Bibliography
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Notice:
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Found 431 entries in the Bibliography.
Showing entries from 151 through 200
| 2016 |
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Schaefer, Robert; Paxton, Larry; Zhang, Yongliang; Published by: Published on: |
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Reidy, Jade; Fear, Robert; Lanchester, Betty; Whiter, Daniel; Kavanagh, Andrew; Paxton, Larry; Zhang, Yongliang; Published by: Published on: |
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Conjugate observations of the evolution of a long-duration polar cap arc in both hemispheres Xing, Zan-Yang; Zhang, Qing-He; Zhang, Yongliang; Sato, Natsuo; Published by: Published on: |
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Conjugate observations of the evolution of a long-duration polar cap arc in both hemispheres Xing, Zan-Yang; Zhang, Qing-He; Zhang, Yongliang; Sato, Natsuo; Published by: Published on: |
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Structure and Variability in the Ionosphere using DMSP/SSUSI and TIMED/GUVI Data Bruntz, Robert; Paxton, Larry; Kil, Hyosub; Schaefer, Robert; Zhang, Yongliang; Miller, Ethan; Published by: Published on: |
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Spatial and Temporal Variability of Atomic Oxygen in The Mesosphere And Lower Thermosphere Yee, Jeng-Hwa; , Russell; Mlynczak, Martin; Christensen, Andrew; Paxton, Larry; Zhang, Yongliang; Skinner, Wilbert; Woods, Thomas; Published by: Published on: |
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Huang, Chao-Song; Wilson, Gordon; Hairston, Marc; Zhang, Yongliang; Wang, Wenbin; Liu, Jing; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Effects of the equatorial ionosphere anomaly on the interhemispheric circulation in the thermosphere Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang; , Hsu; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Influence of Ion Outflow on the Diffuse Aurora Over Varying Levels of Solar EUV Forcing Varney, Roger; Zhang, Binzheng; Published by: Published on: |
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Solar flare impact on FUV based thermospheric O/N2 estimation Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: |
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Profiles of ionospheric storm-enhanced density during the 17 March 2015 great storm Liu, Jing; Wang, Wenbin; Burns, Alan; Yue, Xinan; Zhang, Shunrong; Zhang, Yongliang; Huang, Chaosong; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Profiles of ionospheric storm-enhanced density during the 17 March 2015 great storm Liu, Jing; Wang, Wenbin; Burns, Alan; Yue, Xinan; Zhang, Shunrong; Zhang, Yongliang; Huang, Chaosong; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Satellite FUV remote sensing and its impact to ionospheric modeling Zhang, Yongliang; Paxton, Larry; Bilitza, Dieter; Published by: Published on: |
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NASA Timed Guvi and Dmsp Ssusi Observations of the St. Patricks Day Storm of Paxton, Larry; Zhang, Yongliang; Kil, Hyosub; Mitchell, Elizabeth; Schaefer, Robert; Published by: 41st COSPAR Scientific Assembly Published on: |
| 2015 |
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In this paper, we report our findings on the correlation between the neutral temperature (around the mesopause) and thermospheric column density O/N2\ ratio, along with their response to geomagnetic storms above midlatitude of North America. A temperature/wind Doppler Na lidar, operating at Fort Collins, CO (41\textdegreeN, 105\textdegreeW), and later at Logan, UT (42\textdegreeN and 112\textdegreeW), observed significant temperature increases (temperature anomaly) above 95 km (as much as 55 K at 105 km altitude) during four coronal mass ejection-induced geomagnetic storms (April 2002, November 2004, May 2005, and October 2012). Coincident Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Spectrographic Imager observations indicate significant depletion in the thermospheric O/N2\ ratio at the lidar locations. These observations suggest that the local mesopause warming seen by the lidar is due to transport of the high-latitude joule and particle heated neutrals at the\ E\ and\ F\ layers to the midlatitude region. Yuan, T.; Zhang, Y.; Cai, X.; She, C.-Y.; Paxton, L.; Published by: Geophysical Research Letters Published on: 09/2015 YEAR: 2015 DOI: 10.1002/2015GL064860 |
