Bibliography
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Found 431 entries in the Bibliography.
Showing entries from 101 through 150
| 2018 |
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Statistical Relations Between Field-Aligned Currents and Precipitating Electron Energy Flux Measurements of field-aligned currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment are combined with measurements of far ultraviolet emissions from the Global Ultraviolet Imager on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite to examine the correlation between parallel currents and auroral electron energy flux. The energy flux is derived from the far ultraviolet emissions in the N2 Lyman-Birge-Hopfield bands. We find that energy flux correlates with field-aligned currents in both upward and downward current regions. The correlations vary with magnetic local time with the strongest dependences near magnetic midnight. The data are binned and averaged to construct a model of precipitating particle energy flux as a function of field-aligned current and magnetic local time. With Active Magnetosphere and Planetary Electrodynamics Response Experiment data as input, the model yields accurate estimates of the hemispheric power input from precipitating particles. Robinson, R.; Zhang, Y.; Anderson, B.; Zanetti, L.; Korth, H.; Fitzmaurice, A.; Published by: Geophysical Research Letters Published on: 08/2018 YEAR: 2018 DOI: 10.1029/2018GL078718 |
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A large number (~1,000) of coincident auroral far ultraviolet (FUV) and ground-based ionosonde observations are compared. This is the largest study to date of coincident satellite-based FUV and ground-based observations of the auroral E region. FUV radiance values from the NASA Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics Global Ultraviolet Imager and the Defense Meteorological Satellite Program F16 and F18 Special Sensor Ultraviolet Spectrographic Imager are included in the study. A method is described for deriving auroral ionospheric E region maximum electron density (NmE) and height of maximum electron density (hmE) from N2 Lyman-Birge-Hopfield radiances given in two channels using lookup tables generated with the Boltzmann 3-Constituent (B3C) auroral particle transport and optical emission model. Our rules for scaling (i.e., extracting ionospheric parameters from) ionograms to obtain auroral NmE and hmE are also described. Statistical and visual comparison methods establish statistical consistency and agreement between the two methods for observing auroral NmE, but not auroral hmE. It is expected that auroral nonuniformity will cause the two NmE methods to give inconsistent results, but we have not attempted to quantify this effect in terms of more basic principles, and our results show that the two types of NmE observations are well correlated and statistically symmetrical, meaning that there is no overall bias and no scale-dependent bias. Knight, H.; Galkin, I.; Reinisch, B.; Zhang, Y.; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2018 YEAR: 2018 DOI: 10.1029/2017JA024822 |
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Storm-time variations of atomic nitrogen 149.3 nm emission Net radiances of atomic nitrogen emission line (N-149.3 nm) from the thermosphere are extracted from the FUV spectra observed by TIMED/GUVI on dayside at sunlit latitudes. During geomagnetic storms, the N-149.3 nm intensity is clearly enhanced in the locations where O/N2 depletion and nitric oxide (NO) enhancement are observed. The N-149.3 nm intensity is linearly and tightly correlated with N2 LBHS (140\textendash150 nm) radiance with a fixed LBHS/149.3 nm ratio of \~4.5, suggesting that dissociation of N2 is the dominant source of the N-149.3 nm emission. In the regions without storm disturbances, the N-149.3 nm intensities are closely correlated with solar EUV flux. Zhang, Y.; Paxton, L.J.; Morrison, D.; Schaefer, B.; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 04/2018 YEAR: 2018 DOI: 10.1016/j.jastp.2018.01.023 |
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Conjugate Observations of the Evolution of Polar Cap Arcs in Both Hemispheres We report results from the analysis of a case of conjugate polar cap arcs (PCAs) observed on 5 February 2006 in the Northern Hemisphere by the ground-based Yellow River Station all-sky imager (Svalbard) and in both hemispheres by the space-based DMSP/SSUSI and TIMED/GUVI instruments. The PCA\textquoterights motion in dawn-dusk direction shows a clear dependence on the interplanetary magnetic field (IMF) By component and presents a clear asymmetry between Southern and Northern Hemispheres, that is, formed on the duskside and moving from dusk to dawn in the Northern Hemisphere and vice versa in the other hemisphere. The already existing PCAs\textquoteright motion is influenced by the changes in the IMF By with a time delay of ~70\ min. We also observed strong flow shears/reversals around the PCAs in both hemispheres. The precipitating particles observed in the ionosphere associated with PCAs showed properties of boundary layer plasma. Based on these observations, we might reasonably expect that the topological changes in the magnetotail can produce a strip of closed field lines and local processes would set up conditions for the formation and evolution of PCAs. Xing, Zanyang; Zhang, Qinghe; Han, Desheng; Zhang, Yongliang; Sato, Natsuo; Zhang, Shunrong; Hu, Zejun; Wang, Yong; Ma, Yuzhang; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2018 YEAR: 2018 DOI: 10.1002/2017JA024272 |
