Changes in the solar magnetic
نویسنده
چکیده
The combined observing power of the Yohkoh, SOHO and TRACE spacecrafts, along with the continuing ground-based observations has proved invaluable for the detection of changes in the magnetic morphology preceding coronal mass ejections (CMEs). A wide range of activity from small scale dimmings to large scale eruptions covering half the solar disk have been observed. The relationship between ares and CMEs has also become clearer. Rather than one event causing the other it would seem that it is a global change in the magnetic eld which causes both. Recently there has been a lot of interest in the sigmoid (S-shaped) structures seen in soft X-rays. The likelihood of a CME occuring appears to increase if there is a sigmoidal structure observed. This has formed the basis of more extensive studies into predicting the time and location of a CME from the changes in behaviour of features on the solar disk.
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