A multi-platform investigation of midlatitude sporadic E and its ties to E–F coupling and meteor activity

Abstract. This paper describes the results of a multi-platform observing campaign aimed at studying midlatitude sporadic E (E_s) and associated ionospheric phenomena. The assets used were the digisonde in Boulder, Colorado; the first station of the Long Wavelength Array, LWA1, in New Mexico; the transmitters of the radio station WWV in Colorado; and 61 continuously operating GPS receivers between LWA1 and WWV. The results show that southwestward-directed medium-scale traveling ionospheric disturbances (MSTIDs) were substantially more prevalent when E_s was detected. The amplitudes of these correlate with a plasma frequency up to about 4.5 MHz. For f_p ≳ 5 MHz, the MSTIDs become significantly weaker and basically vanish above  ∼ 6.5 MHz. The prevalence of meteor trail reflections observed with LWA1 also correlates with f_p up to about 4.5 MHz; above this limit, the relationship exhibits a significant turnover. The observed intensity of coherent backscatter from E_s field-aligned irregularities (FAIs) also correlates with inferred plasma frequency. However, this trend continues to higher frequencies with a peak near 6 MHz, followed by a much more subtle turnover. The reflected power from E_s structures observed with LWA1 is significantly more correlated on spatial scales between 10 and 40 km. The magnitude of this correlation increases with f_p up to  ∼  6 MHz, above which it drops. These results are consistent with the following: (1) southwestward-directed MSTIDs are produced via E–F coupling; (2) this coupling is stronger when the E_s layer, seeded by meteor ablation, is more dense; (3) the coupling is substantially diminished for E_s layers harboring extremely dense structures (f_p ≳ 5 MHz).