Bibliography
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Notice:
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Found 215 entries in the Bibliography.
Showing entries from 51 through 100
| 2014 |
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The role of the postsunset vortex in the creation of turbulence in the bottomside F region Lee, Woo; Kil, Hyosub; Kwak, Young-Sil; Paxton, Larry; Published by: Published on: |
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The zonal motion of equatorial plasma bubbles relative to the background ionosphere Kil, Hyosub; Lee, Woo; Kwak, Young-Sil; Zhang, Yongliang; Paxton, Larry; Milla, Marco; Published by: Journal of Geophysical Research: Space Physics Published on: |
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The zonal motion of equatorial plasma bubbles relative to the background ionosphere Kil, Hyosub; Lee, Woo; Kwak, Young-Sil; Zhang, Yongliang; Paxton, Larry; Milla, Marco; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Storm-Time Behaviors of the Thermospheric O/N2 and NO Variations Zhang, Yongliang; Paxton, Larry; Morrison, Daniel; Kil, Hyosub; Marsh, Daniel; Published by: Published on: |
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Equatorial broad plasma depletions associated with the enhanced fountain effect Lee, Woo; Kil, Hyosub; Kwak, Young-Sil; Paxton, Larry; Zhang, Yongliang; Galkin, Ivan; Batista, Inez; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2013 |
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The effect of the 135.6 nm emission originated from the ionosphere on the TIMED/GUVI O/N 2 ratio The column number density ratio of atomic oxygen to molecular nitrogen (O/N2\ ratio) provided by the Global Ultraviolet Imager (GUVI) onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite has been used as a diagnostic of the thermospheric neutral composition. However, a recent study claimed that the GUVI O/N2\ ratio is not a pure thermospheric parameter in low latitudes during periods of low geomagnetic activity. This study quantifies the O/N2\ ratio contamination by the ionosphere using the GUVI observations and model ionosphere acquired from 31 August to 2 September 2002. During this period, the local time of the GUVI observation was near 1500 and the average\ Kp\ index was 2\textdegree. The 135.6 nm emission originated from the ionosphere is estimated using the electron density profiles provided by the Utah State University-Global Assimilation of Ionospheric Measurements model. Our results show that the 135.6 nm emission originated from the equatorial ionization anomaly (EIA) contributes 5 ~ 10\% to the total 135.6 nm intensity and O/N2\ ratio. The EIA feature and longitudinal wave patterns in the GUVI 135.6 nm intensity maps are identified above an altitude of 300 km and show a good agreement with those in the\ F\ region plasma density. However, the EIA feature and longitudinal wave patterns do not appear in the GUVI 135.6 nm intensity maps below an altitude of 300 km and in the GUVI N2\ Lyman-Birge-Hopfield band intensity maps in any altitude. These observations indicate that the longitudinal wave patterns in the GUVI O/N2\ ratio represent the ionospheric phenomenon. Kil, H.; Lee, W.; Shim, J.; Paxton, L.J.; Zhang, Y.; Published by: Journal of Geophysical Research: Space Physics Published on: Jan-02-2013 YEAR: 2013 DOI: 10.1029/2012JA018112 |
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[1]\ We examine the consequence of enhanced atomic oxygen (OI) 135.6 nm emissions due to the recombination of O+ with electrons on the column number density ratio of atomic oxygen to molecular nitrogen (O/N2 ratio) provided by Global Ultraviolet Imager (GUVI) on board the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite. GUVI O/N2 ratio is derived from the measurements of OI 135.6 nm and N2 Lyman-Birge-Hopfield airglow emissions. The OI 135.6 nm emission arises from two sources: photoelectron impact excitation of neutral atomic oxygen and the radiative recombination of O+ with electrons. We estimate the O/N2 ratio disturbance associated with the O+ density enhancement during geomagnetic storms through the case study of the storms on 20 November 2003 and 8 November 2004. The OI 135.6 nm emission enhancement originating from the ionosphere is derived using the Utah State University Global Assimilation of Ionospheric Measurements model ionosphere. Our results show that the O/N2 ratio increase from the equator to middle latitudes during the storm periods is primarily associated with thermospheric neutral composition disturbances. However, the contribution of the OI 135.6 nm emission originating from the ionosphere to the storm time O/N2 ratio increase is substantial in the northern low-middle latitude regions where severe plasma density enhancements occur during the main phase of the storms. Therefore, the ionospheric contribution should be considered for an accurate assessment of the storm time O/N2 ratio increase at low-middle latitudes during these large storm events. Lee, Woo; Kil, Hyosub; Paxton, Larry; Zhang, Yongliang; Shim, Ja; Published by: Journal of Geophysical Research: Space Physics Published on: 12/2013 YEAR: 2013 DOI: 10.1002/2013JA019132 |