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his paper presents the model simulation results of ionospheric E-region parameters during geomagnetic storm on May 2\textendash3, 2010. For this investigation we used the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) developed in West Department of IZMIRAN. GSM TIP model simulations were performed using empirical model of high-energy electron precipitation. The temporal and spatial distributions of the lower ionosphere parameters and minor neutral species are presented. GSM TIP model results of E-region parameters are compared with IRI-2012 model. The differences between model results are discussed. Bessarab, F.S.; Korenkov, Yu.N.; Klimenko, V.V.; Klimenko, M.V.; Zhang, Y.; Published by: Advances in Space Research Published on: 08/2014 YEAR: 2015 DOI: 10.1016/j.asr.2014.08.003 E-region; Electric field; geomagnetic storm; Ionospheric modeling; IRI-2012; Nitric oxide density |
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Explaining solar cycle effects on composition as it relates to the winter anomaly The solar cycle variation of\ F2\ region winter anomaly is related to solar cycle changes in the latitudinal winter-to-summer difference of O/N2. Here we use the National Center for Atmospheric Research\textendashGlobal Mean Model to develop a concept of why the latitudinal winter-to-summer difference of O/N2\ varies with solar cycle. The main driver for these seasonal changes in composition is vertical advection, which is expressed most simply in pressure coordinates. Meridional winds do not change over the solar cycle, so the vertical winds should also not change. The other component of vertical advection is the vertical gradient of composition. Is there any reason that this should change? At solar maximum vertical temperature gradients between 100 and 200 km altitude are strong, whereas they are weak at solar minimum. To maintain the same pressure, the weak vertical temperature gradients at solar minimum must be balanced by weak density gradients and the strong temperature gradients at solar maximum must be balanced by strong density gradients to obtain the same pressure profile. Changes in the vertical density gradients are species dependent: heavy species change more and light species change less than the average density change. Hence, vertical winds act on stronger O/N2\ gradients at solar maximum than they do at solar minimum, and a stronger winter-to-summer difference of O/N2\ occurs at solar maximum compared with solar minimum. Burns, A.; Solomon, S.; Wang, W.; Qian, L.; Zhang, Y.; Paxton, L.; Yue, X.; Thayer, J.; Liu, H.; Published by: Journal of Geophysical Research: Space Physics Published on: 07/2015 YEAR: 2015 DOI: 10.1002/2015JA021220 |
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Thermospheric densities observed by Challenging Minisatellite Payload and Gravity Recovery and Climate Experiment satellites during 2002\textendash2010 and the globally averaged thermospheric densities from 1967 to 2007 have been used to investigate latitudinal, longitudinal, and height dependences of the multiday oscillations of thermospheric densities. The data show that the main multiday oscillations in thermospheric densities are 27, 13.5, 9, and 7 day oscillations. The high-correlation coefficients between the density oscillations and theF10.7\ or\ Ap\ index indicate that these oscillations are externally driven. The 27 day density oscillation, being the strongest, is induced by variations in solar radiation, as well as recurrent geomagnetic activity that is the result of corotating interaction regions (CIRs) and high-speed solar wind streams of coronal hole origin. Density oscillations at periods of 13.5, 9, and 7 days at solar minimum and during the declining phase are stronger than those at solar maximum. These oscillations are mainly associated with recurrent geomagnetic activity due to coronal hole high-speed streams and CIRs. The multiday, periodic oscillations of thermospheric density exhibit strong latitudinal and longitudinal variations in the geomagnetic coordinate and oscillate synchronously at different heights. Oscillations with zonal wave number 0 oscillate globally, whereas those with nonzero wave numbers are strong at high geomagnetic latitudes, and hemispherically asymmetric. They are stronger in the Southern Hemisphere. The spectral distributions of thermospheric densities at different heights have almost the same latitude and longitude structures, but the spectral magnitudes increase with height. Xu, JiYao; Wang, Wenbin; Zhang, Shunrong; Liu, Xiao; Yuan, Wei; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2015 YEAR: 2015 DOI: 10.1002/2014JA020830 |
