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Found 24 entries in the Bibliography.

Showing entries from 1 through 24

2022

Measurement of the vertical atmospheric density profile from the X-ray Earth occultation of the Crab Nebula with Insight-HXMT

\textlessp\textgreater\textlessstrong class="journal-contentHeaderColor"\textgreaterAbstract.\textless/strong\textgreater X-ray Earth occultation sounding (XEOS) is an emerging method for measuring the neutral density in the lower thermosphere. In this paper, the X-ray Earth occultation (XEO) of the Crab Nebula is investigated using the Hard X-ray Modulation Telescope (Insight-HXMT). The pointing observation data on the 30 September 2018 recorded by the low-energy X-ray telescope (LE) of Insight-HXMT are selected and analysed. The extinction light curves and spectra during the X-ray Earth occultation process are extracted. A forward model for the XEO light curve is established, and the theoretical observational signal for light curve is predicted. The atmospheric density model is built with a scale factor to the commonly used Mass Spectrometer Incoherent Scatter Radar Extended model (MSIS) density profile within a certain altitude range. A Bayesian data analysis method is developed for the XEO light curve modelling and the atmospheric density retrieval. The posterior probability distribution of the model parameters is derived through the Markov chain–Monte Carlo (MCMC) algorithm with the NRLMSISE-00 model and the NRLMSIS 2.0 model as basis functions, and the respective best-fit density profiles are retrieved. It is found that in the altitude range of 105–200 km, the retrieved density profile is 88.8 \% of the density of NRLMSISE-00 and 109.7 \% of the density of NRLMSIS 2.0 by fitting the light curve in the energy range of 1.0–2.5 keV based on the XEOS method. In the altitude range of 95–125 km, the retrieved density profile is 81.0 \% of the density of NRLMSISE-00 and 92.3 \% of the density of NRLMSIS 2.0 by fitting the light curve in the energy range of 2.5–6.0 keV based on the XEOS method. In the altitude range of 85–110 km, the retrieved density profile is 87.7 \% of the density of NRLMSISE-00 and 101.4 \% of the density of NRLMSIS 2.0 by fitting the light curve in the energy range of 6.0–10.0 keV based on the XEOS method. Goodness-of-fit testing is carried out for the validation of the results. The measurements of density profiles are compared to the NRLMSISE-00 and NRLMSIS 2.0 model simulations and the previous retrieval results with NASA s Rossi X-ray Timing Explorer (RXTE) satellite. For further confirmation, we also compare the measured density profile to the ones by a standard spectrum retrieval method with an iterative inversion technique. Finally, we find that the retrieved density profile from Insight-HXMT based on the NRLMSISE-00 and NRLMSIS 2.0 models is qualitatively consistent with the previous retrieved results from RXTE. The results of light curve fitting and standard energy spectrum fitting are in good agreement. This research provides a method for the evaluation of the density profiles from MSIS model predictions. This study demonstrates that the XEOS from the X-ray astronomical satellite Insight-HXMT can provide an approach for the study of the upper atmosphere. The Insight-HXMT satellite can join the family of the XEOS. The Insight-HXMT satellite with other X-ray astronomical satellites in orbit can form a space observation network for XEOS in the future.\textless/p\textgreater

Yu, Daochun; Li, Haitao; Li, Baoquan; Ge, Mingyu; Tuo, Youli; Li, Xiaobo; Xue, Wangchen; Liu, Yaning; Wang, Aoying; Zhu, Yajun; Luo, Bingxian;

Published by: Atmospheric Measurement Techniques Published on: may

YEAR: 2022 DOI: 10.5194/amt-15-3141-2022

Responses of Mesosphere and Lower Thermosphere Temperature to the Geomagnetic Storm on 7–8 September 2017

The variations of neutral temperature in the mesosphere and lower thermosphere (MLT) region, during the 7–8 September 2017 intense geomagnetic storm, are studied using observations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. They are also studied using simulations by the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM). The neutral temperature data cover the altitudes from 80 km to 110 km between 83° N and 52° S latitude, obtained from both SABER observations and model simulations. The SABER observations reveal that temperature increases (the maximum increase is larger than 35 K at \textasciitilde108 km) and decreases (the maximum decrease is larger than 20 K at \textasciitilde105 km) during the geomagnetic storm. The storm effects penetrate down to \textasciitilde80 km. In observations, temperature variations corresponding to the storm show hemispheric asymmetry. That is, the variations of temperature are more prominent in the northern hemisphere than in the southern hemisphere. Conversely, the TIMEGCM outputs agree with the observations in general but overestimate the temperature increases and underestimate the temperature decreases at high and middle latitudes. Meanwhile, the simulations show stronger temperature decreases and weaker temperature increases than observations at low latitudes. After analyzing the temperature variations, we suggest that vertical winds may play an important role in inducing these significant variations of temperature in the MLT region.

