In the vastness of space, electromagnetic waves create a cosmic symphony. Among them, whistler-mode chorus waves stand out with their chirping sounds. These waves, usually linked to strong magnetic fields, have been found in a surprising location. NASA's Magnetospheric Multiscale (MMS) mission detected them in Earth's mid-tail neutral sheet, about 1,00,000 km away. The findings were published in Nature.
Previously, scientists believed chorus waves only formed near Earth’s dipolar magnetic field. The new discovery challenges this idea, revealing their presence in regions where magnetic fields are stretched and weaker. This could reshape understanding of how these waves propagate in space.
How Chorus Waves Form
The study confirmed that chorus waves arise from interactions with electrons. MMS recorded these waves on 10 August 2019, 26 Earth radii away. The data showed rising-tone signals with frequencies changing at about 100 Hz per second. Scientists found "electron holes," indicating energy transfer from local electrons to the waves.
These waves travel parallel to magnetic fields with right-hand polarisation. The findings match existing models but suggest chorus waves may form in more areas than previously thought.
Impact on Space Research
Chorus waves play a key role in shaping planetary radiation belts. They influence auroras and help accelerate charged particles in space. Understanding them improves knowledge of space weather and energy transfer in collisionless plasmas.
These discoveries provide new insights into wave-particle interactions. Scientists can now refine models explaining how electromagnetic waves behave in space. The cosmic "birdsong" of chorus waves continues to offer clues about the forces shaping our universe.
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