METHODS OF MEASUREMENTS OF THE LONGITUDINAL MAGNETIC FIELD FOR THE SUNSPOT UMBRA
JIN JIE-HAI(PURPLE MOUNTAIN OBSERVATORY, ACADEMIA SINICA)
The methods of measurements of the longitudinal magnetic field are discussed in this paper by using six models of the sunspot umbra. It is shown (Fig. 1) that the mean relative error is larger that 20%, for H=500—4000G in the determination of the longitudinal magnetic field of a sunspot umbra by means of (Ⅴ/Ⅰ) multiplied by a constant. Moreover, it is derived that the minimum of the mean relative error is 1.0% by means of the following equation where c is a constant. At 0.14)Δλ_1, Δλ_20.40they are all less than 5%.