Numerical simulations of magnetized jets

view Abstract Citations (156) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Numerical Simulations of Magnetized Jets Lind, Kevin R. ; Payne, David G. ; Meier, David L. ; Blandford, Roger D. Abstract Axisymmetric numerical simulations of light, hypersonic jets are presented. We consider both unmagnetized jets and jets carrying dynamically important magnetic field, and contrast their properties. A weakly magnetized jet is decelerated slightly by passing through a series of weak, oblique shocks before encountering a Mach disk and a strong annular shock, located near the outer edges of the contact discontinuity separating the shocked jet fluid from the shocked ambient gas. Much of the matter in the jet bypasses the Mach disk and is deflected by weak oblique shocks and decelerated to subsonic speed at the annular shock. The presence of this annular shock causes the jet thrust to be applied over an area significantly larger than that presented by the jet itself, and hence defines the effective "working surface" for the jet. After gas has passed through the annular shock, it quickly expands and enters a backflowing cocoon which surrounds the jet. One important consequence of the jet thrust being applied at the annular shock rather than the Mach disk is that the overall speed of advance of the jet is reduced to v_s_ ~ M_j_(R_j_/R_a_)c_e_ (where M_j_ is the Mach number of the jet, R_j_ is the radius of the jet, R_a_ is the "effective" radius of the annular shock, and c_e_ is the sound speed in the external medium). Matter near the jet axis which passes through the terminal Mach disk accumulates in a "plug." Gas is discharged from this plug into the cocoon by the intermittent shedding of vortices. As the shocked jet gas is, very hot and has a pressure scale height much greater than the length of the jet, the backflowing cocoon and shocked ambient medium are approximately isobaric. In contrast, when magnetic stresses dominate, the jet is decelerated rapidly via a Mach disk and strong annular shock. The shocked jet fluid is confined to a slender trans-Alfvenic plug which advances ahead of the annular shock and replaces the backflowing cocoon, which arises in weakly magnetized jets, as the repository of shocked jet gas. Highly magnetized jets are preceded by stronger, more oblique bow shocks, and advance more rapidly into the ambient medium than weakly magnetized jets having the same thrust and discharge. The velocity field in the plug is quite irregular, and contains alternate regions of compression and rarefaction along the axis, as well as large-scale vortical motion. These results are not particularly sensitive to the assumed distribution of magnetic field in the jet. The relevance of these simulations to models of double radio sources is briefly discussed. Publication: The Astrophysical Journal Pub Date: September 1989 DOI: 10.1086/167779 Bibcode: 1989ApJ...344...89L Keywords: Computational Astrophysics; Galaxies; Interstellar Magnetic Fields; Radio Jets (Astronomy); Computational Grids; Density Distribution; Gas Pressure; Magnetohydrodynamics; Shock Wave Propagation; Astrophysics; GALAXIES: JETS; HYDROMAGNETICS; SHOCK WAVES full text sources ADS | data products SIMBAD (2) NED (2)