Hydrogen density and proton flux in the topside ionosphere over Arecibo, Puerto Rico, from incoherent scatter observations

Abstract

Incoherent scatter observations of the topside ionosphere over Arecibo, Puerto Rico, have been analyzed and interpreted to give values for the neutral hydrogen density and vertical proton flux throughout a 30 hr period on December 7 and 8, 1965. The neutral hydrogen density is of the order of 10 6 cm −3 at 520km, agreeing well with other recent measurements. A diurnal variation of about 2-1 was found, which confirms recent theoretical predictions. The vertical proton flux attained a maximum value of about 10 9 cm −2 sec −1, being upward in the daytime and downward at night. The daytime flux appears to be of comparable magnitude with the limiting flux permitted, but the shape of the ion density profile suggests that the flux was not actually a limiting flux. For the night in question, the downward proton flux appears to account for the maintenance of the F layer, perhaps with some additional contribution from neutral winds and/or electric fields.