A post-noon enhancement in F-region ionization has been studied using data from the Sondrestrom radar and the NOAA-7 and Triad satellites. This enhancement is seen quite often in Sondrestrom radar data. It is extended in the east-west direction and is the site of elevated electron temperatures. Data from the Triad satellite indicate that the enhancement observed on 9 September 1983 was collocated with intense upward field-aligned currents. The NOAA-7 satellite measured an electron spectrum in association with the event that was peaked at about 1 keV. The appearance of the spectrum suggests that the electrons were accelerated through a potential drop of 1.3kV. The temperature and density of the source electrons was estimated to be 350 eV and 3.5 cm-3, respectively. The spatial relationship between the currents, electric field and electron precipitation is similar to that observed in evening sector auroral arcs. We argue that the F-region arc on the dayside is produced by the same process as the more intense evening sector arcs except that the accelerating potential above the arc is lower. This difference in accelerating potential is a result of the higher source densities in the magnetosphere to which field lines from the dayside arc connect.