Sun, Meng; Li, Zheng; Li, Jingyuan; Lu, Jianyong; Gu, Chunli; Zhu, Mengbin; Tian, Yufeng;

Published by: Universe Published on: feb

YEAR: 2022 DOI: 10.3390/universe8020096

geomagnetic storm; temperature; the mesosphere and lower thermosphere (MLT); TIMEGCM

Impact of Soft Electron Precipitation on the Thermospheric Neutral Mass Density During Geomagnetic Storms: GITM Simulations

In this study, the impact of improving soft (0.1–1 keV) electron precipitation on the F-region neutral mass density has been evaluated using the Global Ionosphere Thermosphere Model (GITM). Two types of electron energy spectra having the same total energy flux and average energy but different spectral shapes have been used to specify the electron precipitation in GITM. One is the Maxwellian spectrum and the other is from an empirical model, Auroral Spectrum and High-Latitude Electric field variabilitY (ASHLEY), which provides stronger (up to 2–3 orders of magnitude) soft electron precipitations than the Maxwellian spectrum. Data-model comparisons indicate that the storm-time orbital averaged neutral density can be increased by 10\%–40\% and is more consistent with the observation if the non-Maxwellian ASHLEY spectrum is used. This study reveals the importance of accurate soft electron precipitation specifications in the whole auroral zone to improving the F-region neutral mass density estimations.

Zhu, Qingyu; Deng, Yue; Sheng, Cheng; Anderson, Philip; Bukowski, Aaron;

Published by: Geophysical Research Letters Published on:

YEAR: 2022 DOI: 10.1029/2021GL097260

ASHLEY; GITM; neutral mass density; soft electron precipitation

Geomagnetic and Solar Dependencies of Midlatitude E-Region Irregularity Occurrence Rate: A Climatology Based on Wuhan VHF Radar Observations

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

Progresses and Challenges to specifying the IT system during weak storms

Deng, Yue; Heelis, Roderick; Paxton, Larry; Lyons, Larry; Nishimura, Toshi; Zhang, Shunrong; Bristow, Bill; Maute, Astrid; Sheng, Cheng; Zhu, Qingyu; , others;

Published by: Published on:

YEAR: 2021 DOI:

Interaction Between an EMSTID and an EPB in the EIA Crest Region Over China

Few observations investigated the interaction between an electrical medium-scale traveling ionospheric disturbance (EMSTID) and an equatorial plasma bubble (EPB). This paper presents another interaction between a southwestward propagating EMSTID and an eastward drifting EPB in the equatorial ionization anomaly (EIA) crest region of China. When the EMSTID and the EPB touched each other, several depletions of the EMSTID (EPB) showed the eastward (westward) velocity disturbances of the EPB (EMSTID) depletions. Besides, phase elongations of the EPB depletions contrarotated as the EMSTID propagated southwestward. However, of important finding is that the interaction of the EMSTID and the EPB could have polarized one depletion of the postmidnight EPB that should have become a fossilized bubble. Inside that polarized EPB depletion were meter-scale irregularities that caused activated radar echoes and enhanced ranged spread F (RSF). The interaction occurred in descending ionosphere and the lower density regions got filled up with an enhanced density plasma. We propose that the EMSTID and the EPB could have electrically coupled with each other, causing an enhanced polarization electric field (PEF) that polarized that EPB depletion; the E × B gradient drift instability (Kelley, 1989) could have caused the meter-scale irregularities when that enhanced PEF was imposed on that reactivated EPB depletion surrounded by that enhanced density plasma. This study provides observational evidence that how an electrical couple of EMSTID and EPB events can activate a postmidnight EPB depletion that should become a fossilized structure.

Sun, Longchang; Xu, JiYao; Zhu, Yajun; Xiong, Chao; Yuan, Wei; Wu, Kun; Hao, Yongqiang; Chen, Gang; Yan, Chunxiao; Wang, Zhihua; Zhao, Xiukuan; Luo, Xiaomin;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2021 DOI: 10.1029/2020JA029005

airglow; EIA crest region; Interaction between MSTID and EPB; Nighttime plasma density enhancement; Polarization of postmidnight EPB; VHF radar echoes and range spread F

2020

Impacts of Binning Methods on High-Latitude Electrodynamic Forcing: Static Versus Boundary-Oriented Binning Methods

