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Found 22 entries in the Bibliography.
Showing entries from 1 through 22
| 2022 |
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Correlations Between Giant Undulations and Plasmapause Configurations In this letter, we report the correlations between giant undulations (GUs) and plasmapause (PP) configurations based on GUs images and corresponding PP crossings of satellites between 2005 and 2019. Typically, GUs occur when the plasmasphere is eroded to form a thin and sharp PP during the storm main phase and early recovery phase. The thicknesses of the PP are usually comparable with the azimuthal wavelengths of the GUs and are smaller than the radial amplitudes of the GUs. The amplitudes and wavelengths are quasi-proportional to the thicknesses of the PP and are inversely quasi-proportional to the ion density gradients around the PP. The radial centers of GUs are typically aligned with the PP surfaces and their radial geocentric locations show positive correlations for different geomagnetic storms. These results would provide both physical insights and model constrains on the magnetosphere-plasmasphere-ionosphere energy coupling and the generation mechanisms of the GUs and plasmapause surface waves. Zhou, Yi-Jia; He, Fei; Yao, Zhong-Hua; Wei, Yong; Zhang, Xiao-Xin; Zhang, Yong-Liang; Published by: Geophysical Research Letters Published on: YEAR: 2022 DOI: 10.1029/2022GL098627 Ionosphere; Giant Undulations; plasmapause; plasmapause surface waves |
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By using Wuhan VHF radar, we show the morphological features of E-region field-aligned irregularity (FAI) occurrence at Wuhan during 2015–2020. Statistical results present that E-region FAI occurrence reaches a maximum after sunset in summer season. According to Doppler spectrum features, type-2 irregularity is predominantly observed at Wuhan. In addition, we observed a remarkable correlation between E-region FAI occurrence and geomagnetic activity, which includes periods of positive correlation and negative correlation depending on different geomagnetic conditions. The strong negative correlation also exists between E-region FAI occurrence and solar activity. In our observed results, we find that E-region FAI occurrence shows a strong linkage with local sporadic E (ES) layer. A quantitative analysis of linear theory of plasma instability in the E-region at midlatitudes is also presented in our study. The calculated results of linear growth rate indicate the importance of plasma density gradient of local ES layer and field-line-integrated Pedersen conductivity on the generation of E-region FAI. The geomagnetic and solar variations of E-region FAI occurrence are also discussed in this study, which show a dependence on the geomagnetic and solar variations of both meteor rate and medium-scale traveling ionospheric disturbance occurrence. Liu, Yi; Zhou, Chen; Xu, Tong; Deng, Zhongxin; Du, Zhitao; Lan, Ting; Tang, Qiong; Zhu, Yunzhou; Wang, Zhuangkai; Zhao, Zhengyu; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2021JA029597 |
| 2021 |
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By using the data of GNSS (Global Navigation Satellite System) observation from Crustal Movement Observation Network of China (CMONOC), ionospheric electron density (IED) distributions reconstructed by using computerized ionospheric tomography (CIT) technique are used to investigate the ionospheric storm effects over Wuhan region during 17 March and 22 June 2015 geomagnetic storm periods. F-region critical frequency (foF2) at Wuhan ionosonde station shows an obvious decrease during recovery phase of the St. Patrick’s Day geomagnetic storm. Moreover, tomographic results present that the decrease in electron density begins at 12:00 UT on 17 March during the storm main phase. Also, foF2 shows a long-lasting negative storm effect during the recovery phase of the 22 June 2015 geomagnetic storm. Electron density chromatography presents the evident decrease during the storm day in accordance with the ionosonde observation. These ionospheric negative storm effects are probably associated with changes of chemical composition, PPEF and DDEF from high latitudes. Feng, Jian; Zhou, Yufeng; Zhou, Yan; Gao, Shuaihe; Zhou, Chen; Tang, Qiong; Liu, Yi; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.008 Ionospheric electron density distributions; ionospheric storm effects; Multiplication algebraic reconstruction technique |
