Physics – Space Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa22a..06g&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SA22A-06
Physics
Space Physics
[2415] Ionosphere / Equatorial Ionosphere, [2427] Ionosphere / Ionosphere/Atmosphere Interactions, [2443] Ionosphere / Midlatitude Ionosphere, [3389] Atmospheric Processes / Tides And Planetary Waves
Scientific paper
For several decades, it has been well known that stratospheric sudden warming (SSW) events dramatically disrupt circulation and temperature in the stratosphere and mesosphere. Recent experimental and modeling efforts present strong evidence of major variations at higher altitudes, from the lower thermosphere to the upper thermosphere and ionosphere, and in a wide range of latitudes. This progress was made possible due to the superposition of several factors: a series of strong SSW events in recent winters; prolonged unusually low levels of solar and geomagnetic activity, which allowed unambiguous determination of ionospheric effects related to the low atmosphere drivers; and coordinated efforts by the space physics community to collect and analyze data during these SSW events. We will summarize recent observational and modeling evidence of strong coupling between the stratosphere and ionosphere during SSW events. The primary features of this coupling include the tidal character of ionospheric variations, large magnitudes, and persistence of variations for several days after the peak of stratospheric warming. Both observations and numerical simulations point to the important roles of quasi-stationary planetary waves, which become strong prior to the stratospheric warmings. As these planetary waves propagate upward and equatorward, they interact non-linearly with tidal modes, producing amplification in the amplitudes of migrating and non-migrating tides in the mesosphere-lower thermosphere region. The tidal winds can modulate electric fields through the ionospheric wind dynamo (at ~115 km). At low latitudes, these modulated electric fields map along magnetic field lines to higher altitudes and produce tidal variations in vertical ion drifts, electron density, and equatorial electrojet. Significant uncertainties in our understanding of the manifestation of stratospheric sudden warmings on the middle and upper atmosphere remain, including the relative roles of different types of planetary waves, gravity waves, solar and lunar tides, changes in the background circulation, and solar activity. They present an exciting challenge for the space physics community.
Chau Jorge L.
Coster Anthea J.
Goncharenko Larisa P.
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