Joy's law (astronomy)

In astronomy, Joy's law describes the distribution of sunspots in active regions and states that the magnitude at which the sunspots are "tilted"—with the leading spot(s) closer to the heliographic equator than the trailing spot(s)―grows with the latitude of these regions.[1][2][3][4] Joy's law provides observational support for the operation of the "alpha effect" in solar dynamo action.[5] It is named after Alfred Harrison Joy.

Sunspot group in the Sun's northern hemisphere with tilt angle

References
  1. Hale GE, Ellerman F, Nicholson SB, Joy AH (1919). "The magnetic polarity of sun-spots". Astrophysical Journal. 49: 153. Bibcode:1919ApJ....49..153H. doi:10.1086/142452.
  2. Wang, Y.-M.; Sheeley, N. R., Jr. (1989). "Average properties of bipolar magnetic regions during sunspot cycle 21". Solar Physics. 124 (1): 81–100. Bibcode:1989SoPh..124...81W. doi:10.1007/BF00146521. S2CID 120540699.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. D'Silva S (1992). "Joy's Law and Limits on the Magnetic Field Strength at the Bottom of the Convection Zone". The Solar Cycle; Proceedings of the National Solar Observatory/Sacramento Peak 12th Summer Workshop, ASP Conference Series (ASP: San Francisco). 27: 168. Bibcode:1992ASPC...27..168D. 1992ASPC...27..168D.
  4. Tian L, Bao S, Zhang H, Wang H (2001). "Relationship in sign between tilt and twist in active region magnetic fields". Astronomy and Astrophysics. 374 (1): 294–300. Bibcode:2001A&A...374..294T. doi:10.1051/0004-6361:20010701.
  5. "NASA/Marshall Solar Physics". solarscience.msfc.nasa.gov. Retrieved 2015-12-10.


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