Van Allen probes Archives

May 17, 2017 by Matt Williams

We Might Have a New Way to Push Back Space Radiation

Artist's depiction with cutaway section of the two giant donuts of radiation, called the Van Allen Belts, that surround Earth. Credit: NASA

Human beings have known for quite some time that our behavior has a significant influence on our planet. In fact, during the 20th century, humanity’s impact on the natural environment and climate has become so profound that some geologists began to refer to the modern era as the “Anthropocene”. In this age, human agency is the most deterministic force on the planet.

But according to a comprehensive new study by an Anglo-American team of researchers, human beings might be shaping the near-space environment as well. According to the study, radio communications, EM radiation from nuclear testing and other human actions have led to the creation of a barrier around Earth that is shielding it against high-energy space radiation.

The study, which was published in the journal Space Science Reviews under the title “Anthropogenic Space Weather“, was conducted by a team of scientists from the US and Imperial College, London. Led by Dr. Tamas Gombosi, a professor at the University of Michigan and the director at the Center for Space Modelling, the team reviewed the impact anthropogenic processes have on Earth’s near-space environment.

These processes include VLF and radio-frequency (RF) radio communications, which began in earnest during the 19th century and grew considerably during the 20th century. Things became more intense during the 1960s when the United States and the Soviet Union began conducting high-altitude nuclear tests, which resulted in massive electromagnetic pulses (EMP) in Earth’s atmosphere.

To top it off, the creation of large-scale power grids has also had an impact on the near-space environment. As they state in their study:

“The permanent existence, and growth, of power grids and of VLF transmitters around the globe means that it is unlikely that Earth’s present-day space environment is entirely “natural” – that is, that the environment today is the environment that existed at the onset of the 19th century. This can be concluded even though there continue to exist major uncertainties as to the nature of the physical processes that operate under the influence of both the natural environment and the anthropogenically-produced waves.”

The existence of radiation belts (or “toroids”) around Earth has been a well-known fact since the late 1950s. These belts were found to be the result of charged particles coming from the Sun (i.e. “solar wind”) that were captured by and held around Earth by it’s magnetic field. They were named Van Allen Radiation Belts after their discover, the American space scientist James Van Allen.

*The twin Radiation Belt Storm Probes, later renamed the Van Allen Probes. Credit: NASA/JHUAPL*

The extent of these belts, their energy distribution and particle makeup has been the subject of multiple space missions since then. Similarly, studies began to be mounted around the same time to discover how human-generated charged particles, which would interact with Earth’s magnetic fields once they reached near-space, could contribute to artificial radiation belts.

However, it has been with the deployment of orbital missions like the Van Allen Probes (formerly the Radiation Belt Storm Probes) that scientists have been truly able to study these belts. In addition to the aforementioned Van Allen Belts, they have also taken note of the VLF bubble that radio transmissions have surrounded Earth with. As Phil Erickson, the assistant director at the MIT Haystack Observatory, said in a NASA press release:

“A number of experiments and observations have figured out that, under the right conditions, radio communications signals in the VLF frequency range can in fact affect the properties of the high-energy radiation environment around the Earth.”

One thing that the probes have noticed was the interesting way that the outward extent of the VLF bubble corresponds almost exactly to the inner and outer Van Allen radiation belts. What’s more, comparisons between the modern extent of the radiations belts from the Van Allen Probe data shows that the inner boundary is much farther away than it appeared to be during the 1960s (when VLF transmissions were lower).

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

What this could mean is that the VLF bubble we humans have been creating for over a century and half has been removing excess radiation from the near-Earth environment. This could be good news for us, since the effects of charged particles on electronics and human health is well-documented. And during periods of intense space weather – aka. solar flares – the effects can be downright devastating.

Given the opportunity for further study, we may find ways to predictably and reliably use VLF transmissions to make the near-Earth environment more human and electronics-friendly. And with companies like SpaceX planning on bringing internet access to the world through broadband internet-providing satellites, and even larger plans for the commercialization of Near-Earth Orbit, anything that can mitigate the risk posed by radiation is welcome.

And be sure to check this video that illustrates the Van Allen Probes findings, courtesy of NASA:

Further Reading: NASA, Space Science Reviews

December 4, 2013December 23, 2015 by Elizabeth Howell

Speedy Particles Whip At Nearly The Speed Of Light In Earth’s Radiation Belts

Artist's conception of NASA’s Van Allen Probes twin spacecraft. Credit: Andy Kale, University of Alberta

The radiation-heavy Van Allen Belts around Earth contain particles that can move at almost the speed of light across vast distances, new research reveals. The information came from an instrument flown aboard the Van Allen Probes twin NASA spacecraft, which launched in 2012.

According to scientists, the process that creates this is similar to what happens in the Large Hadron Collider and other particle accelerators. The magnetic field on the Earth accelerates electrons faster as these particles orbit the planet. While scientists had spotted this process happening at small scales before, the new paper has seen this across hundreds of thousands of kilometers or miles.

“With the Van Allen Probes, I like to think there’s no place for these particles to hide because each spacecraft is spinning and ‘glimpses’ the entire sky with its detector ‘eyes’, so we’re essentially getting a 360-degree view in terms of direction, position, energy, and time,” stated Harlan Spence, principal scientist for the Energetic Particle, Composition, and Thermal Plasma (ECT) instrument aboard the probes, and co-author on the research paper. He is also director of the University of New Hampshire Institute for the Study of Earth, Oceans, and Space.

