磁重联产生的波动对太阳风初始外流加速的三维模拟研究

Magnetohydrodynamics (MHD) waves are ubiquitous in solar atmosphere, and are thought to be important energy source to heat solar corona and solar wind. From observations，it is shown that the small-scale inverted Y-shaped magnetic reconnection excites Alfvén waves, whose energy flux density is sufficient for heating the quiet corona and driving the solar wind. Our 2.5-dimensional numerical simulations demonstrate that inverted Y-shaped magnetic reconnection not only generates the nascent solar wind outflow, but also provokes fast, slow magnetosonic waves and Alfvén waves. This project will use the high-resolution three-dimensional numerical simulation to further study the acceleration of the nascent solar wind outflow via MHD waves excited by inverted Y-shaped magnetic reconnection occurring at the transition region. We will (1) develop a three-dimensional MHD model to describe inverted Y-shaped reconnection with high magnetic Reynolds number; (2) diagnose wave modes excited by fast ejection and collision of the magnetic flux ropes, and the turbulence formed in the intermittent current sheet; (3) analyze the excited waves features, such as amplitude, spectrum, energy flux density, and their steepening, reflection, cascade, dissipation when propagation; (4) evaluate the acceleration of waves through turbulence cascade, mode conversion, phase mixing, and so on. Based upon these researches, the scenario of the waves excited by magnetic reconnection will be improved, and the understanding of the solar wind origin and acceleration will be promoted.

广泛存在于太阳大气磁流体力学波被认为是日冕加热和太阳风加速的重要能量来源。观测研究揭示小尺度倒Y型磁重联可产生阿尔芬波；其携带的能量足以加热日冕和加速太阳风。我们的二维半数值模拟给出倒Y型磁重联不仅形成太阳风初始外流，还激发快慢磁声波及阿尔芬波。本项目拟利用高精度的三维数值模拟，进一步研究过渡区倒Y型磁重联产生的波动加速太阳风初始外流的物理过程；拟：(1)建立高磁雷诺数下倒Y型磁重联的三维数值模型；(2)探讨多尺度磁通量绳的快速抛射和撞击出流区对磁流体力学波的激发及间歇电流片的湍动行为；(3)分析所激发的波动的振幅、频谱、能流通量等特征及上传中的陡化、反射、串级、耗散等物理过程；(4)评估波动通过湍流串级、波模转化、相混合等方式对太阳风初始外流加速的贡献。本研究将有助于完善间歇磁重联激发磁流体力学波的图像，促进对太阳风的起源和加速机制的了解。

磁重联活动和波动是日冕加热和太阳风加速的重要能量来源。本项目通过数值模拟对太阳大气磁重联过程和太阳风中的波动进行了详细研究，具体发现如下：1)磁浮现过程通过磁重联驱动一类似于网络喷流快速的热喷流，并通过其顶端热压及磁压增强触发一类似于色球针状物低速冷喷流，2)太阳风源区倒Y型磁重联可产生类PSP观测的可压缩Alfvénic Spikes，3)太阳大气大尺度电流片是湍动的，倾向于发生激烈的快速磁重联，重联率可达到0.1，4)太阳风中的可压缩成分可表现为传播的慢磁声波及不传播的慢模结构, 5)太阳风中结构的能量在大尺度占主导，波动能量在小尺度和结构的能量接近。该项目研究对于理解太阳风源区物质能量的输运，湍流耗散加热等过程有重要的意义。