We analyze sunspot rotation and magnetic transients in NOAA AR 11429 during two X-class(X5.4 and X1.3)flares using data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.A large leading sunspot with positive magnetic polarity rotated counterclockwise.As expected,the rotation was significantly affected by the two flares.Magnetic transients induced by the flares were clearly evident in the sunspots with negative polarity.They were moving across the sunspots with speed of order 3-7 km s-1.Furthermore,the trend of magnetic flux evolution in these sunspots exhibited changes associated with the flares.These results may shed light on understanding the evolution of sunspots.
Jian-Chuan ZhengZhi-Liang YangJian-Peng GuoKai-Ming GuoHui HuangXuan SongWei-Xing Wan
High-performance computational models are required to make the real-time or faster than rea^-time numerical prediction of adverse space weather events and their influence on the geospace environment. The main objective in this article is to explore the application of programmable graphic processing units （GPUs） to the numerical space weather modeling for the study of solar wind background that is a crucial part in the numerical space weather modeling. GPU programming is realized for our Solar-Interplanetary-CESE MHD model （SIP-CESE MHD model） by numerically studying the solar corona/interplanetary so- lar wind. The global solar wind structures are obtained by the established GPU model with the magnetic field synoptic data as input. Meanwhile, the time-dependent solar surface boundary conditions derived from the method of characteristics and the mass flux limit are incorporated to couple the observation and the three-dimensional （3D） MHD model. The simulated evolu- tion of the global structures for two Carrington rotations 2058 and 2062 is compared with solar observations and solar wind measurements t^om spacecraft near the Earth. The MHD model is also validated by comparison with the standard potential field source surface （PFSS） model. Comparisons show that the MHD results are in good overall agreement with coronal and interplanetary structures, including the size and distribution of coronal holes, the position and shape of the streamer belts, and the transition of the solar wind speeds and magnetic field polarities.
FENG XueShangZHONG DingKunXIANG ChangQingZHANG Yao
We present a newly developed global magnetohydrodynamic(MHD) model to study the responses of the Earth's magnetosphere to the solar wind. The model is established by using the space-time conservation element and solution element(CESE) method in general curvilinear coordinates on a six-component grid system. As a preliminary study, this paper is to present the model's numerical results of the quasi-steady state and the dynamics of the Earth's magnetosphere under steady solar wind flow with due northward interplanetary magnetic field(IMF). The model results are found to be in good agreement with those published by other numerical magnetospheric models.
A new hybrid numerical scheme of combining an E-CUSP(Energy-Convective Upwind and Split Pressure) method for the fluid part and the Constrained Transport(CT) for the magnetic induction part is proposed.In order to avoid the occurrence of negative pressure in the reconstructed profiles and its updated value,a positivity preserving method is provided.Furthermore,the MHD equations are solved at each physical time step by advancing in pseudo time.The use of dual time stepping is beneficial in the computation since the use of dual time stepping allows the physical time step not to be limited by the corresponding values in the smallest cell and to be selected based on the numerical accuracy criterion.This newly established hybrid scheme combined with positivity preserving method and dual time technique has demonstrated the accurateness and robustness through numerical experiments of benchmark problems such as the 2D Orszag-Tang vortex problem and the3 D shock-cloud interaction problem.
Magnetic clouds have the outstanding observational features of low proton temperature and plasma beta value, but numerous observations show that some magnetic clouds often have local high temperature phenomena. The local high temperature protons may be heated by magnetic reconnections within magnetic clouds. Here we take the magnetic cloud on 18–20 October 1995 as an example to discuss the possible heating mechanism. There is a famous protuberance in proton temperature between the front boundary and 11: 00 UT on 19 October 1995. Eight magnetic reconnection events were identified within the magnetic cloud, whose duration was less than 31 hours, and most of these reconnection events occurred within the proton temperature enhanced part of the magnetic cloud. Hence, it is possible for the local protons in the magnetic cloud to be heated by magnetic reconnections.
基于1996—2005年88个引起重大地磁暴的CME(日冕物质抛射)事件、1996—2000年的47个CME事件以及1997—2002年的29个全晕状CME事件,结合ACE卫星在1 AU处的太阳风和行星际磁场观测资料以及Wilcox Solar Observatory(WSO)天文台的太阳光球层磁图,分析了背景太阳风速度和日球电流片对CME到达1 AU处渡越时间预报误差的影响.结果表明,背景太阳风速度与CME渡越时间误差并没有明显的相关性,在考虑了磁云通量管轴相对黄道面夹角的影响后相关性依然不明显.然而日球电流片对CME渡越时间却有明显的影响,对于初速度较小的异侧CME事件,其渡越时间大于同侧事件;而对于具有较大初速度的CME事件,异侧事件的渡越时间明显小于同侧事件.研究结果表明,CME与太阳风以及日球电流片的相互作用并不是简单的对流相互作用,造成高速CME异侧事件快于同侧事件到达地球的因素非常复杂,有待深入研究.
