scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
A partial review of current progress with our understanding of small scale ionospheric
irregularities and of some of the remaining challenges.
St-Maurice Jean-Pierre
ISAS, University of Saskatchewan
The advent of increasingly high temporal and spatial resolution instruments coupled with a
growing global perspective on the subject has meant that even some very basic properties of
ionospheric irregularities have continued to challenge our understanding, this in spite of
impressive progress in our capability to perform sophisticated numerical simulations. A brief
presentation on the subject can only cover a limited range of topics. Here we will only look at
some of the challenges associated with short scale irregularities accessible to ground-based
radars. Even then, there is a long list of questions to choose from such as: the age-old
question of what causes the saturation of E region irregularities at something comparable to
the ion-acoustic speed of the medium; how aspect angles have to grow as individual structures
evolve and how these same aspect angles relate to saturation and to electron heating at high
latitudes; the possible role played by anomalous diffusion; the possible origin of very low
altitude E region echoes; the possible origin of up-down and east-west asymmetries seen in E
region echoes below 105 km at low latitudes; the non-local character of gradient-drift
irregularities higher up; what we know we don't know about so-called 150 km echoes; `wall
echoes' in the lower F region at mid-latitudes; the origin of the systematic lower Doppler
shifts seen by HF radars in comparison to drifts determined from other techniques; the
question of what seeds equatorial spread F and the possible connection with the pre-reversal
enhancement in the low latitude electric field.