THE ORIGIN OF STRONG MAGNETIC-FIELDS IN CIRCUMSTELLAR SIO MASERS

We suggest that the Parker instability, acting in the regions where sh ocks form in response to stellar pulsations, gives rise to the fragmen ts in which SiO masers exist in the atmospheres of evolved stars. The production of maser fragments in this manner is compatible with the Al fven speeds in them greatly exceeding their kinematic and thermal spee ds. The magnetic structure in an evolved star's envelope probably resu lts in momentum transfer to gas from grains subject to radiation press ure being widely distributed even to regions where grains have not yet formed; the consequences for mass loss of the magnetic redistribution of momentum transfer require exploration.