Electrical Tornadoes Power the Auroras!
All things old are new again... Hundred-year-old electrical science has finally come back into fashion! The latest results from the THEMIS satellite fleet leave no wiggle room. The auroras are powered by what they're calling "electrical tornadoes in space." Otherwise known as 100,000+ Amp electric currents.
First a little history for context:
Flip the calendars back a hundred years to the earliest part of the 1900's. There was no TV. There we re no satellites, and no supercomputers. Nonetheless there were scientists. Many of them were experimentalists. That is to say, they worked "hands on" in the lab.
One such experimentalist was Kristian Birkeland (sometimes called "the first space scientist" and "the father of plasma experiments in the laboratory and space"), a Norwegian scientist with an interest in the auroras among other things. From 1896-1903, he led scientific expeditions to the polar regions to get in situ magnetic field measurements in order to determine the source and cause of the auroras. Data in hand, he proceeded to meticulously study the effects of electricity and magnetism in the lab using a terella or "little Earth."
His final assessment was that the auroras were powered from without by electrical currents originating from the sun:
The knowledge gained, since 1896, in radio-activity has favoured the view to which I gave expression in that year, namely, that magnetic disturbances on the earth, and aurora borealis, are due to corpuscular rays emitted by the sun.
In the lingo of his day, "corpuscular rays" were synonymous with what we would call the motion of charged particles, be it emissions from radioactive decay or the motion of electric currents. From other passages of his work, his meaning becomes clear. His suggestion was that electric currents were intimately involved with auroral formation and the magnetic fields associated with the same, moreover that they could be traced all the way back to the sun.
Birkeland's theory was well received in many quarters at its initial debut, but faded from prominence with the introduction of Einstein's relativity and theories of a neutral and electrically inactive cosmos.
However, discoveries of the space age have not always conformed to such a neutral and inactive cosmological picture. Wherever we point our telescopes and other observational devices, we see the magnetic signatures of electric currents. It is now known that highly conductive plasma pervades up to 99.999% of the observable cosmos.
As they say, the truth will out. For some time there was a debate between Kristian Birkeland (who insisted that electric currents powering the auroras came from an external circuit linked to the sun) and Sydney Chapman (who believed that any electrical currents present in the auroras were locally generated). In 1973, the Triad satellite proved experimentum crucis that the currents were not locally generated, but indeed flowed from space into and through the auroras and back out into space to complete the circuit. Such "field-aligned currents" have subsequently been referred to as Birkeland currents in his honor.
However, those who fail to learn from history often repeat it. It seems the astrophysical community didn't entirely heed Birkeland's work, though it is in large part freely available. In late 2007, a much more modern and technologically sophisticated instrument (the fleet of THEMIS satellites) began delivering valuable data back to scientists on Earth about our near-Earth environment (the magnetosphere).Their data indicated that what they called "magnetic flux ropes" were found funneling plasma into the near-Earth environment. Moreover, these "flux ropes" were carrying a 650,000 Amp current!
"The satellites have found evidence of magnetic ropes connecting Earth's upper atmosphere directly to the sun," said David Sibeck, project scientist for the mission at NASA's Goddard Space Flight Center, Greenbelt, Md. "We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras."
Anyone familiar with Maxwell's equations should know that the only method of generating such magnetic fields is via electric currents.
Electric fields are created by differences in voltage: the higher the voltage, the stronger will be the resultant field. Magnetic fields are created when electric current flows: the greater the current, the stronger the magnetic field. An electric field will exist even when there is no current flowing. If current does flow, the strength of the magnetic field will vary with power consumption but the electric field strength will be constant.
The electromagnetic field is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field.
are produced by
The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field. The way in which charges and currents interact with the electromagnetic field is described by Maxwell's equations and the Lorentz force law.
Electric current produces a magnetic field. The magnetic field can be visualized as a pattern of circular field lines surrounding the wire.
Electric current can be directly measured with a galvanometer, but this method involves breaking the circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current.
...steady electric and magnetic fields cannot generate themselves. Instead, they have to be generated by stationary charges and steady currents. So, if we come across a steady electric field we know that if we trace the field-lines back we shall eventually find a charge. Likewise, a steady magnetic field implies that there is a steady current flowing somewhere. All of these results follow from vector field theory (i.e., from the general properties of fields in three-dimensional space), prior to any investigation of electromagnetism.
In conclusion, all steady magnetic fields in the Universe are generated by circulating electric currents of some description.
Despite several obfuscating vagaries of language used in the astrophysical sciences at present ("magnetic reconnection," "magnetic flux ropes," etc.), the data has finally yieldeda largely unassailable conclusion: electric currents do in fact power the auroras.
Earth-bound tornadoes are puny compared to "space tornadoes," which span a volume as large as Earth and produce electrical currents exceeding 100,000 amperes, according to new observations by a suite of five NASA space probes.
Space tornadoes ... generate huge amounts of electrical currents inside the funnel. These currents flow along twisted magnetic field lines from space into the ionosphere where they power several processes, most notably bright auroras such as the Northern Lights...
The THEMIS spacecraft observed these tornadoes, or "flow vortices," at a distance of about 40,000 miles from Earth. Simultaneous measurements by THEMIS ground observatories confirmed the tornadoes' connection to the ionosphere.
As another interesting tidbit, it seems that the auroras, while not always radiating in the visible part of the spectrum are still constantly "switched on" in other bands:
Imagine living on a planet where Northern Lights fill the heavens at all hours of the day. Around the clock, even in broad daylight, luminous curtains shimmer and ripple across the sky, mesmerizing anyone who bothers to look.
News flash: Astronomers have discovered such a planet. Its name is Earth.
"Our own planet has auroras 24 hours a day," says Jim Spann of the Marshall Space Flight Center, "and we can see them even in broad daylight." The trick, he explains, is picking the right wavelength. "If we look at Earth from space using an ultraviolet (UV) filter, we see there are auroras underway at all times. It is a beautiful sight."
So, it seems that Birkeland's notions of externally electrically powered auroras have once again been vindicated by direct observation. Prior observations have also vindicated his notion that such currents should be filamentary and contiguous across space and traceable all the way back to the sun itself.
But what might this mean for Birkeland's other theories? Are they worth a reinvestigation? Birkeland had this to say of the universe:
The experimental investigations which at first were designed to procure analogies capable of explaining phenomena on the earth, such as aurora and magnetic disturbances, were subsequently extended, as was only natural, with the object of procuring information as to the conditions under which the emission of the assumed hello-cathode rays from the sun might be supposed to take place.
The consequence was that attempts were made to knit together all these new discoveries and hypotheses into one cosmogonic theory, in which solar systems and the formation of galactic systems are discussed perhaps rather more from electromagnetic points of view than from the theory of gravitation.
The latter quotation is the stepping off point for the field of Plasma Cosmology, which offers a radically different perspective on the cosmos.
See previous articles:
Sun and Earth Electrically Connected By "Magnetic Portals"
It's Okay to Call the "Magnetic Flux Ropes" Found Connecting the Sun and Earth an Electric Current!
Big Bang vs. Plasma Cosmology: Competing Approaches to Understanding the Universe
An Argument for the Consideration of Electrodynamics in Cosmology