New Delhi: Some planets host radiation belts that do not generate particles themselves, but trap and accelerate particles from nearby stars. Dynamo action
in the churning liquid interiors of some worlds create these geomagnetic fields, with Mercury, Earth, Jupiter, Saturn, Uranus, and Neptune hosting radiation belts in the Solar System. Adnane Osmane from the University of Helsinki has designed a model that explains this phenomenon, with only one variable, the intensity of the surface magnetic field of the planet. The stronger the magnetic field, the higher the speed to which the radiation belts of the planet accelerate the captured particles.
There is however an upper limit to the phenomenon. The particles accelerated by the radiation belts release energy, that reduces the acceleration when the planet’s magnetic field exceeds in intensity. This creates a universal upper limit, beyond which magnetic fields can no longer accelerate particles, irrespective of their intensity. The strength of magnetic fields is measured in teslas. The strength of the magnetic field at the equator of the Earth is about 0.00003 tesla. The maximum amount of energy a planetary magnetic field can impart to a particle is about 7 teraelectronvolts. The same model can be applied to gas giants, and even brown dwarfs, exotic objects that straddle the line between stars and planets.
Research helps in the search for habitable worlds
The theory is based on a combination of direct observations of the solar system with radio telescope data. Osmane was asked to create an explanatory model based on the latest results. The model primarily determines the upper limit for particle acceleration, but can also be used to explore exoplanets. The model reveals which wavelengths can reveal if exoplanets have radiation belts created by magnetic fields, and if so, how strong these magnetic fields are. The research helps in the search for planets suitable to life, as a magnetic field is considered essential to protect the surface from harsh radiation. A paper describing the research has been published in Science Advances.
