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arXiv 1709.09074math.AP
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具有部分高电阻率的二维MHD方程的整体正则性

Global regularity for the 2D MHD equations with partial hyperresistivity

Bo-Qing Dong, Jingna Li, Jiahong Wu

摘要:

本文建立了一个仅含方向高电阻率的二维磁流体动力学方程组解的整体存在性和正则性。更准确地说,$b_1$(磁场的水平分量)的方程仅涉及垂直超扩散(由$Λ_2^{2β} b_1$给出),而$b_2$(垂直分量)的方程仅具有水平超扩散(由$Λ_1^{2β} b_2$给出),其中$Λ_1$和$Λ_2$是方向傅立叶乘法算子,符号分别为$|ξ_1|$和$|ξ_2|$。我们证明了,对于$β>1$,当初始数据足够光滑时,该系统总是具有唯一的全局经典解。该模型是建立在只考虑磁扩散的MHD方程基础上的,它在磁重联和磁湍流的研究中起着重要的作用。在某些物理状态下,在适当的尺度下,磁扩散变得部分(由拉普拉斯算子的一部分给出)。最近有相当多的发展的基本问题,这些方程的经典解决方案是否保持光滑的所有时间。曹武元\cite{CaoWuYuan}和久昭\cite{JiuZhao2}的论文在用全分数Laplacian $(-Δ)^β$和$β>1$给出磁扩散时得到了整体正则性。本文的主要结果只需要方向分数扩散,但我们证明了在所有方向上的正则化。证明利用了对MHD方程中非线性结构的关键观察和傅立叶乘子算子的技术工具,如Hörmander-Mikhlin乘子定理。本文给出的结果对于具有部分磁扩散的二维MHD方程是最尖锐的。

英文摘要:

This paper establishes the global existence and regularity for a system of the two-dimensional (2D) magnetohydrodynamic (MHD) equations with only directional hyperresistivity. More precisely, the equation of $b_1$ (the horizontal component of the magnetic field) involves only vertical hyperdiffusion (given by $Λ_2^{2β} b_1$) while the equation of $b_2$ (the vertical component) has only horizontal hyperdiffusion (given by $Λ_1^{2β} b_2$), where $Λ_1$ and $Λ_2$ are directional Fourier multiplier operators with the symbols being $|ξ_1|$ and $|ξ_2|$, respectively. We prove that, for $β>1$, this system always possesses a unique global-in-time classical solution when the initial data is sufficiently smooth. The model concerned here is rooted in the MHD equations with only magnetic diffusion, which play a significant role in the study of magnetic reconnection and magnetic turbulence. In certain physical regimes and under suitable scaling, the magnetic diffusion becomes partial (given by part of the Laplacian operator). There have been considerable recent developments on the fundamental issue of whether classical solutions of these equations remain smooth for all time. The papers of Cao-Wu-Yuan \cite{CaoWuYuan} and of Jiu-Zhao \cite{JiuZhao2} obtained the global regularity when the magnetic diffusion is given by the full fractional Laplacian $(-Δ)^β$ with $β>1$. The main result presented in this paper requires only directional fractional diffusion and yet we prove the regularization in all directions. The proof makes use of a key observation on the structure of the nonlinearity in the MHD equations and technical tools on Fourier multiplier operators such as the Hörmander-Mikhlin multiplier theorem. The result presented here appears to be the sharpest for the 2D MHD equations with partial magnetic diffusion.

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。

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