[Phys-L] Re: solar cycle

[David Bowman <David_Bowman@GEORGETOWNCOLLEGE.EDU>]

Regarding Anthony's question:

> Sunspots follow a 22-year cycle (return to same polarity), and this
> cycle matches droughts on Earth. As the sunspot numbers increase,
> oceans become warmer. But isn't the Sun's surface cooler during
> these times? How can a cooler solar surface cause the Earth to warm
> up? I've never understood this. Does it have to do with the
> increased solar magnetic activity that heats the corona?

As I recall, I think that during a sunspot maximum the Sun's
luminosity is greater than average because the average temperature
of the background photosphere where there are no sunspots increases
enough to more than compensate for the reduced radiant flux from the
cooler sunspot regions.  Besides this, typically, the frequency of
flares coronal mass ejections, & other active sun processes increases
during sun spot maxima, and the energy released by such things also
heats up the Earth (after the shock wave of particles reaches us a
few days after we see the eruptions).

David Bowman