Another Clue About the Ultra-High Energy Cosmic Rays: Magnetic Turbulence

Space largely seems quite empty! Yet even in the dark voids of the cosmos, ultra-high-energy cosmic rays are streaming through space. The rays contain 10 million times as much energy as the Large Hadron Collider can produce! The origin of the rays though is still the source of many a scientific debate but they are thought to be coming from some of the most energetic events in the universe. A new paper suggests the rays may be linked to magnetic turbulence, coming from regions where magnetic fields get tangled and twisted up. 

Cosmic rays are high-energy particles, typically protons and atomic nuclei. They travel at speeds near the speed of light and are thought to come from different sources such as the Sun, supernova explosions and other events across the universe. As the rays travel through space, they bombard Earth, interacting with molecules in the atmosphere producing secondary particles that rain down. The term cosmic ray often leads to the confusion that they are part of the electromagnetic spectrum. Instead they are streams of charged particles. 

A cousin of the cosmic rays are the ultra-high-energy rays. These are among the most energetic particles in the universe with energies that exceed 10¹⁸ electron volts, this equates to more energy than the energetic particles that escape from the Sun. The origin of these energetic particles is still not clearly understood but they are thought to originate in highly energetic events like active galactic nuclei, gamma ray bursts or the more massive black holes. Just like the typical cosmic rays, the ultra-high energy particles strike molecules in the atmosphere and produce secondary particles. Studying the secondary particles is one way researchers are trying to unravel their nature. 

These previous theories have seemed reasonable but a team of researchers have published their findings about their origins in the Astrophysical Journal Letters. The team suggest the rays have instead originated in magnetic turbulence – the fluctuation of magnetic fields, often occurring in plasmas. Their research found that the magnetic fields get tangled up, swiftly causing the particles to accelerate with an increase in energy. 

According to Luca Comisso, associate research scientist from the Columbia Astrophysics Lab explained that ‘These findings help solve enduring questions that are of great interest to both astrophysicists and particle physicists about how the cosmic rays get their energy.’

The team ran several simulations that demonstrated particle acceleration by magnetic turbulence could accelerate cosmic rays to high energies. Using the Pierre Auger Observatory to measure magnetic turbulence samples, the team found their measurements supported the simulation results. This as perhaps the first successful analysis into ultra-high-energy cosmic rays. 

Source : A New Discovery About the Source of the Vast Energy in Cosmic Rays