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Formation of broad plasma depletions (BPDs) at night in the equatorial F region is understood in association with plasma bubbles. However, we report BPDs that do not show a connection with bubbles. The characteristics of BPDs are investigated using the observations of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite on 31 December 2008, 28 July 2010, and 1 February 2011. On those days, BPDs are detected in the longitude regions where C/NOFS did not detect bubbles prior to the detection of BPDs. The coincident C/NOFS and radar observations over Jicamarca in Peru show the occurrence of BPDs at the time when backscatter echoes are absent and at the height below backscatter echoes. These observations indicate that bubbles are not a prerequisite for those BPDs. The detections of those BPDs can be explained by the uplift of the equatorial F region peak height above the satellite orbit. Published by: Geophysical Research Letters Published on: 07/2014 YEAR: 2013 DOI: 10.1002/grl.50693 |
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Nightside midlatitude ionospheric arcs: TIMED/GUVI observations [1]\ Midlatitude arcs (MLA) are the phenomenon of the nightside enhancements of ionospheric electron density at 20\textdegree-45\textdegree magnetic latitudes in both hemispheres. We investigate the occurrence of MLA and its dependence on season using the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) O I 135.6 nm intensity data between March 2008 and March 2012. The 135.6 nm emission is mainly caused by radiant recombination between O+ ions and electrons in the nightside ionosphere. The GUVI data show that the MLA occurred in all seasons under geomagnetically quiet condition (mean Kp ~ 1.0) and during periods of low solar activity. Hemispheric symmetric MLA were observed during equinox. During solstice, the MLA were seen only in the winter hemisphere. The MLA were more frequently observed at local times between ~21:00 and 02:00 on nightside. They were rarely observed at local times between 03:00 and sun rise. The MLA were observed with an occurrence frequency of ~75\% of the time. Coincident GPS total electron current data confirm that the MLA were due to enhanced ionospheric electron density. GUVI 135.6 nm limb data further show that the altitude of the MLA is higher than that of the equatorial arcs created by the equatorial ionization anomaly or fountain effect. The appearance of the MLA at higher altitude than the equatorial arcs supports the idea that the creation of the MLA is associated with the uplift of the ionosphere by the equatorward neutral wind. Zhang, Yongliang; Paxton, Larry; Kil, Hyosub; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2013 YEAR: 2013 DOI: 10.1002/jgra.50327 |
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Multi-Periodic Auroral and Thermospheric Variations in 2006 Zhang, Yongliang; Paxton, L.; Kil, Hyosub; Published by: Terrestrial, Atmospheric and Oceanic Sciences Published on: 04/2013 YEAR: 2013 DOI: 10.3319/TAO.2012.09.20.01(SEC) |
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Observing the mid-and low-latitude ionosphere-global UV remote sensing Paxton, LJ; Kil, H; Miller, ES; Comberiate, J; Schaefer, RK; Zhang, Y; Team, GUVI; , others; Published by: Published on: |
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Ring current and polar rain auroras Published by: Published on: |
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The Study of the origin of broad plasma depletions in the equatorial F region Oh, S; Lee, W; Kil, H; Kwak, Y; Paxton, L; Zhang, Y; Published by: Published on: |
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Drivers of the hemispheric asymmetry in the low-latitude electron density distribution Kil, H; Kwak, Y; Lee, W; Paxton, L; Zhang, Y; Published by: Published on: |
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Behaviors of the ionospheric and thermospheric disturbances during geomagnetic storms Kil, H; Lee, W; Zhang, Y; Paxton, LJ; Published by: Published on: |
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The effect of the 135.6 nm emission originated from the ionosphere on the TIMED/GUVI O/N2 ratio Kil, H; Lee, WK; Shim, J; Paxton, LJ; Zhang, Y; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Large-scale structures in the Polar Rain Zhang, Yongliang; Paxton, Larry; Kil, Hyosub; Published by: Geophysical Research Letters Published on: |
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Lee, Woo; Kil, Hyosub; Paxton, Larry; Zhang, Yongliang; Shim, Ja; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2012 |
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Park, Jaeheung; Lühra, Hermann; Jakowski, Norbert; Gerzen, Tatjana; Kil, Hyosub; Jee, Geonhwa; Xiong, Chao; Min, Kyoung; Noja, Max; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-05-2012 YEAR: 2012 DOI: 10.1016/j.jastp.2012.03.009 |
