Browsing by Author "Goncharenko, L. P."
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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 Early morning equatorial ionization anomaly from GOLD observations(American Geophysical Union, 2020-07) Laskar, F. I.; Eastes, R. W.; Martinis, C. R.; Daniell, R. E.; Pedatella, N. M.; Burns, A. G.; McClintock, W.; Goncharenko, L. P.; Coster, A.; Milla, Marco; Wang, W.; Valladares, C. E.; Codrescu, M. V.During geomagnetically quiet and solar minimum conditions, spatial variations of the early morning thermosphere‐ionosphere (TI) system are expected to be mainly governed by wave dynamics. To study the postmidnight dynamical coupling, we investigated the early morning equatorial ionization anomaly (EIA) using Global‐scale Observations of the Limb and Disk (GOLD) measurements of OI‐135.6 nm nightglow emission and global navigation satellite system (GNSS)‐based total electron content (TEC) maps. The EIA structures in the OI‐135.6 nm emission over the American landmass resemble, spatially and temporally, those observed in the GNSS‐TEC maps. The early morning EIA (EM‐EIA) crests are well separated in latitude and mostly located over the middle of South America during October–November. In February–April the crests are less separated in latitude and predominantly located over the west coast sector of South America. Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCMX) simulations with constant solar minimum and quiet‐geomagnetic conditions show that EM‐EIA can occur globally and shows properties similar to longitudinal Wave 4 pattern. Thus, we propose that EM‐EIA is driven by dynamical changes associated with the lower atmospheric waves.Item Open Access Equatorial ExB drifts during sudden stratospheric warming events(Instituto Geofísico del Perú, 2009) Chau Chong Shing, Jorge Luis; Galindo, F. R.; Fejer, B. G.; Goncharenko, L. P.Diapositivas presentadas en: CEDAR Workshop 2009 del 28 de junio al 2 de julio de 2009 en Santa Fe, Nuevo México, USA.Item Open Access Equatorial zonal electric fields during the 2002-2003 sudden stratospheric warming event(Instituto Geofísico del Perú, 2009) Olson, Michael E.; Fejer, B. G.; Stolle, C.; Chau Chong Shing, Jorge Luis; Goncharenko, L. P.For nearly fifty years, the Jicamarca Radio Observatory (11.95°S, 76.87°W, 2°N dip latitude) near Lima, Peru, has measured ionospheric plasma drifts. Over the last ten years, measurements of plasma drift velocities have also been measured using radar observations of the equatorial 150 km altitude región (Kudeki and Fawcett, 1993; Chau and Woodman, 2004).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 Restricted Lunar-dependent equatorial ionospheric electrodynamic effects during sudden stratospheric warmings(American Geophysical Union, 2010) Fejer, B. G.; Olson, M. E.; Chau Chong Shing, Jorge Luis; Stolle, C.; Lühr, H.; Goncharenko, L. P.; Yumoto, K.; Nagatsuma, T.We have used plasma drift and magnetic field measurements during the 2001–2009 December solstices to study, for the first time, the longitudinal dependence of equatorial ionospheric electrodynamic perturbations during sudden stratospheric warmings. Jicamarca radar measurements during these events show large dayside downward drift (westward electric field) perturbations followed by large morning upward and afternoon downward drifts that systematically shift to later local times. Ground-based magnetometer measurements in the American, Indian, and Pacific equatorial regions show strongly enhanced electrojet currents in the morning sector and large reversed currents (i.e., counterelectrojets) in the afternoon sector with onsets near new and full moons during northern winter warming periods. CHAMP satellite and ground-based magnetic field observations indicate that the onset of these equatorial afternoon counterelectrojets is longitude dependent. Our results indicate that these large electrodynamic perturbations during stratospheric warming periods are due to strongly enhanced semidiurnal lunar wave effects. The results of our study can be used for forecasting the occurrence and evolution of these electrodynamic perturbations during arctic winter warmings.Item Restricted Numerical modeling of ionospheric effects in the middle‐ and low‐latitude F region during geomagnetic storm sequence of 9-14 September 2005(American Geophysical Union, 