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Transpolar arc observation after solar wind entry into the high-latitude magnetosphere Recently, Cluster observations have revealed the presence of new regions of solar wind plasma entry at the high-latitude magnetospheric lobes tailward of the cusp region, mostly during periods of northward interplanetary magnetic field. In this study, observations from the Global Ultraviolet Imager (GUVI) experiment on board the TIMED spacecraft and Wideband Imaging Camera imager on board the IMAGE satellite are used to investigate a possible link between solar wind entry and the formation of transpolar arcs in the polar cap. We focus on a case when transpolar arc formation was observed twice right after the two solar wind entry events were detected by the Cluster spacecraft. In addition, GUVI and IMAGE observations show a simultaneous occurrence of auroral activity at low and high latitudes after the second entry event, possibly indicating a two-part structure of the continuous band of the transpolar arc. Mailyan, B.; Shi, Q.; Kullen, A.; Maggiolo, R.; Zhang, Y.; Fear, R.; Zong, Q.-G.; Fu, S; Gou, X.; Cao, X.; Yao, Z.; Sun, W.; Wei, Y.; Pu, Z; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2015 YEAR: 2015 DOI: 10.1002/2014JA020912 magnetosphere-ionosphere coupling; transpolar arcs; in situ measurements |
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Electron precipitation models in global magnetosphere simulations General methods for improving the specification of electron precipitation in global simulations are described and implemented in the Lyon-Fedder-Mobarry (LFM) global simulation model, and the quality of its predictions for precipitation is assessed. LFM\textquoterights existing diffuse and monoenergetic electron precipitation models are improved, and new models are developed for lower energy, broadband, and direct-entry cusp precipitation. The LFM simulation results for combined diffuse plus monoenergetic electron precipitation exhibit a quadratic increase in the hemispheric precipitation power as the intensity of solar wind driving increases, in contrast with the prediction from the OVATION Prime (OP) 2010 empirical precipitation model which increases linearly with driving intensity. Broadband precipitation power increases approximately linearly with driving intensity in both models. Comparisons of LFM and OP predictions with estimates of precipitating power derived from inversions of Polar satellite UVI images during a double substorm event (28\textendash29 March 1998) show that the LFM peak precipitating power is \>4\texttimes larger when using the improved precipitation model and most closely tracks the larger of three different inversion estimates. The OP prediction most closely tracks the double peaks in the intermediate inversion estimate, but it overestimates the precipitating power between the two substorms by a factor \>2 relative to all other estimates. LFMs polar pattern of precipitating energy flux tracks that of OP for broadband precipitation exhibits good correlation with duskside region 1 currents for monoenergetic energy flux that OP misses and fails to produce sufficient diffuse precipitation power in the prenoon quadrant that is present in OP. The prenoon deficiency is most likely due to the absence of drift kinetic physics in the LFM simulation. Zhang, B.; Lotko, W.; Brambles, O.; Wiltberger, M.; Lyon, J.; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2015 YEAR: 2015 DOI: 10.1002/2014JA020615 electron precipitation; global magnetosphere simulation; magnetosphere-ionosphere coupling |
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In the current work, temperature and wind data from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite during the years 2002\textendash2007 were used to describe the seasonal variations of the westward propagating 6.5-day planetary wave in the mesosphere and lower thermosphere (MLT). Thermospheric composition data from the TIMED satellite and ionospheric total electron content (TEC) from the International Global Navigation Satellite System (GNSS) Service were then employed to carry out two case studies on the effect of this dissipating wave on the thermosphere/ionosphere. In both cases, there were westward anomalies of ~ 30\textendash40 m s-1\ in zonal wind in the MLT region that were caused by momentum deposition of the 6.5-day wave, which had peak activity during equinoxes. The westward zonal wind anomalies led to extra poleward meridional flows in both hemispheres. Meanwhile, there were evident overall reductions of thermospheric column density O / N2\ ratio and ionospheric TEC with magnitudes of up to 16\textendash24 \% during these two strong 6.5-day wave events. Based on the temporal correlation between O / N2\ and TEC reductions, as well as the extra poleward meridional circulations associated with the 6.5-day waves, we conclude that the dissipative 6.5-day wave in the lower thermosphere can cause changes in the thermosphere/ionosphere via the mixing effect, similar to the quasi-two-day wave (QTDW) as predicted by Yue and Wang (2014). Gan, Q.; Yue, J.; Chang, L.; Wang, W.; Zhang, S.; Du, J.; Published by: Annales Geophysicae Published on: 01/2015 YEAR: 2015 DOI: 10.5194/angeo-33-913-2015 |
