The solar coronal exosphere (fixed at a level where the mean free path is comparable with the scale height) is shown to act like the sheath in a laboratory discharge that builds up an excess positive charge and electric field. Equality of flux for the charged particles (protons and electrons) at the exoaphere is assumed. The exospheric electric potential (for a coronal temperature of lo6 "K) is found to be about 325 V, which makes the protons virtually weightless. The exospheric sheath potential accelerates the thermal protons to a velocity of 258 kmjsec with which they coast to the earth. The proton density in transit varies approximately as the inverse square law, and is 3 cm-s near the earth. Higher velocities and densities are obtained for higher coronal temperatures. An estimate of the exospheric transition region is obtained by applying the hydrodynamic theory of ambipolar diffusion in a gravitational field to the "observed" coronal density distribution. It is found that the ratio of the electric to the gravitational force on the proton builds up from its hydrostatic value of 4 at 2.4Ro to 1 at 8R, from the solar center.