Es-layer characteristics determined from spaced ionosondes

Generation of mesoscale <I>F</I> layer structure and electric fields by the combined Perkins and <I>E<sub>s</sub></I> layer instabilities, in simulations

“…A background northward (southward) electric field would raise (lower) the equilibrium altitude of the E s layer relative to the wind shear, resulting in a westward (eastward) wind component in the E s layer, with an attendant southwestward (northeastward) drift of the frontal structures. Similar considerations apply in the Southern Hemisphere, where the instability theory predicts (and observations support (Goodwin and Summers, 1970)) structures elongated from southwest to northeast.…”

“…It is therefore noteworthy that observations in the nighttime midlatitude ionosphere tend to find frontal structures with this same alignment, whenever the horizontal viewing area is sufficiently large. Spaced ionosonde observations (Goodwin and Summers, 1970), and coherent scatter radar observations (Yamamoto et al, 1994(Yamamoto et al, , 1997Hysell et al, 2004) show nighttime E s layer structure in the Northern (Southern) Hemisphere with a clear statistical tendency to form fronts elongated from northwest to southeast (southwest to northeast), and generally propagating to the southwest (northwest). Similarly for the F layer, all sky images (e.g., Garcia et al, 2000;Saito et al, 2001;Shiokawa et al, 2003) show nighttime structure with the same clear statistical tendency to form fronts, with the same alignment and propagation direction.…”

Coordinated sporadic E layer observations made with Chung-Li 30MHz radar, ionosonde and FORMOSAT-3/COSMIC satellites

“…Among them, Es-a type is characterized by the spreading of the trace in range and commonly occurs in auroral region. Nevertheless, with more and more ionosonde observations, the range spread Es traces are also found in mid-, low-and equatorial latitude regions (Bowman, 1960;Goodwin, 1966;Goodwin and Summers, 1970;From and Whitehead, 1986;Hussey et al, 1998;Maruyama et al, 2006). A number of mechanisms responsible for the formation of the range spread Es trace have been proposed.…”

Wavelength dependence of the linear growth rate of the <I>E<sub>s</sub></I> layer instability

“…Spaced ionosonde observations (Goodwin and Summers, 1970) have revealed the consistent presence of frontal structures in Southern Hemisphere E s layers, with fronts elongated from northwest to southeast. Cosgrove and Tsunoda (2002) noted that this orientation points to the E s layer instability as source.…”

“…Cosgrove and Tsunoda (2002) noted that this orientation points to the E s layer instability as source. Goodwin and Summers (1970) found that the (horizontal) wavelength range for the frontal structures was 10-40 km, with a mean of 24 km. Below we will consider whether this wavelength range is also consistent with an E s layer instability source, and find in the affirmative.…”