Auroras, Fireflies and Seasonality

September 16, 2015

Aurora Quaker Ridge 062215 6

Photographer: John Stetson
Summary Author: John Stetson

Fireflies (Lampyridae) and their bioluminescent lights are seasonal. In southern Maine, fireflies appear in May and can be seen until mid-August but what about the geomagnetic lights known as auroras, is there an aurora season? Often there seems to be some confusion about auroral activity and seasonality. As a solar observer, I have observed and imaged solar flares that have generated Coronal mass ejections (CMEs) and solar wind. Two days later the solar wind traveled 1 AU to Earth and behold, auroral activity.

As observations of CMEs and auroral activity have occurred in every month throughout the year, my thought was that auroral activity has no seasonal component. Perhaps Earth's 23.5 degree tilt might affect the way our magnetosphere meets incoming solar wind. To help solve this conundrum, I contacted an acquaintance, Lauren Woolsey, who is a student of astrophysics. She replied:

“To my knowledge, there is not a tie between Earth's seasons and geomagnetic activity. The cycle of importance is the solar cycle, which is on an 11-year-ish period. There is some variation in the Earth's magnetic field, which would give rise to seasonality of the effects of solar activity. Think of it like a rainstorm. Some parts of the year we have a bigger umbrella, some parts of the year we have a smaller one. The rain itself (the solar activity) doesn't change on that time scale, but how soaked we get (geomagnetic activity) will vary.”    

Image taken June 22, 2015. 

Photo Details: Camera Model: NIKON D300; Les: 10.5 mm f/2.8; Focal Length: 10.5mm (35mm equivalent: 15mm); Aperture: ƒ/2.8; Exposure Time: 30.000 s; ISO equiv: 640; Software: Adobe Photoshop CS4 Macintosh.