The Relations Between The Magnetic Properties And The Geometrical Properties

Sunspots are the most visible manifestations of solar magnetic field concentration. Each well developed sunspot is characterized by the umbra and penumbra. The ancient Chinese have kept detailed but very incomplete records dating back over 2000 years. However, it was the rediscovery of sunspots by Galilei, Scheiner and others around 1611, with the help of the newly invented telescope, that marked the beginning of the systematic study of the Sun in the western world and heralded the dawn of research into the Sun's physical characters. Over the ages the prevailing views on the nature of sunspots have undergone major revisions. The discovery of the Wilson effect in 1769 even completely changed the prevailing picture of the structure of the entire Sun, at least temporarily. Since the umbrae appeared to lie deeper than the rest of the solar surface, it was for a time widely believed that the entire solar interior is dark and hence cool, compared to the bright photosphere outside sunspots.The breakthrough in our understanding of the nature of sunspots came in 1908 when George Ellery Hale first measured a magnetic field in sunspots. Since then the magnetic field has become firmly established as the root cause of the sunspot phenomenon. Because the magnetic field cannot be directly observed, adopting spectrum analysis to obtain magnetic field has become the major technique recently. More frequently, an initial guess of model atmosphere is constructed and used to calculate line profiles. These are then compared with observations. If correspondence between synthetic and observed profiles is insufficient, the model is changed. This process is repeated until a satisfactory fit is achieved. Recently, so-called inversion techniques have become more popular. In general, the least-square fit technique is employed to find a minimum (squared difference between observed and synthetic Stokes parameters). The inversed physical parameters by the minimization, therefore, reflect the atmosphere characters of active region.This thesis simply introduces the sunspot basic knowledge observed in chap-...