Shocking recipe for making killer electrons (w/ Video)

Mar 11, 2010
ESA's mission Cluster consists of four identical spacecraft flying in formation between 19 000 and 119 000 km above the Earth. They study the interaction between the solar wind and Earth’s magnetosphere, or the Sun-Earth connection in 3-D. Credit: ESA

Take a bunch of fast-moving electrons, place them in orbit and then hit them with the shock waves from a solar storm. What do you get? Killer electrons. That's the shocking recipe revealed by ESA's Cluster mission.

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Data from Cluster, and other spacecraft monitoring the magnetosphere, have shown that interplanetary shocks -- caused by coronal mass ejections from the Sun -- can create "killer electrons" in the near-Earth space environment within 15 minutes of the shock reaching the Earth's protective magnetic bubble. Killer electrons are highly energetic particles trapped in the Earth's outer radiation belt. Credit: ESA

Killer electrons are highly trapped in Earth's outer radiation belt, which extends from 12 000 km to 64 000 km above the planet’s surface. During solar storms their number grows at least ten times and they can be dislodged, posing a threat to satellites. As the name suggests, killer electrons are energetic enough to penetrate satellite shielding and cause microscopic lightning strikes. If these electrical discharges take place in vital components, the satellite can be damaged or even rendered inoperable.

On 7 November 2004, the Sun blasted a in Earth’s direction. It was composed of an interplanetary shock wave followed by a large magnetic cloud. When the shock wave first swept over the ESA-NASA solar watchdog satellite SOHO, the speed of the solar wind (the constant flow of solar particles) suddenly increased from 500 km/s to 700 km/s.

Shortly afterwards, the shock wave hit Earth’s protective , known as the magnetosphere. The impact induced a wave front propagating inside the magnetosphere at more than 1200 km/s at geostationary orbit (36 000 km altitude) around Earth. The quantity of energetic electrons in the outer radiation belt started to increase too, according to Cluster’s RAPID instruments (Research with Adaptive Particle Imaging Detectors). Cluster’s four satellites sweep around an elliptical orbit, coming as close as 19 000 km and going out as far as 119 000 km.

Understanding the origin of the killer electrons has been a focus for researchers. Thanks to previous data collected by Cluster and other space missions, scientists proposed two methods by which electrons can be accelerated to such harmful energy levels. One relies on very low frequency (VLF) waves of 3-30 kHz, the other on ultra low frequency (ULF) waves of 0.001-1 Hz. This latest work disentangles the problem.

Which waves are responsible? Both of them. “Both VLF and ULF waves accelerate electrons in Earth’s radiation belts, but with different timescales. The ULF waves are much faster than the VLF, due to their much larger amplitudes,” says Qiugang Zong from Peking University (China) and University of Massachusetts Lowell (USA), lead author of the paper describing this result.
The data show that a two-step process causes the substantial rise of killer electrons. The initial acceleration is due to the strong shock-related magnetic field compression. Immediately after the impact of the interplanetary shock, Earth’s magnetic field lines began wobbling at ultra low frequencies. In turn, these ULF waves were found to effectively accelerate the seed electrons provided by the first step, to become killer electrons.

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Solar activity in November 2004 as seen by the EIT instrument on SOHO. EIT stands for extreme ultraviolet imaging telescope. Credits: ESA/NASA/SOHO

Although the analysis has been a long one, the results have been worth the wait. Now astronomers know how killer electrons are accelerated. “Data from the four Cluster satellites allowed the identification of ULF waves able to accelerate electrons,” says Malcolm Dunlop, Rutherford Appleton Laboratory, Didcot (UK) and co-author of this study.

Thanks to this analysis of Cluster data, if the killer electrons happen to be ejected towards Earth, we now know that they can strike the atmosphere within just 15 minutes. “These new findings help us to improve the models predicting the radiation environment in which satellites and astronauts operate. With solar activity now ramping up, we expect more of these shocks to impact our over the months and years to come,” says Philippe Escoubet, ESA’s Cluster mission manager.

Explore further: Red moon at night; stargazer's delight

More information: Zong, Q.-G., X.-Z. Zhou, Y. F. Wang, X. Li, P. Song, D. N. Baker, T. A. Fritz, P. W. Daly, M. Dunlop, and A. Pedersen (2009), Energetic electron response to ULF waves induced by interplanetary shocks in the outer radiation belt, J. Geophys. Res., 114, A10204, doi:10.1029/2009JA014393

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User comments : 9

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seneca
not rated yet Mar 11, 2010
It's well known, high temperature / particle energy in solar corona could be explained by Alphén waves and the current article just extends this mechanism to Earth stratosphere.

http://en.wikiped...g_theory
Skepticus
not rated yet Mar 11, 2010
I have come across many articles over the years regarding proposed spacecraft-generated magnetic fields, magnetized plasmas...etc, for shielding purposes, but almost all the current approaches focus on physical shielding. Consider the weight penalty, it seems to me some power sources (such as RTG, nuclear) would incur more favorable weigh and mass penalty while providing the same protection. Is it technology limitations, political considerations, or organizational cultural obstruction to new approaches? Or, the field of non-physical shielding technologies such as electromagnetics, are classified and thus non-mentionable? Engineers and scientists, I would dearly want to hear your input, thanks.
daywalk3r
1 / 5 (2) Mar 11, 2010
^^
Skepticus, I think it's more about reliability than "feasibility", when it comes to active or passive shielding, that is..
Skepticus
not rated yet Mar 11, 2010
^^
Skepticus, I think it's more about reliability than "feasibility", when it comes to active or passive shielding, that is..


You mean power systems such as on Voyager 2 (launched in 1977, and still working) were flukes, and nothing made with today's technology will be guaranteed to work reliably?
daywalk3r
2.3 / 5 (3) Mar 11, 2010
You mean power systems such as on Voyager 2 (launched in 1977, and still working) were flukes, and nothing made with today's technology will be guaranteed to work reliably?
Voyager did not have a human crew. When it comes to protecting human lives, reliability is far more of a concern than for situations, where only a robot is involved. And on top of that, in most cases the robot has far higher radiation level tolerances, as it was designed for it, which humans were not..
brant
not rated yet Mar 11, 2010
I have come across many articles over the years regarding proposed spacecraft-generated magnetic fields, magnetized plasmas...etc, for shielding purposes, Is it technology limitations, political considerations, or organizational cultural obstruction to new approaches? Or, the field of non-physical shielding technologies such as electromagnetics, are classified and thus non-mentionable? Engineers and scientists, I would dearly want to hear your input, thanks.


An effective way to power a magnetic shield would require some new power technology. The power density would have to go up many orders of magnitude.

You would need an "aether" cell or something like that. Or a car battery that lasted forever would do it.....

To introduce such technologies(they exist) into society would change the economic structure(who makes the profit) and so on down the line.
So you can hope but I dont see the change happening in the near future..
sender
not rated yet Mar 11, 2010
yay another renewable energy source!
Husky
not rated yet Mar 12, 2010
letsd power the shielding by killer electrons, only halve joking here
SimonX
not rated yet Mar 12, 2010
That's a good point imo.

It's funny seeing reference to power requirements when being bombarded with highly charged particles...

The same arguament could be applied to most vehicles. The biggest factor limiting speed is generally seen as friction. Perhaps more time should be spent looking at the potential to harness these sources of energy...

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