Hale's law

Hale's law states that bipolar sunspot groups have opposite leading-polarity orientations in the Sun’s northern and southern hemispheres, and those orientations reverse with each solar cycle.

Connect

Solar dynamo: The processes inside the Sun that generate and maintain its magnetic field. Its cyclic magnetic-field production underlies Hale’s polarity pattern.
Magnetic polarity: The designation of a magnetic pole or field direction as positive or negative relative to a chosen convention. Hale’s law compares the polarities of leading and trailing sunspots.
George Ellery Hale: An American astronomer who established the magnetic nature of sunspots through spectroscopic observations. His measurements revealed the polarity pattern now named for him.
Solar cycle 24: The solar activity cycle that began in 2008 and reached its sunspot maximum around 2014. Its sunspot groups displayed the polarity orientation expected for that cycle.
Sunspot: A temporary dark region on the Sun’s visible surface, caused by concentrated magnetic fields inhibiting convection. Sunspots reveal the opposite magnetic polarities that define bipolar groups.
Solar hemisphere: Either half of the Sun divided by its equator into northern and southern regions. The law assigns opposite leading polarities to these two regions.
Mount Wilson Observatory: An astronomical observatory in California where major early studies of solar magnetism were conducted. Hale and colleagues used its solar observations to map sunspot polarities.
Solar cycle 25: The solar activity cycle that began around 2019 and is ongoing. Its groups reverse the leading-polarity orientation established during cycle 24.
Bipolar sunspot group: A pair or cluster of sunspots with opposite magnetic polarities, typically aligned roughly east–west. Hale’s law describes the polarity orientation of these groups.
Leading sunspot: The sunspot at the western, forward end of a bipolar group as it crosses the solar disk. Its magnetic polarity is the one whose orientation Hale’s law compares across hemispheres.