AN INTERNATIONAL research team led by Chinese scientists has discovered chorus waves more than 160,000 km away from Earth -- a space phenomenon previously believed to occur only near Earth’s dipole magnetic field regions, according to a study on Thursday. “We observed chorus waves with frequencies below 100 Hz. When we converted the chorus waves into audio output, we obtained a piece of ‘space chorus’ that we can hear,” said Liu Chengming at Beihang University, the paper’s first author, Xinhua news agency reported. In the study, published in the journal Nature, Chengming described the sound as “the chirping of birds”.

 

The Earth’s magnetic field extends into space. When charged particles in the cosmos pass the magnetic field, they can excite chorus waves, or electromagnetic waves with frequency characteristics like birdsongs in the morning. As one of the most intense electromagnetic fluctuations in space, chorus waves have been at the forefront of space physics research.

 

It was widely believed that they only occurred near Earth’s dipole magnetic field regions. Researchers from China, the US, and Sweden analysed vast amounts of data collected by the Magnetospheric Multiscale Mission, a solar-terrestrial probe mission.They discovered chorus waves more than 160,000 km away from Earth and provided a theoretical explanation that nonlinear wave-particle interactions are the cause. Chorus waves play a crucial role in understanding fundamental questions in space and have wide practical implications.