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Conjugate Observations of the Evolution of Polar Cap Arcs in Both Hemispheres We report results from the analysis of a case of conjugate polar cap arcs (PCAs) observed on 5 February 2006 in the Northern Hemisphere by the ground-based Yellow River Station all-sky imager (Svalbard) and in both hemispheres by the space-based DMSP/SSUSI and TIMED/GUVI instruments. The PCA\textquoterights motion in dawn-dusk direction shows a clear dependence on the interplanetary magnetic field (IMF) By component and presents a clear asymmetry between Southern and Northern Hemispheres, that is, formed on the duskside and moving from dusk to dawn in the Northern Hemisphere and vice versa in the other hemisphere. The already existing PCAs\textquoteright motion is influenced by the changes in the IMF By with a time delay of ~70\ min. We also observed strong flow shears/reversals around the PCAs in both hemispheres. The precipitating particles observed in the ionosphere associated with PCAs showed properties of boundary layer plasma. Based on these observations, we might reasonably expect that the topological changes in the magnetotail can produce a strip of closed field lines and local processes would set up conditions for the formation and evolution of PCAs. Xing, Zanyang; Zhang, Qinghe; Han, Desheng; Zhang, Yongliang; Sato, Natsuo; Zhang, Shunrong; Hu, Zejun; Wang, Yong; Ma, Yuzhang; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2018 YEAR: 2018 DOI: 10.1002/2017JA024272 |
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Conjugate Observations of the Evolution of Polar Cap Arcs in Both Hemispheres We report results from the analysis of a case of conjugate polar cap arcs (PCAs) observed on 5 February 2006 in the Northern Hemisphere by the ground-based Yellow River Station all-sky imager (Svalbard) and in both hemispheres by the space-based DMSP/SSUSI and TIMED/GUVI instruments. The PCA\textquoterights motion in dawn-dusk direction shows a clear dependence on the interplanetary magnetic field (IMF) By component and presents a clear asymmetry between Southern and Northern Hemispheres, that is, formed on the duskside and moving from dusk to dawn in the Northern Hemisphere and vice versa in the other hemisphere. The already existing PCAs\textquoteright motion is influenced by the changes in the IMF By with a time delay of ~70\ min. We also observed strong flow shears/reversals around the PCAs in both hemispheres. The precipitating particles observed in the ionosphere associated with PCAs showed properties of boundary layer plasma. Based on these observations, we might reasonably expect that the topological changes in the magnetotail can produce a strip of closed field lines and local processes would set up conditions for the formation and evolution of PCAs. Xing, Zanyang; Zhang, Qinghe; Han, Desheng; Zhang, Yongliang; Sato, Natsuo; Zhang, Shunrong; Hu, Zejun; Wang, Yong; Ma, Yuzhang; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2018 YEAR: 2018 DOI: 10.1002/2017JA024272 |
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Initial Observations with the Ionospheric Photometer on the Chinese Feng Yun 3D Satellite Mao, Tian; Fu, Liping; Wang, Yungang; Jiang, Fang; Hu, Xiuqing; Zhang, Xiaoxin; Sun, Lingfeng; Published by: Published on: |
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Nighttime enhancement of midlatitude ionosphere and its connection to the plasmasphere Hao, Yongqiang; Zhang, Donghe; Xiao, Zuo; Li, Quanhan; Published by: 42nd COSPAR Scientific Assembly Published on: |
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A large number (~1,000) of coincident auroral far ultraviolet (FUV) and ground-based ionosonde observations are compared. This is the largest study to date of coincident satellite-based FUV and ground-based observations of the auroral E region. FUV radiance values from the NASA Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics Global Ultraviolet Imager and the Defense Meteorological Satellite Program F16 and F18 Special Sensor Ultraviolet Spectrographic Imager are included in the study. Knight, HK; Galkin, IA; Reinisch, BW; Zhang, Y; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2018 DOI: 10.1029/2017JA024822 |
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Zhang, Yongliang; Paxton, Larry; Lu, Gang; Yee, Jeng-Hwa; Published by: Published on: |
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Solar EUV flux proxy using multifrequency solar radio flux Zhang, Yongliang; Paxton, Larry; Published by: Space Weather Published on: |