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By using the data of GNSS (Global Navigation Satellite System) observation from Crustal Movement Observation Network of China (CMONOC), ionospheric electron density (IED) distributions reconstructed by using computerized ionospheric tomography (CIT) technique are used to investigate the ionospheric storm effects over Wuhan region during 17 March and 22 June 2015 geomagnetic storm periods. F-region critical frequency (foF2) at Wuhan ionosonde station shows an obvious decrease during recovery phase of the St. Patrick’s Day geomagnetic storm. Moreover, tomographic results present that the decrease in electron density begins at 12:00 UT on 17 March during the storm main phase. Also, foF2 shows a long-lasting negative storm effect during the recovery phase of the 22 June 2015 geomagnetic storm. Electron density chromatography presents the evident decrease during the storm day in accordance with the ionosonde observation. These ionospheric negative storm effects are probably associated with changes of chemical composition, PPEF and DDEF from high latitudes. Feng, Jian; Zhou, Yufeng; Zhou, Yan; Gao, Shuaihe; Zhou, Chen; Tang, Qiong; Liu, Yi; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.008 Ionospheric electron density distributions; ionospheric storm effects; Multiplication algebraic reconstruction technique |
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By using the data of GNSS (Global Navigation Satellite System) observation from Crustal Movement Observation Network of China (CMONOC), ionospheric electron density (IED) distributions reconstructed by using computerized ionospheric tomography (CIT) technique are used to investigate the ionospheric storm effects over Wuhan region during 17 March and 22 June 2015 geomagnetic storm periods. F-region critical frequency (foF2) at Wuhan ionosonde station shows an obvious decrease during recovery phase of the St. Patrick’s Day geomagnetic storm. Moreover, tomographic results present that the decrease in electron density begins at 12:00 UT on 17 March during the storm main phase. Also, foF2 shows a long-lasting negative storm effect during the recovery phase of the 22 June 2015 geomagnetic storm. Electron density chromatography presents the evident decrease during the storm day in accordance with the ionosonde observation. These ionospheric negative storm effects are probably associated with changes of chemical composition, PPEF and DDEF from high latitudes. Feng, Jian; Zhou, Yufeng; Zhou, Yan; Gao, Shuaihe; Zhou, Chen; Tang, Qiong; Liu, Yi; Published by: Advances in Space Research Published on: jan YEAR: 2021 DOI: 10.1016/j.asr.2020.10.008 Ionospheric electron density distributions; ionospheric storm effects; Multiplication algebraic reconstruction technique |
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We present an investigation of the F-region electron temperature to an intense geomagnetic storm that occurred on 5 August 2011. The investigation is based on the incoherent scatter radar measurements at Arecibo Observatory, Puerto Rico (18.3°N, 66.7°W). The electron temperature exhibits a rapid and intensive enhancement after the commencement of the geomagnetic storm. The electron temperature increases by ∼800 K within an hour, which is seldomly reported at Arecibo. At the same time, a depletion of the electron density is also observed. The daytime perturbations of electron density and temperature are anticorrelated with the correlation coefficient, which is −0.88 and −0.91 on the day and the following day of the geomagnetic storm, respectively. According to the Global Ultraviolet Imager measurements, the ratio of atomic oxygen to molecular nitrogen concentration () decreases dramatically during the storm. Our analysis suggests that the enhancement of the electron temperature is due to the depletion of the electron density, which is likely associated with the decrease of . The reduction of maybe caused by a prompt upward plasma motion after the commencement of the geomagnetic storm. Lv, Xiedong; Gong, Yun; Zhang, ShaoDong; Zhou, Qihou; Ma, Zheng; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029836 Arecibo; F-region electron temperature; geomagnetic storm; incoherent scatter radar |
