Joey's Law

Joey's Law is a pattern observed in the orientation of sunspot groups .

Groups of sunspots, as a rule, have a bipolar structure: they consist of two subgroups of different magnetic polarity. In this case, one of the subgroups (“head”) is usually located to the west and somewhat closer to the solar equator, the second (“tail”) is to the east and somewhat further from it. Thus, the line connecting these subgroups (“the axis of the bipolar group”) is inclined relative to the equator.

The pattern expressed by Joey's law is that the slope of the group axis tends to increase with the growth of heliographic latitude .

This pattern was first noted in 1919 in the work of American astronomers ^[1] , and subsequently was repeatedly investigated ^{[2] [3] [4]} and received the name of one of the authors of the pioneering work, A. Joy

A statistical analysis of the coordinates of the spots shows that, although the spread in the tilt angles of individual groups is quite large, the average tilt angle increases from several degrees (for groups close to the equator) to 10-15 ° for high-latitude groups (with latitudes ± 25-30 ° and above). ^{[2] [5]}

At present, it is generally accepted that Joy’s law is due to the action of the Coriolis force , which develops pop-up magnetic fields that form sunspots. ^[3]