit, P. C., Miley, G., Bumba, V., van Nieuwkoop, J., van Hoolst, T., Cox, A., Rutten, R. J., Kleczek, J., de Jager, Cornelis, Jerzykiewicz, M., Zwaan, C., Poedts, S., Sakai, Jun -Ichi, Pecker, J. -C., Heikkila, W., de Jong, T., Wilson, P. R., Müller, E. A., Hoyng, P., Icke, V., Shore, S. N., Achterberg, A., Lucchin, F., Butcher, H., Ne'eman, Y., Heidmann, J., Belton, M. J. S., de Graauw, Th., Waters, L. B. F. M., Pacini, F., Hultqvist, B., Akasofu, S. -I., Vial, J. -C., Schatzman, E., van der Laan, H., Cole, K. D., Vanbeveren, D., Southwood, D., van der Klis, M., and Katgert, Peter

Published
1996
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45. High-energy particle acceleration during the implosion driven by 3-dimensional X-type current loop coalescence in solar flares

Author

Sakai, Jun-ichi, Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Ruelle, D., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Uchida, Yutaka, editor, Canfield, Richard C., editor, Watanabe, Tetsuya, editor, and Hiei, Eijiro, editor

Published
1991
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