Enhanced ­collisionless energy absorption in plasma with strong background magnetization

Strongly magnetized collisionless laser-plasma interaction (LPI) is a largely unexplored subject. Previous research on weakly magnetized LPI, where gyrofrequency ω_c is much lower than plasma frequency ω_p, has shown that magnetization increases the amount of energy absorbed by the plasma by raising the threshold for kinetic inflation and decreasing laser energy backscatter. We studied collisionless LPI with background magnetic fields (B₀) on the kilotesla scale (where  ω_c >> ω_p) to investigate how strong magnetization impacts laser-to-plasma energy transduction. We used a particle-in-cell code to simulate strongly magnetized LPI and found that at resonant B₀ values the laser excites magnetized plasma waves on a picosecond timescale. Collisionless damping of these waves increases the number of hot electrons in the plasma by multiple orders of magnitude in comparison to non-resonant cases, signified by a broadening in the velocity distribution functions and a decrease in transmitted energy. Higher efficiency laser-to-plasma energy transfer is important in a wide variety of applications, from compact x-ray sources for medical devices to inertial confinement fusion. Additionally, the physics behind these interactions may provide insight to phenomena such as the solar coronal heating problem.