DO FIREBALLS IN THE INTERSTELLAR-MEDIUM NECESSARILY IMPLY BLAST WAVE-PROPAGATION

The current version of cosmic fireball (FB) models for understanding t he mechanism of Gamma Ray Bursts (GRBs), expounded by Meszaros, Rees a nd their coworkers (MRC), envisage that the initial leptonic fireball energy is converted into bulk kinetic energy of the polluting baryons and which decelerate by interacting with the interstellar medium (ISM) and form a forward shock. From elementary, yet hitherto overlooked, c onsiderations we show that the relativistic baryons (protons) are unli kely to see the standard ISM as a fluid and interact efficiently with it on the acceptable GRB time scales (0.1-100 s). If we invoke the kno wn value of the ISM spatial diffusion coefficient in the present probl em, we need to assume the existence of very strong magnetic field (sim ilar to 10(4) G) at the BF-ISM interface to alleviate this foregoing p roblem. Alternatively, we must assume that there is indeed strong magn etic turbulence near the interface and the scattering lengh is directl y determined by the much shorter value of the gyro-radii of the proton s. Simultaneously, we need to assume that substantial fraction of the FB energy is converted into magnetic field and remains frozen into the BF to a yield a value of the magnetic field similar to 0.1 G near the expected deceleration radius (r(d) similar to 10(15) - 10(16) cm). St ill it turns out to be far from clear how the BF-ISM interaction can i ndeed be seen as a collision between two fluids and occuring on a time scale shorter than the expected GRB time scales.