Coronal Fe xiv Emission During the Whole Heliosphere Interval Campaign

Abstract

Solar Cycle 24 is having a historically long and weak start. Observations of the Fe xiv corona from the Sacramento Peak site of the National Solar Observatory show an abnormal pattern of emission compared to observations of Cycles 21, 22, and 23 from the same instrument. The previous three cycles have shown a strong, rapid ”Rush to the Poles” (previously observed in polar crown prominences and earlier coronal observations) in the parameter N(t,l,dt) (average number of Fe xiv emission features per day over dt days at time t and latitude l). Cycle 24 displays a weak, intermittent, and slow “Rush” that is apparent only in the northern hemisphere. If the northern Rush persists at its current rate, evidence from the Rushes in previous cycles indicates that solar maximum will occur in early 2013 or late 2012, at least in the northern hemisphere. At lower latitudes, solar maximum previously occurred when the time maximum of N(t,l,365) reached approximately 20° latitude. Currently, this parameter is at or below 30° and decreasing in latitude. Unfortunately, it is difficult at this time to calculate the rate of decrease in N(t,l,365). However, the southern hemisphere could reach 20° in 2011. Nonetheless, considering the levels of activity so far, there is a possibility that the maximum could be indiscernible.