Solar eclipse effects on HF and VLF propagation

A multifrequency oblique-incidence experiment performed during the 10 July 1972 total solar eclipse is described. A definite correlation of VLF phase, HF signal strength, and geomagnetic field behaviour on eclipse day is demonstrated. Because of the relatively high transmitter powers available, ionospheric non-linearities observed during the eclipse period provided additional diagnostic information on oblique-incidence phenomena which are particularly sensitive to inverted Δ.E is not equal to 0 along the propagation path. Turbulence is suggested as a major suppressant of charge-coupled effects in the lower ionosphere. If the observed eclipse behaviour is interpreted entirely in terms of atmospheric irregularities, severe but realistic constraints on mid-eclipse conditions are implied. At mid-eclipse a nearly impulsive perturbation presumably caused by a re-entering rocket was also noted. (author)