选址与日冕观测组知识库

太阳高能活动爆发与活动区内的电流结构有着密切的联系,安培（Ampere）定律■是测量活动区内视向电流密度的理论基础。由于实测的矢量磁场中不可避免地存在随机噪声,因此,应用安培定律的不同形式计算的电流密度存在显著的差异。为了比较不同形式计算结果的差异并从中探索一种实用的电流计算方法,基于太阳动力学天文台（Solar Dynamic Observatory, SDO）/日震学与磁场成像仪（Helioseismic and Magnetic Imager, HMI）在2011年2月15日测量的活动区AR11158的矢量磁图,利用安培定律的微分算法和积分算法分别计算了活动区内视向电流密度的分布图。结果显示,微分算法获得的视向电流密度分布图受随机噪声的影响要远比积分算法获得的结果大,电流分布图中的电流结构没有积分算法获得的结果清晰。另外,在扩大积分环路半径的情况下,所计算的电流分布图中的噪声信号快速降低,视向电流分布图中的电流结构更清晰。但是当继续扩大积分环路半径时,在获得清晰电流分布图的同时,部分精细结构也随之失真。该研究结果论证了适当扩大积分环路计算视向电流分布图可以降低计算结果受随机噪声的影响,从而获得清晰真实的视向电流分布图,但是积分路径的半径过大在消除噪声影响的同时会丢失电流分布中的一些精细结构。因此在实际计算电流的过程中,应该利用高分辨率的矢量磁图,选定合适的积分路径,利用安培定律的积分算法来计算活动区的视向电流,从而帮助我们探索耀斑爆发与活动区内电流结构的关系。

The explosion of energic solar activity is closely related to the current structure in the active region, Ampere's law jz = 1μ ( !× B) z is the theoretical basis for measuring the current density in the active region. Due to the inevitable existence of random noise in the measured vector magnetic field, the current density calculated by using the different form of Ampere's law is significantly different. In order to compare the differences between the calculated results of different form and explore one of the most practical current calculation methods, this article is based on the vector magnetogram in activity region AR11158 measured by SDO ( Solar Dynamic Observatory) /HMI ( Helioseismic and Magnetic Imager) on February 15, 2011. The distribution of the line-of-sight electric current density in the active region is calculated using differential algorithm and integral algorithm of Ampere's law. The results demonstrate that the distribution of line-of-sight electric current density jz obtained by the differential algorithm is more severely affected by random noise than the result obtained by the integral algorithm, the current structures in the current distribution diagram obtained by the integral algorithm is much clearer than the former. In addition, the noise signal of the calculated current distribution map will decrease sharply, as enlarging the radius of the integral loop, the current structure in the obtained current distribution map will become clear. However, when the radius of the integral loop continues to expand, part of the fine structures of the current distribution map will also be distorted when obtaining a clear current distribution diagram. The result of this study demonstrates that the map of current distribution which is calculated by expanding the integral loop properly can reduce the effect on calculation results from random noise, and obtaining a clear and true line-of-sight electric current distribution map. Though the noise is eliminated if the radius of the integral path is too large, some fine structures in the current distribution will be lost. Therefore, during the course of actual calculating electric current. It is suggested to use high-resolution vector magnetogram and use the integral algorithm of Ampere' s law to calculate the line-of-sight electric current in the active region by selecting an appropriate integration path, which can help us to explore the relationship between the eruptive flares and the structures of current in the active region.