The paper presents results of in situ measurements of electron density and electric field fluctuations (Δne, ΔEv' and ΔEH') during a strong spread F event from the SHAR rocket range in India. Intermediate scale ne irregularities were observed in the F region valley over SHAR, which was earlier found to be free from irregularities. Experimental evidence of the validity of the image striation theory is provided through first simultaneous spectral measurement of electron density and electric field in the valley region. Correlation analysis of Δne, ΔEv' and ΔEH' suggests the existence of a sheared flow of current below the F-peak. A new type of irregularity in the intermediate scale having a steep spectrum (n=-3.1) has also been detected in the valley region. A very sharp layer of ionization wherein the electron density increased by a factor of 50 in 10 km vertical extent was detected at 105 km. ¿ 1999 American Geophysical Union