Insect swarms can generate as much static electricity as a storm cloud

Insect swarms can generate as much static electricity as a storm cloud

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The Earth’s atmosphere is always more or less electrified, even in fair weather. The intensity of this electric field depends on many physical and geological factors (rainfall, aerosols, radioactivity, pollution, volcanism, etc.). British scientists recently identified another factor that could explain the observed potential gradient variations: insects. Their electrical charge could lead to changes comparable to meteorological processes.

There are multiple sources of electric charge in the atmosphere and they can affect some natural phenomena such as droplet aggregation and the transport of dust and aerosols. The atmospheric electric field is known to depend on physical and geological processes, but the potential influence of biological sources has not been considered. However, the abiotic factors identified so far are insufficient in themselves to explain the commonly observed variations in atmospheric potential gradients, suggesting that additional causes remain to be discovered.

The scientists therefore hypothesized that organisms living in the lower layers of the atmosphere could contribute to these electric field variations. In particular, it is well known that insects are present in great densities in the lower layers of the atmosphere. Furthermore, it has been shown that many species of flying insects carry an electric charge, on the order of several picocoulombs to several nanocoulombs per individual. ” These observations support the hypothesis that large aggregations of aerial insects are an important source of space charge in the atmosphere. ”, the researchers note.

An increase of almost 1000 volts

The team previously studied how different organisms use static electric fields. In particular, they showed that bees and spiders use electric fields surrounding flowers for foraging and migration. “ Basically, we always wanted to know how physics affects biology, but at some point we realized that biology can also affect physics. », Dr. Ellard Hunting explainedecologist at Bristol’s School of Biological Sciences and first author of the study.

To investigate the extent to which insects could affect the atmospheric electric field, the researchers studied the effects of a swarm of bees at a site containing several hives used for research. The electrical effect was assessed using an electric field monitor and a surveillance camera located near the swarm. ” For about three minutes, part of the migrating swarm passed over the electric field monitor. This revealed a net positive gradient potential (GP) increase of 100 V/m at maximum density ”, reports the team.

(A) Bees passing through the electric field monitor at the experimental site. (B) Model illustrating the potential effect of a bee swarm on atmospheric GP (in V/m). (C) Atmospheric GP and bee swarm density. (D) Cross-correlation analysis between atmospheric GP and bee swarm density. (E) Linear regression analysis between atmospheric GP and bee swarm density. (F) Changes in atmospheric GP in response to another bee swarm event. © ER Hunting et al.

These results suggest that the bee swarm contains enough charge to affect the atmospheric GP, proportional to the swarm density. During other swarm events, the team observed a net positive increase in atmospheric GP reaching nearly 1000 V/m at peak density.

Charge density greater than storm clouds

Various insect species (Hymenoptera, Orthoptera, Lepidoptera, etc.) can form extremely large and dense swarms (up to 10 insects/m3), covering an area of ​​up to 1000 km2. Scientists wanted to estimate the effect of such swarms, particularly those of locusts, on local atmospheric electric fields. ” Using considerations similar to those used here for bees, our analysis reveals that swarms of locusts have the potential to alter their local electrical environment with a magnitude comparable to weather events. “, they conclude.

comparison density load insects weather phenomena
(C) Load densities of several swarming insect species and meteorological phenomena. From top to bottom: honey bee (Apis mellifera), Grasshopper (S. gregaria), moths (Tyria jacobaeae and Aglais io), semi-clear clouds, thunderstorms and electrified dust storms. © ER Hunting et al.

The team then compared their results with meteorological load densities recorded under different conditions (semi-clear weather, thunderstorm, dust storm) reported in the literature. Data show that locusts swarm (Schistocerca gregaria) are capable of exceeding the charge densities observed in storm clouds! On the other hand, Lepidoptera (moths and butterflies), due to their low average density (about 0.01 insects/m3) do not represent a significant source of atmospheric load with regard to meteorological phenomena.

This study therefore highlights the unexplored role of insects in atmospheric electrical variability. This is important because this factor is not currently taken into account in current climate models aimed at capturing the complex interaction between radiation and particles. However, since atmospheric space charge increases the aggregation and movement of airborne particles, it is possible that insect-derived space charges also contribute to the spatial variation of airborne particles.

More broadly, linking biology and physics could help solve many perplexing questions, such as why large dust particles are found so far from the Sahara that cannot be explained by existing ideas. “, emphasizes Professor Giles Harrison, atmospheric physicist at the University of Reading and co-author of the study.

It should be noted that the observed phenomenon is probably relevant to other organisms developing in the atmosphere and carrying an electric charge, especially microbes and birds. ” It would be interesting to study how these organisms interact with other atmospheric processes such as ion and aerosol fluxes. concludes Lov.

source: ER Hunting et al., iScience

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