Developed from recent observations, the model can be used to study exoplanets.
We all know that stars radiate light and much more. But radiation belts can also surround many other celestial bodies, such as planets.
These belts do not generate particles themselves - the belts receive them from nearby stars - but they accelerate the speed of particles in a way that has remained elusive.
, Associate Professor of Space Physics at the University of Helsinki, has now designed a model that explains the phenomenon.
The model has only one variable: the intensity of the planet's surface magnetic field. The stronger the field, the higher the speed to which planets radiationbelt accelerates the particles.
However, this phenomenon has an upper limit. The particles accelerated by the radiation belt release energy. Consequently, this release cancels 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.
Magnetic field strength is measured in teslas. For protons, the upper limit is about 0.0004 tesla, and for electrons about 0.00004 tesla. For comparison, the strength of the magnetic field at Earth's equator is about 0.00003 tesla.
The maximum amount of energy a planet's magnetic field can give to a particle is roughly 7 teraelectronvolts (TeV). That is an enormous amount of energy - more than a trillion times more than the energy of a single photon of light at the visible light wavelenght.
Besides terrestrial planets, the model can be applied to the radiation belts of gas giants and even brown dwarfs, which are classified as between planets and stars.
Osmane's theory is based on analyses conducted at the Johns Hopkins University Applied Physics Laboratory in the United States, combining direct observations of the solar system with radio telescope data.
"Drew L. Turner, who headed the study, is an old acquaintance of mine. He sent me their latest results and asked if I could create an explanatory model."
While the model primarily determines the upper limit for particle acceleration, it can also be used to explore exoplanets.
"The model shows which wavelengths may provide information on whether exoplanets have radiation belts created by magnetic fields and if so, how intense they are."
This also helps in the search for planets suitable for life: a magnetic field that protects the planetary surface from radiation improves its viability by warding off radiation and binding the atmosphere around the planet.
Article was published in Science Advances.
