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Found 41 entries in the Bibliography.
Showing entries from 1 through 41
| 2022 |
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The uncertainties associated with the variations in the thermosphere are responsible for the inaccurate prediction of the orbit decay of low Earth orbiting space objects due to the drag force. Accurate forecasting of the thermosphere is urgently required to avoid satellite collisions, which is a potential threat to the rapid growth of spacecraft applications. However, owing to the imperfections in the physics-based forecast model, the long-range forecast of the thermosphere is still primitive even if the accurate prediction of the external forcing is achieved. In this study, we constructed a novel methodology to forecast the thermosphere for tens of days by specifying the uncertain parameters in a physics-based model using an intelligent optimized particle filtering algorithm. A comparison of the results suggested that this method has the capability of providing a more reliable forecast with more than 30-days leading time for the thermospheric mass density than the existing ones under both weak and severe disturbed conditions, if solar and geomagnetic forcing is known. Moreover, the accurate estimation of the state of thermosphere based on this technique would further contribute to the understanding of the temporal and spatial evolution of the upper atmosphere. Published by: Science China Earth Sciences Published on: jan YEAR: 2022 DOI: 10.1007/s11430-021-9847-9 Forecast; Intelligent optimized particle filter; thermosphere; Uncertain parameters |
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A Simulation Study on the Variation of Thermospheric O/N2 With Solar Activity The ratio of number density of atomic oxygen (O) to that of molecular nitrogen (N2) in the thermosphere (O/N2) on the constant pressure surface, which has complex temporal and spatial characteristics, is widely regarded as an important parameter connecting the terrestrial thermosphere and daytime ionosphere. Previous studies demonstrated that the thermospheric O/N2 increases with increasing solar activity, and the changes in O/N2 with solar activity show significant difference between winter and summer hemispheres. However, the root causes, which are responsible for the solar activity variation of O/N2, are not fully understood. In this study, the contributions of various physical and chemical processes on the response of O/N2 to the solar radiation change were quantitatively investigated through a series of controlled simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model. The simulation results suggested that the chemical processes lead to the increase of thermospheric O/N2 over the globe with increasing solar activity. The increase of O/N2 with solar activity is dominated by the enrichment of O abundance and the loss of N2 abundance in the lower and upper thermosphere, respectively. Moreover, the simulation results suggested that the stronger hemispheric asymmetry is attributed to the stronger thermospheric circulation, which changes the vertical advection of O/N2 through both direct and indirect effects. Li, Zhongli; Luan, Xiaoli; Lei, Jiuhou; Ren, Dexin; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2022JA030305 circulation; O/N2; photochemistry; solar cycle; thermosphere |
| 2021 |
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The Universal Time Variations of the Intensity of Afternoon Aurora in Equinoctial Seasons The afternoon auroral emissions are investigated in the equinoxes for geomagnetically quiet conditions (Kp = 1) using auroral images from ultraviolet imager (UVI) aboard the Polar satellite. They are compared with solar illumination effects (the solar zenith angle [SZA] and the consequent ionospheric conductivity) and the dipole tilt angle, as well as the observational region 1 upward field-aligned currents (FACs) from AMPERE data. The averaged afternoon auroral emissions have pronounced universal time (UT) variations with valley (2.8 photons/cm2/s) at around 01:00–03:00 UT and peak (4.7 photons/cm2/s) at around 17:00–19:00 UT. They generally vary with the solar illumination, the dipole tilt angle and the observed region 1 upward FACs as a function of UT. The afternoon auroral intensity is anticorrelated with the SZA and positively proportional to the solar EUV-produced Pedersen conductivity, region 1 upward FACs and dipole tilt angle. Additionally, they depend weakly on solar flux under geomagnetically quiet conditions. These results suggest that in the afternoon auroral region, the peak auroral emissions are closely associated with the peak conductivity and the maximum upward FACs. Other mechanisms, such as the dipole tilt angle, may also contribute. Further comparison between the northern afternoon aurora and the FACs in the two conjugate hemispheres suggests little contributions on the auroral UT variations from the interhemispheric FACs in the equinoxes. Wang, Lingmin; Luan, Xiaoli; Lei, Jiuhou; Lynch, Kristina; Zhang, Binzheng; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028504 afternoon auroral emissions; auroral hot spots; dipole tilt angle; region 1 upward FACs; solar zenith angle; UT variations |