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Interhemispheric survey of polar cap aurora Reidy, Jade; Fear, RC; Whiter, DK; Lanchester, B; Kavanagh, Andrew; Milan, SE; Carter, JA; Paxton, LJ; Zhang, Y; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Zhang, Yongliang; Paxton, Larry; Jones, James; Published by: Space Weather Published on: |
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SSUSI and SSUSI-Lite: Providing space situational awareness and support for over 25 years Paxton, Larry; Schaefer, Robert; Zhang, Yongliang; Kil, Hyosub; Hicks, John; Published by: Johns Hopkins APL Technical Digest Published on: |
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Observations and Modeling of Atomic/Molecular Composition in the Thermosphere Solomon, Stanley; Eastes, Richard; McClintock, William; Paxton, Larry; Zhang, Yongliang; Published by: Published on: |
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Deng, Y; Chen, Z; , Wang; Sheng, Cheng; , Jin; Zhang, Yongliang; Paxton, Larry; Deng, Xiaohua; Huang, Chung-Ming; Published by: Published on: |
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Thermospheric Neutral Composition Response to External Forcings Fedrizzi, Mariangel; Karol, Svetlana; Yudin, Valery; Fuller-Rowell, Timothy; Codrescu, Mihail; Olsen, Jack; Paxton, Larry; Zhang, Yongliang; Published by: Published on: |
| 2017 |
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The Storm Time Evolution of the Ionospheric Disturbance Plasma Drifts In this paper, we use the C/NOFS and ROCSAT-1 satellites observations to analyze the storm time evolution of the disturbance plasma drifts in a 24\ h local time scale during three magnetic storms driven by long-lasting southward IMF Bz. The disturbance plasma drifts during the three storms present some common features in the periods dominated by the disturbance dynamo. The newly formed disturbance plasma drifts are upward and westward at night, and downward and eastward during daytime. Further, the disturbance plasma drifts are gradually evolved to present significant local time shifts. The westward disturbance plasma drifts gradually migrate from nightside to dayside. Meanwhile, the dayside downward disturbance plasma drifts become enhanced and shift to later local time. The local time shifts in disturbance plasma drifts are suggested to be mainly attributed to the evolution of the disturbance winds. The strong disturbance winds arisen around midnight can constantly corotate to later local time. At dayside the westward and equatorward disturbance winds can drive the F region dynamo to produce the poleward and westward polarization electric fields (or the westward and downward disturbance drifts). The present results indicate that the disturbance winds corotated to later local time can affect the local time features of the disturbance dynamo electric field. Zhang, Ruilong; Liu, Libo; Le, Huijun; Chen, Yiding; Kuai, Jiawei; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2017 YEAR: 2017 DOI: 10.1002/2017JA024637 |
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The non--storm time corrugated upper thermosphere: What is beyond MSIS? Observations in the recent decade have revealed many thermospheric density corrugations/perturbations under nonstorm conditions (Kp \< 2). They are generally not captured by empirical models like Mass Spectrometer Incoherent Scatter (MSIS) but are operationally important for long-term orbital evolution of Low Earth Orbiting satellites and theoretically for coupling processes in the atmosphere-ionosphere system. We review these density corrugations by classifying them into three types which are driven respectively by the lower atmosphere, ionosphere, and solar wind/magnetosphere. Model capabilities in capturing these features are discussed. A summary table of these corrugations is included to provide a quick guide on their magnitudes, occurring latitude, local time, and season. Liu, Huixin; Thayer, Jeff; Zhang, Yongliang; Lee, Woo; Published by: Space Weather Published on: 06/2017 YEAR: 2017 DOI: 10.1002/swe.v15.610.1002/2017SW001618 |
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Geospace system responses to the St. Patrick's Day storms in 2013 and 2015 This special collection includes 31 research papers investigating geospace system responses to the geomagnetic storms during the St. Patrick\textquoterights Days of 17 March 2013 and 2015. It covers observation, data assimilation, and modeling aspects of the storm time phenomena and their associated physical processes. The ionosphere and thermosphere as well as their coupling to the magnetosphere are clearly the main subject areas addressed. This collection provides a comprehensive picture of the geospace response to these two major storms. We provide some highlights of these studies in six specific areas: (1) global and magnetosphere/plasmasphere perspectives, (2) high-latitude responses, (3) subauroral and midlatitude processes, (4) effects of prompt penetration electric fields and disturbance dynamo electric fields, (5) effects of neutral dynamics and perturbation, and (6) storm effects on plasma bubbles and irregularities. We also discuss areas of future challenges and the ways to move forward in advancing our understanding of the geospace storm time behavior and space weather effects. Zhang, Shun-Rong; Zhang, Yongliang; Wang, Wenbin; Verkhoglyadova, Olga; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2017 YEAR: 2017 DOI: 10.1002/2017JA024232 |
