AGU: Sun’s prolonged minimum: Stretched conveyor belt

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AGU: Sun’s prolonged minimum: Stretched conveyor belt

Post by bystander » Wed Aug 04, 2010 12:34 pm

Sun’s prolonged minimum linked to stretched conveyor belt
American Geophysical Union | Journal Highlights | 03 Aug 2010
The Sun goes through cycles lasting approximately 11 years that include phases with increased magnetic activity, more sunspots, and more solar flares, and phases with less activity. The level of activity on the Sun can affect navigation and communications systems on Earth. Puzzlingly, solar cycle 23, which ended recently, lasted longer than previous cycles, with a prolonged phase of low activity that scientists had difficulty explaining.

A new analysis suggests that one reason for the long cycle could be changes in the Sun’s conveyor belt. Just as Earth’s global ocean circulation transports water and heat around the planet, the Sun has a conveyor belt in which plasma flows along the surface toward the poles, sinks, and returns toward the equator, transporting magnetic flux along the way. Recent measurements show that in solar cycle 23, the poleward flow extended all the way to the poles, while in previous solar cycles the flow turned back toward the equator at about 60 degrees latitude. Furthermore, from mass conservation, the return flow was slower in cycle 23 than in previous cycles.

Dikpati et al. use simulations to model how the solar plasma conveyor belt affects the solar cycle. The authors find that the longer conveyor belt and the slower return flow could have caused the longer duration of cycle 23. The results should help scientists better understand the factors controlling the timing of the solar cycles and could lead to better predictions.
Impact of changes in the Sun's conveyor-belt on recent solar cycles - M Dikpati et al

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NSF: Extended Lower Solar Activity: Changes in Sun's Conveyo

Post by bystander » Fri Aug 13, 2010 1:24 pm

Extended Period of Lower Solar Activity Linked to Changes in Sun's Conveyor Belt
National Science Foundation | 12 Aug 2010
A new analysis of the unusually long solar cycle that ended in 2008 suggests that one reason for the long cycle could be a stretching of the sun's conveyor belt, a current of plasma that circulates between the sun's equator and its poles.

The sun goes through cycles lasting approximately 11 years that include phases with increased magnetic activity, more sunspots, and more solar flares, and phases with less activity.

The level of activity on the sun can affect navigation and communications systems on Earth.

The results of this study should help scientists better understand the factors controlling the timing of solar cycles and could lead to better predictions.

The study was conducted by Mausumi Dikpati, Peter Gilman, and Giuliana de Toma, all scientists in the High Altitude Observatory at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., and by Roger Ulrich at the University of California, Los Angeles.

The results appeared on July 30 in the journal Geophysical Research Letters. The study was funded by the National Science Foundation (NSF), NCAR's sponsor, and by NASA.

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