Birkeland Current

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NASA Satellites Rediscover Birkland's Research

Flux ropes from space produce the equivalent of a 30,000 volt battery delivering 650,000 Amps into the Artic. Credit, Jonathan Eastwood, NASA
File:Magnetic rope.svg
Simple model of a filamentary current structure in a low-density plasma, such as a Birkland Current. Currents flow parallel to the magnetic field. The lines in the figure represent both current paths and magnetic field lines. The magnetic field derives partly from an external axial field and partly from the toroidal field produced by the current itself (see Alfven and Falthammar, 1963). The current is strongest at the axis and becomes weaker further away from the axis as depicted by the decreasing thickness of the lines.

THEMIS Spacecraft recently re-discovered Birkeland currents, though without reference to Kristian Birkeland's work published in 1908 (Norwegian Aurora Polaris Expedition, Vol I & II). A NASA journalist has likened the interaction to a 30kV battery in space, noting "THEMIS discovered a flux rope pumping a 650,000 Amp current into the Arctic."

Earth-Sun Weird Magnetic Link

Every eight minutes, gateways for particles open and close

By Dan Talpalariu, Science Editor
3rd of November 2008

According to NASA scientists, every 8 minutes —about the time it takes one to read this article— there's a peculiar and still unexplained event going on way overhead. The magnetosphere —the protective magnetic bubble that envelops the planet, Earth's equivalent of the heliosphere —opens up, providing a direct magnetic connection with the Sun, situated 93 million miles (150 million kilometers) away. Tons of high-energy particles pass undisturbed, carried by the solar wind, through the gateway of the magnetosphere, before it is shut once again.

It's called a flux transfer event or 'FTE',” shares David Sibeck, a space physicist from the Goddard Space Flight Center. “Ten years ago, I was pretty sure they didn't exist, but now the evidence is incontrovertible.” There's even more to just that, he indicates, as the FTE phenomenon may take place twice more often than previously accepted. The series of 4 Cluster-type spacecrafts of the European Space Agency, as well as NASA's 5 THEMIS probes, have closely and intensely studied and measured the process, while flying in close proximity of it.

They eventually demonstrated the process was real. While Earth's magnetic field presses against the Sun's, every 8 minutes they merge into a cylindrically shaped portal about the width of the Earth. “We used to think the connection was permanent and that solar wind could trickle into the near-Earth environment anytime the wind was active. We were wrong. The connections are not steady at all. They are often brief, bursty and very dynamic,” explains Sibeck.

Based on his latest calculations, he states, “I think there are two varieties of FTEs: active and passive. Passive FTEs may not be very important, but until we know more about them we can't be sure.” The active form allows for an easier access of the particles, while the passive one induces more resistance. Done: the FTE that has possibly begun when you started reading this has now ended.

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THEMIS Spacecraft Fleet Thwarts Magnetic Shield Leaks Theory

New research predicts next solar storms will be stronger

By Dan Talpalariu, Science Editor, 17th of December 2008

A new study supported by NASA and the National Science Foundation has reached more thorough results related to the way solar storms affect the Earth's magnetic shields, making the old views inaccurate. Depending on the alignment with the Sun's magnetic field, our own develops two huge holes which allow large amounts of solar particles to breach it. Based on some characteristics of the field, researchers can now determine the strength of the upcoming solar storms.

The magnetic field of the Earth behaves as a protective wall against the constant pummeling of the Sun's particle jets thrown towards us. Given that the ions and electrons of the jets are electrically charged, the planetary field can successfully respond to their charge and deflect most of them. Previous theories stated that when the Sun's field was facing a direction opposed to that of ours, giant doors would open for the particles to pass unscathed, and when the directions were similar, the gates would shut.

The new research, based on the results of NASA's Time History of Events and Macroscale Interactions during Substorms mission (THEMIS), comprised of a fleet of five spacecraft that measured the size of the leak, indicated that the opposite is, in fact, valid. "Twenty times more solar particles cross the Earth's leaky magnetic shield when the sun's magnetic field is aligned with that of the Earth compared to when the two magnetic fields are oppositely directed," explained Marit Oieroset from the University of California, Berkeley, quoted by Scientific Blogging.[1]

"The discovery overturns a long-standing belief about how and when most of the solar particles penetrate Earth's magnetic field, and could be used to predict when solar storms will be severe. Based on these results, we expect more severe storms during the upcoming solar cycle,"[2]

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Article: Los Alamos National Laboratory

Understanding of solar wind structure might be wrong

Los Alamos scientist suggests new approach to measuring flow from the sun

LOS ALAMOS, New Mexico, September 9, 2010—A scientist examining the solar wind suggests that our understanding of its structure may need significant reassessment. The plasma particles flowing from the Sun and blasting past the Earth might be configured more as a network of tubes than a river-like stream, according to Joseph Borovsky of Los Alamos National Laboratory’s Space Science and Applications group.

In a paper in this week’s Physical Review Letters, “Contribution of Strong Discontinuities to the Power Spectrum of the Solar Wind,” (Physical Review Letters 105, 111102 [2010]), Borovsky challenges the concept that the solar wind is of fairly uniform structure, and therefore, our entire interpretation of spacecraft data may not be correct.

“For decades we have been interpreting the spectrum of fluctuations in the solar wind as a measurement of turbulence in the wind. However, it turns out that impurities (discontinuities) in plasma dominate the signal. Hence, the spectrum is not a clean measurement of turbulence, and it may not even be a measurement of turbulence,” Borovsky said. In simpler terms, perhaps, we couldn’t see the forest for the trees.

“Because we might be misunderstanding the solar wind, we might be misunderstanding its impact on the Earth’s environment. Understanding solar wind allows us to understand the initiation and evolution of geomagnetic storms,” said Herbert Funsten, chief scientist for the International, Space & Response Division at Los Alamos.

Borovosky argues that the discontinuities are part of a structure to the solar wind that looks like spaghetti, with the discontinuities being the boundaries between adjacent noodles (magnetic tubes). In this concept, the wind plasma is structured rather than being homogeneous. He suggests that the spaghetti structure of the solar-wind plasma reflects the “magnetic carpet” on the surface of the Sun, with the spaghetti in the wind being loose strands of the magnetic carpet.

“We have also argued that the spectrum measured in the wind is a ‘remnant’ of the carpet on the Sun rather than a signature of turbulence in the wind plasma,” he says.

The research data came from NASA’s ACE satellite, which has been operating upstream of the Earth since 1998. A satellite “sits” in the wind and makes measurements as the wind blows past supersonically (typically Mach 8 or so, typically 300 - 700 km/sec). The information about the measurements is telemetered to Earth and delivered to institutions such as Los Alamos, where data-analysis software converts the satellite readings into physical measurement quantities such as wind speed, wind density, wind temperature, magnetic-field direction. Those physical quantities are put into publicly available data sets, which researchers can use to interpret the space weather, to make comparisons with theoretical models, and generally try to better understand the space environment surrounding the planet.



  1. More Severe Storms During Upcoming Solar Cycle Predicted, Marit Oieroset,
  2. Vassilis Angelopoulos, University of California, Los Angeles, Principal THEMIS Investigator