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Geospace system responses to the St. Patrick's Day storms in 2013 and 2015 This special collection includes 31 research papers investigating geospace system responses to the geomagnetic storms during the St. Patrick\textquoterights Days of 17 March 2013 and 2015. It covers observation, data assimilation, and modeling aspects of the storm time phenomena and their associated physical processes. The ionosphere and thermosphere as well as their coupling to the magnetosphere are clearly the main subject areas addressed. This collection provides a comprehensive picture of the geospace response to these two major storms. We provide some highlights of these studies in six specific areas: (1) global and magnetosphere/plasmasphere perspectives, (2) high-latitude responses, (3) subauroral and midlatitude processes, (4) effects of prompt penetration electric fields and disturbance dynamo electric fields, (5) effects of neutral dynamics and perturbation, and (6) storm effects on plasma bubbles and irregularities. We also discuss areas of future challenges and the ways to move forward in advancing our understanding of the geospace storm time behavior and space weather effects. Zhang, Shun-Rong; Zhang, Yongliang; Wang, Wenbin; Verkhoglyadova, Olga; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2017 YEAR: 2017 DOI: 10.1002/2017JA024232 |
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The quasi-6~day wave and its interactions with solar tides Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) temperature measurements between 20 and 110\ km altitude and \textpm50\textdegree latitude during 2002\textendash2015 are employed to reveal the climatological characteristics of the quasi-6\ day wave (Q6DW) and evidence for secondary waves (SW) resulting from its nonlinear interactions with solar tides. The mean period is 6.14d with a standard deviation (σ) of 0.26d. Multiyear-mean maximum amplitudes (3\textendash5\ K, σ \~ 4\ K) occur within the mesosphere-lower thermosphere (MLT) region between 75 and 100\ km during day of year (DOY) 60\textendash120 and 180\textendash300 in the Northern Hemisphere and DOY 0\textendash110 and 200\textendash300 in the Southern Hemisphere. Amplitudes approach 10\ K in some individual years. At midlatitudes downward phase progression exists from 100 to 35\ km with a mean vertical wavelength of about 70\ km. Signatures of SW due to Q6DW-tide interactions appear at distinct space-based zonal wave numbers (ks) in temperature spectra constructed in the reference frame of the TIMED orbit. However, SW produced by several different tides can collapse onto the same (ks) value, rendering their relative contributions indistinguishable. Nevertheless, by determining the space-based wave amplitudes attached to these values of (ks), and demonstrating that they are a large fraction of the interacting wave amplitudes, we conclude that the aggregate contributions of the SW to the overall wave spectrum must be significant. Because the SW have periods, zonal wave numbers, and latitude-height structures different from those of the primary waves, they contribute additionally to the complexity of the wave spectrum. This complexity is communicated to the ionosphere through collisions or through the dynamo electric fields generated by the total wave spectrum. Forbes, Jeffrey; Zhang, Xiaoli; Published by: Journal of Geophysical Research: Space Physics Published on: 03/2017 YEAR: 2017 DOI: 10.1002/2017JA023954 |
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Far ultraviolet instrument technology The far ultraviolet (FUV) spectral range (from about 115 nm to 180 nm) is one of the most useful spectral regions for characterizing the upper atmosphere (thermosphere and ionosphere). The principal advantages are that there are FUV signatures of the major constituents of the upper atmosphere as well as the signatures of the high-latitude energy inputs. Because of the absorption by thermospheric O2, the FUV signatures are seen against a \textquotedblleftblack\textquotedblright background, i.e., one that is not affected by ground albedo or clouds and, as a consequence, can make useful observations of the aurora during the day or when the Moon is above the horizon. In this paper we discuss the uses of FUV remote sensing, summarize the various techniques, and discuss the technological challenges. Our focus is on a particular type of FUV instrument, the scanning imaging spectrograph or SIS: an instrument exemplified by the Defense Meteorological Satellite Program Special Sensor Ultraviolet Imager and Thermosphere Ionosphere Mesosphere Energetics and Dynamics Global Ultraviolet Imager. The SIS combines spatial imaging of the disk with limb profiles as well as spectral information at each point in the scan. Paxton, Larry; Schaefer, Robert; Zhang, Yongliang; Kil, Hyosub; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/jgra.v122.210.1002/2016JA023578 |