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Latitudinal and Solar Cycle Variability of Thermosphere Composition at the Solstices Qian, Liying; Burns, Alan; Wang, Wenbin; Solomon, Stanley; Zhang, Yongliang; Published by: Published on: |
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Zhang, Qian; Guan, Zhaoyong; Li, Minggang; Published by: Published on: |
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The climatological characteristics of UHF-band scintillations over the low-latitude region of China were investigated by analyzing the observations recorded at three stations of our Zhang, Hongbo; Liu, Yumei; Wu, Jian; Xu, T; Sheng, D; Published by: Published on: YEAR: 2015 DOI: 10.5194/angeo-33-93-2015 |
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Global Satellite Based Remote Sensing of the Ionosphere Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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UV Observations of Hemispheric Asymmetry Schaefer, Robert; Paxton, Larry; Wolven, Brian; Zhang, Yongliang; Romeo, Giuseppe; Published by: Published on: |
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Auroral dynamics and space weather Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Auroral precipitation models and space weather Newell, Patrick; Liou, Kan; Zhang, Yongliang; Sotirelis, Thomas; Mitchell, EJ; Mitchell, Elizabeth; Published by: Auroral dynamics and space weather Published on: |
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Structures in Polar Rain Auroras Zhang, Yongliang; Paxton, Larry; Kil, Hyosub; Published by: Auroral Dynamics and Space Weather Published on: |
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GPS phase scintillation at high latitudes during two geomagnetic storms Prikryl, Paul; Ghoddousi-Fard, Reza; Ruohoniemi, John; Thomas, Evan; Zhang, Y; Paxton, LJ; Published by: Auroral dynamics and space weather Published on: |
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Variations in the thermospheirc compositions Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Remote Sensing of the Magnetospheric Processes from Auroral Observations I Posters Zhang, Yongliang; Paxton, Larry; Wing, Simon; Published by: Published on: |
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GUVI and SSUSI Observations of the St. Patrick's Day Storms Paxton, Larry; Schaefer, Robert; Zhang, Yongliang; Bust, Gary; Kil, Hyosub; Published by: Published on: |
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Dynamics of the Dayside Aurora as Viewed from the South Pole McEwen, Donald; Sivjee, Gulamabas; Zhang, Yongliang; Published by: Published on: |
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Determining magnetotail reconnection location from polar rain energy dispersion Zhang, Yongliang; Wing, Simon; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: |
| 2014 |
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Geomagnetic control of equatorial plasma bubble activity modeled by the TIEGCM with Kp Describing the day-to-day variability of Equatorial Plasma Bubble (EPB) occurrence remains a significant challenge. In this study we use the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM), driven by solar (F10.7) and geomagnetic (Kp) activity indices, to study daily variations of the linear Rayleigh-Taylor (R-T) instability growth rate in relation to the measured scintillation strength at five longitudinally distributed stations. For locations characterized by generally favorable conditions for EPB growth (i.e., within the scintillation season for that location), we find that the TIEGCM is capable of identifying days when EPB development, determined from the calculated R-T growth rate, is suppressed as a result of geomagnetic activity. Both observed and modeled upward plasma drifts indicate that the prereversal enhancement scales linearly with Kp from several hours prior, from which it is concluded that even small Kpchanges cause significant variations in daily EPB growth. Carter, B.; Retterer, J.; Yizengaw, E.; Groves, K.; Caton, R.; McNamara, L.; Bridgwood, C.; Francis, M.; Terkildsen, M.; Norman, R.; Zhang, K.; Published by: Geophysical Research Letters Published on: 08/2014 YEAR: 2014 DOI: 10.1002/2014GL060953 |