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Global Effects of a Polar Solar Eclipse on the Coupled Magnetosphere-Ionosphere System It is well-known that solar eclipses can significantly impact the ionosphere and thermosphere, but how an eclipse influences the magnetosphere-ionosphere system is still unknown. Using a coupled magnetosphere-ionosphere-thermosphere model, we examined the impact on geospace of the northern polar-region eclipse that occurred on June 10, 2021. The simulations reveal that the eclipse-induced reduction in polar ionospheric conductivity causes large changes in field-aligned current, cross-polar cap potential and auroral activity. While such effects are expected in the northern hemisphere where solar obscuration occurred, they also occurred in the southern hemisphere through electrodynamic coupling. Eclipse-induced changes in monoenergetic auroral precipitation differ significantly between the northern hemisphere and southern hemisphere while diffuse auroral precipitation is interhemispherically symmetric. This study demonstrates that the geospace response to a polar-region solar eclipse is not limited just to the eclipse region but has global implications. Chen, Xuetao; Dang, Tong; Zhang, Binzheng; Lotko, William; Pham, Kevin; Wang, Wenbin; Lin, Dong; Sorathia, Kareem; Merkin, Viacheslav; Luan, Xiaoli; Dou, Xiankang; Luo, Bingxian; Lei, Jiuhou; Published by: Geophysical Research Letters Published on: YEAR: 2021 DOI: 10.1029/2021GL096471 auroral activity; magnetosphere-ionosphere coupling; polar solar eclipse |
| 2020 |
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Li, Qiaoling; Huang, Fuqing; Zhong, Jiahao; Zhang, Ruilong; Kuai, Jiawei; Lei, Jiuhou; Liu, Libo; Ren, Dexin; Ma, Han; Yoshikawa, Akimasa; , others; Published by: Journal of geophysical research: space physics Published on: |
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Published by: Space Weather Published on: |
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Prominent daytime TEC enhancements under the quiescent condition of January 2017 UltraViolet Imager (GUVI) for the longitude and latitude bins of 30 and 10, respectively. However, as shown in Figure 3c, the O/N 2 ratio from Global UltraViolet Imager (GUVI) had no Huang, Fuqing; Lei, Jiuhou; Zhang, Ruilong; Li, Na; Gu, Shengyang; Yu, You; Liu, Libo; Owolabi, Charles; Ning, Baiqi; Li, Guozhu; , others; Published by: Geophysical Research Letters Published on: YEAR: 2020 DOI: 10.1029/2020GL088398 |
| 2019 |
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Topside ionospheric conditions during the 7—8 September 2017 geomagnetic storm The uplooking total electron contents (TECs) from the GRACE, SWARM-A, TerraSAR-X, and MetOp-A satellites and in situ electron density (Ne) from SWARM-A were utilized to investigate the topside ionospheric conditions during the 7–8 September 2017 geomagnetic storm. The rate of TEC index (ROTI) and rate of density index (RODI), which are derivative indices of TEC and Ne, respectively, were also used to characterize the topside ionospheric irregularities. The main results of this study are as follows: (1) There were significant enhancements seen in the uplooking TEC during the first main phase of the storm. (2) The uplooking TEC did not show unusual enhancement at the morning and evening local times in the Asian-Australian sector during the recovery phase of the storm. (3) Prominent TEC hemispheric asymmetry at the middle and high latitudes was observed at both day and night sectors. (4) Long-duration recovery of topside TEC with respect to the prestorm condition was also detected in this event. (5) Nighttime ROTI enhancements were presented in a wide latitudinal range from the equator to the poles during the main phases of the storm. (6) The ionospheric electric field disturbances associated with IMF-Bz fluctuations probably played a very important role in triggering ionospheric irregularities during the relatively weak geomagnetic activity on 7 September, which implies that ionospheric irregularities do not necessarily occur under the severe geomagnetic conditions only. Jimoh, Oluwaseyi; Lei, Jiuhou; Zhong, Jiahao; Owolabi, Charles; Luan, Xiaoli; Dou, Xiankang; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2019 DOI: 10.1029/2019JA026590 |
| 2018 |
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The Lyman-Birge-Hopfield-long band dayglow emissions near 1,700\ \r A, which were observed by the ultraviolet imager on board Polar satellite, are characterized as a cosine-like function of the solar zenith angle. These emissions are mainly excited by the solar extreme ultraviolet produced photoelectrons acting on the nitrogen molecules. The amplitude and phase factors are used to quantify the cosine-like function and subsequently develop a dayglow model. In this study, a model is developed by considering broader dayglow emission areas outside the auroral oval, as the dayglow intensities in the dayside can exceed the auroral brightness, especially in summer. Also, this model is constructed by considering the seasonal variations of the two factors. It is demonstrated that, besides the strong solar cycle and universal time dependencies, the amplitude factors of the cosine-like function show prominent seasonal variations, which are associated with the solar zenith angle changes. The amplitude factors are the largest in summer and smallest in winter. In addition, the dayglow phase factors show nearly constant values within each season, but throughout the year, they are higher in summer and equinoctial months and lower in winter. The dayglow model can benefit the investigation of global auroral patterns for all seasons. Wang, Lingmin; Luan, Xiaoli; Lei, Jiuhou; Dou, Xiankang; Published by: Space Weather Published on: 07/2018 YEAR: 2018 DOI: 10.1029/2018SW001954 |