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A new auroral boundary determination algorithm based on observations from TIMED/GUVI and DMSP/SSUSI An automatic auroral boundary determination algorithm is proposed in this study based on the partial auroral oval images from the Global Ultraviolet Imager (GUVI) aboard the Thermosphere\textendashIonosphere-Mesosphere Energetics and Dynamics satellite and the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) aboard the Defense Meteorological Satellite Program (DMSP F16). This algorithm based on the fuzzy local information C-means clustering segmentation can be used to extract the auroral oval poleward and equatorward boundaries from merged images with filled gaps from both GUVI and SSUSI. Both extracted poleward and equatorward boundary locations are used to fit the global shape of the auroral oval with a off-center quasi-elliptical fitting technique. Comparison of the extracted auroral oval boundaries with those identified from the DMSP SSJ observations demonstrates that this new proposed algorithm can reliably be used to construct the global configuration of auroral ovals under different geomagnetic activities at different local times. The statistical errors of magnetic latitudes of the fitted auroral oval boundaries were generally less than 3\textdegree at 2 sigma and indicate that the the fitted boundaries agree better with b2e and b5e than b1e and b6 boundaries. This proposed algorithm provides us with a useful tool to extract the global shape and position of the auroral oval from the partial auroral images. Ding, Guang-Xing; He, Fei; Zhang, Xiao-Xin; Chen, Bo; Published by: Journal of Geophysical Research: Space Physics Published on: 01/2017 YEAR: 2017 DOI: 10.1002/jgra.v122.210.1002/2016JA023295 |
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Reidy, JA; Fear, RC; Whiter, DK; Lanchester, BS; Kavanagh, AJ; Paxton, LJ; Zhang, Y; Lester, Mark; Published by: Journal of Geophysical Research: Space Physics Published on: |
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of TIMED/GUVI to derive the O/N2 [14], and the data of TIMED/GUVI which are recorded by as the data of Polar BEAR/AIRS and TIMED/GUVI. This method uses the intensity ratio of OI Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin; Published by: Published on: |
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of TIMED/GUVI to derive the O/N2 [14], and the data of TIMED/GUVI which are recorded by as the data of Polar BEAR/AIRS and TIMED/GUVI. This method uses the intensity ratio of OI Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin; Published by: Published on: |
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The quasi-6 day wave and its interactions with solar tides Q6DW in the lower thermosphere; the [O]/[N 2 ] variations were measured by Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) Forbes, Jeffrey; Zhang, Xiaoli; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2017 DOI: 10.1002/2017JA023954 |
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A New More Accurate Calibration for TIMED/GUVI Schaefer, RK; Aiello, J; Wolven, BC; Paxton, LJ; Romeo, G; Zhang, Y; Published by: Published on: |
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TIMED/GUVI Observations of Aurora, Ionosphere, Thermosphere and Solar EUV Variations Zhang, Yongliang; Paxton, Larry; Schaefer, Robert; Published by: Published on: |
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The causes of thermospheric composition variations during and after major geomagnetic storms Wang, Wenbin; Burns, Alan; Zhang, Yongliang; Liu, Jing; Published by: Published on: |
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Monitoring Geospace Variations Through Remote Sensing III Posters Zhang, Yongliang; Paxton, Larry; Sibeck, David; Schaefer, Robert; Published by: Published on: |
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Oberheide, Jens; Krier, Christopher; Gan, Quan; Nischal, Nirmal; Zhang, Yongliang; Chang, Loren; Published by: Published on: |
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Burns, Alan; Wang, Wenbin; Zhang, Yongliang; Qian, Liying; Published by: Published on: |
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Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin; Published by: Published on: |
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Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin; Published by: Published on: |
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Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin; Published by: Published on: YEAR: 2017 DOI: 10.1007/978-3-319-49184-410.1007/978-3-319-49184-4_29 |
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Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin; Published by: Published on: YEAR: 2017 DOI: 10.1007/978-3-319-49184-410.1007/978-3-319-49184-4_29 |
