The behaviour of the upper ionosphere over North America at sunset

On the mechanism of the post-midnight winter NmF2 enhancements: dependence on solar activity

“…Therefore, the electron density variation is primary with respect to the electron temperature variation in the scope of the nighttime N m F 2 increasing mechanism. This is dierent from the mechanism of summer evening N m F 2 enhancement noted by Evans (1965Evans ( , 1974, and Eccles and Burge (1973) which results from a collapse of the F 2 -layer when the electron temperature decreases at sunset. This produces a strong surge of downward plasma¯ux into the F 2 -region (Evans, 1974), which along with the F 2 -layer uplifting produces a well-pronounced evening N m F 2 enhancement (Eccles and Burge, 1973).…”

Comment on “The winter anomaly in the middle‐latitude F region during the solar minimum period observed by the Constellation Observing System for Meteorology, Ionosphere, and Climate” by W. K. Lee, H. Kil, Y.‐S. Kwak, Q. Wu, S. Cho, and J. U. Park

“…In the presence of photoionization, uplift of the ionosphere by equatorward wind causes a significant increase in electron density due to a reduction in the recombination reaction rate between O + and molecular gases ”. This is a well‐known effect of the midlatitude N m F 2 evening increase discussed in many publications [e.g., Evans , ; Rishbeth , ; Kohl et al , ; Eccles et al , ; Eccles and Burge , ].…”

Morphology of NmF2 nighttime increases in the Eurasian sector

“…An additional contribution to the NmF2 increase is provided by the equatorward meridional thermospheric wind uplifting F2-layer into low rate recombination region during evening hours. This wind eect was shown to be more important (Eccles and Burge, 1973).…”

“…This evening NmF2 increase was discussed by Evans (1965) using Millstone Hill observations. Computer simulation studies (Sterling et al, 1969;Strobel and McElroy, 1970;Eccles and Burge, 1973) and subsequent observations (Evans, 1974) have shown that the summer evening NmF2 increase results from a collapse of the F2-layer that occurs when the electron temperature decreases at sunset. This produces large downward¯uxes of the ions above hmF2.…”