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In this study, multiple data sets from Beidou geostationary orbit satellites total electron contents (TECs), ionosonde, meteor radar, magnetometer, and model simulations have been used to investigate the ionospheric responses in the Asian-Australian sector during the September 2017 geomagnetic storm. It was found that long-duration daytime TEC enhancements that lasted from 7 to 12 September 2017 were observed by the Beidou geostationary orbit satellite constellation. This is a unique event as the prominent TEC enhancements persisted during the storm recovery phase when geomagnetic activity became quiet. The Thermosphere-Ionosphere Electrodynamics Global Circulation Model predicted that the TEC enhancements on 7\textendash9 September were associated with the geomagnetic activity, but it showed significant electron density depletions on 10 and 11 September in contrast to the observed TEC enhancements. Our results suggested that the observed long-duration TEC enhancements from 7 to 12 September are mainly associated with the interplay of ionospheric dynamics and electrodynamics. Nevertheless, the root causes for the observed TEC enhancements seen in the storm recovery phase are unknown and require further observations and model studies. Lei, Jiuhou; Huang, Fuqing; Chen, Xuetao; Zhong, Jiahao; Ren, Dexin; Wang, Wenbin; Yue, Xinan; Luan, Xiaoli; Jia, Mingjiao; Dou, Xiankang; Hu, Lianhuan; Ning, Baiqi; Owolabi, Charles; Chen, Jinsong; Li, Guozhu; Xue, Xianghui; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2018 YEAR: 2018 DOI: 10.1029/2017JA025166 |
| 2017 |
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Regional differences of the ionospheric response to the July 2012 geomagnetic storm The July 2012 geomagnetic storm is an extreme space weather event in solar cycle 24, which is characterized by a southward interplanetary geomagnetic field lasting for about 30\ h below -10\ nT. In this work, multiple instrumental observations, including electron density from ionosondes, total electron content (TEC) from Global Positioning System, Jason-2, and Gravity Recovery and Climate Experiment, and the topside ion concentration observed by the Defense Meteorological Satellite Program spacecraft are used to comprehensively present the regional differences of the ionospheric response to this event. In the Asian-Australian sector, an intensive negative storm is detected near longitude ~120\textdegreeE on 16 July, and in the topside ionosphere the negative phase is mainly existed in the equatorial region. The topside and bottomside TEC contribute equally to the depletion in TEC, and the disturbed electric fields make a reasonable contribution. On 15 July, the positive storm effects are stronger in the Eastside than in the Westside. The topside TEC make a major contribution to the enhancement in TEC for the positive phases, showing the important role of the equatorward neutral winds. For the American sector, the equatorial ionization anomaly intensification is stronger in the Westside than in the Eastside and shows the strongest feature in the longitude ~110\textdegreeW. The combined effects of the disturbed electric fields, composition disturbances, and neutral winds cause the complex storm time features. Both the topside ion concentrations and TEC reveal the remarkable hemispheric asymmetry, which is mainly resulted from the asymmetry in neutral winds and composition disturbances. Kuai, Jiawei; Liu, Libo; Lei, Jiuhou; Liu, Jing; Zhao, Biqiang; Chen, Yiding; Le, Huijun; Wang, Yungang; Hu, Lianhuan; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2017 YEAR: 2017 DOI: 10.1002/2016JA023844 |
| 2016 |
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In this paper, an ionospheric electron density reanalysis algorithm was used to generate global optimized electron density during the 17\textendash18 March 2013 geomagnetic storm by assimilating ~10 low Earth orbit satellites based and ~450 ground global navigation satellite system receiver-based total electron content into a background ionospheric model. The reanalyzed electron density could identify the large-scale ionospheric features quite well during storm time, including the storm-enhanced density, the positive ionospheric storm effect during the initial and main phases, and the negative ionospheric storm effect during the recovery phase. The simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model can reproduce similar large-scale ionospheric disturbances as seen in the reanalysis results. Both the reanalysis and simulations show long-lasting (\>17 h) daytime negative storm effect over the Asia sector as well as hemispheric asymmetry during the recovery phase. Detailed analysis of the Global Ultraviolet Imager-derived O/N2 ratio and model simulations indicate that the polar ward meridional wind disturbance, the downward E \texttimes B drift disturbance and O/N2 depletion might be responsible for the negative storm effect. The hemispheric asymmetry is mainly caused by the geomagnetic field line configuration, which could cause hemispheric asymmetry in the O/N2 depletion. Yue, Xinan; Wang, Wenbin; Lei, Jiuhou; Burns, Alan; Zhang, Yongliang; Wan, Weixing; Liu, Libo; Hu, Lianhuan; Zhao, Biqiang; Schreiner, William; Published by: Journal of Geophysical Research: Space Physics Published on: 11/2016 YEAR: 2016 DOI: 10.1002/jgra.v121.910.1002/2016JA022984 |
