Scientists working with Nasa's Van Allen Probes spacecraft have discovered a zebra stripe pattern in one of two radiation belts that surround Earth.

According to data from the probes, high-energy electrons in the inner radiation belt display a pattern that resembles slanted zebra stripes. Scientists believed increased solar wind activity was the force behind any radiation belt structures. However, the appearance of the zebra stripes in low wind suggest they are created by the Earth's movement.

Aleksandr Ukhorskiy, lead author of the paper at the John Hopkins Applied Physics Laboratory, said: "It is because of the unprecedented resolution of our energetic particle experiment, RBSPICE, that we now understand that the inner belt electrons are, in fact, always organised in zebra patterns.

NASA image radiation belt around Earth
Two giant belts of radiation surround Earth. The inner belt is dominated by electrons and the outer one by protons. NASA

"Furthermore, our modelling clearly identifies Earth's rotation as the mechanism creating these patterns. It is truly humbling, as a theoretician, to see how quickly new data can change our understanding of physical properties."

The spacecraft, formerly known as the Radiation Belt Storm Probes, are two robotic spacecraft being used to study the Van Allen radiation belt that surrounds our planet. They were launched in August 2012.

Nasa is conducting the mission as part of the Living with a Star programme, as understanding the radiation belt environment has implications on spacecraft operations, spacecraft system design and astronaut safety.

The tilt in the Earth's magnetic field axis allows the planet's rotation to generate an oscillating, weak electric field that permeates through the entire inner radiation belt.

Like a viscous fluid, the global oscillations slowly stretch and fold, creating the pattern. It can then be observed across the belt, extending from above Earth's atmosphere, about 500 miles above the planet's surface up to roughly 8,000 miles.

The radiation belts are dynamic, doughnut-shaped regions around our planet, which are made up of high-energy particles. Both electrons and charged particles called ions are trapped by the Earth's magnetic field.

Radiation levels across the belts are affected by solar activity that causes energy and particles to flow into near-Earth space. During active times, radiation levels can dramatically increase, which can create hazardous space weather conditions that harm orbiting spacecraft and endanger humans in space.

David Sibeck, mission scientist, said: said: "The RBSPICE instrument has remarkably fine resolution and so it was able to bring into focus a phenomena that we previously didn't even know existed."

Louis Lanzerotti, co-author of the study, told RedOrbit: "It is amazing how Earth's space environment, including the radiation belts, continue to surprise us even after we have studied them for over 50 years. Our understanding of the complex structures of the belt contribute to the eventual goal of providing accurate space weather modelling."

The findings were published in the journal Nature.