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A steep plasma density gradient has been observed in the middle-latitude F region during large geomagnetic storms. This phenomenon can be understood as a special form of the middle-latitude ionization trough (hereafter trough), but its causal linkage has not yet been clarified. We investigate the association of the steep density gradient and the trough by comparing their morphologies and occurrence locations using the satellite and ground observation data during the 11\textendash12 April 2001 storm. Steep density gradients are detected in the dusk sector at the equatorward edges of the aurora by the Defense Meteorological Satellite Program (DMSP) F13 spacecraft. The locations of the steep density gradients coincide with the locations of the ionospheric footprints of the plasmapause identified by the Imager for Magnetopause-to-Aurora Global Exploration satellite. These observations demonstrate that the steep density gradient is created at the typical location of the trough. However, the steep density gradient is not produced by the formation of an intense trough during the storm. The temporal evolution of the total electron content maps shows that the steep density gradient observed at dusk by DMSP is associated with the plasma density enhancement in the dayside and its corotation into the dusk sector. The severe plasma density enhancement in middle latitudes, in combination with the trough and presumably the plasma depletion in high latitudes by the neutral composition change, produces the steep density gradient in the subauroral region during the storm. Park, S.; Kim, K.-H.; Kil, H.; Jee, G.; Lee, D.-H.; Goldstein, J.; Published by: Journal of Geophysical Research Published on: 05/2012 YEAR: 2012 DOI: 10.1029/2011JA017349 |
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Intense polar rain electrons and associated field aligned currents Zhang, Y; Wing, S; Paxton, LJ; Kil, H; Published by: Published on: |
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The Source of Tidal Signatures in the TIMED/GUVI O/N2 Ratio Kil, H; Lee, W; Shim, J; Paxton, LJ; Zhang, Y; Published by: Published on: |
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Persistent longitudinal features in the low-latitude ionosphere Kil, H; Lee, WK; Kwak, Y-S; Oh, S-J; Paxton, LJ; Zhang, Y; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2011 |
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Published by: Geophysical Research Letters Published on: Jan-10-2011 YEAR: 2011 DOI: 10.1029/2011GL049432 |
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Nightside polar rain aurora boundary gap and its applications for magnetotail reconnection Zhang, Yongliang; Paxton, L.; Kil, Hyosub; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2011JA016884 |
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O and N 2 disturbances in the F region during the 20 November 2003 storm seen from TIMED/GUVI Kil, H.; Kwak, Y.-S.; Paxton, L.; Meier, R.; Zhang, Y.; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2010JA016227 |
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The source of the longitudinal asymmetry in the ionospheric tidal structure Kil, H.; Kwak, Y.-S.; Oh, S.-J.; Talaat, E.; Paxton, L.; Zhang, Y.; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2011JA016781 |
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Temporal and spatial components in the storm-time ionospheric disturbances Kil, Hyosub; Paxton, L.; Kim, Khan-Hyuk; Park, Sarah; Zhang, Yongliang; Oh, Seung-Jun; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2011JA016750 |
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Electrified MSTIDs at Low Latitudes Miller, ES; Kil, H; Makela, JJ; Paxton, LJ; Talaat, ER; Published by: Published on: |
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Longitudinal asymmetry in the crest intensity of the ionospheric tidal structure Kil, H; Paxton, LJ; Zhang, Y; Kwak, Y; Oh, S; Published by: Published on: |
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Onset conditions of bubbles and blobs: A case study on 2 March 2009 Kil, H; Choi, H-S; Heelis, RA; Paxton, LJ; Coley, WR; Miller, ES; Published by: Geophysical Research Letters Published on: YEAR: 2011 DOI: 10.1029/2011GL046885 |
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O and N2 disturbances in the F region during the 20 November 2003 storm seen from TIMED/GUVI Kil, H; Kwak, Y-S; Paxton, LJ; Meier, RR; Zhang, Y; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Periodic Variations in Aurora, Thermosphere and Ionosphere: Solar Cycle Dependence Published by: Published on: |
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Published by: Aeronomy of the Earth s Atmosphere and Ionosphere Published on: YEAR: 2011 DOI: https://doi.org/10.1007/s12040-011-0114-1 |
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This chapter reviews recent advances in our understanding of the characteristics and driving mechanisms of the longitudinal plasma density structure in the low-latitude F region. Various ionospheric observations have shown the development of a longitudinal wave-like pattern in plasma density. Typically, the wave number-4 (wave-4) pattern is pronounced during July\textendashSeptember, and the wave-3 pattern is pronounced during December\textendashJanuary. Variation of the longitudinal plasma density pattern with local time and season is causally linked to vertical plasma drift in the F region (or E-region dynamo electric fields). The wave-4 pattern is of special interest to the ionosphere-thermosphere community because this phenomenon is closely associated with the diurnal eastward propagating zonal wave number 3 tide (DE3). This idea is supported by observations of annual variation of the DE3 amplitude and diurnal variation of the DE3 phase that are consistent with the annual and diurnal variations of the wave-4 patterns in plasma density and dynamo electric fields. The connection of the ionospheric wave-3 pattern presumably to the diurnal eastward propagating zonal wave number 2 tide (DE2) further demonstrates the significant role of atmospheric tides in the formation of large-scale ionospheric structures. Formation of the large-scale longitudinal structures of the ionosphere is attributed to the modulation of the E-region dynamo electric fields by atmospheric tides, but recent studies indicate that the ionosphere and thermosphere can be directly modulated by the penetration of atmospheric tides into the F-region height. Published by: Published on: YEAR: 2011 DOI: 10.1007/978-94-007-0326-1_26 |
