The dynamics of quasi-periodic ripples in the high-latitude F-region

This study extends the investigation of quasi-periodic ripples in the F-region electron content reported by Birch and Hargreaves (2020a) to determine their flow velocity and wavelength, using data from the EISCAT Svalbard radars (the 42m antenna being field-aligned and the 32m scanning in a circular pattern at a fixed angle from the field). The ripples were extracted from the 42m electron content between altitudes 213 and 389 km in the noon and midnight sectors using a bandpass filter which reduces the noise component while removing long-term trends. These ripples were found to have an average periodicity of about 21 min in the noon sector and 27 min at night. Using the 32m line-of-sight velocity data, they were also found to propagate in the noon sector at about 467 m/s in a westerly direction with a wavelength of 581 km, and in the night sector at about 283 m/s in a southerly direction with a wavelength of 454 km. The directions compare favourably with modelled plasma flows from the SuperDARN network of coherent scatter radars.