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The Ionosphere at Middle and Low Latitudes Under Geomagnetic Quiet Time of December 2019 The ionospheric electron density shows remarkable day-to-day variability due to solar radiance, geomagnetic activity and lower atmosphere forcing. In this report, we investigated the ionospheric variations at middle and low latitudes during a period under geomagnetic quiet time (Kpmax = 1.7) from November 30 to December 8, 2019. During the quiescent period, the ionosphere is not undisturbed as expected in the Asian-Australian and the American sectors. Total electron content (TEC) has multiple prominent enhancements at middle and low latitudes in the two sectors, and TEC depletions also occur repeatedly in the Asian-Australian sector. The low-latitude electric fields vary significantly, which is likely to be modulated by the notably changing tides in the mesosphere and lower thermosphere region. It is worth noting that the variations of TEC and the electric fields are not consistent in the two sectors, particularly on December 4–6. Further investigation reveals that the increase in TEC depends on altitude. The TEC enhancements are mainly contributed by the altitude below 500 km in both two sectors, which indirectly reflects that the driving sources may come from the lower atmosphere. Especially, a mid-latitude band structure continuously appears at all local times in the North American sector on December 6–8, which is also mainly contributed by the altitude below 500 km. Kuai, Jiawei; Li, Qiaoling; Zhong, Jiahao; Zhou, Xu; Liu, Libo; Yoshikawa, Akimasa; Hu, Lianhuan; Xie, Haiyong; Huang, Chaoyan; Yu, Xumin; Wan, Xin; Cui, Jun; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028964 low-latitude electric fields; the ionosphere variations in solar minimum; the ionospheric day-to-day variations; the ionospheric disturbance; the ionospheric variations; topside ionosphere |
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Inhibition of F3 Layer at Low Latitude Station Sanya During Recovery Phase of Geomagnetic Storms A special F2 layer stratification structure named F3 layer occurs frequently in equatorial and low latitude ionosphere during summer daytime. In this study, a new phenomenon of decreasing occurrence of the F3 layer, and narrowing differences of virtual heights between the F3 and F2 layers in the recovery phase of geomagnetic storms is reported. We named this phenomenon as the inhibition of F3 layer event (IFLE). Using the ionosonde observations during summer of 2012–2015 at Sanya (18.3°N, 109.6°E, dip latitude 12.6°N), we found that IFLE occurred during 14 geomagnetic storms (−127 nT ≤ Dstmin ≤ −22 nT), which was accompanied by the thinning and lowering bottom ionosphere, and decreasing the crest-to-trough ratio of total electron content (TEC). Together with the ion drift data measured by Defense Meteorological Satellite Program F18, we suggest that the IFLE is mainly caused by the westward disturbance dynamo electric field (DDEF; downward drift velocity), taking disadvantage of the formation of the F3 layer. The observed decrease in the crest-to-trough ratio of TEC also indicates that the westward DDEF should prompt IFLE by providing less plasma from the equatorial region to the low latitude. Hence, IFLE then can be a good indicator to show how the magnetosphere-ionospheric coupling process affects the low and equatorial ionosphere. Notably, the results also indicate that even a very weak geomagnetic storm can generate significant changes in ionospheric state at low latitude. Jin, Yuyan; Zhao, Biqiang; Li, Guozhu; Li, Zishen; Zhou, Xu; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029850 F3 layer; Geomagnetic storms; westward disturbance dynamo electric field |
