ABSTRACT

Measurements by NASA’s Advanced Composition Explorer show that in 2009 and early 2010 the intensity of galactic cosmic rays reached the highest level of the space era. These higher intensities occurred during a very unusual solar-minimum period that also featured a record low interplanetary magnetic field strength and a very weak solar wind. However, when compared to the Be-10 record in polar ice cores, and C-14 in tree rings, the space era has experienced a relative minimum in cosmic-ray intensity. This talk will discuss why the recent solar minimum allowed cosmic rays to penetrate more easily to Earth orbit, describe the implications for the space radiation environment, compare present-day cosmic-ray intensities to those in the past, and describe efforts to relate the cosmic ray record over the last 10,000 years to long-term solar-activity.