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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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Storm-time behaviors of O/N2 and NO variations Algorithms have been developed to extract net nitric oxide (NO) radiances in the wavelength range of 172\textendash182\ nm from the dayside TIMED/GUVI spectrograph data and convert them to NO column density (100\textendash150\ km). The thermospheric O/N2 column density ratios (referenced from an altitude ~135\ km with a N2column density of 1017\ cm-2) are also obtained from the spectrograph data. The spatial resolution of the NO and O/N2 products along the GUVI orbit is 240\ km. The coincident O/N2 ratio and NO column density maps during a few geomagnetic storms reveal two major features: (1) Storm-time O/N2 depletion and NO enhancement extend from high to mid and low latitudes. They are anti-correlated on a global scale, (2) the NO enhancement covers a wider longitude and latitude region than O/N2 depletion on a local scale. The similarity between O/N2 depletion and NO enhancement on global scale is due to storm-time equatorward meridional wind that brings both O/N2 depleted and NO enhanced air from high to low latitudes. The altitude dependence of the storm-time meridional wind, different peaks altitudes of the local O/N2 and NO variations, and long life time of NO (one day or longer) may explain the different behaviors of O/N2 and NO on a local scale. Zhang, Y.; Paxton, L.J.; Morrison, D.; Marsh, D.; Kil, H.; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 07/2014 YEAR: 2014 DOI: 10.1016/j.jastp.2014.04.003 geomagnetic storm; Thermospheric nitric oxide; Thermospheric O/N2 ratio |
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OVATION Prime-2013: Extension of auroral precipitation model to higher disturbance levels OVATION Prime (OP) is an auroral precipitation model parameterized by solar wind driving. Distinguishing features of the model include an optimized solar wind-magnetosphere coupling function (dΦMP/dt) which predicts auroral power significantly better than\ Kp\ or other traditional parameters, the separation of aurora into categories (diffuse aurora, monoenergetic, broadband, and ion), the inclusion of seasonal variations, and separate parameter fits for each magnetic latitude (MLAT) \texttimes magnetic local time (MLT) bin, thus permitting each type of aurora and each location to have differing responses to season and solar wind input\textemdashas indeed they do. We here introduce OVATION Prime-2013, an upgrade to the 2010 version currently widely available. The most notable advantage of OP-2013 is that it uses UV images from the GUVI instrument on the satellite TIMED for high disturbance levels (dΦMP/dt \> 1.2 MWb/s which roughly corresponds toKp = 5+ or 6-). The range of validity is approximately 0 \< dΦMP/dt <= 3.0 MWb/s (Kp\ about 8+). Other upgrades include a reduced susceptibility to salt-and-pepper noise, and smoother interpolation across the postmidnight data gap. The model is tested against an independent data set of hemispheric auroral power from Polar UVI. Over the common range of validity of OP-2010 and OP-2013, the two models predict auroral power essentially identically, primarily because hemispheric power calculations were done in a way to minimize the impact of OP-2010s noise. To quantitatively demonstrate the improvement at high disturbance levels would require multiple very large substorms, which are rare, and insufficiently present in the limited data set of Polar UVI hemispheric power values. Nonetheless, although OP-2010 breaks down in a variety of ways above\ Kp = 5+ or 6-, OP-2013 continues to show the auroral oval advancing equatorward, at least to 55\textdegree MLAT or a bit less, and OP-2013 does not develop spurious large noise patches. We will also discuss the advantages and disadvantages of other precipitation models more generally, as no one model fits best all possible uses. Newell, P.; Liou, K.; Zhang, Y.; Sotirelis, T.; Paxton, L.; Mitchell, E.; Published by: Space Weather Published on: 06/2014 YEAR: 2014 DOI: 10.1002/swe.v12.610.1002/2014SW001056 |
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On the solar cycle variation of the winter anomaly Constellation Observing System for Meteorology, Ionosphere and Climate, Ionosonde, and Global Ultraviolet Imager data have been used to investigate the solar cycle changes in the winter anomaly (the winter anomaly is defined as the enhancement of the F2 peak electron density in the winter hemisphere over that in the summer hemisphere) in the last solar cycle. There is no winter anomaly in solar minimum, and an enhancement of about 50\% in winter over summer ones on the same day of the year at solar maximum. This solar cycle variation in the winter anomaly is primarily due to greater winter to summer differences of [O]/[N2] in solar maximum than in solar minimum, with a secondary contribution from the effects of temperature on the recombination coefficient between O+ and the molecular neutral gas. The greater winter increases in electron density in the Northern Hemisphere than in the Southern Hemisphere appear to be related to the greater annual variation of [O]/[N2] in the north than in the south. Burns, A.; Wang, W.; Qian, L.; Solomon, S.; Zhang, Y.; Paxton, L.; Yue, X.; Published by: Journal of Geophysical Research: Space Physics Published on: 06/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.610.1002/2013JA019552 |
