HF ECHOES FROM IONIZATION POTENTIALLY PRODUCED BY HIGH-ALTITUDE DISCHARGES

The presence of ionization associated with high-altitude discharges ha s been detected using an HF radar operating at 2.2, 2.5, and 2.8 MHz. On several occasions, oblique echoes lasting several hundred ms at nig ht and 1 --> 10 s during the day were observed. The echoes turned on i n several interpulse times of 70 ms and were generally correlated with strong lightning activity prior to onset. The angles of arrival of sf erics detected at three goniometer stations were used to determine the distance to thunderstorms. The data are consistent with specular refl ections from columns of ionization produced at 55-65 km altitude and h aving minimum electron densities of 6 x 10(4) - 10(5) cm(-3). The sour ce of the ionization is believed to be High-altitude discharges.