The Sun's General Magnetic Field

WITH their admirable experimental technique, Babcock and Babcock have been able to measure certain very small line displacements in the Sun's spectrum, from which they deduce a general magnetic field of the order of −1 gauss. In order to draw this conclusion they use (although implicitly) two theories: (1) the theory of the Zeeman effect, connecting the line displacements with the magnetic field in a small homogeneous volume of gas; (2) the theory of magneto-turbulence in the photosphere, which, as Babcock's ‘point’ measurements include many thousand granulae, is necessary for computing the average.