Space-time structured plasma waves*

Electrostatic waves play a critical role in nearly every branch of plasma physics from fusion to advanced accelerators, to astro, solar, and ionospheric physics. The properties of planar electrostatic waves are fully determined by the plasma conditions, such as density, temperature, ionization states, or details of the distribution functions. Here we demonstrate that electrostatic wavepackets structured with space-time correlations can have properties that are independent of the plasma conditions. Specifically, these packets can travel at any group velocity, even backwards with respect to their phase fronts, while maintaining a localized energy density. These linear, propagation-invariant wavepackets can be constructed with or without orbital angular momentum by superposing natural modes of the plasma and can be ponderomotively excited by structured laser pulses like the flying focus.