Sand storms and electricity

For years, scientists have noticed rapidly varying electric fields inside dust storms and dust devils, the whirlwinds that skitter across many desert areas. Now, field tests in the western Sahara reveal that the fields—generated when windblown sand grains rub together—loft desert dust much more effectively than previously recognized, creating larger and longer lasting storms than wind alone[1].

When wind begins to blow across a sandy, dusty surface, the lightest particles aren’t the first to move. That’s because much of the dust is either stuck to larger particles or tucked between them. But when sand grains start to bounce across the surface, they strike other grains and shake loose the dust, which then rises into the air just above the ground. All that bouncing and jostling also generates static electricity.
When this happens, the larger sand grains typically lose electrons to the lighter dust particles, giving the dust a negative charge. The dust particles are blown higher into the air more readily, whereas the now positively charged sand grains usually remain closer to ground level. That separation of charges creates an electric field that may help electrify some of the dust still bound to sand grains, thus boosting even more of it into the air.

Previous studies have suggested that electric fields generated during the early stages of a sandstorm would have that effect, but nobody had made field measurements to support the idea, says Francesca Esposito, a planetary scientist at the National Institute for Astrophysics in Naples, Italy.

Atmospheric dust may have a powerful effect on climate, absorbing sunlight and warming the atmosphere at some altitudes while shading and cooling underlying layers of air.

Esposito is now trying to recreate the same experiment on Mars.

[1] Esposito et al: The role of the atmospheric electric field in the dust-lifting process in Geophysical Research Letters – 2016

No comments:

Post a Comment