2011-05-27) Klimenko, M. V.; Klimenko, V. V.; Ratovsky, K. G.; Goncharenko, L. P.; Sahai, Y.; Fagundes, P. R.; Jesus, R. de; Abreu, A. J. de; Vesnin, A. M.This study presents the Global Self‐Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) numerical simulations of the 9–14 September 2005 geomagnetic storm effects in the middle‐ and low‐latitude ionosphere. Recent modifications to the GSM TIP model include adding an empirical model of high‐energy electron precipitation and introducing a high‐resolution (1 min) calculation of region 2 field‐aligned currents and a cross‐cap potential difference. These modifications resulted in better representation of such effects as penetration of the magnetospheric convection electric field to lower latitudes and the overshielding. The model also includes simulation of solar flare effects. Comparison of model results with observational data at Millstone Hill (42.6°N, 71.5°W, USA), Arecibo (18.3°N, 66.8°W, Puerto Rico), Jicamarca (11.9°S, 76.9°W, Peru), Palmas (10.2°S, 48.2°W, Brazil), and San Jose Campos (23.2°S, 45.9°W, Brazil) shows good agreement of ionospheric disturbances caused by this storm sequence. In this paper we consider in detail the formation mechanism of the additional layers in an equatorial ionosphere during geomagnetic storms. During geomagnetic storms, the nonuniform in height zonal electric field is generated at the geomagnetic equator. This electric field forms the additional layers in the F region of equatorial ionosphere.Item Open Access Observations of the April 2002 geomagnetic storm by the global network of incoherent scatter radars(European Geosciences Union (EGU), 2005-01) Goncharenko, L. P.; Salah, J. E.; Van Eyken, A.; Howells, V.; Thayer, J. P.; Taran, V. I.; Shpynev, B.; Zhou, Q.; Chau Chong Shing, Jorge LuisThis paper describes the ionospheric response to a geomagnetic storm beginning on 17 April 2002. We present the measurements of ionospheric parameters in the F-region obtained by the network of eight incoherent scatter radars. The main effects of this storm include a deep decrease in the electron density observed at high and middle latitudes in the pre-noon sector, and a minor enhancement in the density observed in the daytime sector at middle latitudes. Extreme plasma heating (>1000-3000 K) is observed at high latitudes, subsiding to 200-300K at subauroral latitudes. The western hemisphere radar chain observed the prompt penetration of the electric field from auroral to equatorial latitudes, as well as the daytime enhancement of plasma drift parallel to the magnetic field line, which is related to the enhancement in the equatorward winds. We suggest that in the first several hours after the storm onset, a negative phase above Millstone Hill (pre-noon sector) results from counteracting processes - penetration electric field, meridional wind, and electrodynamic heating, with electrodynamic heating being the dominant mechanism. At the lower latitude in the pre-noon sector (Arecibo and Jicamarca), the penetration electric field becomes more important, leading to a negative storm phase over Arecibo. In contrast, in the afternoon sector at mid-latitudes (Kharkov, Irkutsk), effects of penetration electric field and meridional wind do not counteract, but add up, leading to a small (~15%), positive storm phase over these locations. As the storm develops, Millstone Hill and Irkutsk mid-latitude radars observe further depletion of electron density due to the changes in the neutral composition.Item Open Access Quiet time ionospheric variability over Arecibo during sudden stratospheric warming events(American Geophysical Union, 2010-09-11) Chau Chong Shing, Jorge Luis; Aponte, N. A.; Cabassa, E.; Sulzer, M. P.; Goncharenko, L. P.; González, S. A.We present observations of the F‐region ionosphere over Arecibo, Puerto Rico (18.34°N, 66.75°W), during the January–February 2008 and January–February 2009 sudden stratospheric warming (SSW) events. For the first period (2008), we have used incoherent scatter radar (ISR) electron density and temperature measurements from the Arecibo Observatory (AO), as well as relative total electron content (TEC) derived from a dual‐frequency GPS receiver. For the second event (2009), during which we observed the largest recorded stratospheric warming, we have used the relative GPS TEC. Our analysis indicates that the ionosphere over Arecibo exhibits perturbations after the SSW, the effects are most visible during the daytime. The