arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2002.11380physics.plasm-phmath-phmath.MPmath.SP
收藏

磁化伏拉索夫-安培系统与伯恩斯坦-朗道佯谬

The Magnetized Vlasov-Ampère system and the Bernstein-Landau paradox

Frédérique Charles, Bruno Després, Alexandre Rege, Ricardo Weder

摘要:

研究了在恒定外磁场作用下静电等离子体无碰撞运动中的Bernstein-Landau佯谬。Bernstein-Landau佯谬是指在磁场存在的情况下,电场和电荷密度涨落随时间具有振荡行为。这与朗道阻尼完全不同,在没有磁场的情况下,电场在很长时间内趋于零。我们从新的观点考虑这个问题。我们不像通常那样分析线性磁化Vlasov-Poisson系统,而是研究线性磁化Vlasov-Ampère系统。我们将磁化Vlasov-Ampère系统表示为能量有限的Hilbert状态空间中的具有自伴磁化Vlasov-Ampère算子的薛定谔方程。磁化的弗拉索夫-安培算子有一套完整的正交本征函数,其中包括伯恩斯坦模式。磁化的Vlasov-Ampère系统的解在本征函数中的展开显示了随时间的振荡行为。我们证明了最佳条件下的扩张的收敛性,只假设初始状态有有限的能量。这解决了最近在文献中提出的问题。伯恩斯坦模式是不完整的。为了得到一个完整的系统,必须增加与回旋频率的所有整数倍处的本征值相关联的本征函数。这些特殊的等离子体振荡实际上是独立存在的,没有其他模式的激发。当磁场为零时,磁化的Vlasov-Ampère算子的谱由于其定义域的急剧变化而从纯点急剧变化到其核的正交补中的绝对连续.这就解释了伯恩斯坦-朗道悖论。

英文摘要:

We study the Bernstein-Landau paradox in the collisionless motion of an electrostatic plasma in the presence of a constant external magnetic field. The Bernstein-Landau paradox consists in that in the presence of the magnetic field, the electric field and the charge density fluctuation have an oscillatory behavior in time. This is radically different from Landau damping, in the case without magnetic field, where the electric field tends to zero for large times. We consider this problem from a new point of view. Instead of analyzing the linear magnetized Vlasov-Poisson system, as it is usually done, we study the linear magnetized Vlasov-Ampère system. We formulate the magnetized Vlasov-Ampère system as a Schrödinger equation with a selfadjoint magnetized Vlasov-Ampère operator in the Hilbert space of states with finite energy. The magnetized Vlasov-Ampère operator has a complete set of orthonormal eigenfunctions, that include the Bernstein modes. The expansion of the solution of the magnetized Vlasov-Ampère system in the eigenfunctions shows the oscillatory behavior in time. We prove the convergence of the expansion under optimal conditions, assuming only that the initial state has finite energy. This solves a problem that was recently posed in the literature. The Bernstein modes are not complete. To have a complete system it is necessary to add eigenfunctions that are associated with eigenvalues at all the integer multiples of the cyclotron frequency. These special plasma oscillations actually exist on their own, without the excitation of the other modes. In the limit when the magnetic fields goes to zero the spectrum of the magnetized Vlasov-Ampère operator changes drastically from pure point to absolutely continuous in the orthogonal complement to its kernel, due to a sharp change on its domain. This explains the Bernstein-Landau paradox.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