日米高エネルギー密度科学セミナーが1月17日 9:00am（日本時間）からオンラインにて開催されました。

　　講　　師：　佐野孝好　准教授

　　タイトル：　磁化プラズマ中の大振幅定在ホイッスラー波による粒子加速とプラズマ加熱

背景磁場により磁化されたプラズマ中では，臨界密度を超えて高密度領域まで伝播するホイッスラー波という円偏光波が生じます．対向するホイッスラー波が重なり定在波を形成すると，背景磁場の強さによって，波のエネルギーが電子へ変換されたり，あるいはイオンだけ選択的に変換されるという興味深い現象が生じます．レーザー光から高密度プラズマ粒子への新しいエネルギー変換過程として，宇宙プラズマや核融合研究の観点からも興味深いお話でした．

–Speaker—
Associate Professor Takayoshi Sano
Institute of Laser Engineering, Osaka University

–Title–
Particle acceleration and plasma heating in magnetized plasmas by large-amplitude standing whistler waves

–Abstract–
Laser-plasma interaction in a strong magnetic field has attractive properties regarding particle acceleration and plasma heating. We are focusing on the role of a standing wave created by counter-propagating circularly polarized whistler waves. It has been shown that electrons in standing whistler waves are efficiently accelerated to relativistic speeds [1]. In the standing wave, the electrons are rapidly pulled up from nonrelativistic velocities to the relativistic regime by cyclotron resonance with two waves [2]. As a result, it is possible to accelerate all electrons in a solid to MeV or much faster electrons. On the other hand, cyclotron resonance of electrons does not occur if the background magnetic field is too strong. Instead, it has been shown that ions are selectively heated in standing whistler waves [3,4]. Since whistler waves have no cut-off density, they can penetrate high-density plasmas. Therefore, the ability to heat bulk ions, but not electrons, to 10 keV or higher is exciting from the perspective of laser fusion [4]. Experimental verification of these acceleration mechanisms in a strong magnetic field would be valuable in the future.

[1] T. Sano, et al., Phys. Rev. E 96, 043209 (2017).
[2] S. Isayama, et al., Astrophys. J. 946, 68 (2023).
[3] T. Sano et al., Phys. Rev. E 100, 053205 (2019).
[4] T. Sano et al., Phys. Rev. E 101, 013206 (2020).