Dust in the Wind
Sep 10, 2009

A recent report describes an unexpected alignment of Sahara dust grains in the atmosphere above La Palma in the Canary Islands. The vertical alignment of the dust grains is caused by electrical polarization by the Earth's electric field.

The article published February 10, 2009, describes the discovery in a way that makes it seem recent and serendipitous. It was made after mounting the PlanetPol polarimeter on the William Herschel Telescope (part of the Isaac Newton Group of Telescopes).

However, these observations (by the same investigators) date back to at least 2007, when a paper on this topic was published in the Atmospheric Chemistry and Physics Journal (Ulanowski et al, 2007). The original paper is a good analysis of the dust alignment and models the dynamics of the dust grains assuming gravitational forces, the fluid flow of the surrounding atmosphere, and the electric field strength.

The polarization of the dust particles was “unexpected” and seems to be the first observation of its kind. However, it should not be surprising given different fundamental assumptions. Earth carries a net charge relative to its local electrical environment in space. In essence, the Earth’s atmosphere is a capacitor with a radially oriented, variable electric field. It has been shown that atmospheric conductivity is decreased with haze, particulates, water vapor, etc. The electric field over part of the capacitor is intensified by these effectors.

The fair weather electric field at the Earth’s surface is about 120 volts-per-meter. It is interesting that the investigators estimated that the electric field orienting the Saharan dust grains was on the order of 2000 volts-per-meter (the E-field below dust storms can be many thousands of volts). If the dielectric properties of the Earth’s atmosphere are changed by the presence of the dust particles, creating a less conductive dielectric, then the electric field strength will build locally. The electric field strengths can be considerable, as high as 20,000 volts-per-meter at ground level during dust storms, even tens of kilometers from the storm (Kamra, 1972).

It seems that a side effect of the electric field enhancement in particulate clouds is the polarization of the dust grains. This polarization changes the radiative properties of the atmosphere in ways not included in current climate models. In addition, the electric field strength also enables the dust grains to travel great distances. For example, to take an excerpt from Ulanowski’s paper:

“Interestingly, it appears that some hitherto unknown atmospheric process counteracts gravitational settling of larger atmospheric dust particles (Maring et al., 2003), as models of long-range dust transport often underestimate the larger particle fraction (Colarco et al., 2003, Ginoux et al., 2001), and dust samples collected after fallout events show that large numbers of “giant” dust particles (larger than 62.5 micrometers) can be carried thousands of kilometers from their source (Middleton et al., 2001).”

A widespread and inherent electrical field in the Earth’s atmosphere that is altered by the traveling dust cloud might be part of the missing answer. In essence, the cloud of dust particles maintains an increased electric field in its locality simply by altering the conductivity of the Earth’s atmosphere. It carries its enhanced electric field with it. In fact, the electrical field effects of the dust cloud extend beyond its locality and can influence the conductivity of the atmosphere kilometers away, as was mentioned above. It is likely that similar mechanisms are at work on Mars.

Regional dust storms are not uncommon on Mars, but occasionally the regional storms organize into planet-wide events. The mechanism where dust particles increase the electric field through their presence, allowing more dust particles to become suspended, is an example of what engineers would call a positive feedback loop. In the proper circumstances, a small number of regional storms could combine, greatly altering the electrical field strength not just locally, but to a large extent beyond the storm itself. There is a widespread reinforcing effect that feeds on itself, and this is the nature of a positive feedback loop.

There has been some work done on the potential electrical properties of Martian dust storms and dust devils but all these studies begin with the assumption that the electric fields are generated locally through charge separation. Obviously, none have approached the problem from the perspective that an ambient electric field exists between the planet’s surface and the outer reaches of its atmosphere. I would propose installing polarimetry equipment in a subsequent Mars lander to observe the polarization properties of particulate matter in the Martian atmosphere. One would predict that the particles are aligned along an “unexpectedly” strong electric field in the middle atmosphere.

It is remarkable the degree to which scientists in various fields are surprised by the electrical nature of the Universe. I also find it interesting that our physical sciences have become dominated by a mindset that allows for only local causality rather than allowing for a broader connectedness. It took a very long time for conventional wisdom to accept that the Earth was electrically connected to the Sun. The logical next step in accepting that electricity flows between a star and its planets is allowing that the Earth exists in a lively electrical environment in its orbit around the Sun. That electrical environment reaches right down to the biosphere, impacting our climate both directly and indirectly.

By Tom Wilson