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Topside ionospheric total electron content (TEC) observations from multiple low-Earth orbit (LEO) satellites have been used to investigate the local time, altitudinal, and longitudinal dependence of the topside ionospheric storm effect during both the main and recovery phases of the March 2015 geomagnetic storm. The results of this study show, for the first time, that there was a persistent topside TEC depletion that lasted for more than 3 days after the storm main phase at most longitudes, except in the Pacific Ocean region, where the topside TECs during the storm recovery phase were comparable to the quiet time ones. The observed depletion in the topside ionospheric TEC was relatively larger at higher altitudes in the evening sector and greater at local times closer to midnight. Moreover, the topside TEC patterns observed by MetOp-A (832 km) were different from those seen by other LEO satellites with lower orbital altitudes during the storm main phase and at the beginning of the recovery phase, especially in the evening sector. This suggests that the physical processes that control the storm time behavior of topside ionospheric response to storms are altitude-dependent. Zhong, Jiahao; Wang, Wenbin; Yue, Xinan; Burns, Alan; Dou, Xiankang; Lei, Jiuhou; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2016 YEAR: 2016 DOI: 10.1002/2016JA022469 |
| 2015 |
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Ionosphere equatorial ionization anomaly observed by GPS radio occultations during 2006--2014 A large number of Global Position System (GPS) radio occultation (RO) observations have been accumulated in the University Corporation for Atmospheric Research (UCAR) Constellation Observation System for Meteorology, Ionosphere and Climate (COSMIC) Data Analysis and Archive Center (CDAAC) especially since the launch of COSMIC mission. This study made use of these RO data to study the morphology of ionosphere equatorial ionization anomaly (EIA) statistically during 2006\textendash2014. The ionospheric peak density (NmF2) and peak height (hmF2) derived from the RO electron density profiles as well as the derived magnetic latitude of both crests and trough, the trough width, and the crest-to-trough ratio (CTR) of NmF2 are analyzed systematically. The corresponding seasonal, local time, and solar activity variations and the hemispheric asymmetry are identified and discussed. Most morphology agree well with previous studies and could be explained by the corresponding variations of neutral wind/composition and ExB vertical drift. We also found some interesting features. During May\textendashAugust, magnetic latitude of the trough could be up to ~5\textdegree north of the equator especially around noontime, and the local time difference corresponding best developed EIA between both hemispheres could be up to ~6\ h. Both crests even move equator-ward with the increase of solar activity in the morning sector except June solstice. Yue, Xinan; Schreiner, William; Kuo, Ying-Hwa; Lei, Jiuhou; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 07/2015 YEAR: 2015 DOI: 10.1016/j.jastp.2015.04.004 |
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Characteristics and mechanisms of the annual asymmetry of thermospheric mass density In this paper, globally-averaged, thermospheric total mass density, derived from the orbits of \~5000 objects at 250, 400, and 550 km that were tracked from 1967 to 2006, has been used to quantitatively study the annual asymmetry of thermospheric mass density and its mechanism(s). The results show that thermospheric mass density had a significant annual asymmetry, which changed from year to year. The annual asymmetry at the three altitudes varied synchronously and its absolute value increased with altitudes. The results suggest that there is an annual asymmetry in solar EUV radiation that is caused by the difference in the Sun-Earth distance between the two solstices and the random variation of solar activity within a year. This change in radiation results in an annual change in the thermospheric temperature and thus the scale height of the neutral gas, and is the main cause of the annual asymmetry of thermospheric mass density. The annual asymmetry of mass density increases with altitude because of the accumulating effect of the changes in neutral temperature and scale height in the vertical direction. Ma, RuiPing; Xu, JiYao; Wang, Wenbin; Chen, GuangMing; Yuan, Wei; Lei, Jiuhou; Burns, Alan; Jiang, Guoying; Published by: Science China Earth Sciences Published on: 04/2015 YEAR: 2015 DOI: 10.1007/s11430-014-5020-3 annual asymmetry of thermospheric mass density; solar EUV radiation; Sun-Earth distance |
| 2014 |
