Although space is thought to be devoid of matter and silent, the space environment around the Earth contains high energy particles in magnetic and electric fields. The particles are continuously in a violent storm of electromagnetic waves, known as plasma waves. Just like the waves of the ocean, these plasma waves create a sound that can be captured with the right tools. The sounds are out of this world, and have different characteristics depending on the region of the magnetosphere they are recorded in.
The radio waves are called different names according to what they sound like. There are chirps, whistles, hisses, and what sound like entire flocks of alien birds, or the calls of mysterious deep sea creatures. The different sounds are caused by a number of factors coming together, including regions of dense and sparse plasma, day and night side temperatures, lighting strikes in the atmosphere, and instances of magnetic reconnection — explosions of tangled magnetic fields.
The sounds were recorded by using the two Van Allen Probes that NASA has deployed. The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) payloads on the probes measure the electric and magnetic waves, which are then shifted to the audible frequency. The observations help scientists protect satellites and communications infrastructure deployed in space from the turbulent space weather.