Evolution of coronal magnetic fields

太阳磁场将太阳内部与光球和日冕相耦合，在那里它驱动加热过程和喷发现象。在日冕中，磁能是准静态地建立起来的，直到它远远超过储存在势磁结构中的能量为止。这种过剩能量间歇性地部分通过大型喷发现象释放，例如日冕物质抛射、耀斑和喷发日冕，但也通过小的喷发现象释放，例如爆炸事件和纳米和微型耀斑，它们可能是加热太阳日冕的中心。磁场矢量的大多数测量限于光球层，因此需要将磁场从光球层外推到日冕中。在这个项目中，我们建议使用一个非线性无力优化代码来计算光球层测量的3D日冕磁场。日冕磁场的无力描述是合理的，因为低电晕和中日冕中存在低？等离子体。这项研究旨在调查活动区的时间准静态演变，目的是深入了解耀斑和日冕物质抛射以及爆炸事件和微型耀斑所需的条件。

The solar magnetic field couples the solar interior with the photosphere and corona where it drives heating processes and eruptive phenomena. In the corona the magnetic energy is quasi-statically built up until it exceeds by far the energy stored in a. potential magnetic configuration. This excess energy is intermittently released in parts by large eruptive phenomena, e.g. coronal mass ejections, flares and eruptive prominences, but also through small ones, such as explosive events and nano- and micro- flares which are probably central for heating the solar corona. Most measurements of the magnetic field vector are restricted to the photosphere, so that the magnetic field needs to be extrapolated from there into the corona. Within this project we propose to use a non-linear force-free optimization code to compute the 3D coronal magnetic field from photospheric measurements. A force-free description of the coronal magnetic field is justified due to the low ß plasma in the low and middle corona. The study aims to investigate the temporal quasi-static evolution of active regions with the aim of getting insights into the conditions required for flares and CMEs, as well as for explosive events and micro flares.