Asymmetry in diurnal variation of electron density in D region over Kunming

Based on MF radar database from August 2008 to July 2009 at Kunming (25.6 °N, 103.8 °N), the diurnal of electron density in the D region has been examined. The previous asymmetries of the electron density about local noon in the range of 66km-80km are observed, and at a fixed zenith angle it is shown an asymmetry in the diurnal variation of electron density existing in all the seasons. Particularly the asymmetry is more evident in winter that the rate of the asymmetry increases as increasing height, with a tendency for higher electron densities in the morning below 76km. Seen from the study at solar zenith angle of 48.6°, the diurnal asymmetry is a common feature at all altitudes and for all months with maximum of asymmetry of 3.34 and 3.33 occurring at 66km on October 2008 and at 70km on April 2009, respectively.