University of Maryland
Atlantic Building, Room 2400 4:30 PM Monday, November 2, 2009
Coffee, Tea & Snacks 4:15-4:30 PM

Dean Pesnell
Goddard Space Flight Center (GSFC)

What Is Solar Minimum and Why Should We Care?

The study of solar minimum has been a poor cousin to solar maximum due to the large variations seen in the Sun during maximum. Solar activity is low or absent during solar minimum and all of the phenomena that follow the sunspot number are also smaller in frequency and strength. Even the definition of solar minimum is difficult because the main indicator of solar activity is zero for an extended period of time. But the Sun presents a different face at minimum. The magnetic field is weaker but far more symmetric, almost a dipole for the few minimum that have been measured. A similar behavior is seen in the corona measured by coronagraphs and magnetic fields measured in the heliosphere. Particle fluxes in the solar wind are smaller. As a result the scattering of galactic cosmic rays is reduced and a larger flux of GCRs is be seen at Earth. The current solar minimum has been extreme in having weaker surface fields than previous measurements, few spots for longer than average, and an interesting signature in Earth¹s magnetic field. We shall discuss these magnetic signatures and the implications for Space Weather and climate of a time with weak solar activity.