First VHF radar observation of midlatitude F‐region field‐aligned irregularities

We describe the first midlatitude F‐region VHF radar observations of small‐scale Field‐Aligned Irregularities (FAI). Looking northward at ∼ 34° elevation the locus of perpendicularity with the geomagnetic field B remains inside the radar beam, such that FAI can be observed, at radar ranges from 350 to over 800 km or F region altitudes from 200 to 500 km, approximately. The preliminary results presented here show the large‐scale (> 20 km) configuration of small‐scale (322.6 cm, half the radar wavelength) F‐region irregularities as well as typical spectral results. Our most important finding is that at least on some occasions there is a quasi‐periodic variation in time and space, on scales of approximately 12 minutes and 50 km, of the observed plasma instabilities.