Nonlinear ablative Rayleigh-Taylor instability: Increased growth due to self-generated magnetic fields

Area of Science:

• Plasma Physics
• Magnetohydrodynamics
• Astrophysical Phenomena

Background:

• The ablative Rayleigh-Taylor (RT) instability is a key process in inertial confinement fusion (ICF) and astrophysical systems.
• Self-generated magnetic fields, particularly from the Biermann battery mechanism, are increasingly recognized as significant factors influencing plasma dynamics.
• Understanding the interplay between RT instability and magnetic fields is crucial for predicting and controlling ICF target performance.

Purpose of the Study:

• To investigate the influence of self-generated magnetic fields on the growth rate of nonlinear ablative RT instability.
• To develop and validate a scaling law for the magnetic field's effect on RT instability growth with perturbation height and wavelength.
• To elucidate the physical mechanisms through which magnetic fields impact heat transport and instability evolution.

Main Methods:

• Extended-magnetohydrodynamic (MHD) simulations were employed to model the RT instability in the presence of self-generated magnetic fields.
• Analysis focused on the magnetic flux generation, Hall parameter variations, and heat transport effects (thermal conduction and Righi-Leduc).
• The proposed scaling law was validated against simulation results.

Main Results:

• Magnetic fields generated by the Biermann battery mechanism were found to enhance the RT instability growth rate.
• A scaling law for this enhancement was proposed, correlating with perturbation height and wavelength.
• The Hall parameter was significantly enhanced for short-wavelength spikes due to Nernst compression.
• Magnetic fields impacted spike growth by suppressing thermal conduction and deflecting heat via the Righi-Leduc effect.
• The dominant magnetic field effect shifted from Righi-Leduc (small Hall parameters) to suppressed thermal conduction (large Hall parameters).

Conclusions:

• Self-generated magnetic fields play a critical role in accelerating RT instability growth.
• The proposed scaling law provides a framework for understanding magnetic field effects on RT instability in ICF.
• Considering magnetic field physics, including thermal transport modifications, is essential for accurate modeling of perturbed ICF hot spots.