| 2010 |
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This study investigates the temporal evolution of the large plasma depletions observed by ROCSAT-1 and DMSP near 295°E during the 29–30 October 2003 storm. The presence of a penetration electric field around the detection time of the large plasma depletions is supported by the observation of high upward ion drift velocity and formation of an intense equatorial ionization anomaly in the American sector. However, these ionospheric disturbances occur in broad longitude regions; a short-range polarization electric field may adequately explain the creation of the large plasma depletions. The penetration electric field may trigger the Rayleigh–Taylor instability and produce abnormally large plasma depletions during the storm. The TIMED/GUVI and CHAMP observations provide an insight for the evolution of the large depletions several hours after their formation. The large depletions appear as arch-shaped emission depletions in the TIMED/GUVI image and as symmetric depletions paired in the magnetic north and south in the CHAMP observation. These characteristics can be explained by the “plasma depletion shell” phenomenon (Kil et al., 2009) produced by the westward shear flow of the ionosphere during the storm. Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-03-2010 YEAR: 2010 DOI: 10.1016/j.jastp.2009.10.019 |
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Is DE2 the source of the ionospheric wave number 3 longitudinal structure? Kil, H.; Paxton, L.; Lee, W.; Ren, Z.; Oh, S.-J.; Kwak, Y.-S.; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2010JA015979 |
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On and N2 disturbances in the F region during the 20 November 2003 storm seen from TIMED/GUVI Kil, Hyosub; Paxton, Larry; Kwak, Young-Sil; Meier, Robert; Zhang, Yongliang; Published by: 38th COSPAR Scientific Assembly Published on: |
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Kwak, Y; Kil, H; Lee, W; Cho, K; Published by: Published on: |
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Night-side mid-latitude 135.6 nm intensity enhancements: TIMED/GUVI observations Zhang, Y; Paxton, LJ; Talaat, ER; Kil, H; Published by: Published on: |
| 2009 |
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Formation of a plasma depletion shell in the equatorial ionosphere An accurate description of the irregularity region defined by a plasma bubble is critically important in understanding the dynamics of the region and its effects on radio scintillation. Here we describe a plasma depletion region as a \textquotedblleftdepletion shell\textquotedblright and show how two-dimensional optical images from space can be used to define the shape of the depletion shell. Our simple model calculation demonstrates that the space-based optical observation can detect the plasma-depleted magnetic flux tubes only near the F-peak height. The backward C-shape in bubble images from optical observations is the trace of the plasma depletion shell near the F-peak height. The westward tilt of bubbles at the magnetic equator can also be explained by this shell structure. The in situ measurement of the ion velocity at night in the topside shows the decrease of the eastward plasma drift with an increase of latitude. The formation of the plasma depletion shell is consistent with the latitudinal/altitudinal shear in the zonal plasma flow. Kil, Hyosub; Heelis, Roderick; Paxton, Larry; Oh, Seung-Jun; Published by: Journal of Geophysical Research Published on: 11/2009 YEAR: 2009 DOI: 10.1029/2009JA014369 Equatorial ionosphere; plasma depletion shell; zonal shear flow |
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Paxton, LJ; Zhang, Y; Kil, H; Schaefer, RK; Comberiate, J; Christensen, AB; Published by: Published on: |
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The Variability of the Zonal Plasma Drift in the Equatorial F Region Kil, H; Kang, C; Oh, S; Kwak, Y; Lee, W; Paxton, LJ; Published by: Published on: |
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Published by: Bulletin of the Korean Space Science Society Published on: |
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Wu, Quian; Solomon, SC; Kuo, Y-H; Killeen, TL; Xu, JiYao; Published by: Geophysical research letters Published on: |
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The day-to-day variability of the occurrence of equatorial plasma bubbles Oh, Seung; Kil, Hyosub; Paxton, Larry; Kim, Yong; Published by: Published on: |
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Global observations of the equatorial ionosphere by UV remote sensing Paxton, Larry; Comberiate, Joseph; Kil, Hyosub; Schaefer, Robert; Wolven, Brian; Zhang, Yongliang; Morrison, Daniel; Published by: Published on: |
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Kwak, Y; Kil, H; Oh, S; Lee, W; Forbes, JM; Cho, K; Published by: Published on: |