Comparison of power spectra of magnetic field data from ISEE-1 and -2 recorded simultaneously on both sides of the magnetopause showed that power level inside the matgnetosphere varied with power level outside in the magnetosheath and suggested that the same frequencies were enhanced on the two sides of the boundary. Power levels were two to three orders of magnitude lower inside than outside the magnetosphere, indicating that wave energy was transmitted inside from the sheath, through a locally stable magnetopause.