Fig. 7

a Increase in STEC fluctuation (\(\Delta\)(STEC)) at the beginning of a 100 s ionospheric heating experiment cycle which are proposed as a proxy for GPS phase scintillations. Subsequent decay is proposed to be due to nonlinear processes involving EB waves of spatial scale 10 cm which produce the scintillations. b Spectrum of Stimulated Electromagnetic Emissions (SEE) observed from ground-based receivers during the heating experiment for \(\omega _0\) = 5.67kHz. The spectral line offset 10 kHz below the pump frequency (DM) is associated with irregularity spatial scales of 10 m across the magnetic field and proposed to be associated with irregularities nearer the Fresnel scale resulting in only weak scintillations. The spectral line upshifted by 20kHz (BUM) is proposed to be the proxy for 10 cm so-called Super-Small-Striations (SSS) that produce the strong GPS phase scintillations observed during the experiment. (Adapted from Mahmoudian et al. (2018))