论文标题
磁静脉外推的矢量磁图的预处理
Preprocessing of vector magnetograms for magnetohydrostatic extrapolations
论文作者
论文摘要
语境。了解3D磁场以及染色体和过渡区域中的血浆很重要。一种方法是基于磁液静态(MHS)状态的假设,将磁场和等离子体从光球上的常规测得的矢量磁图中推断出来。但是,光电数据可能与MHS假设不一致。因此,我们必须研究MHS系统所要求的光磁场对光磁场的限制。此外,应在应用MHS外推之前相应地转换数据。 目标。我们旨在获得一组表面积分作为MHS系统的标准,并使用这组积分来预处理磁力图。 方法。通过应用高斯定理并假设在太阳上存在一个孤立的活性区域,我们将体积中的磁能和力与光球的表面积分相关联。采用相同的方法来获得对光磁场的限制,作为MHS系统的必要标准。我们使用一种优化方法来预处理数据,以最大程度地减少与标准的偏差以及测量值。 结果。通过将病毒定理应用于活动区域,我们发现用于计算无力场能量的边界积分通常低估了大型活性区域的磁能。我们还发现,MHS假设仅需要净洛伦兹净力的x-组件,而净扭矩的Z组分为零。这些零组件是Aly无力场标准的一部分。但是,净力和扭矩的其他组件可能是非零的值。根据新标准,我们预处理磁力图,使其与MHS系统更加一致,同时又与原始数据更接近。
Context. Understanding the 3D magnetic field as well as the plasma in the chromosphere and transition region is important. One way is to extrapolate the magnetic field and plasma from the routinely measured vector magnetogram on the photosphere based on the assumption of the magnetohydrostatic (MHS) state. However, photospheric data may be inconsistent with the MHS assumption. Therefore, we must study the restriction on the photospheric magnetic field, which is required by the MHS system. Moreover, the data should be transformed accordingly before MHS extrapolations can be applied. Aims. We aim to obtain a set of surface integrals as criteria for the MHS system and use this set of integrals to preprocess a vector magnetogram. Methods. By applying Gauss' theorem and assuming an isolated active region on the Sun, we related the magnetic energy and forces in the volume to the surface integral on the photosphere. The same method was applied to obtain restrictions on the photospheric magnetic field as necessary criteria for a MHS system. We used an optimization method to preprocess the data to minimize the deviation from the criteria as well as the measured value. Results. By applying the virial theorem to the active region, we find the boundary integral that is used to compute the energy of a force-free field usually underestimates the magnetic energy of a large active region. We also find that the MHS assumption only requires the x-, y-component of net Lorentz force and the z-component of net torque to be zero. These zero components are part of Aly's criteria for a force-free field. However, other components of net force and torque can be non-zero values. According to new criteria, we preprocess the magnetogram to make it more consistent with the MHS system and, at the same time close, to the original data.