Northern preference for terrestrial electromagnetic energy input from space weather

Terrestrial space weather involves the transfer of energy and momentum from the solar wind into geospace. Despite recently discovered seasonal asymmetries between auroral forms and the intensity of emissions between northern and southern hemispheres, seasonally averaged energy input into the ionosphere is still generally considered to be symmetric. Here we show, using Swarm satellite data, a preference for electromagnetic energy input at 450km altitude into the northern hemisphere, on both the dayside and the nightside, when averaged over season. We propose that this is explained by the offset of the magnetic dipole away from Earth's center. This introduces a larger separation between the magnetic pole and rotation axis in the south, creating different relative solar illumination of northern and southern auroral zones, resulting in changes to the strength of reflection of incident Alfven waves from the ionosphere. Our study reveals an important asymmetry in seasonally averaged electromagnetic energy input to the atmosphere. Based on observed lower Poynting flux on the nightside this asymmetry may also exist for auroral emissions. Similar offsets may drive asymmetric energy input, and potentially aurora, on other planets. Seasonally averaged energy input into the ionosphere from geospace is generally considered to be symmetric. Here, the authors show preference for electromagnetic energy input at 450km altitude into the northern hemisphere, on both the dayside and the nightside, when averaged over season.

Automated summary

The study found that the offset of the magnetic dipole on Earth causes a seasonal asymmetric electromagnetic energy input to the Northern Hemisphere, which may also exist on other planets.