Introducing Current Estimation for Fractal Models of Electrical Discharges

The FRActal Model of Electrostatic Discharges (FraMED) has a history of successfully simulating mesoscale lightning on Earth. It was recently adapted to expand its applicability to other solar system bodies. In particular, we introduced one-way coupling with NASA’s Global Reference Atmospheric Models (GRAMs) and the Explicit Planetary Isentropic-Coordinate model (EPIC). Our early results quantitatively and qualitatively match discharges observed on both Earth and Jupiter. The aforementioned atmospheric models let us derive the conventional breakdown, which serves as a reference value to define initiation and propagation thresholds for the discharge, especially when those are not readily available in the peer-reviewed literature. We introduce an electrification scheme based on the Gardiner-Ziegler parameterization to estimate the cloud charge density using the particle size and distribution. The resulting electrostatic environment serves as initial conditions for developing streamer- or leader-like channels. Our fractal model reflects the stochastic, branching nature of lightning propagation, but the steps associated with each iteration cannot be directly correlated to a temporal value. Following an overview of the multi-model coupling used to simulate the atmospheric conditions, this work introduces a backwards-compatible approach to estimate the simulated discharge’s timescale, which leads to an approximation of the current in the discharge’s channel. Time-based characteristics further connect theoretical modeling to frequency ranges and timescales. This can ultimately inform instrument designs for lightning and TLEs on Earth and beyond. We compare simulations for Earth and Jupiter to data from the FORTE, GOES-16, Voyager 1, Galileo, and Juno missions. Upon validation, we propose to extend this methodology to other solar system bodies where data is limited.