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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Longitudinal development of low-latitude ionospheric irregularities during the geomagnetic storms of July 2004 Guozhu Li Beijing National Observatory of Space Environment (BNOSE), IGGCAS During the period 22–28 July 2004, three geomagnetic storms occurred due to a sequence of coronal mass ejections. In this paper we present and discuss the ionospheric observations from a set of in situ satellites and ground-based GPS total electron content and scintillation receivers, a VHF radar, and two chains of ionosondes (300°E and 120°E, respectively) that provide the evolutionary characteristics of equatorial and low-latitude ionospheric irregularities versus longitude during these storm periods. It is found that the irregularities occurred over a wide longitudinal range, extending from around 300°E to 120°E on storm days 25 and 27 July 2004. On 25 July plasma bubbles (PBs) began premidnight in America and postmidnight in Southeast Asia. On 27 July the occurrence of irregularities followed the sunset terminator and was observed sequentially after sunset from American to Southeast Asian longitudes. Past studies have reported that storm time low latitude ionospheric irregularities are mostly confined to a narrower longitude range,
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Atmospheric Wave Effects in the Equatorial MLT Gurubaran Subramanian Indian Institute of Geomagnetism The low latitude atmospheric and ionospheric regions are unique in many ways. Intense tropical convection sets up a variety of atmospheric waves that propagate up and through their interactions with the background flow produce alternating easterly and westerly winds in the middle atmosphere. The Coriolis frequency is small in the low latitude region and that allows long-period equatorially trapped waves to propagate from their source regions in the lower atmosphere to higher altitudes. Within the mesosphere-lower thermosphere (MLT) region, the sun-synchronous atmospheric tides are the dominant dynamical features and owe their existence to the absorption of solar radiation by water vapour in the troposphere and ozone in the stratosphere. In recent years, the presence of non-migrating tides in the MLT region has been demonstrated by satellite observations and its importance in producing the longitudinal redistribution of ionization within the low latitude F-region has been emphasized. There have been studies that examined the signatures of planetary waves and tides in the low latitude ionosphere but none could provide experimental evidence for any planetary wave or tidal component to directly modulate the ionospheric parameters. It is firmly believed that much of the quiet-time space weather in the upper atmosphere is contributed by upward propagating waves of lower atmospheric origin but what spectrum of waves penetrate the MLT region and produce observable effects in the upper atmosphere is not known. These aspects emphasize the complexities in the interplay of several dynamical and electrodynamical processes in the low latitude MLT and ionospheric (MLTI) regions. This talk will present the state-of-the-art in our understanding of the role of dynamical processes in MLTI coupling with highlights from recent results obtained using ground-based radar and magnetometer data sets and some new insights revealed by satellite observations on non-migrating tides.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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