The role of hot carriers in enhancing the radiation resistance of GaAs solar cells has been investigated. The laser-pulse induced, short-circuit current response method was used to study solar cell degradation caused by radiation damage. Samples were subject to radiation doses in the range 1 x 10(14) - 4 x 10(16) electron cm(-2) and then probed with laser pulses with 7 ns duration and 3.7 eV energy. We have developed a non-stationary theory of minority carrier flow in the active region of the solar cell. The theory allows a description of the temporal evolution of the short-circuit current and the dependence on irradiation dose. The model agrees well with experimental results using a single fitting parameter. This parameter is the carrier capture cross-section of radiation center E5 in the p-region emitter of the solar cell. The value of the cross-section was determined to be 0.1 x 10(-12) cm(2) from the results under non-stationary condition. This is seven times lower than that deduced from the current-voltage characteristics in the dark for a similar solar cell. The difference can be explained by a strong reduction of capture cross-section with increased carrier energy. Our results suggest that the observed cross-section reduction is caused by carrier accumulation at energies comparable with the optical phonon energy. (C) 2011 Elsevier B.V. All rights reserved.