strongest signatures are observed in the TEC measurements, represented by large enhancements (with respect to non SSW days), particularly during daytime hours. However, the local time dependence of these enhancements is not the same in the two events. In addition, the data show that our results are consistent with the larger than normal daytime vertical drift differences observed at the magnetic equator over Jicamarca. The electron temperature is also affected during the daytime due to changes in electron density, indicating that the electron temperatures is influenced, indirectly, by changes in planetary wave activity in the lower altitudes.Item Open Access Quiet time variability over Arecibo and Jicamarca during SSWs(Instituto Geofísico del Perú, 2010) Chau Chong Shing, Jorge Luis; Aponte, N. A.; Cabassa, E.; Sulzer, M. P.; Goncharenko, L. P.; González, S. A.Diapositivas presentadas en el 2010 CEDAR Workshop, University of Colorado, Boulder, CO, 20-25 June 2010.Item Open Access Quiet variability of equatorial E × B drifts during a sudden stratospheric warming event(American Geophysical Union, 2009-03-03) Chau Chong Shing, Jorge Luis; Fejer, B. G.; Goncharenko, L. P.We present strong evidence that during the January 2008 minor sudden stratospheric warming (SSW) event, the equatorial vertical E × B drifts exhibit a unique and distinctive daytime pattern. We do not think one event causes the other, however both events might be related through the global effects of planetary waves. The drifts were measured by the Jicamarca Incoherent scatter radar located under the magnetic equator. We have observed an anomalous temporal variation of the vertical E × B drifts during the minor SSW event, showing a semidiurnal variation with very large amplitudes lasting for several days. Large differences in the E × B drifts were observed during a period of large increase of temperature and a large decrease of mean zonal wind, in the high latitude stratosphere (60°–90°N). This high correlation is an unexpected finding which might shed new light on sources and mechanisms of quiet-time ionospheric variability.Item Open Access The equatorial and low latitude ionosphere during stratospheric sudden waming events(Instituto Geofísico del Perú, 2010) Chau Chong Shing, Jorge Luis; Fejer, B. G.; Goncharenko, L. P.; González, A.Diapositivas presentadas en Nagoya University, Japan, March 24 2010.Item Open Access The equatorial ionosphere over Jicamarca during the January 2009 sudden stratospheric warming(Instituto Geofísico del Perú, 2009) Chau Chong Shing, Jorge Luis; Galindo, F. R.; Milla, Marco; Kudeki, E.; Reyes, P. M.; Goncharenko, L. P.; Fejer, B. G.Diapositivas presentadas en 2009 Joint Assembly. The Meeting of the Americas. 24-27 May 2009. Toronto, Ontario, Canada.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.Item Open Access Variations of low-latitude geomagnetic fields and Dst index caused by magnetospheric substorms(American Geophysical Union, 2004-05-25) Huang, Chao-Song; Foster, J. C.; Goncharenko, L. P.; Reeves, G. D.; Chau Chong Shing, Jorge Luis; Yumoto, K.; Kitamura, K.We present observations of periodic magnetospheric substorms and corresponding ionospheric disturbances. Since the periodic substorms occur during a stable interplanetary magnetic field, we are able to identify which ionospheric signatures are caused solely by substorms. We find that the low-latitude ionospheric electric field perturbation after substorm onsets is eastward on the dayside and westward on the nightside and that the ground magnetometer northward (H) deviations at middle and low latitudes show an increase (a positive bay) after each substorm onset, no matter whether the magnetometers are located on the dayside or on the nightside. The nightside magnetometer H deviations are closely correlated with the inner magnetospheric magnetic field Bz component during the dipolarization process. The Dst index shows a significant increase of 20–40 nT after each substorm onset. We propose that the increase in the magnetometer H field and Dst index in response to substorm onsets is related to the field dipolarization. In this scenario the nightside magnetosphere earthward of the near-Earth neutral line is highly compressed during the dipolarization, and the magnetic flux density within the inner magnetosphere is greatly enhanced, resulting in an increase in the ground magnetometer H component and in Dst.