5 Facts About Earth’s Radiation Donuts 🍩

Did you know that our planet is surrounded by giant,

donut-shaped clouds of radiation?

Here’s what you need to know.

1. The radiation

belts are a side effect of Earth’s magnetic field

The Van Allen radiation belts exist because fast-moving charged

particles get trapped inside Earth’s natural magnetic field, forming two

concentric donut-shaped clouds of radiation. Other planets with global magnetic

fields, like

Jupiter, also have radiation belts.

2. The radiation

belts were one of our first Space Age discoveries

Earth’s radiation belts were first

identified in 1958 by Explorer 1, the first U.S. satellite. The

inner belt, composed predominantly of protons, and the outer belt, mostly

electrons, would come to be named the Van Allen Belts, after James Van Allen,

the scientist who led the charge designing the instruments and studying the

radiation data from Explorer 1.

3. The Van Allen

Probes have spent six years exploring the radiation belts

In 2012, we launched the twin Van Allen Probes to

study the radiation belts. Over the past six years, these spacecraft have

orbited in and out of the belts, providing brand-new data about how the

radiation belts shift and change in response to solar activity and other

factors.

4. Surprise! Sometimes

there are three radiation belts

Shortly after launch, the Van Allen Probes detected a

previously-unknown third

radiation belt, created by a bout of strong solar activity. All the

extra energy directed towards Earth meant that some particles trapped in our

planet’s magnetic field were swept out into the usually relatively empty region

between the two Van Allen Belts, creating an additional radiation belt.

5. Swan song for the

Van Allen Probes

Originally designed for a two-year mission, the Van Allen

Probes have spent more than six years collecting data in the harsh radiation

environment of the Van Allen Belts. In spring 2019, we’re changing their orbit to bring the perigee — the part of the

orbit where the spacecraft are closest to Earth — about 190 miles lower. This

ensures that the spacecraft will eventually burn up in Earth’s atmosphere,

instead of orbiting forever and becoming space junk.

Because the Van Allen Probes have proven to be so hardy,

they’ll continue collecting data throughout the final months of the mission

until they run out of fuel. As they skim through the outer reaches of Earth’s

atmosphere, scientists and engineers will also learn more about how atmospheric

oxygen can degrade satellite measurements — information that can help build

better satellites in the future.

Keep up with the latest on the mission on Twitter, Facebook

or nasa.gov/vanallenprobes.