Joy's Law (astronomy)

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In astronomy, Joy's Law describes sunspots and states that their tendency to be "tilted" (with the leading spot closer to the equator than the following spots) grows with the heliographic 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.


  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: 81–100. Bibcode:1989SoPh..124...81W. doi:10.1007/BF00146521. 
  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. 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". Retrieved 2015-12-10.