Browsing by Author "Calderón, C."
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Item Restricted Dependence of equatorial F region vertical drifts on season and solar cycle(American Geophysical Union, 1979-10-01) Fejer, B. G.; Farley, D. T.; Woodman Pollitt, Ronald Francisco; Calderón, C.Vertical drift measurements have been made at Jicamarca for more than half a solar cycle. The data from periods of high and low activity are appreciably different. Daytime drift velocities during sunspot minimum are usually larger than during the maximum, while the opposite is true for nighttime periods. The evening reversal occurs earlier during sunspot minimum than during the maximum, but the morning reversal is not altered. The period of eastward electric field (upward drift) is thus shortest during sunspot minimum and local winter. By integrating the drift velocity data with respect to time, one can obtain a measure of the total potential drop between reversal points (near the terminators). This drop is largest at solar maximum. There is also a pronounced seasonal variation, with a minimum in mid-December during both solar minimum and maximum. The general features of the data cannot be explained solely on the basis of tidal winds driving an E region dynamo; polarization fields related to the F region dynamo are of major importance, particularly in helping to explain the enhancement of the daytime upward drift which often occurs shortly before the drift reverses to downward in the evening. In order to account quantitatively for the observed variations, however, numerical models considerably more sophisticated than those presently available are needed.Item Restricted Solar cycle effects on the electric fields in the equatorial ionosphere(American Geophysical Union, 1977-11-01) Woodman Pollitt, Ronald Francisco; Rastogi, R. G.; Calderón, C.The horizontal east‐west electric fields in the equatorial F region are estimated by using the vertical electron drift data over Jicamarca, Peru. The reversal of the electric field from west to east near the sunrise hours is not affected by solar cycle, but the evening reversal is found to occur about 1 hour earlier during low‐sunspot years. The average value of the electric field magnitude during noon hours is the same for different portions of the solar cycle; however, the day to day variation is larger during years of low solar activity. The postsunset increase of the electric field is characteristic of high‐sunspot periods only. Abnormal reversals of the electric field are seen on some occasions during the daytime hours, and these events are associated with the equatorial counter electrojets.