An investigation into the horizontal structure of spread-Es

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

“…As a result, the discrete echoes are expected to occur more easily at higher frequency end than in lower frequency domain. From and Whitehead (1986) and Barnes (1992) suggested that the range spread Es echoes in ionogram are very likely the result of the scattering/reflection of the electron density irregularities at the sizes of about 1-3 km in the Es layer. Therefore, concurrent measurements of 30 MHz radar backscatter and range spread Es echoes strongly indicate that the electron density irregularities at various sizes from meter to kilo-meter scale existed simultaneously in the Es layer.…”

“…From and Whitehead (1986) speculated that the range spread Es echoes come from small clouds of ionization with very short lifetime for about 2 or 3 s, which are difficult to explain the origins. Barnes (1992), however, considered long-lasting (much longer than a few seconds) ionization clouds at sizes of about 1-3 km that are moving in the Es layer are the primary reflectors responsible for the spread Es trace in ionogram. Hussey et al (1998) attributed the range spread Es echoes to oblique reflections from a non-uniform and horizontally inhomogeneous layer.…”

On spread-<i>E<sub>s</sub></i> effects in the ionosphere before earthquakes

“…The three-dimensional current system which can arise under the action of acoustic disturbances on inhomogeneous E s -layers was analysed in Liperovsky et al (1997). Usually the nighttime sporadic layer is an inhomogeneous cloud with horizontal size of a few tens of kilometers and a vertical size up to a kilometer (see also Barnes, 1992Barnes, , 1993. The cloud is surrounded with weakly ionized plasma of less density.…”

“…This phenomenon was studied in a number of works Correspondence to: V. A. Liperovsky (liper@ifz.ru) (Bowman, 1985;Whitehead, 1989;Barnes, 1992;Mathews, 1998). Spread-E s is observed as diffusivity of the traces of sporadic E-layers on ionograms of vertical sounding stations.…”

Ionospheric Irregularities

“…A number of independent sources of information point to the existence of such waves. Barnes [1992] inferred the presence of structures with dimensions of about 1 km embedded in larger, drifting plasma clouds from soundings of the layers. Kilometric horizontal structuring was clearly visible in data from a sounding rocket that penetrated a structured E s layer [Kelley et al, 1995] and in VHF radio scintillations from satellite signals traversing the layers [Maruyama et al, 2000].…”