Question

Jupiter’s aurorae are affected by its moons.

(a) Are these aurorae visible?

(b) What gas(es) produce them?

(c) How can Jupiter’s moons affect where the solar wind hits Jupiter?

Answer 1

(a)   Auroras are caused by charged particles hitting a planet’s atmosphere at high speed. Jupiter’s visible vibrant blue aurora is triggered by eruptions of charged ions from the moon Io, which is pulled and squashed by the gravity of Jupiter and its other big moons. Jupiter also has an aurora in the ultraviolet part of the spectrum, and this is caused by the rapid spin of the planet itself. Jupiter, also have auroras over their polar regions, but these are not just seen in the visible part of the spectrum. There are also auroras in the UV and X-ray portions of the spectrum, invisible to the naked eye, but extremely vivid when looked at with the right instruments.

(b) What causes each of the auroras is different, and until now scientists were not sure what created Jupiter’s X-ray aurora. They knew that it was largely the result of oxygen, carbon and sulphur ions being accelerated to near the speed of light before they hit Jupiter’s atmosphere, but not what caused them to speed up.

(c)   The solar wind is a stream of charged particles coming from the Sun. It varies over time, and is most intense when then Sun releases coronal mass ejections – huge bursts of magnetised particles often associated with solar flares and magnetic storms.

By comparing the intensity of Jupiter’s X-ray aurora and the variation in the solar wind, the team were able to conclude that the solar wind triggers this aurora. Detailed analysis of the X-ray emissions also show that they peak in regions close to Jupiter’s magnetic poles, and so likely come from the outer edges of the planet’s protective magnetic bubble (magnetosphere), where direct interaction with the solar wind takes place.