A recent narrow-band-filtered CCD image by Mendillo et al. (1990) has shown that a sodium corona, produced near Io, extends at least 400 Jupiter radii in the planet's equatorial plane. Isophotes indicate that the polar to equatorial extents are in ~1 to 3 proportions. The image can be reproduced by a model which includes both a high- and an intermediate-speed distribution, with source rates of 2.2 and 1.1¿1026 atoms s-1, respectively. The high-speed distribution was ejected from Io with a velocity tangential to the satellite orbit of 57 km s-1 (~74 km s-1 relative to Jupiter) plus an isotropic Maxwellian velocity distribution of ~25 km s-1. This distribution likely corresponds to a charge exchange source of plasma torus sodium ions which are neutralized in the near-Io atmosphere and are ejected relative to Jupiter with a corotational velocity (74 km s-1) plus a thermal ion (25 km s-1) Maxwellian distribution. The intermediate speed distribution was ejected from Io with a tangential speed near 20 km s-1 (37 km s-1 relative to Jupiter) plus an isotropic Maxwellian velocity distribution of ~12 km s-1. This distribution corresponds to the same nonthermal sodium atoms earlier identified near Io in the sodium directional features (Pilcher et al., 1984). Modeled Doppler profiles of the sodium D lines show that moderate resolution spectroscopy would prove to be highly diagnostic of both the velocity distribution of the source near Io and the resulting periodic time variations expected. On the scale of a few astronomical units, the sodium corona displays a cometary comalike appearance because of the acceleration of sodium atoms induced by solar radiation pressure. Finally, at distances of roughly 1000 planetary radii the effects of the ~400-hour photoionization lifetime of sodium atoms should begin to become apparent in observed radial profiles. ¿American Geophysical Union 1991