HYDROFLASH: A 2-D Nuclear EMP Code Founded on Finite Volume Techniques

Abstract

The basic mechanisms that govern the generation of an electromagnetic pulse (EMP) following a nuclear detonation in the atmosphere, including heights of burst (HOB) relevant to surface bursts (0 km), near surface bursts (0-2 km), air bursts (2-20 km) and high-altitude bursts (> 20 km), are reviewed. Previous computational codes developed to treat the source region and predict the EMP are discussed. A new 2-D hydrodynamic code (HYDROFLASH) that solves the fluid equations for electron and ion transport in the atmosphere and the coupled Maxwell equations using algorithms extracted from the Conservation Law (CLAW) package for solving multi-dimensional hyperbolic equations with finite volume techniques has been formulated. Simulations include the ground, atmospheric gradient, and an azimuthal applied magnetic field as a first approximation to the geomagnetic field. HYDROFLASH takes advantage of multiprocessor systems by using domain decomposition together with the Message Passing Interface (MPI) protocol for parallel processing. A detailed description of the model is presented along with computational results for a generic 10 kiloton (kT) burst detonated at 0 and 10 km altitude. Nuclear EMPThe detonation of a nuclear weapon is accompanied by the release of tremendous amounts of energy (several to thousands of tera-Joules, depending on yield) in a very short period of time (less than a microsecond) and in the form initially of X-rays, γ -rays, neutrons, and radioactive debris. Approximately 70-80% of the weapon yield is emitted as radiation (primarily X-rays but also neutrons and gammas) while 20-30% comes out as debris kinetic energy. For a detonation in sea-level air the X-rays are absorbed within a few meters of the burst and the air temperature in this volume is instantaneously raised to millions of degrees. This deposited energy then evolves over milliseconds and seconds into a hot, expanding fireball that consists of blast and shock waves, that emits intense optical and UV radiation, and that, for near surface bursts, vaporizes or entrains copious amounts of solid materials. While most of the energy produced by a nuclear detonation is dissipated during this radiative and hydrodynamic phase, very little coherent electromagnetic radiation is produced. In fact, it is only during the very early prompt phase (t < a few tens of microseconds) of the detonation, when weapon leakage γ -rays and neutrons are radiated and absorbed in the air, that a strong coherent electromagnetic pulse (EMP) is generated. The γ-rays comprise a small fraction of the total yield ranging from 0.1% -0.5% depending on the weapon design and have absorption scale lengths in air at sea level in the range of hundreds of meters depending on their energy. Compton scattering of the γ-rays in air leads to the production of a Compton current (mainly relativistic electrons) that in turn radiates an electromagnetic pulse.Conversion of the prompt, unscattered γ-ray energy to EMP occurs within one microsecond of the detonation. A second phase of EM...

A Simulation of the Nuclear High‐Altitude Electromagnetic Pulse (HEMP) Produced by the X‐Ray in the Ionosphere

“…Since the 1960s, scientists have found that the nuclear explosion was a strong source of the electromagnetic pulse (e.g., Berthold et al., 1960; Bomke et al., 1960, 1964; Casaverde et al., 1963; Cotterman, 1965; Crook et al., 1963; Dinger & Garner, 1963; Field & Greifinger, 1967; Latter & LeLevier, 1963; Wittwer et al., 1974). The majority of previous studies on HEMP have used γ‐rays rather than X‐rays as the energy source (e.g., Leuthiiuser, 1992; Li et al., 2020; Longmire, 1978; Meng, 2013; Roussel‐Dupré, 2017; Zhang & Zhang, 2018). This is appropriate for observers situated below 40 km in altitude (Higgins et al., 1973; Karzas & Latter, 1965; Price, 1974), because X‐rays have been absorbed within several tens of meters from the burst, thus only energetic γ‐rays with several kilometers free path can proceed at low altitudes.…”

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).…”