Presentation Abstract

Session: Lower Atmosphere
Presentation Number: P17.21
Title: A Decade of Diminishing Sunspot Vigor
Presentation Start: 6/13/2011 7:30:00 AM
Presentation End: 6/16/2011 8:30:00 AM
Authors: W. C. Livingston1, M. Penn1, L. Svalgard2
1National Solar Obs., 2Stanford University.
Abstract: 1A Decade of Diminishing Sunspot Vigor
William Livingston1
Matt Penn1
Leif Svalgard2
Sunspots are small dark areas on the solar disk where internal magnetism, 1500 to 3500 Gauss, has been buoyed to the surface. (Spot life times are the order of one day to a couple of weeks or more. They are thought to be dark because convection inhibits the outward transport of energy there). Their “vigor” can be described by spot area, spot brightness intensity, and magnetic field. From 2001 to 2011 we have measured field strength and brightness at the darkest position in umbrae of 1750 spots using the Zeeman splitting of the Fe 1564.8 nm line. Only one observation per spot per day is carried out during our monthly telescope time of 3-4 days average. Over this interval the temporal mean magnetic field has declined about 500 Gauss and mean spot intensity has risen about 20%. We do not understand the physical mechanism behind these changes or the effect, if any, it will have on the Earth environment.