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tokens: wave. Thus, there is a continuous flux of particles crossing R c from below. These particles get accelerated to high LF and advected with the Alfvén wave as a result of the strong electric field 2 in the charge starvation zone. The continuous loss of particles from the interior of R c causes the e ± density to decrease with time, and the region that was not charge starved before becomes charge starved. We estimate the speed at which R c moves inward. The current amplitude ( I aw ) associated with the Alfvén wave packet along is roughly independent of R; I aw is the integral of current density over the cross-section of the wave packet. Thus, the number of particles that cross R c per unit time and are subsequently advected by the Alfvén wave is ∼ I aw /2 q . The cross-sectional area of the wave packet, A aw , increases as R 3 as the wave follows the dipole field lines. Therefore, d R c /d t ∼ − I aw /(2 qnA aw ). This result can be recast in a slightly more convenient form as d R c /d t ∼ − n c /2 n; I aw / A aw ∼ j , and j can be written in terms of n c and n using equations ( 4 ) and ( 6 ). A corollary of this result is that e ± present in the NS magnetosphere are depleted (advected by the wave) on a time of the order of 〈 n / n c 〉 R c / c , which is a few ms. Thus far, we have discussed how the Alfvén current below R c supplies a flux of particles into the charge starvation region where they are quickly accelerated and advected by the wave. We now describe how particles the Alfvén wave packet encounters at the head of the wave at R > R c also get trapped and advected by the wave. Charge particles of one sign – those that experience the force of the field in the forward direction – are swept up by the wavefront and compressed into a thin sheet of width much smaller than λ aw and forced to move with the wave. Particles of the opposite charge move in the reverse direction, along , at a speed of ≈ c for about half a wavelength and there they start accumulating in a thin sheet; these results follow from equation ( 16 ) for γ. The Coulomb field in the thin sheet increases with time as more charges are swept up by the wave and accumulate in the sheet: where R is the location of the wavefront at time t . The Coulomb field strength exceeds the wave-field E d for , and at that point the sheet starts spreading in the longitudinal direction at close to the speed of light. Since the Coulomb fields at the front and the back sides of the sheet do not decrease as the width of the sheet increases, the spreading continues until the sheet thickness becomes ∼λ aw /2. Particles in the sheet now overlap with particles of opposite charge in the adjoining half-wavelength of the Alfvén packet, thereby partially shielding E cou . The physics of the system is that charge particles of one sign swept up at the front of the Alfvén wave packet, within λ aw of R c , accumulate in a thin sheet near the leading front. The sheet starts to spread longitudinally, after about