Magnetized Astrophysical Plasma: Three- Dimensional Resistive MHD Simulations of Gradient-Driven Anisotropic Dissipation in AGN Jet Feedback
Mahdieh Khalili
Mahdiyeh Khalili, Researcher, Department of Physics, Qazvin, Iran.
Manuscript received on 15 November 2025 | First Revised Manuscript received on 13 December 2025 | Second Revised Manuscript received on 17 March 2026 | Manuscript Accepted on 15 April 2026 | Manuscript published on 30 April 2026 | PP: 3-7 | Volume-6 Issue-1, April 2026 | Retrieval Number: 100.1/ijap.A107206010426 | DOI: 10.54105/ijap.A1072.06010426
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© The Authors. Published by Lattice Science Publication (LSP). This is an open-access article under the CC-BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Abstract: Understanding how energy is transported in hot, magnetized plasmas surrounding galaxies remains a central challenge in astrophysics. While turbulence and magnetic reconnection have been widely studied, the role of entropy gradients has typically been treated as passive. In this work, we demonstrate—using high-resolution three-dimensional resistive magnetohydrodynamic (RMHD) simulations of AGN jet feedback in the elliptical galaxy NGC 720—that entropy gradients actively organize plasma dynamics and drive anisotropic energy dissipation. We introduce a novel diagnostic, the Normalized Entropy Gradient (NEG), defined as N(mathbf{r}) = frac {l_0 |nabla S|} {S_0}, tag {1} where S = k_ {rm B} T n_e^ {-2/3} is the specific entropy. Our simulations reveal coherent vortical structures strongly aligned with magnetic field lines, quantified by an alignment parameter mathcal{A} = 0.76 pm 0.07 (corresponding to a mean angle of 28^circ pm 4^circ). This alignment is sustained only when anisotropic thermal conduction (Braginskii model) and localized resistivity are included in the total pressure relation P_ {rm tot} = P_ {rm gas} + |mathbf{B}|^2/2. We identify the underlying mechanism as Gradient-Driven Anisotropic Dissipation (GDAD), wherein entropy gradients preferentially channel energy along magnetic field lines via field-aligned heat flux and localized Ohmic dissipation. The energy budget shows thermal energy dominates (3.2 pm 0.3 times 10^ {59} erg), but magnetic (0.9 pm 0.1 times 10^ {59} erg) and kinetic components (1.1 pm 0.2 times 10^ {59} erg) play critical roles in sustaining anisotropy. Our results reproduce multi-wavelength signatures observed by Chandra (ObsID: 318) and VLA radio data within uncertainties, and GDAD provides testable predictions for future X-ray missions such as XRISM and Athena. All simulation data and analysis scripts will be publicly archived with a persistent DOI upon acceptance, ensuring full reproducibility. This work establishes, for the first time, that entropy gradients are primary drivers—not passive tracers—in the self-organization of astrophysical plasmas via the GDAD feedback loop.
Keywords: Resistive MHD; AGN Feedback; Entropy Gradients; Anisotropic Dissipation; Magnetic Reconnection; Plasma Self Organization
Scope of the Article: Astrophysics