Electric Currents Over Crustal Magnetic Anomalies Implicated in Martian Auroras

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Acceleration and Guidance of Ions and Electrons Along Field Lines (Diagram)

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Mars is more-or-less a dead planet. Its atmosphere is thin, its magnetic field is nearly non-existent. But, it hasn't yet given up the ghost completely. There is still remnant crustal magnetism in the southern hemisphere. Results support the conclusion that there are weak but pervasive auroras in the southern hemisphere and that they are electrical in nature.

In a press release from December 2005 it was revealed that hundred of auroras had been detected in the skies over Mars, largely congregated over the southern hemisphere. This was a shock to scientists since Mars does not have a global magnetic field like that of Earth. Instead, it appeared that the auroras were associated with patches of magnetic field locked into the crust of the planet, mostly in the southern hemisphere.

The fact that the auroras exist came as quite a surprise. But, they have also helped as a tool to visualize the magnetic anomalies by measuring the auroral flash rate to extrapolate the strength of the magnetic fields in particular regions.

However, scientists appear to be perplexed by the mechanisms involved with the auroras.

While "magnetic reconnection" sounds like a promising candidate, it has been strongly argued against by the Nobel prize winning plasma physicist Hannes Alfvén and more recently by electrical engineer Don Scott in peer reviewed papers. Both have argued that an electrical interpretation is both more appropriate and necessary in order to fully understand astrophysical plasma processes.

A slightly newer report on the Martian auroras, coupled with the observations of Norwegian scientist Kristian Birkeland should be able to resolve the issue, if astronomers can set aside their outdated preconceived notions excluding electricity's role from the discussion of the solar system and the cosmos.

In a press release from early 2006, it was noted that charged particles were being accelerated in the atmosphere of the south polar region, contributing to the polar auroras.

Furthermore, the associated presentation clarified that ions (positively charged particles such as atoms stripped of one or more electrons) were being accelerated in one direction, while electrons were being accelerated in the opposite direction.

But what does it all mean? Simply put, electric currents are interacting with the atmosphere of Mars, predominantly in the regions around the southern hemispheric crustal magnetic anomalies. That electric current, much like the current from the sun that interacts with the Earth's upper atmosphere, is a likely culprit for Mars' auroras as well.

How do we know this these charged particles are part of an electric current? By the definition of a current, really. A current is a net motion of like charged particles in a circuit. Keep in mind that the motion of the particles may be extraordinarily slow, a drift really. There are three basic kinds of current: 1) conventional current (a net motion of positively charged protons or ions in the same direction) 2) electron flow or electron current (a net motion of negatively charged electrons in the same direction, considered to be the opposite direction of "conventional current" in electrical diagrams) 3) bi-directional flow (positively charged particles flow one way around a circuit, negatively charged particles flow the opposite way around the circuit). See Which Way Does the "Electricity" Really Flow? by William Beatty for a description of electric currents.

By these fairly simple definitions, we can see that the charged particles are involved in a bi-directional flow (ions are flowing one way, while electrons are flowing the other).

Where scientists have expressed surprise and confusion at the fact that charged particles are able to follow magnetic field lines of the patchy crustal magnetism, an electrical explanation may provide clarity.

Perhaps the missing ingredient is the "field-aligned current" or Birkeland current, named after the Norwegian scientist Kristian Birkeland who successfully predicted in the early 1900's an electrical interaction between the sun and Earth by way of currents of charged particles (Birkeland's "'pencil' cathode rays") flowing along the intervening interplanetary magnetic fields through the rarefied gases (plasma) filling the void.

The findings at Mars should also not be surprising in light of recent unattributed reconfirmation of Birkeland's currents (a 650,000 Ampere current between the sun and Earth's upper atmosphere mentioned in a previous article) which were originally experimentally verified in 1973 by the Triad satellite.

Likewise, the finding should not be surprising in light of a similar million Ampere current found flowing between Io and Jupiter's auroral footprints (interestingly, Ganymede and Europa were similarly implicated as having auroral footprints and may be involved in similar electrical processes). More recent results suggest that Io may be caught in an electric circuit closing in both the northern and southern hemispheres of Jupiter, and not just the northern hemisphere as was previously believed.

Thus it appears that electrons are involved in a circuit beginning in one hemisphere and traversing past Io to arrive in the other hemisphere. It may also be that the circuit closes (as all circuits must) through Jupiter! A recent (January 2008) edition of Astronomy magazine asked the question of whether Jupiter is powered by a z-pinch (a type of electrical discharge in plasma).

Returning from the auroras of Earth and Jupiter, it seems that electrical interactions ("field-aligned" or Birkeland currents) are key to understanding the mechanisms behind auroras on any number of planets in the solar system. It is also necessary to consider that the interplanetary medium is filled with a conductive rarefied plasma and not the "perfect vacuum" espoused by scientists of prior eras. As such, the experimental results of pioneering scientists such as Birkeland, Langmuir and Alfvén should not be overlooked. After all, they have worked with and provided many insights in the realm of discharges in rarefied gases (today known as a subset of the plasma physics field). Birkeland's work The Norwegian Aurora Polaris Expedition 1902-1903, especially, should not be overlooked as a seminal work in understanding our local space plasma environment and beginning to understand interactions near other ponderable bodies in the solar system and the cosmos at large.

If astronomers are willing to set aside their preconception that currents cannot flow through the conductive plasma of space, we might yet be able to unlock some of the persistent conundrums of the space age.

See also:
It's Okay to Call the "Magnetic Flux Ropes" Found Connecting the Sun and Earth an Electric Current!