GRB 021004: Reverse Shock Emission
  We show that the re-brightening in the GRB 021004 optical afterglow light curve around ~ 0.1 day can be explained within the framework of the standard fireball model. The superposition of a forward and reverse shock emissions result in the peculiar behavior. With the standard values of parameters obtained in other afterglow observations, we can construct an example case in which theoretical estimates reasonably fit the broadband observations. Therefore, the peculiarity of the light curve might be a common feature in early gamma-ray burst afterglows. 
Shiho Kobayashi and Bing Zhang