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

• Main Author: J. Helmboldt
• Format: Article
• Language: English
• Published: Copernicus Publications 2016-05-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/34/529/2016/angeo-34-529-2016.pdf

This paper describes the results of a multi-platform observing campaign aimed at studying midlatitude sporadic <i>E</i> (<i>E</i>_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 <i>E</i>_s was detected. The amplitudes of these correlate with a plasma frequency up to about 4.5 MHz. For <i>f</i>_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 <i>f</i>_p up to about 4.5 MHz; above this limit, the relationship exhibits a significant turnover. The observed intensity of coherent backscatter from <i>E</i>_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 <i>E</i>_s structures observed with LWA1 is significantly more correlated on spatial scales between 10 and 40 km. The magnitude of this correlation increases with <i>f</i>_p up to  ∼  6 MHz, above which it drops. These results are consistent with the following: (1) southwestward-directed MSTIDs are produced via <i>E</i>–<i>F</i> coupling; (2) this coupling is stronger when the <i>E</i>_s layer, seeded by meteor ablation, is more dense; (3) the coupling is substantially diminished for <i>E</i>_s layers harboring extremely dense structures (<i>f</i>_p ≳ 5 MHz).