Magnetospheric Accretion and Ejection of Matter in Resistive Magnetohydrodynamic Simulations

Abstract

The ejection of matter in the close vicinity of a young stellar object is investigated, treating the accretion disk as a gravitationally bound reservoir of matter. By solving the resistive MHD equations in 2D axisymmetry using our version of the Zeus-3D code with newly implemented resistivity, we study the effect of magnetic diffusivity in the magnetospheric accretion-ejection mechanism. Physical resistivity was included in the whole computational domain so that reconnection is enabled by the physical as well as the numerical resistivity. We show, for the first time, that quasi-stationary fast ejecta of matter, which we call micro-ejections, of small mass and angular momentum fluxes, can be launched from a purely resistive magnetosphere. They are produced by a combination of pressure gradient and magnetic forces, in presence of ongoing magnetic reconnection along the boundary layer between the star and the disk, where a current sheet is formed. Mass flux of micro-ejection increases with increasing magnetic field strength and stellar rotation rate, and is not dependent on the disk to corona density ratio and amount of resistivity.

THE ROLE OF FAST MAGNETIC RECONNECTION ON THE RADIO AND GAMMA-RAY EMISSION FROM THE NUCLEAR REGIONS OF MICROQUASARS AND LOW LUMINOSITY AGNs

“…Lately, similar mechanisms involving magnetic activity and reconnection in the core regions of compact sources to explain their emission spectra have been also invoked by other authors (see, e.g., Igumenshchev 2009;Soker 2010;Uzdensky & Spitkovsky 2014;Dexter et al 2014;Huang et al 2014). In particular, magnetic reconnection between the magnetospheric lines of the central source and those anchored into the accretion disk resulting in the ejection of plasmons has been detected in numerical MHD studies (see, e.g., Romanova et al 2002Romanova et al , 2011Zanni & Ferreira 2009, 2013Čemeljić et al 2013). The recent numerical relativistic MHD simulations of magnetically arrested accretion disks by Tchekhovskoy et al (2011); McKinney et al (2012) and Dexter et al (2014) also evidence the development of magnetic reconnection in the magnetosphere of the BH and are consistent with the scenario above.…”

“…As remarked, other contemporary works have also explored magnetic processes in the surrounds of BH systems and other compact sources to explain their emission (see, e.g., Soker 2010;Čemeljić et al 2013;Uzdensky & Spitkovsky 2014;Huang et al 2014). In particular Huang et al (2014) investigated magnetic reconnection in the surrounds of BH binary systems (microquasars) employing a radiatively inefficient advectiondominated accretion flow (RIAF) to describe the accretion disk combined with a jet model.…”

Radiative GRMHD simulations of accretion and outflow in non-magnetized neutron stars and ultraluminous X-ray sources

“…One interesting application of our study could be an extension to supersoft sources (SSS) (Long et al 1981;van den Heuvel et al 1992) and ultraluminous supersoft sources (ULS) (Urquhart & Soria 2016). ULSs are characterized by peak temperatures of around 10 6 K, with bolometric luminosities at a few times 10 39 erg s −1 and photospheres at radii of around 10 4 km.…”

Magnetic torques on T Tauri stars: accreting vs. non-accreting systems

“…The general consensus is that the angular momentum evolution of CTTs is controlled by the interaction of the stellar magnetic field with the surrounding accretion disk and its environment. The star-disk magnetospheric interaction and the associated outflows have been extensively studied in the literature, using either semi-analytic models (e.g., Ghosh & Lamb 1979;Collier Cameron & Campbell 1993;Lovelace et al 1995;Armitage & Clarke 1996;Agapitou & Papaloizou 2000;Ferreira et al 2006;Matt & Pudritz 2005b;Mohanty & Shu 2008;Sauty et al 2011, and references therein) or numerical simulations (e.g., Hayashi et al 1996;Goodson et al 1997;Miller & Stone 1997;Küker et al 2003;Zanni & Ferreira 2009Čemeljić et al 2013;Kulkarni & Romanova 2013;Romanova et al 2013;Čemeljić 2019, and references therein). Within this scenario, several mechanisms have been proposed to explain the rotation periods of CTTs.…”