Mechanical heating of the interstellar medium. I. The source and rate
A simple model is presented for the evolution of a supernova disturbance in the very low density, high temperature, interstellar matrix in order to explore consequences of such disturbances on the interstellar clouds. It is assumed that higher density material is sufficiently common to impede the velocity field. It is further assumed that thermal conduction is magnetically quenched between the matrix and H I regions. The individual disturbances evolve very rapidly (tauapprox.3 x 10/sup 5/ years) to very large sizes (Rapprox.140 pc) without appreciable radiative cooling before the interior pressure becomes comparable to the ambient pressure. The net effect of the overlapping of ancient disturbances is then shown to be capable of determining this ambient presure.The work done by such blast waves in compressing interstellar clouds is estimated. An individual disturbance is found to lose at least a modest fraction of its energy in this way. The calculated power input to individual clouds is very large, resulting in large-amplitude vibrations similar to what is observed. The heating is partly impulsive (most clouds should contain at least one shock of modest strength at any time) and partly quasi-steady due to vibrational dissipation. Within large uncertainties and variations, the material temperatures are expected to be less than 100 K for n> or approx. =6 cm/sup -3/ and approach 10/sup 4/ K for n< or approx. =0.3 cm/sup -3/. Between these densities, the temperature depends sensitively on density, elemental depletions, and fractional ionization. Thus the power input is of the magnitude required to provide a cloud, intercloud segregation of material. Unlike earlier models, however, the heating is not intrinsically accompanied by ionization. Finally, the net acceleration of clouds by these blast waves is found to be small unless the clouds initially have n< or approx. =0.2 cm/sup -3/.
- Research Organization:
- Space Physics Laboratory, Department of Physics, University of Wisconsin
- OSTI ID:
- 5556122
- Journal Information:
- Astrophys. J.; (United States), Vol. 234:3
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
COSMIC GASES
SHOCK HEATING
INTERSTELLAR SPACE
SHOCK WAVES
SUPERNOVAE
DISTURBANCES
H1 REGIONS
INTERSTELLAR MAGNETIC FIELDS
MECHANICAL VIBRATIONS
MECHANICS
NEBULAE
SUPERNOVA REMNANTS
THERMAL CONDUCTION
WAVE PROPAGATION
COSMIC RADIO SOURCES
ENERGY TRANSFER
ERUPTIVE VARIABLE STARS
FLUIDS
GASES
HEAT TRANSFER
HEATING
MAGNETIC FIELDS
PLASMA HEATING
SPACE
STARS
VARIABLE STARS
640105* - Astrophysics & Cosmology- Galaxies