Research Brief

RF energy as a forcing on cloud microphysics on anthropogenic clouds.

Published laboratory and modeling work on how laser, infrared, radio-frequency, and microwave energy interact with cloud droplets and condensation. This is the background reading behind our inquiry into GeoPulse microwave beams, the delivery mechanism under study.

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Laser filaments

Henin et al. measured laser-induced condensation once relative humidity exceeds 70%, attributing it to local photochemical formation of ppm-range hygroscopic HNO₃ (Henin et al., 2011); Wolf (2017) reviews filaments as 0.1–1 mm diameter structures spanning hundreds of meters with plasma densities of 10¹⁵–10¹⁷ cm⁻³, aimed at fog dissipation, water-vapor condensation, and cloud albedo for radiative forcing management (Wolf, 2017); Kasparian et al. frame the same work as “a step towards modulating precipitation” (Kasparian et al., 2011, 2012); Sun et al. got condensation with ~350 ps, ~25 MW pulses well below the ~3–10 GW self-focusing threshold, via ice-crystal and droplet fragmentation plus laser-induced airflow (Sun et al., 2016).

A compact microwave applicator

Camacho Hernandez et al. (2022) tested a compact microwave applicator: an open-cell ceramic foam separator reduced 99.9% of the entrained droplet volumetric flow, and adding microwave exposure raised this to 99.99% while preventing droplet re-entrainment and water clogging (Hernandez et al., 2022).

Nucleation in an optical radiation field

Chernyak and Evgrafova (2008) modeled homogeneous nucleation kinetics in supersaturated vapor in an optical radiation field, treating the nucleus temperature as differing from the equilibrium vapor temperature due to light absorption and latent-heat removal (Chernyak & Evgrafova, 2008).

Radiation from an oscillating charged cloud droplet

Grigoriev et al. (2025) derived the electromagnetic radiation intensity of an oscillating charged cloud droplet including charge and surface-tension relaxation, finding the highest intensity for an ideally conducting droplet (an order of magnitude above a finite-conductivity droplet), with the lowest for a dielectric droplet with frozen-in charge (Григорьев et al., 2025).

Mid-infrared absorption by cloud droplets

Brewster et al. (2014) measured mid-infrared (3–5 μm) absorption by a cloud-droplet suspension, deriving an interfacial radiative phase-transition probability of 5 × 10⁻⁸ and 3–4% surface absorption efficiency at 60 °C and 1 atm, decreasing to 3 × 10⁻⁸ at 75 °C, with the results implying a strong temperature dependence of cloud condensation nuclei concentration (roughly a factor of two from 60 °C to 75 °C) and the mechanism being most important for droplets below 20 μm diameter (Brewster et al., 2014; Kibria, 2015). This is infrared, not RF, but it is the clearest quantified radiative phase-transition result in the cloud-droplet literature.

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