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Gravity wave activity and dissipation in the height range from the low stratosphere to the low thermosphere (25\textendash115 km) covering latitudes between 50\textdegreeS and 50\textdegreeN are statistically studied by using 9-year (January 22, 2002\textendashDecember 31, 2010) SABER/TIMED temperature data. We propose a method to extract realistic gravity wave fluctuations from the temperature profiles and treat square temperature fluctuations as GW activity. Overall, the gravity wave activity generally increases with height. Near the equator (0\textdegree\textendash10\textdegree), the gravity wave activity shows a quasi-biennial variation in the stratosphere (below 40 km) while from 20\textdegree to 30\textdegree, it exhibits an annual variation below 40 km; in low latitudes (0\textdegree\textendash30\textdegree) between the upper stratosphere and the low thermosphere (40\textendash115 km), the gravity wave activity shows a semi-annual variation. In middle latitudes (40\textdegree\textendash50\textdegree), the gravity wave activity has a clear annual variation below 85 km. In addition, we observe a four-monthly variation with peaks occurring usually in April, August, December in the northern hemisphere and in February, June, October in the southern hemisphere, respectively, above 85 km in middle latitudes, which has been seldom reported in gravity wave activity. In order to study the dissipation of gravity wave propagation, we calculate the gravity wave dissipation ratio, which is defined as the ratio of the gravity wave growth scale height to the atmosphere density scale height. The height variation of the dissipation ratio indicates that strong gravity wave dissipation mainly concentrates in the three height regions: the stratosphere (30\textendash60 km), the mesopause (around 85 km) and the low thermosphere (above 100 km). Besides, gravity wave energy enhancement can be also observed in the background atmosphere. Shuai, Jing; Zhang, ShaoDong; Huang, ChunMing; YI, Fan; Huang, KaiMing; Gan, Quan; Gong, Yun; Published by: Science China Technological Sciences Published on: 05/2014 YEAR: 2014 DOI: 10.1007/s11431-014-5527-z climatology; dissipation; gravity wave; middle and high atmosphere; SABER; TIMED |
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Presented is an analysis of the occurrence of postsunset Equatorial Plasma Bubbles (EPBs) detected using a Global Positioning System (GPS) receiver at Vanimo. The three year data set shows that the EPB occurrence maximizes (minimizes) during the equinoxes (solstices), in good agreement with previous findings. The Vanimo ionosonde station is used with the GPS receiver in an analysis of the day-to-day EPB occurrence variability during the 2000 equinox period. A superposed epoch analysis (SEA) reveals that the altitude, and the change in altitude, of the F layer height is \~1 standard deviation (1σ) larger on the days for which EPBs were detected, compared to non-EPB days. These results are then compared to results from the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), which show strong similarities with the observations. The TIEGCM is used to calculate the flux-tube integrated Rayleigh-Taylor (R-T) instability linear growth rate. A SEA reveals that the modeled R-T growth rate is 1σ higher on average for EPB days compared to non-EPB days, and that the upward plasma drift is the most dominant contributor. It is further demonstrated that the TIEGCM\textquoterights success in describing the observed daily EPB variability during the scintillation season resides in the variations caused by geomagnetic activity (as parameterized by Kp) rather than solar EUV flux (as parameterized by F10.7). Geomagnetic activity varies the modeled high-latitude plasma convection and the associated Joule heating that affects the low-latitude F region dynamo, and consequently the equatorial upward plasma drift. Carter, B.; Yizengaw, E.; Retterer, J.; Francis, M.; Terkildsen, M.; Marshall, R.; Norman, R.; Zhang, K.; Published by: Journal of Geophysical Research: Space Physics Published on: 04/2014 YEAR: 2014 DOI: 10.1002/jgra.v119.410.1002/2013JA019570 |
