Browsing by Author "Coster, A. J."
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Item Open Access Connections between the stratosphere and ionosphere(Instituto Geofísico del Perú, 2009) Goncharenko, L. P.; Coster, A. J.; Rideout, W.; Zhang, S.Diapositivas presentadas en: CEDAR Workshop 2009 del 28 de junio al 2 de julio de 2009 en Santa Fe, Nuevo México, USA.Item Restricted Impact of sudden stratospheric warmings on equatorial ionization anomaly(American Geophysical Union, 2010-10-07) Goncharenko, L. P.; Coster, A. J.; Chau Chong Shing, Jorge Luis; Valladares, C. E.We investigate the ionospheric response to several stratospheric sudden warming events which occurred in Northern Hemisphere winters of 2008 and 2009 during solar minimum conditions. We use GPS total electron content data in a broad latitudinal region at ±40° geographic latitude and a single longitude, 75°W. In all cases, we find a strong daytime ionospheric response to stratospheric sudden warmings. This response is characterized by a semidiurnal character, large amplitude, and persistence of perturbations for up to 3 weeks after the peak in high‐latitude stratospheric temperatures. The ionospheric perturbations at the lower latitudes usually begin a few days after the peak in stratospheric temperature and are observed as an enhancement of the equatorial ionization anomaly (EIA) in the morning sector and a suppression of the EIA in the afternoon sector. There is also evidence of a secondary enhancement in the postsunset hours. Once observed in the low latitudes, the phase of semidiurnal perturbations progressively shifts to later local times in subsequent days. This progressive shift occurs at a different rate for different stratospheric warming events. The large magnitude and persistence of ionospheric perturbations, together with the predictability of stratospheric sudden warmings several days in advance, present an opportunity to investigate these phenomena in a systematic manner which may eventually lead to a multiday forecast of low‐latitude ionosphere conditions.Item Open Access Unexpected connections between the stratosphere and ionosphere(American Geophysical Union, 2010-05) Goncharenko, L. P.; Chau Chong Shing, Jorge Luis; Liu, H. -L.; Coster, A. J.The coupling of the ionosphere to processes from below remains an elusive and difficult problem, as rapidly changing external drivers from above mask variations related to lower atmospheric sources. Here we use superposition of unique circumstances, current deep solar minimum and a record-breaking stratospheric warming event, to gain new insights into causes of ionospheric perturbations. We show large (50–150%) persistent variations in the low-latitude ionosphere (200–1000 km) that occur several days after a sudden warming event in the high-latitude winter stratosphere (30 km). We rule out solar irradiance and geomagnetic activity as explanations of the observed variation. Using a general circulation model, we interpret these observations in terms of large changes in atmospheric tides from their nonlinear interaction with planetary waves that are strengthened during sudden warmings. We anticipate that further understanding of the coupling processes with planetary waves, accentuated during the stratospheric sudden warming events, has the potential of enabling the forecast of low-latitude ionospheric weather up to several days in advance.