Comparing Poynting flux dominated magnetic tower jets with kinetic-energy dominated jets

TL;DR

This study uses high-resolution MHD simulations to compare the behavior, stability, and evolution of magnetic tower jets with kinetic-energy dominated jets, revealing effects of thermal losses and rotation on their dynamics.

Contribution

It provides new insights into magnetic tower outflows, their stability, and their connection to both laboratory experiments and astrophysical jets, highlighting the effects of thermal losses and rotation.

Findings

Magnetic towers are significantly affected by thermal energy losses and rotation.

Current-driven perturbations are amplified in cooling and rotating cases.

Weakly magnetized jets break into collimated clumps over time.

Abstract

Magnetic Towers represent one of two fundamental forms of MHD outflows. Driven by magnetic pressure gradients, these flows have been less well studied than magneto-centrifugally launched jets even though magnetic towers may well be as common. Here we present new results exploring the behavior and evolution of magnetic tower outflows and demonstrate their connection with pulsed power experimental studies and purely hydrodynamic jets which might represent the asymptotic propagation regimes of magneto-centrifugally launched jets. High-resolution AMR MHD simulations (using the AstroBEAR code) provide insights into the underlying physics of magnetic towers and help us constrain models of their propagation. Our simulations have been designed to explore the effects of thermal energy losses and rotation on both tower flows and their hydro counterparts. We find these parameters have significant effects on the stability of magnetic towers, but mild effects on the stability of hydro jets. Current-driven perturbations in the Poynting Flux Dominated (PDF) towers are shown to be amplified in both the cooling and rotating cases. Our studies of the long term evolution of the towers show that the formation of weakly magnetized central jets within the tower are broken up by these instabilities becoming a series of collimated clumps which magnetization properties vary over time. In addition to discussing these results in light of laboratory experiments, we address their relevance to astrophysical observations of young star jets and outflow from highly evolved solar type stars.