Comment on "Generation of Electromagnetic Pulses from Plasma Channels Induced by Femtosecond Light Strings"
Authors: Gennady Shvets, Igor Kaganovich, and Edward Startsev
Date of PPPL Report: September 2002
Submitted to: Physical Review Letters
In a recent Letter, Cheng et al. calculated/predicted several new effects: that (a) fraction of the short laser pulse momentum can be imparted to plasma electrons via collisional damping of the laser, thereby exciting a long-lived (longer than an oscillation period) plasma wave, which (b) gives rise to a spatially uniform dipole moment of a plasma, which (c) emits far-field narrow-band radiation at the plasma frequency wp over the recombination time of the plasma. We claim that the calculation of the effect (a) is in error and the predicted effects (b,c) do not occur as described. In fact, predicted narrow-band emission at wp would not occur even if the momentum transfer and the dipole excitation were calculated correctly.