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The responses of ionospheric topside diffusive fluxes to two geomagnetic storms in October 2002 O+ field-aligned ambipolar diffusive velocities Vd and fluxes Фd in the topside ionosphere have been calculated from the observed profiles of electron density, ion, and electron temperatures during a 30 day incoherent scatter radar experiment conducted at Millstone Hill (288.5\textdegreeE, 42.6\textdegreeN) from 4 October to 4 November 2002. Two geomagnetic storms took place during this period. During the negative phases (depleted electron densities) of these two storms, the magnitudes of the daytime upward Vd and Фd were less than their averaged quiet time values. Whereas at nighttime, the downward Vd and Фd were sometimes larger than the averaged quiet time values. The variations in diffusive velocity and flux during the storm main and recovery phases were caused by changes in the ionospheric scale height or the shapes of ionospheric density profiles. The negative storm effect further reduced daytime diffusive flux. During these two storms, positive ionosphere phases (enhanced electron densities) were also observed. The diffusive velocity was much smaller during the period of positive storm effect, which led to a smaller diffusive flux than the quiet time one, although electron density was higher. It appears that storm time variations in diffusive velocity were more the results of storm time changes in the plasma vertical profile, rather than the cause of these plasma density changes. Chen, Guang-Ming; Xu, JiYao; Wang, Wenbin; Lei, Jiuhou; Zhang, Shun-Rong; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2014 YEAR: 2014 DOI: 10.1002/2014JA020013 diffusion; geomagnetic storm; scale height; topside ionosphere |
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Simulations of the equatorial thermosphere anomaly: Geomagnetic activity modulation The modulation of geomagnetic activity on the equatorial thermosphere anomaly (ETA) in thermospheric temperature under the high solar activity condition is investigated using the Thermosphere Ionosphere Electrodynamics General Circulation Model simulations. The model simulations during the geomagnetically disturbed interval, when the north-south component of the interplanetary magnetic field (Bz) oscillates between southward and northward directions, are analyzed and also compared with those under the quiet time condition. Our results show that ionospheric electron densities increase greatly in the equatorial ionization anomaly (EIA) crest region and decrease around the magnetic equator during the storm time, resulting from the enhanced eastward electric fields. The impact of both the direct heat deposition at high latitudes and the modulation of the storm time enhanced EIA crests on the ETA are subsequently studied. The increased plasma densities over the EIA crest region enhance the field-aligned ion drag that accelerates the poleward meridional winds and consequently their associated adiabatic cooling effect. This process alone produces a deeper temperature trough over the magnetic equator as a result of the enhanced divergence of meridional winds. Moreover, the enhanced plasma-neutral collisional heating at higher latitudes associated with the ionospheric positive storm effect causes a weak increase of the ETA crests. On the other hand, strong changes of the neutral temperature are mainly confined to higher latitudes. Nevertheless, the changes of the ETA purely due to the increased plasma density are overwhelmed by those associated with the storm time heat deposition, which is the major cause of an overall elevated temperature in both the ETA crests and trough during the geomagnetically active period. Associated with the enhanced neutral temperature at high latitudes due to the heat deposition, the ETA crest-trough differences become larger under the minor geomagnetic activity condition than under the quiet time condition. However, when geomagnetic activity is further elevated, the ETA crests tend to be masked by high temperatures at middle and high latitudes. Lei, Jiuhou; Wang, Wenbin; Thayer, Jeffrey; Luan, Xiaoli; Dou, Xiankang; Burns, Alan; Solomon, Stanley; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2014 YEAR: 2014 DOI: 10.1002/2014JA020152 equatorial thermosphere anomaly; geomagnetic activity; ion-neutral coupling; positive ionospheric storm |
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Responses of the lower thermospheric temperature to the 9 day and 13.5 day oscillations of recurrent geomagnetic activity and solar EUV radiation have been investigated using neutral temperature data observed by the TIMED/SABER (Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) instrument and numerical experiments by the NCAR-TIME-GCM (National Center for Atmospheric Research\textendashthermosphere-ionosphere-mesosphere electrodynamics\textendashgeneral circulation model). The TIMED/SABER data analyzed were for the period from 2002 to 2007 during the declining phase of solar cycle 23. The observations show that the zonal mean temperature in the lower thermosphere oscillated with periods of near 9 and 13.5 days in the height range of 100\textendash120 km. These oscillations were more strongly correlated with the recurrent geomagnetic activity than