The answer first
Motion in Earth’s liquid outer core sustains a magnetic field. The solar wind compresses that field on the dayside and stretches it into a long magnetotail.
During magnetic reconnection, stored energy accelerates particles along field lines. Collisions with upper-atmosphere atoms and molecules produce auroral light.
The idea that changes the view
An aurora is not the shield simply holding—it is energy crossing the boundary and reaching the atmosphere.
What most explanations leave out
A magnetic field is not the only reason Earth retains an atmosphere, and Mars’s atmospheric loss has multiple causes.
Evidence and named signals
- Satellites map magnetospheric boundaries.
- Auroral colors correspond to atmospheric species and altitude.
- MAVEN measures ongoing atmospheric escape at Mars.
What remains uncertain
Storm intensity depends on solar-wind speed, density, and magnetic orientation.
Why it matters—or what you can observe
The same coupling that makes auroras can disturb satellites, radio, navigation, and power systems.
Related StarPixels video · 0:40
A Solar Storm Set Telegraphs on Fire
In 1859, the aurora became part of the electrical grid.
Open the video companionFurther reading and primary sources
- NASA magnetosphereSource checked 2026-07-16
- NASA MAVENSource checked 2026-07-16
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