The time-dependent global model is employed to examine the temporal behavio
r of the electron density and temperature in helicon plasmas. The power abs
orption calculated from the solutions of the Maxwell equations is used in s
olving the power balance equation and a balance model for the neutral gas i
s considered to find its density self-consistently. The numerical results s
uccessfully explain neutral gas depletion and the occurrence of two distinc
t modes of pulsed helicon discharge, which have been observed experimentall
y. (C) 1999 American Institute of Physics. [S1070-664X(99)01701-2].