MOdified Gravity (MOG) is a covariant modification of Einstein's general relativity. This theory one the current alternatives to dark matter models. We describe dynamics collisionless self-gravitating systems in context MOG. By studying weak field approximation this theory, we derive equations governing systems. More specifically, consider Jeans instability for fluid and stellar new mass limit ${\stackrel{\texttildelow{}}{M}}_{J}$ wave-number ${\stackrel{\texttildelow{}}{k}}_{J}$....

This study investigates the thermal stability of thin accretion disks in high-energy astrophysical systems, incorporating effects magnetic fields, winds, and coronae. We analyze how these factors influence disk stability, focusing on conditions under which fields enhance scenarios where winds coronae can either stabilize or destabilize disk. Our results reveal that increasing corona parameters raises thickness reduces temperature, thereby affecting gas, radiation, pressures. These...

The formation of massive black holes and their coevolution with host galaxies are pivotal areas modern astrophysics. Spherical accretion onto a central point mass serves as foundational frame- work in cosmological simulations, semianalytical models, observational studies. This extends the classical spherical model by incorporating gravitational potential galaxies, including contributions from stellar components dark matter halos. Numerical solutions spanning parsec-scale to...

We examine the effect of thermal conduction on low-angular momentum hot accretion flow (HAF) around non-rotating black holes accreting mass at very low rate. While doing so, we adopt conductive heat flux in saturated form, and solve set dynamical equations corresponding to a steady, axisymmetric, viscous, advective using numerical methods. study thermodynamical properties matter terms input parameters, namely energy ($\varepsilon_0$), angular ($\ell_0$), viscosity parameter ($\alpha$),...

We examine the effects of a hydrodynamical wind on advection dominated accretion flows with thermal conduction in presence toroidal magnetic field under self-similar treatment. The disk gas is assumed to be isothermal. For steady state structure such set self similar solutions are presented. mass-accretion rate $\dot{M}$ decreases radius $r$ as $\dot{M}\propto r^{s+1/2}$, where $s$ an arbitrary constant. show that existence will lead enhance velocity. Cooling outflows or winds noticeable and...

By taking into account the effect of a toroidal magnetic field and its corresponding heating, we determine thickness advection-dominated accretion flows. We consider an axisymmetric, rotating, steady viscous–resistive, magnetized flow under stage. The dominant mechanisms energy dissipation are assumed to be turbulence viscosity diffusivity. adopt self-similar assumption in radial direction obtain dynamical quantities, i.e. radial, azimuthal, sound Alfvén velocities. Our results show that...

We find the dispersion relation for tightly wound spiral density waves in surface of rotating, self-gravitating disks framework Modified Gravity (MOG). Also, Toomre-like stability criterion differentially rotating has been derived both fluid and stellar disks. More specifically, can be expressed terms a matter threshold over which instability occurs. In other words local written as $\Sigma_0<\Sigma_{\text{crit}}(v_s,\kappa,\alpha,\mu_0)$, where $\Sigma_{\text{crit}}$ is function $v_s$ (sound...

The observation of the hot gas surrounding Sgr $A^*$ and a few other nearby galactic nuclei imply that electron proton mean free paths are comparable to capture radius. So, accretion flows is likely proceed under week-collision conditions. Hence, thermal conduction has been suggested as possible mechanism by which sufficient extra heating provided in ADAF disks. We consider effects presence toroidal magnetic field an advection-dominated flow around compact object. For steady-state structure...

The ability to predict the future behavior of solar activity has become extremely import due its effect on environment near Earth. Predictions both amplitude and timing next cycle will assist in estimating various consequences space weather. level is usually expressed by international sunspot number (Rz). Several prediction techniques have been applied achieved varying degrees success domain prediction. We a index (Rz) 24 using neural network method. technique used analyze time series...

The main aim of this paper is studying the effect toroidal magnetic field on structure Advection-Dominated Accretion Flows (ADAF) in presence turbulence viscosity and diffusivity due to respectively. We use self-similar assumption radial direction solve magnetohydrodynamic (MHD) equations for hot accretion disk. spherical coordinate $ (r, \theta, \varphi) our equation. component considered all three components velocity \mathbf{v}\equiv (v_{r}, v_{\theta}, v_{\varphi}) are present work....

We construct self-similar inflow-outflow solutions for a hot viscous-resistive accretion flow with large scale magnetic fields that have odd symmetry respect to the equatorial plane in $B_\theta$, and even $B_r$ $B_\phi$. Following previous authors, we also assume polar velocity $v_\theta$ is nonzero. focus on four parameters: $\beta_{r0}$, $\beta_{\phi0}$ (the plasma beta parameters associated field components at plane), resistivity $\eta_0$, density index $n=-d\ln\rho/d\ln r$. The...

We present the effect of a hydrodynamical wind on structure and surface temperature vertically self-gravitating magnetized advection-dominated accretion flows (ADAFs) using self-similar solutions. Also model for an axisymmetric, steady-state, hot flow threaded by toroidal magnetic field has been formulated. The is based α-prescription turbulence viscosity. It found that thickness radial velocity disc are reduced significantly as gets stronger. In particular, solutions indicated advection...

