Radiation magnetohydrodynamics modeling of an impulsively driven chromospheric jet in the solar atmosphere

TL;DR

This work presents a two-moment, gray radiative MHD simulation of an impulsively driven chromospheric jet in a stratified solar atmosphere, coupling the evolution of the radiation energy density $E_r$ and flux ${\bf F}_r$ to the plasma dynamics via M1 closure and $G^0$, ${\bf G}$ source terms. The jet is triggered by a localized Gaussian vertical-velocity pulse at $y=1.75$ Mm and propagates into the optically thin corona, with opacities chosen to reflect coronal conditions and a reduced speed of light $\hat{c}=0.1c$ to render the computation tractable. The results show a macrospicule-like jet attaining $\sim8$ Mm height and $\sim2\times10^5$ K leading edge, with internal temperatures around $8\times10^4$ K and vertical speeds up to $\sim60$ km s$^{-1}$ at the shock; radiative transport drives a linear growth of $E_r$ to $\sim1.75$ J m$^{-3}$ while the radiative flux declines, indicating efficient optically thin cooling that promotes downward flows and jet dissipation. The analysis demonstrates that self-consistent radiative transfer, rather than prescribed losses, is essential to capture energy exchange and the dissipation of macrospicule-like jets in the solar corona. Overall, the work provides a feasible framework for studying chromospheric jets with coupled MHD and radiative transfer, offering insights into energy budgets and the role of radiation in jet evolution.

Abstract

In this paper, we present a numerical simulation of an impulsively driven chromospheric jet in the solar atmosphere using the non-ideal magnetohydrodynamic (MHD) equations coupled with frequency- and angle-averaged radiation transport equations. These include the dynamics of the radiation energy density and radiation flux. The jet is initiated by a localized Gaussian pulse applied to the vertical velocity component in the upper chromosphere (y = 1.75 Mm), producing a collimated plasma structure that exhibits characteristics similar to macrospicules. We focus on the formation and evolution of the chromospheric jet as it propagates through an optically thin region encompassing the upper chromosphere and solar corona, where both the Planck-averaged absorption and Rosseland-averaged scattering opacities are low. Although radiation transport terms only slightly affect the jet's morphology, they play a significant role in governing radiative processes in the corona. In particular, radiation transport contributes to the dissipation of the chromospheric jet, which effectively acts as a radiative cooling mechanism as the jet evolves through the optically thin solar corona.

Figures (7)

• Figure 1: (Left) The logarithm of temperature in Kelvin (dashed line), the logarithm of mass density in kg m$^{-3}$ (dash dot line), and the logarithm of gas pressure in Pa (dotted line) versus height, $y$ in Mm, for the C7 equilibrium solar atmosphere model at the initial time ($t=0$ s) of the simulation. The vertical dashed line (black) represents the location of the transition region at about $y\sim 2.1$ Mm. (Right) Representation of the magnetic field lines in the 2D domain at $t=0$ s.
• Figure 2: Top row: Spatial profiles of temperature (in Kelvin) at $t=100$ s (left), $t=400$ s (center), and $t=800$ s (left). Bottom row: Vertical component of velocity $V_{y}$ in km s$^{-1}$ with velocity vector field at the exact three times as temperature.
• Figure 3: Time signatures of the vertical velocity, $v_{y}$, in km s$^{-1}$ (a)-(b), the temperature, in Kelvin (c)-(d), the radiation energy density, $E_{r}$, in J m$^{-3}$ (e)-(f), and the radial component of the radiation flux, $F_{r}$, in J m$^{-2}$ s$^{-1}$ (g)-(h), collected at the point $x=5.6, y = 4$ Mm (left panels) and $x=8.5, y = 14$ Mm (right panels).
• Figure 4: Distance-time diagrams of the vertical velocity $v_{y}$, in km s$^{-1}$ (left), and the logarithm of mass density, $\rho$, in kg m$^{-3}$ (right).
• Figure 5: (Top) Spatial profiles of radiation energy density $E_{r}$ (in J m$^{-3}$), magnitude of the radiation flux $|{\bf F_{r}}|$ in J m$^{-2}$ s$^{-1}$ (middle), and the ratio $E_{r}/e_{int}$ (bottom), at the times $t=100$ s (left), $t=400$ s (center), and $t=800$ s (right). The vectors (in black) represent the velocity vector field, and the contour (in black) represents a constant mass density of $10^{-14}$ kg m$^{-3}$.