NASA solves mystery of eerie ‘whistling’ in upper atmosphere

NASA has solved a mystery around eerie ‘whistling’ plasma waves in space – and found that they’re partially responsible for beautiful ‘Northern lights’ displays on Earth.

Scientists have known that particles energised by the sun are sometimes scattered into Earth’s upper atmosphere, where they can contribute to aurora (northern lights).

New research using data from NASA’s Van Allen Probes mission and FIREBIRD II CubeSat has shown that a common plasma wave in space is likely responsible for the loss of high-energy electrons into Earth’s atmosphere.

Known as whistler mode chorus, the waves have characteristic rising tones — reminiscent of the sounds of chirping birds.

Far from being an empty void, the space around Earth is a jungle of invisible fields and tiny particles.

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Dictating the movements of these particles, Earth’s magnetic environment traps electrons and ions in concentric belts encircling the planet. These belts, called the Van Allen Radiation Belts, keep most of the high-energy particles at bay.

Sometimes however, the particles escape, careening down into the atmosphere.

Typically, there is a slow drizzle of escaping electrons, but occasionally impulsive bunches of particles, called microbursts, are scattered out of the belts.

In early 2016, the Van Allen Probes observed chorus waves and immediately after, FIREBIRD II saw microbursts.

The new results confirm that the chorus waves play an important role in controlling the loss of energetic electrons.