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

Abstract

Abstract. This paper describes the results of a multiplatform 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) southwestwarddirected 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).

All‐Sky Tracking of Sporadic Field‐Aligned Irregularities as a Novel Probe of Thermospheric Winds

“…Because the video carrier is only amplitude modulated, it is extremely spectrally narrow ( 35 Hz wide) and thus these Doppler measurements require no demodulation. Helmboldt () also showed that an arc of backscattering sources is often seen to the north within 55.25‐MHz observations that is consistent with coherent backscatter from field‐aligned irregularities within the region, presumably associated with .…”

“…This is reasonably consistent with the properties of dense clouds observed by several other authors, often in association with so‐called quasiperiodic echoes (e.g., Bernhardt, ; Bowman, ; Pan & Tsunoda, ; Hysell et al, ; Hysell & Burcham, ; Larsen, ). In fact, using a different set of LWA1 observations in combination with data from the Boulder, Colorado, Digisonde, Helmboldt () found that the northern arc of sources associated with FAIs appeared most prominently when layers with large peak densities (foEs 4 MHz) were present.…”

Observations of the Electrodynamical Ties Between Sporadic E and the Plasmasphere

“…near local midnight, i.e., 15 UT and 07 UT in Korea and Idaho, respectively. There is significant evidence that disturbances driven by polarization electric fields are more prevalent when FoEs is lower (J. F. Helmboldt, 2012;J. Helmboldt, 2016).…”

“…Also in both cases, the peak E S electron density as traced by FoEs was lower (∼2.5 MHz) near local midnight, that is, 15 and 07 UT in Korea and Idaho, respectively. There is significant evidence that disturbances driven by polarization electric fields are more prevalent when FoEs is lower (Helmboldt, 2012, 2016). Both the ap and F 10.7 indices were relatively low, as expected near solar minimum.…”

“…This implied that they may be tied to so‐called electrobuoyancy waves in the F region similar to those observed by Otsuka et al (2004), which are likely enhanced by E S polarization electric fields (Cosgrove et al, 2004; Yokoyama et al, 2009). Indeed, there is a significant history of observations of correlations between electrobuoyancy waves and E S (Cosgrove, 2013; Helmboldt, 2012, 2016). Likewise, the CPIs could be directly tied to E S polarization electric fields.…”