MICROWAVE BACKGROUND SIGNALS FROM TANGLED MAGNETIC-FIELDS

An inhomogeneous cosmological magnetic field will create Alfven-wave m odes that induce a small rotational velocity perturbation on the last scattering surface of the microwave background radiation. The Alfven-w ave mode survives Silk damping on much smaller scales than the compres sional modes. This, in combination with its rotational nature, ensures that there will be no sharp cutoff in anisotropy on are min scales. W e estimate that a magnetic field which redshifts to a present value of 3 x 10(-9) G produces temperature anisotropies at the 10 mu K level a t and below 10 are min scales. A tangled magnetic field, which is larg e enough to influence the formation of large scale structure, is there fore potentially detectable by future observations. [S0031-9007(98)074 61-4].