The longevity of electrostatic charge on suspended atmospheric dust grains
Abstract
Mobilized collections of particles may become charged through a range of processes and play critical roles in numerous geophysical and planetary systems. The effects of charge in granular flows can be spectacular--the large-scale discharges observed during volcanic eruptions are perhaps the most dramatic example. Yet, even the more subtle effects of particle charging can have profound consequences for planetary-wide geomorphology, habitability, and the presence of life. For instance, the towering equatorial dunes of Titan may be composed of aerosol (tholin) clusters held together by electrostatic forces. The ubiquitous perchlorates—chemicals toxic to life—on the Martian surface may be generated through reactions catalyzed by charged windblown dust. On a primordial Earth, charged volcanic flows have been implicated in the production of the compounds necessary for life. While the importance of charging in particle-laden flows has long been recognized, many microphysical aspects underlying electrification remain debated or poorly understood. While most studies to date have focused on elucidating the charging processes themselves, comparatively little effort has been expended understanding the stability of charge on particles once electrified. Such gap in knowledge is surprising given that many of the processes that invoke particle electrification require that charge be present on particles for long timescales. Here, we discuss the results of a set of experiments designed to explore the longevity of electrostatic charge on airborne particles after a single charging event. Using a novel charge-sensing, acoustic levitator we were able to track the charge on sub-millimeter-sized particles of different compositions suspended in gas for week-long periods. We find that the stability of charge on particles depends strongly on both humidity and pressure, supporting the idea that electrostatic processes in granular flows are modulated by water films. Depending on ambient conditions, the charge on particles can decay on timescales of days to months. Our work suggests that charged dust particles in some environments act as naturally occurring electrets, or grains with quasi-permanent electric charge.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A41N2837M
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 1622 Earth system modeling;
- GLOBAL CHANGE