[1] An ionosonde study using data from Wallops Island, Virginia (37.95°N, 284.53°E, 67.5°dip angle), over a full solar cycle from 1996 to 2006 has been conducted. A pattern recognition algorithm is used to analyze these ionograms in order to determine the statistics of midlatitude spread F. An ionogram displays spread F both horizontally and vertically, which are defined as range and frequency spread F, respectively. Range and frequency spreading can occur either simultaneously or separately. Seasonal and solar cycle variations have been studied using the data set; both are significant and are somewhat different for range and frequency spread F. Correlations of spread F duration with F10.7, Kp, and AE are investigated. The results provide insights into causative sources for both types of midlatitude spread F.

On 21 August 2017, a total solar eclipse crossed North America. Two Vertical Incident Pulsed Ionospheric Radar ionosondes were operated, one deployed under totality at Lusk, Wyoming, and another south of totality, 313 km away from the geomagnetic meridian in Boulder, Colorado. The two Vertical Incident Pulsed Ionospheric Radar systems were synchronized for precise observation of both vertical and oblique group and phase paths. Hand‐scaled values of virtual heights and critical frequencies are presented. Arrival angles were computed using phase interferometry and used to compute equivalent vertical critical frequencies at the oblique midpoint. Oblique propagation geometry and horizontal gradients allowed measurement of F2 layer during ionosphere G condition where foF1 exceed foF2 after totality.