| 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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Polar cap arcs: Sun-aligned or cusp-aligned? Zhang, Y.; Paxton, L.J.; Zhang, Qinghe; Xing, Zanyang; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 08/2016 YEAR: 2016 DOI: 10.1016/j.jastp.2016.06.001 Polar cap arcs Cusp Reconnection Kelvin Helmholtz Instability Velocity shear Field aligned current |
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Polar cap arcs: Sun-aligned or cusp-aligned? Zhang, Y.; Paxton, L.J.; Zhang, Qinghe; Xing, Zanyang; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 08/2016 YEAR: 2016 DOI: 10.1016/j.jastp.2016.06.001 Polar cap arcs Cusp Reconnection Kelvin Helmholtz Instability Velocity shear Field aligned current |
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Disturbance dynamo is an important dynamic process during magnetic storms. However, very few direct observations of dynamo-induced plasma drifts and ion composition changes in the equatorial ionosphere are available. In this study, we use measurements of the Defense Meteorological Satellite Program (DMSP) satellites to identify the characteristics of the disturbance dynamo process in the topside equatorial ionosphere near dawn during the magnetic storm with a minimum Dst of -223 nT on 17 March 2015. Data from four DMSP satellites with equatorial crossings at 0245, 0430, 0630, and 0730 LT are available for this case. The dynamo process was first observed in the postmidnight sector 3\textendash4.7 h after the beginning of the storm main phase and lasted for 31 h, covering the second storm intensification and the initial 20 h of the recovery phase. The dynamo vertical ion drift was upward (up to 150\textendash200 m s-1) in the postmidnight sector and downward (up to ~80 m s-1) in the early morning sector. The dynamo zonal ion drift was westward at these locations and reached ~100 m s-1. The dynamo process caused large enhancements of the O+ concentration (the ratio of the oxygen ion density to the total ion density) at the altitude of 840 km near dawn. The O+ concentration increased from below 60\% during the prestorm period to 80\textendash90\% during the storm time. More specifically, the O+ density was increased, and the H+ density was decreased. The variations of the O+ concentration were well correlated with the vertical ion drift. Huang, Chao-Song; Wilson, Gordon; Hairston, Marc; Zhang, Yongliang; Wang, Wenbin; Liu, Jing; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2016 YEAR: 2016 DOI: 10.1002/2016JA023072 |
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Longitudinal variations of thermospheric composition at the solstices O/N2, measured by the Global Ultraviolet Imager on board the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite, has large longitudinal variations at the solstices, which are simulated well in upper atmosphere general circulation models. These longitudinal variations are caused by the displacement of the Earth\textquoterights magnetic poles from the geographic ones. The location of a magnetic pole affects the latitude at which the winds, driven by heating in summer, converge in the subauroral region of the winter hemisphere. In the magnetic pole\textquoterights longitude sector, this convergence occurs at relatively low latitudes, which results in the maximum values of O/N2 also occurring at relatively low latitudes. These latitudes have a relatively small solar zenith angle, contributing to a strong winter anomaly. In the zonally opposite longitude sector, maximum values of O/N2 occur at relatively high latitudes because the summer-to-winter wind convergence also occurs at relatively high latitudes. These high latitudes have a relatively large solar zenith angle, so ionization is weak, contributing to a weak winter anomaly. Therefore, the displacement between the magnetic and geographic poles not only results in a strong longitudinal variation of O/N2 but also results in a strong longitudinal variation of the ionosphere winter anomaly. Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2016 YEAR: 2016 DOI: 10.1002/2016JA022898 |
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Solar cycle variations of thermospheric composition at the solstices We examine the solar cycle variability of thermospheric composition (O/N2) at the solstices. Our observational and modeling studies show that the summer-to-winter latitudinal gradient of O/N2 is small at solar minimum but large at solar maximum; O/N2 is larger at solar maximum than at solar minimum on a global-mean basis; there is a seasonal asymmetry in the solar cycle variability of O/N2, with large solar cycle variations in the winter hemisphere and small solar cycle variations in the summer hemisphere. Model analysis reveals that vertical winds decrease the temperature-driven solar cycle variability in the vertical gradient of O/N2 in the summer hemisphere but increase it in the winter hemisphere; consequently, the vertical