Midlatitude Sporadic E. A Typical Paradigm of Atmosphere-Ionosphere Coupling
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This paper provides a comprehensive update on sporadic E layers that is placed in the context of atmosphere-ionosphere coupling, exemplified here by the fundamental windshear theory processes that govern sporadic E layer formation and variability. Some basics of windshear theory are provided first, followed by a summary of key experimental results, their interpretation and physical understanding. The emphasis is placed on the wind shear control of the diurnal and sub-diurnal variability and altitude descent of sporadic E layers and the key role behind these properties of the diurnal and semidiurnal tides. Furthermore, the paper summarizes recent observations that establish a role also for the planetary waves in sporadic E layer occurrence and long-term variability. The possible mechanisms behind this interaction are examined and evidence is presented which shows that planetary waves affect sporadic E layers indirectly though the amplitude modulation of tides at lower altitudes in the MLT region. Only a brief mention is made about gravity wave effects on sporadic E, which apparently exist but cannot be as crucial in layer forming as thought in the past. There is now enough evidence to suggest that mid- and low-latitude sporadic E is not as “sporadic” as the name implies but a regularly occurring ionospheric phenomenon. This may suggest that the sporadic E layer physics can be incorporated in large-scale atmosphere-ionosphere coupling models.
KeywordsSporadic E layers Windshear theory Atmosphere-ionosphere coupling Atmospheric tides Planetary waves Gravity waves
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- J.M. Forbes, Tidal and planetary waves, in The Upper Mesosphere and Lower Thermosphere, a Review of Experiment and Theory, ed. by R.M. Johnson, T.L. Killen (1994), p. 67 Google Scholar
- C. Haldoupis, D. Pancheva, Planetary waves and midlatitude sporadic E layers: Strong experimental evidence for a close relationship. J. Geophys. Res. 107 (2002). doi: 10.1029/2001JA000212
- J.R. Holton, An Introduction to Dynamic Meteorology (Academic Press, San Diego, 1982) Google Scholar
- M.C. Kelley, The Earth’s Ionosphere: Plasma Physics and Electrodynamics, 2nd edn. (Academic Press, San Diego, 2009) Google Scholar
- D. Pancheva, C. Haldoupis, C.E. Meek, A.H. Manson, N.J. Mitchell, Evidence of a role for modulated atmospheric tides in the dependence of sporadic E on planetary waves, J. Geophys. Res. 108 (2003). doi: 10.1029/2002JA009788
- L.G. Smith, A sequence of rocket observations of nighttime sporadic E. J. Atmos. Sol.-Terr. Phys. 32, 1427 (1970) Google Scholar