arXiv subjects

Michael C. Sitarz

Publications and source records attributed to Michael C. Sitarz.

4 recordsLinked to original sources

arXiv2025

Counter-Streaming Beams in Collisionless Pair Plasma Instability Systems II: Spectral Cone and Spectral Wave Mode Analysis

Energetic astrophysical phenomena, such as $γ$-ray bursts, supernova explosions, and magnetar flares occur in collisionless plasmas and involve various plasma kinetic and magnetohydrodynamic instabilities. In this paper, we explore the spectral trends of the Weibel instability using spectral analysis of particle-in-cell simulations. Power dependence on viewing angle and frequency are explored and the relation to the results of the first paper in this series is discussed.

physics.plasm-ph↗

arXiv2025

Counter-Streaming Beams in Collisionless Pair Plasma Instability Systems III: Collisionless Heating, Acceleration, and Radiation

Energetic astrophysical phenomena, such as $γ$-ray bursts and supernova explosion-driven shocks in collisionless plasmas, involve various plasma kinetic instabilities, such as the Weibel instability. These systems support various types of particle acceleration and radiation through a variety of mechanisms. In this paper, we explore the energy transformations and dynamical effects of violent filament mergers seen between the large current filaments formed by the Weibel instability. The radiative processes involved in the Weibel instability filament building are also discussed in relation to jitter and synchrotron radiation.

physics.plasm-ph↗

arXiv2025

Counter-Streaming Beams in Collisionless Pair Plasma Instability Systems I: Evolution and Parameterization of the Weibel Instability

Energetic astrophysical phenomena, such as $γ$-ray bursts and supernova explosion-driven shocks in collisionless plasmas, involve various plasma kinetic instabilities, such as the Weibel instability. In this paper, we explore the evolution of the Weibel instability using the spectral analysis and physical field evolution of particle-in-cell simulations. Effects of varying parameters of the initial counter-streaming beams are detailed in reference to the total evolutionary timeline of the instability. Generation of a secondary instability and excitation of electromagnetic waves primary decay have been observed. We also discuss the filament mergers during the instability decay.

physics.plasm-ph↗

arXiv2023

Pair Plasma Cascade in Rotating Black Hole Magnetospheres with Split Monopole Flux Model

An electron-positron cascade in the magnetospheres of Kerr Black Holes (BH) is a fundamental ingredient to fueling the relativistic $γ$-ray jets seen at the polar regions of galactic supermassive BHs (SMBH). This leptonic cascade occurs in the "spark gap" region of a BH magnetosphere where the unscreen electric field parallel to the magnetic field is present, hence it is affected by the magnetic field structure. A previous study explored the case of a thin accretion disk, representative of Active Galactic Nuclei (AGN). Here we explore the case of a quasi-spherical gas distribution, as is expected to be present around the SMBH Sgr A* in the center of our Milky Way galaxy, for example. The properties and efficiency of the leptonic cascade are studied. The findings of our study and the implications for SMBH systems in various spectral and accretion states are discussed. The relationships and scalings derived from varying the mass of the BH and background photon spectra are further used to analyze the leptonic cascade process to power jets seen in astronomical observations. In particular, one finds the efficiency of the cascade in a quasi-spherical gas distribution peaks at the jet axis. Observationally, this should lead to a more prominent jet core, in contrast to the thin disk accretion case, where it peaks around the jet-disk interface. One also finds the spectrum of the background photons to play a key role. The cascade efficiency is maximum for a spectral index of two, while harder and softer spectra lead to a less efficient cascade.

astro-ph.HE↗