12. Balloon-Borne Electric Field Mills
Red lightning events in the upper atmosphere can be investigated using a novel method: balloon-borne electric field mills These specialised tools monitor the vertical component of the atmospheric electric field at different altitudes, therefore generating important information on the electrical environment in which red lightning episodes take place. Usually installed on high-altitude balloons capable of reaching heights of 30 km or more, the electric field mills enable stratospheric measurements where many red lightning events start. These devices comprise a revolving vane that alternately exposes and shields a sensor plate, therefore allowing high accuracy monitoring of the electric field strength and polarity. GPS trackers and telemetry equipment on the balloons enable researchers to link observed red lightning incidents with real-time data transmitted to ground stations. The capacity of balloon-borne electric field mills to produce vertical profiles of the atmospheric electric field gives one of their main benefits: it offers understanding of how the electrical structure of the atmosphere varies with height. Understanding the conditions under which red lightning forms and how these events, in turn, influence the nearby electrical environment depends on this knowledge. The mobility of balloon-borne equipment enables focused observations in regions prone to red lightning activity or in concert with particular meteorological conditions. Launching several balloons simultaneously allows researchers to generate a three-dimensional map of the electric field distribution, therefore offering hitherto unheard-of precision on the spatial properties of the electrical environment connected with red lightning. The information gathered by these equipment greatly advances our knowledge of the initiation processes of red lightning, the spread of electrical discharges in the high atmosphere, and the general energy balance of these events. By helping to validate and improve theoretical models of red lightning generation and behaviour, this technology also advances our knowledge of atmospheric electricity and its function in the Earth’s climate system.