Analysis indicates that the shock wave that separates from a spark kernel is a strong detonation for times up to 1 mu s. Through coupling of the 1/5-power law recently discovered by V.S. Arpaci et al. (Combust. Flame 135 (2003) 315-322) with thermal model, the temperature of the kernel is shown to decay in time its t(-8/5). (c) 2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved.