How much more can sunspots tell us about the solar dynamo?

Norton, Aimee A. and Jones, Eric H. and Liu, Y. and Hayashi, K. and Hoeksema, J. T. and Schou, Jesper (2012) How much more can sunspots tell us about the solar dynamo? In: 28th International Astronomical Union Symposium (IAU 2012): Solar and Astrophysical Dynamos and Magnetic Activity, 27-31 Aug 2012, Beijing, China.


Sunspot observations inspired solar dynamo theory and continue to do so. Simply counting them established the sunspot cycle and its period. Latitudinal distributions introduced the tough constraint that the source of sunspots moves equator-ward as the cycle progresses. Observations of Hale's polarity law mandated hemispheric asymmetry. How much more can sunspots tell us about the solar dynamo? We draw attention to a few outstanding questions raised by inherent sunspot properties. Namely, how to explain sunspot rotation rates, the incoherence of follower spots, the longitudinal spacing of sunspot groups, and brightness trends within a given sunspot cycle. After reviewing the first several topics, we then present new results on the brightness of sunspots in Cycle 24 as observed with the Helioseismic Magnetic Imager (HMI). We compare these results to the sunspot brightness observed in Cycle 23 with the Michelson Doppler Imager (MDI). Next, we compare the minimum intensities of five sunspots simultaneously observed by the Hinode Solar Optical Telescope Spectropolarimeter (SOT-SP) and HMI to verify that the minimum brightness of sunspot umbrae correlates well to the maximum field strength. We then examine 90 and 52 sunspots in the north and south hemisphere, respectively, from 2010 - 2012. Finally, we conclude that the average maximum field strengths of umbra 40 Carrington Rotations into Cycle 24 are 2690 Gauss, virtually indistinguishable from the 2660 Gauss value observed at a similar time in Cycle 23 with MDI.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Paper)
Refereed: Yes
Item Status: Live Archive
Additional Information: © International Astronomical Union 2013.
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - No Department
Date Deposited: 02 Aug 2013 03:34
Last Modified: 05 Sep 2017 00:53
Uncontrolled Keywords: dynamo; magnetic fields; sunspots
Fields of Research : 09 Engineering > 0906 Electrical and Electronic Engineering > 090606 Photonics and Electro-Optical Engineering (excl. Communications)
02 Physical Sciences > 0204 Condensed Matter Physics > 020402 Condensed Matter Imaging
02 Physical Sciences > 0201 Astronomical and Space Sciences > 020109 Space and Solar Physics
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering
Identification Number or DOI: 10.1017/S1743921313002172

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