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Ionospheric day-to-day variability is essential for understanding the space environment, while it is still challenging to properly quantify and forecast. In the present work, the day-to-day variability of F2 layer peak electron densities (NmF2) is examined from both observational and modeling perspectives. Ionosonde data over Wuhan station (30.5°N, 114.5°E; 19.3°N magnetic latitude) are compared with simulations from the specific dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (SD-WACCM-X) and the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) in 2009 and 2012. Both SD-WACCM-X and TIEGCM are driven by the realistic 3 h geomagnetic index and daily solar input, and the former includes self-consistently solved physics and chemistry in the lower atmosphere. The correlation coefficient between observations and SD-WACCM-X simulations is much larger than that of the TIEGCM simulations, especially during dusk in 2009 and nighttime in 2012. Both the observed and SD-WACCM-X simulated day-to-day variability of NmF2 reveal a similar day-night dependence in 2012 that increases large during the nighttime and decreases during the daytime, and shows favorable consistency of daytime variability in 2009. Both the observations and SD-WACCM-X simulations also display semiannual variations in nighttime NmF2 variability, although the month with maximum variability is slightly different. However, TIEGCM does not reproduce the day-night dependence or the semiannual variations well. The results emphasize the necessity for realistic lower atmospheric perturbations to characterize ionospheric day-to-day variability. This work also provides a validation of the SD-WACCM-X in terms of ionospheric day-to-day variability. Zhou, Xu; Yue, Xinan; Liu, Han-Li; Lu, Xian; Wu, Haonan; Zhao, Xiukuan; He, Jianhui; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028589 Ionosphere; day-to-day variability; ionosonde; NmF2; TIEGCM; WACCM-X |
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Development of a NIR camera for the BALBOA mission More than 500 years ago, when Vasco Núñez de Balboa traveled to the New World, he must not have realized that his legacy would not only be cast in currency, but branded for space Zhou, Xiaoyan; Rafol, Don; Michell, Robert; Hampton, Don; Geach, Christopher; Published by: 43rd COSPAR Scientific Assembly. Held 28 January-4 February Published on: |
| 2020 |
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A case study of isolated auroral spots based on DMSP data This study employed ultraviolet images and particle data to investigate isolated auroral spots away from the Earth\textquoterights auroral oval. Data from SSUSI (Special Sensor Ultraviolet Spectrographic Imager) and SSJ (Special Sensor J) mounted on the DMSP (Defence Meteorological Satellite Program) spacecraft were examined. The isolated auroral spots were observed by DMSP F16/SSUSI and F17/SSUSI on 29 May 2010 during the recovery phase of a moderate geomagnetic storm with a minimum SYM-H index of -70 nT. The auroral spots were observed between 18:00\textendash21:00 MLT and corotated with the Earth, but stayed almost at the same magnetic latitude (MLAT) of -60\textdegree. It is found that the isolated auroral spots were produced mainly by energetic ring current ions at energies above ~10\ keV. The enhancement in the electron flux with energy below ~200\ eV was also observed for the isolated auroral spots. The MLAT of the electron flux was nearly 2\textdegreehigher than that for the precipitating ions. Zhou, Su; Chen, Yuqing; Zhang, Jin; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 01/2020 YEAR: 2020 DOI: 10.1016/j.jastp.2019.105176 Isolated auroral spots; Proton aurora; Subauroral electron precipitation |
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Comparison of Reference Heights of O/N 2 and ∑O/N 2 Based on GUVI Dayside Limb Measurement We define a new thermospheric concept, the reference heights of O/N2, referring to a series of thermospheric heights corresponding to the fixed ratios of O to N2 number density. Here, based on Global Ultraviolet Imager (GUVI) limb measurement, we compare O/N2 column density ratio (∑O/N2) and the reference heights of O/N2. We choose the transition height of O and N2 (transition height hereafter), a special reference height at which O number density is equal to N2 number density, to verify the connection with ∑O/N2 during geomagnetically quiet periods. It is found that transition height and ∑O/N2 have noticeable negative correlation with correlation coefficient of -0.887. An empirical model of transition height (O/N2 model hereafter) is established based on nonlinear least-squares-fitting method. The considerable correlation (greater than 0.96), insignificant errors (less than 4\%) and the great influencing weight of ∑O/N2 to reference heights indicate the validity of O/N2 model and the existence of quantitative relation between ∑O/N2 and transition height. Besides, it is verified that the similar quantitative relation also exists between ∑O/N2 and reference heights of other O/N2 values. Namely, using the O/N2 model coefficients, we can roughly get the whole altitude profiles of O/N2 within 6\% precision for any given ∑O/N2. Yu, Tingting; Ren, Zhipeng; Yu, You; Yue, Xinan; Zhou, Xu; Wan, Weixing; Published by: Space Weather Published on: 01/2020 YEAR: 2020 DOI: 10.1029/2019SW002391 |