gradient of O/N2 does not change much in the summer hemisphere over a solar cycle, but it increases greatly from solar minimum to solar maximum in the winter hemisphere; this seasonal asymmetry in the solar cycle variability in the vertical gradient of O/N2 causes a seasonal asymmetry in the vertical advection of O/N2, with small solar cycle variability in the summer hemisphere and large variability in the winter hemisphere, which in turn drives the observed seasonal asymmetry in the solar cycle variability of O/N2. Since the equatorial ionization anomaly suppresses upwelling in the summer hemisphere and strengthens downwelling in the winter hemisphere through plasma-neutral collisional heating and ion drag, locations and relative magnitudes of the equatorial ionization anomaly crests and their solar cycle variabilities can significantly impact the summer-to-winter gradients of O/N2 and their solar cycle variability. Qian, Liying; Burns, Alan; Solomon, Stanley; Wang, Wenbin; Zhang, Yongliang; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2016 YEAR: 2016 DOI: 10.1002/2016JA022390 |
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We investigate the interhemispheric circulation at the solstices, in order to understand why O/N2\ is larger in the northern hemisphere winter than in the southern hemisphere winter. Our studies reveal that the equatorial ionosphere anomaly (EIA) significantly impacts the summer-to-winter wind through plasma-neutral collisional heating, which changes the summer-to-winter pressure gradient, and ion drag. Consequently, the wind is suppressed in the summer hemisphere as it encounters the EIA but accelerates after it passes the EIA in the winter hemisphere. The wind then converges due to an opposing pressure gradient driven by Joule heating in auroral regions and produces large O/N2\ at subauroral latitudes. This EIA effect is stronger near the December solstice than near the June solstice because the ionospheric annual asymmetry creates greater meridional wind convergence near the December solstice, which in turn produces larger O/N2\ in the northern hemisphere winter than in the southern hemisphere winter. Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang; Hsu, V.; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2016 YEAR: 2016 DOI: 10.1002/2015JA022169 Equatorial ionization anomaly; interhemispheric circulation; ionosphere winter anomaly; plasma-neutral collisional heating; thermosphere composition; vertical advection |
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With the development of modern technology, especially the development of information technology at high speed, the ultraviolet early warning system plays an increasingly important role. In the modern warfare, how to detect the threats earlier, prevent and reduce the attack of precision-guided missile has become a new challenge. Because the ultraviolet warning technology has high environmental adaptability, the low false alarm rate, small volume and other advantages, in the military field applications it has been developed rapidly. According to current application demands for solar blind ultraviolet detection and warning, this paper proposes a reconnaissance and early-warning optical system, which covers solar blind ultraviolet (250nm-280nm) and dual field. This structure takes advantage of a narrow field of view and long focal length optical system to achieve the target object detection, uses wide-field and short focal length optical system to achieve early warning of the target object. It makes use of an ultraviolet beam-splitter to achieve the separation of two optical systems. According to the detector and the corresponding application needs of two visual field of the optical system, the calculation and optical system design were completed. After the design, the MTF of the two optical system is more than 0.8@39lp/mm. A single pixel energy concentration is greater than 80\%. Wang, Wen-cong; Jin, Dong-dong; Shao, Fei; Hu, Hui-jun; Shi, Yu-feng; Song, Juan; Zhang, Yu-tu; Yong, Liu; Published by: Published on: YEAR: 2016 DOI: 10.1117/12.2236440 |
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With the development of modern technology, especially the development of information technology at high speed, the ultraviolet early warning system plays an increasingly important Wang, Wen-cong; Jin, Dong-dong; Shao, Fei; Hu, Hui-jun; Shi, Yu-feng; Song, Juan; Zhang, Yu-tu; Yong, Liu; Published by: Published on: YEAR: 2016 DOI: 10.1117/12.2236440 |
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Middle-latitude ionospheric irregularities and scintillation during geomagnetic storms Pi, Xiaoqing; Mannucci, Anthony; Valant-Spaight, Bonnie; Viereck, Rodney; Zhang, Yongliang; Published by: Published on: |
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Far ultraviolet imaging of the aurora Paxton, Larry; Zhang, Yongliang; Published by: Published on: |
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Zhang, Yongliang; Paxton, Larry; Fuller-Rowell, Timothy; Jones, James; Published by: Published on: |