Main parameters of turbulence in star-forming regions from observations ofH2O maser emission

Long-term monitoring of the H2O maser emission of a number of sources has s hown that the radial-velocity deviations from the mean drift value are char acterized by a short-period chaotic velocity component. This enables determ ination of the main parameters of turbulent motions in the maser condensati ons u(0), tau(0), and R-0-the characteristic velocity, lifetime, and scale size for the turbulent motions. The values found for these quantities corre spond to Strouhal numbers xi(0) = u(0)tau(0)/R-0 much less than 1, so that it is possible to estimate the coefficient of turbulent diffusion as D-T co ngruent to u(0)(2)tau(0)/3. Turbulence with xi(0) much less than 1 can be c aused by either noncompressible gas motions or motions that involve a mixtu re of chaotically propagating shock waves. In the latter case, the paramete r xi(0) also determines the mean relative compression of the gas Delta V/V congruent to xi(0). The determination of the coefficient of turbulent diffu sion D-T and the viscosity v(T) congruent to D-T for various types of turbu lence is discussed in detail.