with the solar EUV variability of the same periods. The 9 day and 13.5 day oscillations of lower thermospheric temperature had greater amplitudes at high latitudes than at low latitudes; they also had larger amplitudes at higher altitudes, and the oscillations could penetrate down to ~105 km, depending on the strength of the recurrent geomagnetic activity for a particular time period. The data further show that the periodic responses of the lower thermospheric temperature to recurrent geomagnetic activity were different in the two hemispheres. In addition, numerical experiments have been carried out using the NCAR-TIME-GCM to investigate the causal relationship between the temperature oscillations and the geomagnetic activity and solar EUV variations of the same periods. Model simulations showed the same periodic oscillations as those seen in the observations when the real geomagnetic activity index, Kp, was used to drive the model. These numerical results show that recurrent geomagnetic activity is the main cause of the 9 day and 13.5 day variations in the lower thermosphere temperature, and the contribution from solar EUV variations is minor. Furthermore, we also found that consecutive coronal mass ejection events could cause long-duration enhancements in the lower thermospheric temperature that strengthen the 9 day and 13.5 day signals, and this kind of phenomenon mostly occurred between 2002 and 2005 during the declining phase of solar cycle 23. Jiang, Guoying; Wang, Wenbin; Xu, JiYao; Yue, Jia; Burns, Alan; Lei, Jiuhou; Mlynczak, Martin; Rusell, James; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.610.1002/2013JA019406 13.5 day variation; 9 day variation; Joule heating; lower thermospheric temperature; recurrent geomagnetic activity; solar EUV radiation |
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Predictability and Ensemble Modeling of the Space-Atmosphere Interaction Region Matsuo, Tomoko; Fuller-Rowell, Timothy; Akmaev, Rashid; Wang, Houjun; Fang, Tzu-Wei; Ide, Kayo; Kleist, Daryl; Whitaker, JS; Yue, Xinan; Codrescu, Mihail; , others; Published by: Published on: |
| 2013 |
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Annual asymmetry in thermospheric density: Observations and simulations [1]\ In this paper, the Challenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) observations during 2002\textendash2010 are utilized to study the variation of the annual asymmetry in thermospheric density at 400 km under low solar activity condition (F10.7 = 80) based on the method of empirical orthogonal functions (EOFs). The derived asymmetry index (AI) in thermospheric density from the EOF analysis shows a strong latitudinal variation at night but varies a little with latitudes in daytime. Moreover, it exhibits a terdiurnal tidal signature at low to middle latitudes. The global mean value of the AI is 0.191, indicating that a 47\% difference in thermosphere between the December and June solstices in the global average. In addition, the NCAR Thermosphere-Ionosphere Electrodynamics Global Circulation Model (TIEGCM) is used to explore the possible mechanisms responsible for the observed annual asymmetry in thermospheric density. It is found that the standard simulations give a lower AI and also a weaker day-to-night difference. The simulated AI shows a semidiurnal pattern in the equatorial and low-latitude regions in contrast with the terdiurnal tide signature seen in the observed AI. The daily mean AI obtained from the simulation is 0.125, corresponding to a 29\% December-to-June difference in thermospheric density at 400 km. Further sensitivity simulations demonstrated that the effect of the varying Sun-Earth distance between the December and June solstices is the main process responsible for the annual asymmetry in thermospheric density, while the magnetic field configuration and tides from the lower atmosphere contribute to the temporal and spatial variations of the AI. Specifically, the simulations show that the Sun-Earth distance effect explains 93\% of the difference in thermospheric density between December and June, which is mainly associated with the corresponding changes in neutral temperature. However, our calculation from the density observations reveals that the varying Sun-Earth distance effect only accounts for ~67\% of the December-to-June difference in thermosphere density, indicating that the TIEGCM might significantly underestimate the forcing originating from the lower atmosphere. Lei, Jiuhou; Dou, Xiankang; Burns, Alan; Wang, Wenbin; Luan, Xiaoli; Zeng, Zhen; Xu, JiYao; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2013 YEAR: 2013 DOI: 10.1002/jgra.50253 Annual asymmetry; Empirical orthogonal functions; Sun-Earth distance; Upper thermosphere |
