scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...
scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...
scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...
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STP12 Abstracts<br />
Berlin, 12 - 16 July <strong>2010</strong><br />
SCOSTEP Symposium <strong>2010</strong><br />
Atmospheric Wave Effects in the Equatorial MLT<br />
Gurubar<strong>an</strong> Subram<strong>an</strong>i<strong>an</strong><br />
Indi<strong>an</strong> <strong>Institut</strong>e of Geomagnetism<br />
The low latitude atmospheric <strong>an</strong>d ionospheric regions are unique in m<strong>an</strong>y ways. Intense<br />
tropical convection sets up a variety of atmospheric waves that propagate up <strong>an</strong>d through their<br />
interactions with the background flow produce alternating easterly <strong>an</strong>d westerly winds in the<br />
middle atmosphere. The Coriolis frequency is small in the low latitude region <strong>an</strong>d that allows<br />
long-period equatorially trapped waves to propagate from their source regions in the lower<br />
atmosphere to higher altitudes. Within the mesosphere-lower thermosphere (MLT) region, the<br />
sun-synchronous atmospheric tides are the domin<strong>an</strong>t dynamical features <strong>an</strong>d owe their<br />
existence to the absorption of solar radiation by water vapour in the troposphere <strong>an</strong>d ozone in<br />
the stratosphere. In recent years, the presence of non-migrating tides in the MLT region has<br />
been demonstrated by satellite observations <strong>an</strong>d its import<strong>an</strong>ce in producing the longitudinal<br />
redistribution of ionization within the low latitude F-region has been emphasized. There have<br />
been studies that examined the signatures of pl<strong>an</strong>etary waves <strong>an</strong>d tides in the low latitude<br />
ionosphere but none could provide experimental evidence for <strong>an</strong>y pl<strong>an</strong>etary wave or tidal<br />
component to directly modulate the ionospheric parameters. It is firmly believed that much of<br />
the quiet-time space weather in the upper atmosphere is contributed by upward propagating<br />
waves of lower atmospheric origin but what spectrum of waves penetrate the MLT region <strong>an</strong>d<br />
produce observable effects in the upper atmosphere is not known. These aspects emphasize<br />
the complexities in the interplay of several dynamical <strong>an</strong>d electrodynamical processes in the<br />
low latitude MLT <strong>an</strong>d ionospheric (MLTI) regions. This talk will present the state-of-the-art<br />
in our un<strong>der</strong>st<strong>an</strong>ding of the role of dynamical processes in MLTI coupling with highlights<br />
from recent results obtained using ground-based radar <strong>an</strong>d magnetometer data sets <strong>an</strong>d some<br />
new insights revealed by satellite observations on non-migrating tides.
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