Nav: Home

Research resolves a debate over 'killer electrons' in space

October 04, 2016

New findings by a UCLA-led international team of researchers answer a fundamental question about our space environment and will help scientists develop methods to protect valuable telecommunication and navigation satellites. The research is published in the journal Nature Communications.

Using measurements from the first U.S. satellite that traveled to space, Explorer 1 physicist James Van Allen discovered in 1958 that space is radioactive. The Earth is surrounded by two doughnut-shaped rings of highly charged particle radiation -- an inner ring of high-energy electrons and positive ions and an outer ring of high-energy electrons -- that are now known as Van Allen Radiation Belts. Flying close to the speed of light, the high-energy particles that populate the belts create a harsh environment for satellites and humans in space.

In recent years, there has been much scientific interest in understanding the Van Allen belts. New technologies now require that telecommunication satellites spend a great deal of time in those belts and that GPS satellites operate in the heart of the belts. With the increasingly smaller size of space electronics has come greater vulnerability of satellites to space radiation, according to Yuri Shprits, a research geophysicist with Earth, Planetary and Space Sciences in the UCLA College and a member of the international team.

The particles that are most dangerous to spacecraft are known as relativistic and ultra-relativistic electrons. The ultra-relativistic, or "killer electrons," are especially hazardous and can penetrate the most protected and valuable satellites in space, Shprits said. While it is possible to protect the satellites from relativistic particles, shielding from ultra-relativistic particles is practically impossible, he added.

Understanding the dynamics of these particles has been a major challenge for scientists since Van Allen discovered space radiation. Since the late 1960s, scientists have made many observations to try to understand the loss of electrons from the Van Allen belts.

One of the proposed theories was that particles are scattered into the atmosphere by electromagnetic ion cyclotron waves. These waves are produced by the injection of ions that are heavier than electrons and carry a lot of energy. These waves can potentially scatter electrons into the atmosphere. Up until recently, that remained the most likely candidate for the loss of electrons.

In 2006, Shprits and colleagues proposed another mechanism. They suggested that more than 99 percent of the particles suddenly were lost, as electrons diffused into interplanetary space, no longer trapped by the Earth's magnetic field. The team conducted additional studies that provided more evidence for this mechanism.

The scientists' modeling of large numbers of electrons at relativistic energies seemed to favor this mechanism and did not require the scattering of electron by electromagnetic ion cyclotron waves. However, it remained unclear which mechanism operated or dominated during storms, and which mechanism explains the most dramatic dropouts of electrons in the space environment.

The loss of particles is difficult to pinpoint. Both types of loss mechanisms are intensified during storms, making it difficult to distinguish one from the other.

Fortunately for the scientists, several factors combined to help them resolve the dispute. A January 2013 storm in the Van Allen belts allowed the researchers to use detectors to measure the particles' distributions and direction. The most intense relativistic and ultra-relativistic electrons were discovered in different locations in the belts. And the ultra-relativistic particles were located deep inside the magnetosphere (and were not affected by the electron loss to the magnetopause, which is the boundary between the Earth's magnetic field and the solar wind).

The researchers' detailed measurements -- including particle speed, velocity direction and radial distributions -- all showed that the waves were indeed scattering particles into the atmosphere but affected only ultra-relativistic electrons, not relativistic particles.

"Our findings resolve a fundamental scientific question about our space environment and may help develop methods of cleaning up the radiation belts from harmful radiation and make the environment around the Earth friendlier for satellites," Shprits said. He is principal investigator of an April mission in which a satellite containing a UCLA-built collection of instruments was launched from Vostochny, Siberia. That work is expected to provide scientists worldwide with measurements of radiation in space and advance space sciences for years to come.
-end-
Other members of the team are scientists from UCLA (researchers Alexander Drozdov and Adam Kellerman, and postdoctoral scholar Hui Zhu); Germany's GFZ Research Centre for Geosciences in Potsdam (Irina Zhelavskaya and Nikita Aseev, who were visiting scholars at UCLA for six months in 2015-16; Shprits holds a joint appointment here); Stanford University (Maria Spasojevic); University of Colorado, Boulder (Maria Usanova and Daniel Baker); Augsburg College in Minneapolis (Mark Engebretson); UC Berkeley (Oleksiy Agapitov, who also has an appointment at Ukraine's University of Kyiv); Finland's University of Oulu (Tero Raita); and the University of New Hampshire (Harlan Spence).

Funding sources for the Nature Communications research included the University of California Office of the President, National Science Foundation, NASA and the Helmholtz Association Recruiting Imitative program.

University of California - Los Angeles

Related Magnetic Field Articles:

Massive photons in an artificial magnetic field
An international research collaboration from Poland, the UK and Russia has created a two-dimensional system -- a thin optical cavity filled with liquid crystal -- in which they trapped photons.
Adhesive which debonds in magnetic field could reduce landfill waste
Researchers at the University of Sussex have developed a glue which can unstick when placed in a magnetic field, meaning products otherwise destined for landfill, could now be dismantled and recycled at the end of their life.
Earth's last magnetic field reversal took far longer than once thought
Every several hundred thousand years or so, Earth's magnetic field dramatically shifts and reverses its polarity.
A new rare metals alloy can change shape in the magnetic field
Scientists developed multifunctional metal alloys that emit and absorb heat at the same time and change their size and volume under the influence of a magnetic field.
Physicists studied the influence of magnetic field on thin film structures
A team of scientists from Immanuel Kant Baltic Federal University together with their colleagues from Russia, Japan, and Australia studied the influence of inhomogeneity of magnetic field applied during the fabrication process of thin-film structures made from nickel-iron and iridium-manganese alloys, on their properties.
'Magnetic topological insulator' makes its own magnetic field
A team of U.S. and Korean physicists has found the first evidence of a two-dimensional material that can become a magnetic topological insulator even when it is not placed in a magnetic field.
Scientists develop a new way to remotely measure Earth's magnetic field
By zapping a layer of meteor residue in the atmosphere with ground-based lasers, scientists in the US, Canada and Europe get a new view of Earth's magnetic field.
Magnetic field milestone
Physicists from the Institute for Solid State Physics at the University of Tokyo have generated the strongest controllable magnetic field ever produced.
New world record magnetic field
Scientists at the University of Tokyo have recorded the largest magnetic field ever generated indoors -- a whopping 1,200 tesla, as measured in the standard units of magnetic field strength.
Researchers discover link between magnetic field strength and temperature
Researchers recently discovered that the strength of the magnetic field required to elicit a particular quantum mechanical process corresponds to the temperature of the material.
More Magnetic Field News and Magnetic Field Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#541 Wayfinding
These days when we want to know where we are or how to get where we want to go, most of us will pull out a smart phone with a built-in GPS and map app. Some of us old timers might still use an old school paper map from time to time. But we didn't always used to lean so heavily on maps and technology, and in some remote places of the world some people still navigate and wayfind their way without the aid of these tools... and in some cases do better without them. This week, host Rachelle Saunders...
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.