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A specific imaging spectrometer based on a concentric off-axis dual reflector system is proposed, free of astigmatism and coma. The described imaging spectrometer consists of four spherical mirrors and a plane grating. The analytic theory of aberrations and the optical path-length concept are used to derive the astigmatism elimination and coma removal. It is shown that the astigmatism in these imaging spectrometers is eliminated by characterizing three angles, and the coma is corrected when unequal mirror radii are configured in collimating and condensing optics. The developed aberration principle is verified by comparing the performance of the astigmatism-eliminated spectrometer with the spectrometer which has neither astigmatism nor coma. Chen, Ting; Tang, Yi; Zhang, Li; Chang, Yue; Zheng, Cheng; Published by: Applied Optics Published on: 01/2014 YEAR: 2014 DOI: 10.1364/AO.53.000565 |
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The thermospheric O/N2 and NO products from TIMED/GUVI The Global Ultraviolet Imager (GUVI) on TIMED satellite detects FUV (~ 110-185nm) emissions from the thermosphere and ionosphere. The major emission features include HI (Lyman α Zhang, Yongliang; Paxton, Larry; Kil, Hyosub; Published by: 40th COSPAR Scientific Assembly Published on: |
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The relationship between solar wind entry processes and transpolar arc formation Mailyan, Bagrat; Shi, Quanqi; Maggiolo, Romain; Zong, Qiugang; Cao, Xin; Zhang, Yongliang; Yao, Zhonghua; Fu, SuiYan; Wei, Yong; Pu, Zuyin; Published by: Published on: |
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Investigation of the Tidal Signatures in the Thermosphere Using the TIMED/GUVI Data Kil, Hyosub; Paxton, Larry; Zhang, Yongliang; Kwak, Young-Sil; Lee, Woo; Published by: Published on: |
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Composition and the Winter Anomaly Burns, Alan; Wang, Wenbin; Qian, Liying; Solomon, Stanley; Zhang, Yongliang; Paxton, Larry; Thayer, Jeffrey; Published by: Published on: |
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Paxton, LJ; Schaefer, RK; Zhang, Y; Bust, GS; Kil, H; Published by: Published on: |
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Simultaneous observations of Birkeland currents by the constellation of Iridium satellites and N2 Lyman\textendashBirge\textendashHopfield (LBH) auroral emissions measured by the Global Ultraviolet Imager (GUVI) onboard the Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics (TIMED) satellite are used to establish relationships between large-scale upward field-aligned currents and electron precipitation during stable current configurations. The electron precipitation was inferred from GUVI data using a statistical relationship between LBH intensity and electron energy flux. LBH emissions with \>5\% contribution from protons, identified by Lyman-alpha intensity, were excluded from the analysis. The Birkeland currents were derived with a spatial resolution of 3\textdegree in latitude and 2 h in local time. For southward interplanetary magnetic field (IMF), the electron precipitation occurred primarily within and near large-scale upward currents. The correspondence was less evident for northward IMF, presumably because the spatial variability is large compared to the areas of interest so that the number of events identified is smaller and the derived statistical distributions are less reliable. At dusk, the correlation between upward current and precipitation was especially high, where a larger fraction of the electron precipitation is accelerated downward by a field-aligned potential difference. Unaccelerated electron precipitation dominated in the morning sector, presumably induced by scattering of eastward-drifting energetic electrons into the loss cone through interaction with whistler-mode waves (diffuse precipitation) rather than by field-aligned acceleration. In the upward Region 1 on the dayside, where electron precipitation is almost exclusively due to field-aligned acceleration, a quadratic relationship between current density and electron energy flux was observed, implying a linear current\textendashvoltage relationship in this region. Current density and electron energy flux in the regions of the large-scale upward currents from pre-midnight through dawn to noon are essentially uncorrelated consistent with a dominance of diffuse electron precipitation to the incident energy flux. Korth, Haje; Zhang, Yongliang; Anderson, Brian; Sotirelis, Thomas; Waters, Colin; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2014 DOI: 10.1002/2014JA019961 Birkeland Currents; Auroral Emissions; electron precipitation; Current-Precipitation Relationship; Current-Voltage Relationship |