# Evidence for Alfvén waves powering auroral arc via a static electric potential drop

## TL;DR

This study shows that Alfvén waves power Earth's auroras by creating an electric potential drop that accelerates particles.

## Contribution

The paper provides quantitative evidence that Alfvén waves transfer energy to the auroral acceleration region via a static electric potential drop.

## Key findings

- Alfvén waves carry energy from the magnetosphere to the auroral acceleration region.
- The energy from Alfvén waves forms a static electric potential drop that accelerates particles.
- Auroral particle behavior on Earth and Jupiter suggests the mechanism is universal.

## Abstract

Natural light displays known as the aurora provide a captivating glimpse into the electromagnetic dynamics in space plasmas. Aurorae are not exclusive to Earth but also observed on celestial bodies including planets and even comets. Previous studies have unveiled two fundamental auroral acceleration mechanisms: electric potential and Alfvénic acceleration. However, the relation of the energy processes associated with the auroral acceleration region has remained unclear mainly due to the lack of quantitative analysis. Employing quantitative assessment of energy budget using multi-platforms from the magnetosphere to auroral ionosphere, our findings underscore the interplay between these two mechanisms. Here we show that energy carried by Alfvén waves travels from the magnetosphere to the auroral acceleration region, forming an electric potential drop that accelerates particles to produce aurorae. Similarities in auroral particle behaviors between Earth and Jupiter suggest the applicability of the terrestrial scenario to Jupiter and potentially other celestial bodies in the Universe.

Two main acceleration mechanisms in the auroral acceleration region are electric potential and Alfvénic acceleration but associated energy dynamics are not completely resolved. Here, the authors show that Alfvén waves power the Earth’s auroral arc through a static potential drop in the auroral acceleration region.