Analytic Model for the Time-dependent Electromagnetic Field of an Astrophysical Jet

Abstract

An analytic model of the time-dependent electric and magnetic fields of an astrophysical jet is presented. These fields satisfy the time-dependent Faraday's law and describe a jet with increasing length. The electric field contains both electrostatic and inductive parts. The electrostatic part corresponds to the rate of injection of toroidal magnetic flux, while the sum of the electrostatic and inductive parts results in the electric field parallel to the magnetic field being zero everywhere. The pinch force associated with the electric current provides a peaked pressure on the jet axis and a pressure minimum at the radius where the poloidal magnetic field reverses direction.

Neutral-charged-particle Collisions as the Mechanism for Accretion Disk Angular Momentum Transport

“…The bidirectional jet electric currents are directed away from the accretion disk in the small radius region (ion accumulation region). The slight r component of the outof-plane electric current and its associated azimuthal magnetic field B f produce J r B f forces that drive bidirectional astrophysical jets flowing away from the disk plane; this adds to axial pressure gradients that also drive a flow away from the disk plane (Bellan 2016(Bellan , 2020. This jet generation configuration is topologically analogous to the Caltech astrophysical jet experiment (Hsu & Bellan 2002;You et al 2005;Kumar & Bellan 2009) where a poloidal current is produced by a power supply imposing a radial electric field between a conducting disk in the z = 0 plane and a coplanar conducting annulus surrounding the disk and separated by a small gap.…”

Caltech Lab Experiments and the Insights They Provide Into Solar Corona Phenomena

“…These models are not only relevant to solar physics, but also to magnetospheric physics and to astrophysics which can have similar physics but at very different scales from the lab or the Sun. Examples of such theoretical models are the following: A model showing why flux ropes tend to be collimated (Bellan, 2003) A model for how accretion disks and astrophysical jets form a complete electric circuit that transfers angular momentum in a conservative way much like a generator transfers angular momentum via wires to a distant motor (Bellan, 2016a, 2018d) A model providing a time‐dependent analytic solution for an astrophysical jet (Bellan, 2020) A model for how energetic particles are created in the presence of sub‐Dreicer electric fields (Marshall & Bellan, 2019) A model providing an intuitive explanation for fast collisionless magnetic reconnection (Yoon & Bellan, 2017, 2019a) in the electron MHD context, that is, the context where the timescale is so fast that ions can be considered stationary, and the reconnection length scale is short compared to the ion skin depth, so Hall terms and electron inertia are important. A model showing that ions experience fast stochastic heating during fast collisionless reconnection (Yoon & Bellan, 2018, 2019b) A model showing how the reverse current associated with coronal mass ejection drives EUV fronts in the solar corona (Wongwaitayakornkul et al., 2019) …”

“…After the spider legs have merged, the lengthening jet behaves in a manner consistent with ideal MHD, that is, consistent with the assumption that the electric field vanishes in the frame moving with the jet. Having E = 0 in the jet frame is an essential property of a numerical simulation of the jet experiment (Zhai et al., 2014) and of an analytic model of the lengthening jet (Bellan, 2020).…”

Nonlinear harmonics coupled by parallel wave propagations in a time-dependent plasma flow

“…For magnetically confined plasmas, magnetohydrodynamic instabilities [1][2][3] have been studied in order to achieve stable confinement [4,5]. On the other hand, instabilities in space plasmas, such as the ionosphere [6], magnetosphere [7], solar wind [8], coronal loop [9], and astrophysical jet [10,11] have been studied in order to understand field and particle behavior.…”