... Optical data are used to measure the heliolatitude and heliolongitude of the AR, its extent and area, the slope of the axis of a sunspot group with respect to the equator, and the magnitude and polarity of the magnetic field in sunspots. ...
... Optical data are used to measure the heliolatitude and heliolongitude of the AR, its extent and area, the slope of the axis of a sunspot group with respect to the equator, and the magnitude and polarity of the magnetic field in sunspots. ...