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A superposed epoch analysis is performed to investigate the relative impact of the solar wind/interplanetary magnetic field (IMF) on geomagnetic activity, auroral hemispheric power, and auroral morphology during corotating interaction regions (CIRs) events between 2002 and 2007, when auroral images from Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Imager were available. Four categories of CIRs have been compared. These were classified by the averaged IMF Bz and the time of maximum solar wind dynamic pressure around the CIR stream interface or onset time. It is found that during CIR events: (1) The peaks of auroral power and Kp were largely associated with dominant southward Bz, whereas auroral activity also became stronger with increases of solar wind speed, density, and dynamic pressure. (2) The percentage and absolute increases of auroral hemispheric power with solar wind speed were much greater under dominantly northward Bz conditions than under dominantly southward Bz conditions. (3) The enhancement of the auroral power and Kp with increasing solar wind speed followed the same pattern, for both dominantly southward and northward Bz conditions, regardless of the behavior of solar wind density and dynamic pressure. These results suggest that, during CIR events, southward Bz played the most critical role in determining geomagnetic and auroral activity, whereas solar wind speed was the next most important contributor. The solar wind dynamic pressure was the less important factor, as compared with Bz and solar wind speed. Relatively strong auroral precipitation energy flux (\> ~3 mW/m2) occurred in a wider auroral oval region after the stream interface than before it for both dominantly northward and southward Bz conditions. These conditions enhanced the auroral hemispheric power after the stream interface. Intense auroral precipitation (\> ~4 mW/m2) generally occurred widely at night under dominantly southward Bz conditions, but the location of this precipitation in the auroral oval was different when it was associated with different solar wind density and speed conditions. Luan, Xiaoli; Wang, Wenbin; Lei, Jiuhou; Burns, Alan; Dou, Xiankang; Xu, JiYao; Published by: Journal of Geophysical Research: Space Physics Published on: 03/2013 YEAR: 2013 DOI: 10.1002/jgra.50195 auroral morphology; corotating interaction regions; solar wind/IMF forcing |
| 2012 |
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Huang, Yanshi; Deng, Yue; Lei, Jiuhou; Ridley, Aaron; Lopez, Ramon; Allen, Robert; Butler, Brandon; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-02-2012 YEAR: 2012 DOI: 10.1016/j.jastp.2011.05.013 |
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Thayer, J.; Liu, X.; Lei, J.; Pilinski, M.; Burns, A.; Published by: Journal of Geophysical Research Published on: Jan-01-2012 YEAR: 2012 DOI: 10.1029/2012JA017832 |
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Superposed epoch analyses of thermospheric response to CIRs: Solar cycle and seasonal dependencies Liu, Jing; Liu, Libo; Zhao, Biqiang; Lei, Jiuhou; Thayer, Jeffrey; McPherron, Robert; Published by: Journal of Geophysical Research Published on: Jan-01-2012 YEAR: 2012 DOI: 10.1029/2011JA017315 |
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Annual and semiannual variations of thermospheric density: EOF analysis of CHAMP and GRACE data Lei, Jiuhou; Matsuo, Tomoko; Dou, Xiankang; Sutton, Eric; Luan, Xiaoli; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2011 |
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Energy input into the upper atmosphere associated with high-speed solar wind streams in 2005 Deng, Yue; Huang, Yanshi; Lei, Jiuhou; Ridley, Aaron; Lopez, Ramon; Thayer, Jeffrey; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2010JA016201 |
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Rapid recovery of thermosphere density during the October 2003 geomagnetic storms Lei, Jiuhou; Thayer, Jeffrey; Lu, Gang; Burns, Alan; Wang, Wenbin; Sutton, Eric; Emery, Barbara; Published by: Journal of Geophysical Research Published on: Jan-01-2011 YEAR: 2011 DOI: 10.1029/2010JA016164 |
| 2010 |
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Longitudinal modulation of the O/N2 column density retrieved from TIMED/GUVI measurement He, Maosheng; Liu, Libo; Wan, Weixing; Lei, Jiuhou; Zhao, Biqiang; Published by: Geophysical Research Letters Published on: Jan-10-2010 YEAR: 2010 DOI: 10.1029/2010GL045105 |
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Ram, Tulasi; Lei, J.; Su, S.-Y.; Liu, C.; Lin, C.; Chen, W.; Published by: Geophysical Research Letters Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009GL041038 |
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Ionosphere response to recurrent geomagnetic activity: Local time dependency Pedatella, N.; Lei, J.; Thayer, J.; Forbes, J.; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009JA014712 |
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Ionospheric response to the initial phase of geomagnetic storms: Common features Wang, Wenbin; Lei, Jiuhou; Burns, Alan; Solomon, Stanley; Wiltberger, Michael; Xu, JiYao; Zhang, Yongliang; Paxton, L.; Coster, Anthea; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009JA014461 |
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Lei, Jiuhou; Thayer, Jeffrey; Burns, Alan; Lu, Gang; Deng, Yue; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009JA014754 |
| 2009 |
