The process by which an existing magnetic field of ∼10²–10³ T may be amplified by an order of magnitude along the axis of laser propagation in underdense plasma by an intense laser pulse is investigated. The mechanism underlying the effect is understood to be ponderomotive in nature, initiated by the drift motion of electrons displaced by the laser pulse as they relax towards the axis, and sustained by a combination of quasistatic magnetic field structures and electron Hall and diamagnetic currents. We employ two- and three-dimensional particle-in-cell simulations to numerically investigate the process and find qualitative agreement with the scaling relations found in our theory model. The lifetime of the process is considered, and we find the major factor limiting its growth and lifetime is ion motion, which disrupts the electron currents necessary to sustain the induced magnetic field. This field is found to be of sufficient strength, and is long-lived enough to be relevant for study in relation to applications in radiation production and laboratory astrophysics.

研究了通过强激光脉冲沿激光传播轴在低密度等离子体中将 ∼10 ² –10 ³ T的现有磁场放大一个数量级的过程。该效应的潜在机制被理解为本质上是有质的，由电子在向轴松弛时被激光脉冲位移的漂移运动，并由准静态磁场结构和电子霍尔和抗磁电流的组合维持。我们采用二维和三维的细胞内粒子模拟对这个过程进行数值研究，并找到与我们理论模型中发现的比例关系的定性一致性。考虑了该过程的寿命，我们发现限制其生长和寿命的主要因素是离子运动，它破坏了维持感应磁场所需的电子流。发现该领域具有足够的强度，并且足够长，足以与辐射产生和实验室天体物理学中的应用相关的研究相关。