Coronal Fe XIV Emission During the Whole Heliosphere Interval Campaign

TL;DR

This study analyzes Fe XIV coronal emission patterns during Solar Cycle 24, revealing an abnormal, weak 'Rush to the Poles' that suggests a delayed or possibly indiscernible solar maximum, especially in the northern hemisphere.

Contribution

It provides the first detailed comparison of Fe XIV emission patterns in Cycle 24 with previous cycles, highlighting unusual solar activity behavior.

Findings

Weak, intermittent 'Rush to the Poles' in Cycle 24

Potential early 2013 or late 2012 solar maximum in the north

Uncertain timing of solar maximum due to low activity levels

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{\deg} latitude. Currently, this parameter is at or below 30{\deg}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{\deg} in 2011. Nonetheless, considering the levels of activity so far, there is a possibility that the maximum could be indiscernible