Simultaneous ionospheric drift observations by different techniques at low and mid-latitudes

The results of ionospheric E-region irregularities observations in France and Africa using the close-spaced antennas method (D1 method) are compared to simultaneous 'Doppler shift' measurements (coherent radar method) as low latitude and with simultaneous radio meteor measurements (D2 method) at mid latitude. The 'apparent' velocity measured by the D1 method at the dip equator is in good agreement with the phase velocity of the type 2 irregularities observed by coherent radar at 21.3 MHz which is known to be a good approximation of the electron velocity in the E-region during day-time. At mid-latitude, the 'real' velocity deduced by the complex correlation analysis from the D1 results at 2.1 MHz is equal to the drift velocity measured by the radio meteor method at the same altitude and can be associated with the neutral gas velocity in the E-region. An explanation for the difference in low and mid-latitude is derived.