Comparison of equilibrium ohmic and nonequilibrium swarm models for monitoring conduction electron evolution in high‐altitude EMP calculations

Abstract

Atmospheric electromagnetic pulse (EMP) events are important physical phenomena that occur through both man‐made and natural processes. Radiation‐induced currents and voltages in EMP can couple with electrical systems, such as those found in satellites, and cause significant damage. Due to the disruptive nature of EMP, it is important to accurately predict EMP evolution and propagation with computational models. CHAP‐LA (Compton High Altitude Pulse‐Los Alamos) is a state‐of‐the‐art EMP code that solves Maxwell ′s equations for gamma source‐induced electromagnetic fields in the atmosphere. In EMP, low‐energy, conduction electrons constitute a conduction current that limits the EMP by opposing the Compton current. CHAP‐LA calculates the conduction current using an equilibrium ohmic model. The equilibrium model works well at low altitudes, where the electron energy equilibration time is short compared to the rise time or duration of the EMP. At high altitudes, the equilibration time increases beyond the EMP rise time and the predicted equilibrium ionization rate becomes very large. The ohmic model predicts an unphysically large production of conduction electrons which prematurely and abruptly shorts the EMP in the simulation code. An electron swarm model, which implicitly accounts for the time evolution of the conduction electron energy distribution, can be used to overcome the limitations exhibited by the equilibrium ohmic model. We have developed and validated an electron swarm model previously in Pusateri et al. (2015). Here we demonstrate EMP damping behavior caused by the ohmic model at high altitudes and show improvements on high‐altitude, upward EMP modeling obtained by integrating a swarm model into CHAP‐LA.

Transformation of the Shape and Spectrum of an Ultrawideband Electromagnetic Pulse in a “Gigantic” Coaxial Line Filled with Magnetized Plasma

“…Interpretation of the observations can be complicated significantly by the nonlinear effects stimulated by powerful EMPs, primarily the ionization effects [8,9]. At present, numerical models are actively being developed, which allow predicting the shape of an EMP as the pulse propagates through the atmosphere and ionosphere [10][11][12]. At the same time, a rather promising approach, which is important for both verification of the developed models and physical demonstration of possible effects, is laboratory simulation performed in special laboratory plasma devices and based on the similarity parameters [13].…”

Gigantic Coaxial Line for Experimental Studies of the Interaction of Nanosecond Electromagnetic Pulses with an Ionized Gas Medium

“…Initially, the works in this research line were stimulated by the discovery of pulsed radio emissions of high-energy events in space and the top layers of the atmosphere [4,5]. At present, the models for the atmosphere conductivity dynamics in the EMP field are being actively developed [6,7]. Similar models are necessary to understand the physics of high-altitude discharges (see [8] and the references therein), and the processes induced by lightning EMPs [9], including those in the presence of flows of high-energy charged particles (see [10] and the references therein).…”

A Novel Method to Simulate the High‐Altitude Nuclear Electromagnetic Pulse Under the Asymmetrical Situation

“…Several 1‐D simulations (Meng, 2013; Wei & Kiang, 2016) and 3‐D simulations (Friedman et al, 2015, 2016; Kruger, 2012, 2016) were introduced. Investigations of conductivity models were carried out (Pusateri et al, 2016; R. Roussel‐Dupré, 2017).…”