The gravitational instability of a filamentary molecular cloud in non-ideal magnetohydrodynamics is investigated. filament assumed to be hydrostatic equilibrium. We add the effect ambipolar diffusion which threaded by an initial uniform axial magnetic field along its axis. write down fluid equations cylindrical coordinates and perform linear perturbation analysis. integrate resultant differential then derive numerical dispersion relation. find that, more efficient leads enhancement growth...

We carry out the self-similar solutions of viscous-resistive accretion flows around a magnetized compact object. consider an axisymmetric, rotating, isotheral steady flow which contains poloidal magnetic field central star. The dominant mechanism energy dissipation is assumed to be turbulence viscosity and diffusivity due explore effect on rotating disk in presence constant diffusivity. show that dynamical quantities ADAFs are sensitive advection parameters. Increase $\alpha$ coefficient...

Observations of the hot gas, which is surrounding Sgr A* and a few other nearby galactic nuclei, imply that mean free paths electron proton are comparable to gas capture radius. So, accretion flows likely proceed under week collision conditions. As result thermal conduction by ions has considerable contribution in transfer realized heat mechanisms. We study 2D advective disk bathed poloidal magnetic field central accretor presence conduction. find self-similar solutions for an axisymmetric,...

Self-similar and semi-analytical solutions are found for the height-averaged equations govern dynamical behavior of a polytropic, self-gravitating disk under effects winds, around nascent object. In order to describe time evolution system, we adopt radius dependent mass loss rate, then highlight its importance on both traditional $\alpha$ innovative $\beta$ models viscosity prescription. agreement with some other studies, our represent that Toomre parameter is less than one in most regions...

This study investigates the detectability of intermediate-mass black holes (IMBHs) within mass range $10^2-10^5$ solar masses in globular star clusters NGC 1399 at a frequency 300.00 MHz. Employing theoretical Bondi accretion model and empirical fundamental plane hole accretion, we estimate IMBH based on bolometric luminosity X-ray/radio luminosities, respectively. By simulating 3-hour observation 77 cluster candidates using Square Kilometer Array, identify radio detection benchmarks...

We have explored the structure of hot magnetized accretion flow with thermal conduction. The importance conduction in flows has been confirmed by observations gas surrounding Sgr $A^*$ and a few other nearby galactic nuclei. For steady state such set self similar solutions are presented. In this paper, we actually tried to re-check solution presented Abbassi et al. (2008) using physical constrain. study find that Eq 29 places new constrain limits answers 2008. paper parameter space which it...

This paper explores the effects of large-scale magnetic fields in hot accretion flows for asymmetric configurations with respect to equatorial plane. The solutions that we have found show field can significantly affect dynamics flow and also cause notable outflows outer parts. Previously, treated a viscous resistive accreting disc presence an odd symmetric B-field about Now, extend our earlier work by taking into account another configuration is no longer symmetric. We provide structures...

The Jeans analysis is studied in the first post-Newtonian limit. In other words, relativistic effects on local gravitational instability are considered for systems where characteristic velocity of system and corresponding field higher than what permitted Newtonian dispersion relation propagation small perturbations found approximation using two different techniques. A new mass derived compared to standard mass. this limit, make be smaller Furthermore, fractional difference between these...

The combined impact of rotation and magnetic fields on oscillations stellar fluids is still not well known theoretically. It mixes Alfvén inertial waves. Neutron stars are a place where both effects may be at work. We aim to solve this problem in the context r-mode instability neutron stars, as it appears when these modes coupled gravitational radiation. consider rotating spherical shell filled with viscous fluid infinite electrical conductivity analyse propagation model perturbations...

Abstract We solved the set of two-dimensional magnetohydrodynamic (MHD) equations for optically thin black hole accretion flows incorporating toroidal component magnetic field. Following global and local MHD simulations disks, field inside disk is decomposed into a large-scale fluctuating The effects in transferring angular momentum dissipating energy are described through usual α description. by assuming steady-state radially self-similar approximation r − θ plane spherical coordinate...

We examine the effect of self-gravity in a rotating thick-disk equilibrium presence dipolar magnetic field. In first part, we find self-similar solution for non-self-gravitating disks. The that have found shows pressure and density profiles are strongly modified by self-consistent toroidal introduce 3 dimensionless variables $C_B$, $C_c$, $C_t$ indicate relative importance component field ($C_B$), centrifugal ($C_c$) thermal ($C_t$) energy with respect to gravitational potential central...

The evolution of disk galaxies in modified gravity is studied by using high-resolution N-body simulations. More specifically, we use the weak field limit two theories, i.e., nonlocal (NLG) and scalar-tensor-vector known as MOG, ignore existence dark matter halo. On other hand, construct same models standard model compare their dynamics with galactic gravity. It turns out that there are serious differences between these different viewpoints. For example, explicitly show gravity, host faster...