Recovering Solar Toroidal Field Dynamics from Sunspot Location Patterns

• Published in: The Astrophysical journal 2005-09, Vol.630 (2), p.1194-1205
• Main Authors: Norton, Aimee A, Gilman, Peter A
• Format: Article
• Language: English
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/431961

We analyze both Kitt Peak magnetogram data and MDI continuum intensity sunspot data to search for the following solar toroidal band properties: width in latitude and the existence of a tipping instability (longitudinal m = 1 mode) for any time during the solar cycle. In order to determine the extent to which we can recover the toroidal field dynamics, we forward-model artificially generated sunspot distributions from subsurface toroidal fields that we have assigned certain properties. Sine-curve fitting of Kitt Peak magnetogram data provided an upper limit of 15 to the tipping amplitude but could not adequately separate the tip from the width of the toroidal band. We then analyzed two sunspot distribution parameters using MDI and model data: the average latitudinal separation of sunspot pairs as a function of longitudinal separation and the number of sunspot pairs creating a given angle with respect to the east-west direction. A toroidal band of 10 width with a constant tipping of 5 best fits MDI data early in the solar cycle, when the sunspot band is at high latitudes (>18.5). A toroidal band of 20 width with a tipping amplitude decreasing in time from 5 to 0 best fits MDI data late in the solar cycle when the sunspot band is at low latitudes (