Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa22a..01i&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SA22A-01
Physics
[2411] Ionosphere / Electric Fields, [2415] Ionosphere / Equatorial Ionosphere, [2427] Ionosphere / Ionosphere/Atmosphere Interactions, [3389] Atmospheric Processes / Tides And Planetary Waves
Scientific paper
The large-scale, seasonally-dependent modulation and redistribution of ionospheric plasma at low latitudes can almost certainly be attributed to the complex forcing of the thermosphere by atmospheric tides. Since the close correspondence of the longitudinal structure of tidal forcing with the morphology of the paired equatorial bands of the ionospheric anomaly was discovered, modification of the dynamo currents in the E-region by tidal neutral winds has been identified as the likely causative mechanism. Certainly, the vertical plasma drifts near the equator measured by DMSP satellites and now the C/NOFS mission indicate that electric fields have a zonal structure that matches the predicted or modeled winds at lower altitudes. However, these electric fields can also originate with conductivity gradients at E-region altitudes that can be affected by tidal winds, particularly at the terminators. Tidal forcing also introduces a strong zonal structure in neutral temperatures in the E-region. This temperature structure is likely related to the zonal structure in O/N2 observed recently by the TIMED mission, which in turn drives additional zonally-dependent modulation of low-latitude plasma density. Finally, in light of new modeling simulations and observational work from CHAMP, the propagation of some tidal energy upward to affect the F-layer directly is likely important driver in dark as well as sunlit conditions. It is clear that without a comprehensive set of measurements of all the critical parameters during both daytime and nighttime, closure on the questions surrounding the mechanism by which the F-layer is affected by tides originating in the troposphere cannot be achieved.
Crowley Geoff
England Scott
Englert Christoph R.
Forbes Jeffrey M.
Frey Harald U.
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