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Comparison of reference heights of O/N2 and∑ O/N2 based on GUVI dayside limb measurement Yu, Tingting; Ren, Zhipeng; Yu, You; Yue, Xinan; Zhou, Xu; Wan, Weixing; Published by: Space weather Published on: |
| 2019 |
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Isolated Auroral Spots Observed by DMSP/SSUSI This work reports auroral spots event observed by the SSUSI instruments on board the DMSP spacecraft between 22 and 23 July 2009 during the recovery phase of a moderate magnetic storm. The spots were observed between 18:00 and 02:00 magnetic local time and stayed at ~60\textdegree magnetic latitude. They lasted for ~10 hr and corotated with ~64\% of the Earth\textquoterights rotational speed. In situ observations indicate that the isolated auroral spots were produced by energetic ions at energies between 10 and 240 keV, with significantly anisotropic electron (30\textendash300 keV) precipitations. It is expected that the energetic ions originate from the ring current and can be scattered by the EMIC waves through cyclotron resonance. The energetic electrons can be precipitated by the nonresonant interaction between the electrons and EMIC waves, which is suggested by previous works. Zhou, Su; Luan, Xiaoli; Pierrard, Viviane; Han, Desheng; Published by: Journal of Geophysical Research: Space Physics Published on: 10/2019 YEAR: 2019 DOI: 10.1029/2019JA026853 |
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Effect of MgF2 deposition temperature on Al mirrors in vacuum ultraviolet High reflectivity of mirrors is very important for many applications in the vacuum ultraviolet, such as for space observation, synchrotron radiation. This paper focuses on the substrate temperature\textquoterights effect on the performance of Al mirrors when depositing the upper MgF2 layer. Al films are deposited on the substrates at room temperature by thermal evaporation, and a 5 nm MgF2 film is deposited on Al coating at room temperature immediately. Heating the substrate to various temperatures ranging from room temperature to 350\textdegree, then a 20 nm MgF2 film is deposited on the surface of Al/MgF2. The thickness of each layer is characterized using grazing incidence x-ray reflectivity. The reflectivity of sample is measured at the incident angle of 5\textdegree in the wavelength range of 105~130 nm. The reflectivity of all samples fabricated at above room temperature is higher than the sample at room temperature below 115nm. The reflectivity of mirror at 350\textdegree temperature is lower than other mirrors, and the reflectivity of the samples at 300\textdegree and 200\textdegree is similar. There are more black dots on the surface of mirror at 350\textdegree than 300\textdegree, and no black dot on the surface of mirror at 200\textdegree. The measured results using surface profiler show that the black dots are small holes that increase the roughness of mirror and reduce the reflectivity. So the best temperature for depositing the upper MgF2 layer is in 200~300\textdegree to obtain high reflectivity of Al mirrors in vacuum ultraviolet. Wang, Fengli; Li, Shuangying; Zhang, Zhuangzhuang; Wang, Zhanshan; Zhou, Hongjun; Huo, Tonglin; Published by: Published on: YEAR: 2019 DOI: 10.1117/12.2540004 |
| 2018 |
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Scientific Ballooning for Imaging Earth's Aurora under the Sun Zhou, Xiaoyan; Rafol, SB; Hampton, Donald; He, Yutao; Lummerzheim, Dirk; Michell, Robert; Published by: Published on: |
| 2016 |
