Mandal Devshree, Vashistha Ayushi, Das Amita
Institute for Plasma Research, HBNI, Bhat, Gandhinagar, 382428, India.
Homi Bhabha National Institute, Mumbai, 400094, India.
Sci Rep. 2021 Jul 21;11(1):14885. doi: 10.1038/s41598-021-94029-3.
An electromagnetic (EM) pulse falling on a plasma medium from vacuum can either reflect, get absorbed or propagate inside the plasma depending on whether it is overdense or underdense. In a magnetized plasma, however, there are usually several pass and stop bands for the EM wave depending on the orientation of the magnetic field with respect to the propagation direction. The EM wave while propagating in a plasma can also excite electrostatic disturbances in the plasma. In this work Particle-In-Cell simulations have been carried out to illustrate the complete transparency of the EM wave propagation inside a strongly magnetized plasma. The external magnetic field is chosen to be perpendicular to both the wave propagation direction and the electric field of the EM wave, which is the X mode configuration. Despite the presence of charged electron and ion species the plasma medium behaves like a vacuum. The observation is understood with the help of particle drifts. It is shown that though the two particle species move under the influence of EM fields their motion does not lead to any charge or current source to alter the dispersion relation of the EM wave propagating in the medium. Furthermore, it is also shown that the stop band for EM wave in this regime shrinks to a zero width as both the resonance and cut-off points approach each other. Thus, transparency to the EM radiation in such a strongly magnetized case appears to be a norm.
从真空入射到等离子体介质上的电磁（EM）脉冲，根据等离子体是过密还是欠密，可能会发生反射、被吸收或在等离子体内部传播。然而，在磁化等离子体中，根据磁场相对于传播方向的取向，电磁波通常存在多个通带和阻带。电磁波在等离子体中传播时也会激发等离子体中的静电扰动。在这项工作中，进行了粒子模拟以说明电磁波在强磁化等离子体内部传播时的完全透明性。选择外部磁场与波传播方向和电磁波的电场都垂直，这是X模配置。尽管存在带电的电子和离子种类，但等离子体介质的行为就像真空一样。借助粒子漂移来理解这一观测结果。结果表明，尽管两种粒子在电磁场的影响下运动，但它们的运动不会导致任何电荷或电流源来改变在介质中传播的电磁波的色散关系。此外，还表明在这种情况下，随着共振点和截止点相互靠近，电磁波的阻带宽度缩小到零。因此，在这种强磁化情况下，对电磁辐射的透明性似乎是常态。
