Pulsating Auroras: Patches That Blink Across the Sky Like Breathing
After the most intense phase of a substorm, the sky may fill with broad diffuse patches that pulse every few seconds. These are pulsating auroras, less famous than green curtains but extremely valuable for studying the magnetosphere.
What we are seeing
Patches may extend for tens or hundreds of kilometres and brighten in irregular sequences. The apparent motion is not a luminous cloud moving up and down, but a change in the precipitation of electrons into the upper atmosphere.
The connection with space waves
Inside the magnetosphere, electromagnetic waves can interact with trapped electrons and alter their paths. Some electrons are scattered along magnetic field lines towards the atmosphere, producing pulses of light.
Why they matter
- They reveal energy transfer between magnetosphere and atmosphere.
- They can continue for hours after a substorm.
- Their shapes expose invisible processes occurring thousands of kilometres above Earth.
When an aurora pulsates, the sky makes a distant wave–particle interaction visible.
How to recognise them
Look for broad diffuse areas that brighten and fade without forming sharp curtains. Video or time-lapse often reveals the rhythm better than the eye. They are frequently observed after magnetic midnight during the recovery phase.