Northern preference for terrestrial electromagnetic energy input from space weather

Area of Science:

• Geophysics
• Space Weather
• Atmospheric Physics

Background:

• Terrestrial space weather involves solar wind energy transfer into geospace.
• Seasonal asymmetries in auroral forms and emissions between hemispheres are known.
• Seasonally averaged ionospheric energy input is generally assumed to be symmetric.

Purpose of the Study:

• To investigate hemispheric asymmetries in seasonally averaged electromagnetic energy input into the ionosphere.
• To determine the cause of observed energy input asymmetries.
• To explore potential implications for auroral emissions and planetary space weather.

Main Methods:

• Analysis of Swarm satellite data at 450 km altitude.
• Seasonal averaging of electromagnetic energy input.
• Modeling the influence of the Earth's magnetic dipole offset.

Main Results:

• A preference for electromagnetic energy input into the Northern Hemisphere was observed, on both dayside and nightside.
• The Earth's offset magnetic dipole is proposed as the cause of this asymmetry.
• Different relative solar illumination of auroral zones due to dipole offset affects Alfvén wave reflection.

Conclusions:

• A significant asymmetry exists in seasonally averaged electromagnetic energy input to Earth's atmosphere.
• This asymmetry may also affect auroral emissions, particularly on the nightside.
• Similar magnetic field offsets on other planets could drive asymmetric energy input and aurora.