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The long-duration positive ionospheric storm effect that occurred on 15 December 2006 is investigated using a combination of ground-based Global Positioning System (GPS) total electron content (TEC), TOPEX and Jason-1 TEC, and topside ionosphere/plasmasphere TEC, GPS radio occultation, and tiny ionospheric photometer (TIP) observations from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. This multi-instrument approach provides a unique view of the ionospheric positive storm effect by revealing the storm time response in different altitude regions. The ground-based GPS TEC, TOPEX/Jason-1 TEC, and topside ionosphere/plasmasphere TEC all reveal significant enhancements at low latitudes to midlatitudes over the Pacific Ocean region during the initial portions of the storm main phase from 0000–0400 universal time (UT) on 15 December. At low latitudes, the topside ionosphere/plasmasphere TEC increase represents greater than 50\% of the TEC enhancement that is observed by ground-based GPS receivers. Moreover, electron density profiles obtained using the technique of GPS radio occultation demonstrate that the F layer peak height increased by greater than 100 km during this time period. The effects of soft particle precipitation are also apparent in the COSMIC observations of topside ionosphere/plasmasphere TEC. The positive storm effects over the Pacific Ocean region remain present in the equatorial ionization anomaly crest regions beyond 1200 UT on 15 December. This long-lasting positive storm effect is most apparent in ground-based GPS TEC and COSMIC TIP observations, while only a small increase in the topside ionosphere/plasmasphere TEC after 0400 UT is observed. This indicates that the long-lasting positive storm effect occurs predominantly at F region altitudes and, furthermore, that refilling of the topside ionosphere and plasmasphere is not the primary mechanism for producing the long-lasting positive storm phase during this event. The observations suggest that the enhanced eastward electric field and equatorward neutral wind are likely to play a significant role in the generation of long-lasting positive storm effects. Pedatella, N.; Lei, J.; Larson, K.; Forbes, J.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2009 DOI: https://doi.org/10.1029/2009JA014568 |
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Lei, Jiuhou; Thayer, Jeffrey; Burns, Alan; Lu, Gang; Deng, Yue; Published by: preparation for JGR Published on: |
| 2008 |
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Periodic modulations in thermospheric composition by solar wind high speed streams Crowley, G.; Reynolds, A.; Thayer, J.; Lei, J.; Paxton, L.; Christensen, A.; Zhang, Y.; Meier, R.; Strickland, D.; Published by: Geophysical Research Letters Published on: Jan-01-2008 YEAR: 2008 DOI: 10.1029/2008GL035745 |
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Rotating solar coronal holes and periodic modulation of the upper atmosphere Lei, Jiuhou; Thayer, Jeffrey; Forbes, Jeffrey; Sutton, Eric; Nerem, Steven; Published by: Geophysical Research Letters Published on: |
| 2007 |
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Zhang, M; Lin, W; Klein, S; Backmeister, J; Bony, S; Cederwall, R; Del Genio, A; Hack, J; Loeb, N; Lohmann, U; , others; Published by: Published on: |
| 2006 |
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The first long-duration incoherent scatter (IS) radar observations over Millstone Hill (42.6°N, 288.5°E) and EISCAT Svalbard radar (ESR, 78.15°N, 16.05°E) from October 4 to November 4, 2002 are compared with the newly updated version of the IRI model (IRI2001). The present study showed that: (1) For the peak parameters hmF2 and foF2, the IRI results are in good agreement with the observations over Millstone Hill, but there are large discrepancies over ESR. For the B parameters, the table option of IRI produces closer values to the observed ones with respect to the Gulyaeva’s option. (2) When the observed F2 peak parameters are used as input of IRI, the IRI model produces the reasonably results for the bottomside profiles during daytime over Millstone Hill, while it gives a lower bottomside density during nighttime over Millstone Hill and the whole day over ESR than what is observed experimentally. Moreover, IRI tends to overestimate the topside Ne profiles at both locations. (3) The Ti profiles of IRI can generally reproduce the observed values, whereas the IRI-produced Te profiles show large discrepancies with the observations. Overall comparative studies reveal that the agreement between the IRI predictions and experimental values is better over Millstone Hill than that over ESR. Lei, Jiuhou; Liu, Libo; Wan, Weixing; Zhang, Shun-Rong; Van Eyken, A.P.; Published by: Advances in Space Research Published on: YEAR: 2006 DOI: https://doi.org/10.1016/j.asr.2005.01.061 Ionosphere; incoherent scatter radar; Modelling and forecasting; International reference ionosphere |
| 2005 |
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Effects of neutral compositions on the ionospheric positive storms during the recovery phase Published by: Published on: |
| 2004 |
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Modeling Low Latitude Ion Densities During Magnetic Storms de La Beaujardiere, O; Retterer, J; Crowley, G; Basu, B; Welsh, J; Baker, C; Mellein, J; Valladares, C; Rich, F; Cooke, D; , others; Published by: Published on: |
| 1985 |
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LANDBOUWHOGESCHOOL, WAGENINGEN; GEBRUIK, GEGEVENS; OVERLEG, OVERNAME; DE PROJECTLEIDER, MET; Published by: Published on: |
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