The research was led by University of Alberta physicist Ian Mann, and is available in Nature Communications. “People have considered that this acceleration process might be present but we haven’t been able to see it clearly until the Van Allen Probes,” Mann stated.

Source: University of New Hampshire

February 28, 2013December 23, 2015 by Nancy Atkinson

Surprising Third Radiation Belt Found Around Earth

Two giant swaths of radiation, known as the Van Allen Belts, surrounding Earth were discovered in 1958. In 2012, observations from the Van Allen Probes showed that a third belt can sometimes appear. The radiation is shown here in yellow, with green representing the spaces between the belts. Credit: NASA/Van Allen Probes/Goddard Space Flight Center

In September of 2012, scientists with the newly launched Van Allen Probes got permission to turn on one of their instruments after only three days in space instead of waiting for weeks, as planned. They wanted to turn on the Relativistic Electron Proton Telescope (REPT) so that its observations would overlap with another mission called SAMPEX (Solar, Anomalous, and Magnetospheric Particle Explorer), that was soon going to de-orbit and re-enter Earth’s atmosphere.

Now, they are very glad they did, as something happened that no one had ever seen before. A previously unknown third radiation belt formed in the Van Allen Radiation Belts that encircle Earth. The scientist watched – in disbelief – while their data showed the extra belt forming, then suddenly disappear, like it had been cut away with a knife. They have not yet seen a recurrence of a third belt.

“First we thought our instruments weren’t working correctly,” said Dan Baker, a member of the Van Allen Probes team from the University of Colorado at Boulder, “but we quickly realized we were seeing a real phenomenon.”

What happened is that shortly before REPT was turned on, solar activity on the Sun had sent energy toward Earth that caused the radiation belts to swell. The energetic particles then settled into a new configuration, showing an extra, third belt extending out into space.

“By the fifth day REPT was on, we could plot out our observations and watch the formation of a third radiation belt,” says Shri Kanekal, the deputy mission scientist for the mission. “The third belt persisted beautifully, day after day, week after week, for four weeks.”

This graph shows energetic electron data gathered by the Relativistic Electron-Proton Telescope (REPT) instruments, on the twin Van Allen Probes satellites in eccentric orbits around the Earth, from Sept. 1, 2012 to Oct. 4, 2012 (horizontal axis). It shows three discrete energy channels (measured in megaelectron volts, or MeV). The third belt region (in yellow) and second slot (in green) are highlighted, and exist up until a coronal mass ejection (CME) destroys them on Oct. 1. The vertical axis in each is L*, effectively the distance in Earth radii at which a magnetic field line crosses the magnetic equatorial plane. Credit: LASP

Since their discovery in 1958, we’ve known that the Van Allen radiation belt is composed of two donut-shaped layers of energetic charged particles around the planet Earth, held in place by its magnetic field.

The scientists are now incorporating what they saw into new models of the radiation belts – a region that can sometimes swell dramatically in response to incoming energy from the Sun, impacting satellites and spacecraft or pose potential threats to human space flight.

The belts are normally between 200 to 60,000 kilometers above Earth; the new ring was much further out.

Launched on August 30, 2012 as the Radiation Belt Storm Probes mission, the twin probes were renamed in honor of the belts’ discoverer, astrophysicist James Van Allen. Observations of the belts have shown they are dynamic and mysterious. However, this type of dynamic three-belt structure was never seen, or even considered, theoretically.

A coronal mass ejection (CME) from the Sun on August 31, 2012, the event that caused a third ring to form in the Van Allen radiation belts. Credit: NASA

The Energetic Particle, Composition, and Thermal Plasma (ECT) suite of instruments on board the probes were designed to help understand how populations of electrons moving at nearly the speed of light and penetrating ions in space form or change in response to variable inputs of energy from the Sun.

Already, what the team has learned is re-writing the textbooks of what is known about the Van Allen belts.

“These events we’ve recorded are extraordinary and are already allowing us to refine and confirm our theories of belt dynamics in a way that will lead to predictability of their behavior,” said astrophysicst Harlan Spence, principal investigator for the ECT, “which is important for understanding space weather and ultimately for the safety of astronauts and spacecraft that operate within such a hazardous region of geospace.”

At a press briefing today, the team was asked why this third ring had never been observed before.

“We’ve never had the capability before to see something like this, said Nicky Fox, Van Allen Probes deputy project scientist. “The fact that we had such an amazing discovery within days of turning them on shows we still have mysteries to discover and explain. What the Van Allen Probes have shown is that the advances in technology and detection made by NASA have already had an almost immediate impact on basic science.”

Baker added, “As the philosopher Yogi Bera once said, you can observe a lot just by looking. This shows that when you open new eyes on the Universe you can invariably find new things.”

The team will be seeking to understand what the third ring mean for astronauts and satellites, even though the new ring is farther out, the regions in Earth orbit are magnetically connected to the new region that formed.

“Knowing more about this and understanding more about the belt is important for having better models and being able to predict the lifetimes of spacecraft,” said Fox.

“The rings, satellites, the space station are all affected by space weather,” said Mona Kessel, Van Allen Probes program scientist. “We don’t completely understand what we’ve seen, but we are modeling it and trying to piece this all together, so stay tuned.”

The team has published a paper in the journal Science.

For more info: NASA, University of New Hampshire