IL NUOVO CIMENTO VOL. 77 B, N. 2 11 Ottobre 1983 Strong Hydromagnetic Cylindrical Shock in a Rotating Gas. S. KUMAR and R. PRAKASH 2~hysics Department, Agra College - Agra-282002, India (ricevuto il 28 Marzo 1983) Summary.- The Chisnell-Chester-~Whitham method has been used to study the propagation of strong diverging cylindrical hydromagnetie shock waves through a rotating gas. In the presence of an axial magnetic field the problem is investigated under two distinct conditions, viz. i) when the ratio of densities on either side of the shock nearly equals (y § 1)/(y -- 1), where y is the usual ratio of specific heats, or ii) when the applied field is large. An analytical relation for the shock velocity has been obtained. It is shown that, for smaller values of the propagation distance r, the shock velocity must decreasc with shock propagation; for larger values of r, however, it must increase with further advancement of the shock. The shock propagation distance corrcsponding to the minimum value of the shock ve- locity has been obtained. It is seen that an increase in theinitial angular velocity of the rotating gas increases the shock velocity. The expressions for the radial particle velocity and the pressure immediately behind the shock have been obtained. Cases corresponding to propagation with constant shock strength have been explored. Finally, the results obtained here have been compared with those for weak shock. PACS. 52.30. - Plasma flow; magnetohydrodynamics. PACS. 47.65. - Magnetohydrodynamics and electrohydrodynamics. 1. - Introduction. The study of the propagation of hydromagnetic shocks is relevant to the phenomenon of thunder. K~y~A~ et al. (1) and KU•A• and P]~AKASH (2) have (1) S. KUlgAlt, A. K. KULSnRESTHA and P. CHATURANI: ~UOVO Cimento B, 70, 39 (1982). (~) S. KVMA~ and R. P~AXAS~I: t)roe. Indian Soc. Theor. Appl. Mech., 27, 11 (1982). 191