Browsing by Author "Goncharenko, L."
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Item Open Access Equatorial and low latitude ionospheric effects due to planetary wave atmospheric forcing(Instituto Geofísico del Perú, 2010) Chau Chong Shing, Jorge Luis; Goncharenko, L.; Fejer, B.; Liu, H.Diapositivas presentadas en First Latin American, FMT Workshop 2010, Ica, Peru, November 22- 26, 2010.Item Restricted Ionospheric and thermospheric variations associated with prompt penetration electric fields(American Geophysical Union, 2012-08-10) Lu, G.; Goncharenko, L.; Nicolls, M. J.; Maute, A.; Coster, A.; Paxton, L. J.This paper presents a comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field (PPEF) event that took place on 9 November 2004, using the Thermosphere‐Ionosphere‐Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local‐time variations in vertical ion drift in the middle‐ and low‐latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT‐latitude electron density profile from the simulation depicts clearly a super‐fountain effect caused by the PPEF, including the initial slow‐rise of the equatorial F‐layer peak height, the split of the F‐layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low‐latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time‐dependent, high‐latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ∼120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar. The simulation results are validated with several key observations from IS radars, ground GPS‐TEC network, and the TIMED‐GUVI O/N2column density ratio. The model‐data intercomparison also reveals some deficiencies in the TIMEGCM, particularly the limitations imposed by its upper boundary height as well as the prescribed O+ flux.Item Open Access Ionospheric disturbances associated with stratospheric sudden warmings(Instituto Geofísico del Perú, 2009) Goncharenko, L.; Coster, A.; Rideout, W.; Chau Chong Shing, Jorge Luis; Valladares, C.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 Ionospheric effects of recent stratospheric sudden warmings(Instituto Geofísico del Perú, 2011) Goncharenko, L.; Coster, A.; Chau Chong Shing, Jorge Luis; Valladares, C. E.Recent studies have shown large variations in low-latitude ionospheric parameters occurring after stratospheric sudden warming events. We use observations of vertical ion drift from Jicamarca ISR and GPS total electron content data in the Western Hemisphere for winters of 2008-2009 and 2009-2010 to illustrate main features of ionospheric changes related to stratospheric sudden warmings. The common feature in all events is the increase in the electron density during the morning hours and the decrease in the afternoon, related to amplification of 12-hour signature in low-latitude vertical ion drifts. This feature persists for several days after the peak in stratospheric temperature. The observed phenomena is related to quasistationary planetary waves, which have a high amplitude level prior to the stratospheric warmings. Non-linear interaction of planetary waves with tides leading to increase in tidal amplitudes in the low latitude lower thermosphere and modulation of E-region electric field with subsequent mapping to the F-region is thought to be the primary mechanism responsible for the observed ionospheric response. We investigate the characteristics of ionospheric oscillations with planetary wave periods between 2 and 30 days and in a wide range of latitudes in context of variations in stratospheric parameters.Item Restricted Ionospheric effects of sudden stratospheric warming during moderate-to-high solar activity: Case study of January 2013(American Geophysical Union, 2013-09-24) Goncharenko, L.; Chau Chong Shing, Jorge Luis; Cóndor, P.; Coster, A.; Benkevitch, L.A major sudden stratospheric warming (SSW) occurred in January 2013 during moderate-to-high solar activity conditions. Observations during the winter of 2012/2013 reveal strong ionospheric disturbances associated with this event. Anomalous variations in vertical ion drift measured at the geomagnetic equator at Jicamarca (12°S, 77°W) are observed for over 40 days. We report strong perturbations in the total electron content (TEC) that maximize in the crests of equatorial ionization anomaly, reach 100% of the background value, exhibit significant longitudinal and hemispheric asymmetry, and last for over 40 days. The magnitude of ionospheric anomalies in both vertical drifts and TEC is comparable to the anomalies observed during the record-strong SSW of January 2009 that coincided with the extreme solar minimum. This observation contrasts with results of numerical simulations that predict weaker ionospheric response to the tidal forcing during high solar activity.Item Open Access Ionospheric variations during January 2009 stratospheric sudden warming(Instituto Geofísico del Perú, 2009) Goncharenko, L.; Coster, A.; Rideout, W.; Chau Chong Shing, Jorge Luis; Liu, H. -L.; Valladares, C. E.The stratospheric sudden warming peaking in January 2009 was the strongest and most prolonged on record. We report significant ionospheric variations is association with this event, which are especially pronounced at low latitudes. Large increase in the vertical drifts is observed at Jicamarca, displaying 12-hour signature with upward drifts in the morning hours and downward drifts in the afternoon hours, with pattern persisting for several days. Analysis of GPS TEC data indicates that variations in electron density are observed in a large range of longitudes and latitudes. The entire daytime ionosphere is affected, with morning increase in low-latitude TEC exceeding 100% of the mean value, and afternoon decrease in TEC approaching ~50% of the mean value. These variations are consistent with ionospheric disturbances observed during other stratospheric warming events. We suggest the observed phenomena is related to planetary waves, which have a high amplitude level prior to the stratospheric warmings. Interaction of planetary waves with tides and modulation of tides can lead to changes in the low-latitude electric field through the wind dynamo process, which in turn is responsible for a largescale redistribution of ionospheric electron density.Item Restricted Multimodel comparison of the ionosphere variability during the 2009 sudden stratosphere warming(American Geophysical Union, 2016-07-18) Pedatella, N. M.; Fang, T.-W.; Jin, H.; Sassi, F.; Schmidt, H.; Chau Chong Shing, Jorge Luis; Siddiqui, T. A.; Goncharenko, L.A comparison of different model simulations of the ionosphere variability during the 2009 sudden stratosphere warming (SSW) is presented. The focus is on the equatorial and low‐latitude ionosphere simulated by the Ground‐to‐topside model of the Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Model plus Global Ionosphere Plasmasphere (WAM+GIP), and Whole Atmosphere Community Climate Model eXtended version plus Thermosphere‐Ionosphere‐Mesosphere‐Electrodynamics General Circulation Model (WACCMX+TIMEGCM). The simulations are compared with observations of the equatorial vertical plasma drift in the American and Indian longitude sectors, zonal mean F region peak density (NmF2) from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites, and ground‐based Global Positioning System (GPS) total electron content (TEC) at 75°W. The model simulations all reproduce the observed morning enhancement and afternoon decrease in the vertical plasma drift, as well as the progression of the anomalies toward later local times over the course of several days. However, notable discrepancies among the simulations are seen in terms of the magnitude of the drift perturbations, and rate of the local time shift. Comparison of the electron densities further reveals that although many of the broad features of the ionosphere variability are captured by the simulations, there are significant differences among the different model simulations, as well as between the simulations and observations. Additional simulations are performed where the neutral atmospheres from four different whole atmosphere models (GAIA, HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere), WAM, and WACCMX) provide the lower atmospheric forcing in the TIME‐GCM. These simulations demonstrate that different neutral atmospheres, in particular, differences in the solar migrating semidiurnal tide, are partly responsible for the differences in the simulated ionosphere variability in GAIA, WAM+GIP, and WACCMX+TIMEGCM.