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Solar activity dependence of nightside aurora in winter conditions The dependence of the nightside (21:00\textendash03:00 MLT; magnetic local time) auroral energy flux on solar activity was quantitatively studied for winter/dark and geomagnetically quiet conditions. Using data combined from Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager and Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations, we separated the effects of geomagnetic activity from those of solar flux on the nightside auroral precipitation. The results showed that the nightside auroral power was reduced by ~42\% in solar maximum (F10.7 = 200 sfu; solar flux unit 1 sfu = 10-22 W m-2 Hz-1) with respect to that under solar minimum (F10.7 = 70 sfu) for the\ Kp = 1 condition, and this change rate became less (~21\%) for the\ Kp = 3 condition. In addition, the solar cycle dependence of nightside auroral power was similar with that from both the premidnight (21:00\textendash23:00 MLT) and postmidnight (01:00\textendash03:00 MLT) sectors. These results indicated that as the ionospheric ionization increases with the enhanced auroral and geomagnetic activities, the solar activity dependences of nightside auroral power become weaker, at least under geomagnetically quiet conditions. Zhou, Su; Luan, Xiaoli; Dou, Xiankang; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2016 YEAR: 2016 DOI: 10.1002/2015JA021865 auroral conjugate effects; auroral geomagnetic activity variation; auroral imaging scaling; auroral solar cycle variation |
| 2015 |
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The August 2011 URSI World Day campaign: Initial results During a 10-day URSI World Day observational campaign beginning on August 1, 2011, an isolated, major geomagnetic storm occurred. On August 5,\ Kp\ reached values of 8-and\ Dst\ dropped to -113\ nT. The occurrence of this isolated storm in the middle of a 10-day URSI World Day campaign provides and unprecedented opportunity to observe the coupling of solar wind energy into the magnetosphere and to evaluate the varied effects that occur in the coupled magnetosphere\textendashionosphere\textendashthermosphere system. Dramatic changes in the ionosphere are seen at every one of the active radar stations, extending from Greenland down to equatorial Peru in the American sector and at middle latitudes in Ukraine. Data from TIMED and THEMIS are shown to support initial interpretations of the observations, where we focus on processes in the middle latitude afternoon sector during main phase, and the formation of a dense equatorial ionosphere during storm recovery. The combined measurements strongly suggest that the changes in ionospheric conditions observed after the main storm phase can be attributed in large part to changes in the stormtime thermosphere. This is through the generation of disturbance dynamo winds and also global neutral composition changes that either reduce or enhance plasma densities in a manner that depends mainly upon latitude. Unlike larger storms with possibly more sustained forcing, this storm exhibits minimal effects of persistent meridional stormtime wind drag, and little penetration of solar wind electric potentials to low latitudes. It is, therefore, an outstanding example of an impulsive event that exhibits longer-term effects through modification of the background atmosphere. Immel, Thomas; Liu, Guiping; England, Scott; Goncharenko, Larisa; Erickson, Philip; Lyashenko, Mykhaylo; Milla, Marco; Chau, Jorge; Frey, Harald; Mende, Stephen; Zhou, Qihou; Stromme, Anja; Paxton, Larry; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 11/2015 YEAR: 2015 DOI: 10.1016/j.jastp.2015.09.005 |
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Solar Activity Dependence of Night Side Aurora in Winter/Dark Conditions Luan, Xiaoli; Zhou, Su; Dou, Xiankang; Published by: Published on: |
| 2004 |
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Magnetotail behavior during storm time “sawtooth injections” Lui, ATY; Hori, T; Ohtani, S; Zhang, Y; Zhou, XY; Henderson, MG; Mukai, T; Hayakawa, H; Mende, SB; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2003 |
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We have developed a lidar to study the temperature structure of the nighttime mesopause region over the Arecibo Observatory (18.35N, 66.75W) by measuring the lineshape of the Friedman, Jonathan; Tepley, Craig; Raizada, Shikha; Zhou, Qihou; Hedin, Jonas; Delgado, Rub\; Published by: Journal of atmospheric and solar-terrestrial physics Published on: |
| 2002 |
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Talaat, ER; DeMajistre, R; Paxton, L; Yee, J; Goncharenko, LP; Crowley, G; Azeem, S; Shpynev, B; Zhou, Q; Kil, H; , others; Published by: Published on: |
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