typical velocity of the revived shock[@cf95]. The adoption of a smaller velocity will not influence our followup conclusion qualitatively. Notice that $\Delta M$ obtained here is 10 orders of magnitude smaller than the maximum $\Delta M$, but 5 orders of magnitude larger than the “atmosphere” mass discussed by Usov[@usov97]. We will call the structure formed by the fallback materials a [*massive atmosphere*]{} rather than a thin crust (following Usov[@usov97; @usov98]).

We now estimate the depth of this atmosphere. The column density of the atmosphere is $\sigma_{\rm a} \sim \Delta M /
(4\pi R^2)\sim 8.0 \times 10^3 B_{12}^2 P^{-2}v_9^{-2} R_6^4
M_1^{-1}$ g cm$^{-2}$. The bottom pressure of the atomsphere is thus $p_{\rm b} = (GM\sigma_{\rm a}/ R^2)\sim 1.0 \times 10^{18}
B_{12}^2 v_9^{-2} R_6^2 P^{-2}$ dynes cm$^{-2}$. According to the equation of state[@fow26] $$p=1.8\times 10^{12}\rho^{5/3}~~{\rm dynes~cm^{-2}},
\label{eos}$$ for a nonrelativistic, completely degenerate gas (since the density is much smaller tha $10^6$ g cm$^{-3}$, see below), the bottom density is about $\rho_{\rm b}=5.8\times 10^5$ g cm$^{-3}$ for $P=10$ms. Therefore the scale height of a strange star atomsphere is $h_0\sim \sigma_{\rm a}/ \rho_{\rm b}\sim 1.4\times 10^2$ cm for a 10ms pulsar (thinner crust for longer period pulsars). We note that such a atmosphere scale 