An outstanding issue in the general circulation model simulations for Earth\textquoterights upper atmosphere is the inaccurate estimation of Joule heating, which could be associated with the inaccuracy of empirical models for high-latitude electrodynamic forcing. The binning methods used to develop those empirical models may contribute to the inaccuracy. Traditionally, data are binned through a static binning approach by using fixed geomagnetic coordinates, in which the dynamic nature of the forcing is not considered and therefore the forcing patterns may be significantly smeared. To avoid the smoothing issue, data can be binned according to some physically important boundaries in the high-latitude forcing, that is, through a boundary-oriented binning approach. In this study, we have investigated the sensitivity of high-latitude forcing patterns to the binning methods by applying both static and boundary-oriented binning approaches to the electron precipitation and electric potential data from the Defense Meteorological Satellite Program satellites. For this initial study, we have focused on the moderately strong and dominantly southward interplanetary magnetic field conditions. As compared with the static binning results, the boundary-oriented binning approach can provide a more confined and intense electron precipitation pattern. In addition, the magnitudes of the electric potential and electric field in the boundary-oriented binning results increase near the convection reversal boundary, leading to a ~11\% enhancement of the cross polar cap potential. The forcing patterns obtained from both binning approaches are used to drive the Global Ionosphere and Thermosphere Model to assess the impacts on Joule heating by using different binning patterns. It is found that the hemispheric-integrated Joule heating in the simulation driven by the boundary-oriented binning patterns is 18\% higher than that driven by the static binning patterns.

Zhu, Qingyu; Deng, Yue; Richmond, Arthur; Maute, Astrid; Chen, Yun-Ju; Hairston, Marc; Kilcommons, Liam; Knipp, Delores; Redmon, Robert; Mitchell, Elizabeth;

Published by: Journal of Geophysical Research: Space Physics Published on: 01/2020

YEAR: 2020 DOI: 10.1029/2019JA027270

Electric field; high latitude; Joule heating; particle precipitation

Statistical structure of nighttime O2 aurora from SABER and its dependence on geomagnetic and solar activities in winter

O 2 aurora is one kind of important molecular aurorae that is not fully understood yet. It is hard to be investigated due to the contamination by nightglow. In this work, we studied O 2

Gao, Hong; Xu, JiYao; Chen, Guang-Ming; Zhu, Yajun; Liu, Weijun; Wang, Chi;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2020 DOI: 10.1029/2020JA028302

Comparison of electron density and temperature from the CSES satellite with other space-borne and ground-based observations

In this paper we provide a comprehensive comparison of in situ electron density (Ne) and temperature (Te) measured by Langmuir probe (LAP) on board the China Seismo‐

Yan, Rui; Zhima, Zeren; Xiong, Chao; Shen, Xuhui; Huang, Jianping; Guan, Yibing; Zhu, Xinghong; Liu, Chao;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2020 DOI: 10.1029/2019JA027747

2017

A Novel Study on the Technique for Far Deriving Ultraviolet O/N Dayglow 2 from Thermospheric Emissions

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:

YEAR: 2017 DOI:

A Novel Study on the Technique for Deriving O/N 2 from Thermospheric Far Ultraviolet Dayglow Emissions

Zhang, Yongchao; Zhu, Jun; Yin, Huan; Zhang, Xiaoxin;

Published by: Published on:

YEAR: 2017 DOI:

Springer Proceedings in Physics3rd International Symposium of Space Optical Instruments and ApplicationsA Novel Study on the Technique for Deriving O/N2 from Thermospheric Far Ultraviolet Dayglow Emissions

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

2015

Characteristics of ionospheric north-south asymmetry and their relationship with irregularity

Using the empirical ionospheric model, the flux-tube integrated electron density and the ratio between the F-region Pedersen conductivity and the total E- and F-region Pedersen conductivity are calculated to investigate the characteristics of the ionospheric asymmetry after sunset during a solar cycle. Furthermore, two indices representing the asymmetric strength of the parameters respectively are defined to study its relationship with the occurrences of the irregularities during different seasons and with different solar activities. The results indicate that the electron density and the Pedersen conductivity ratio show north-south remarkable hemispheric asymmetry at different solar energy levels. The asymmetric strengths represent the dependence on seasons and solar activities, and their variation depending on seasons and solar activities show a negative correlation with the occurrences of the equatorial irregularities and also have a negative relation with the linear growth rate of the generalized Rayleigh-Taylor instability.

Luo, Weihua; Zhu, Zhengping; Lan, Jiaping; Li, Xuejing;

Published by: Wuhan University Journal of Natural Sciences Published on: 06/2015

YEAR: 2015 DOI: 10.1007/s11859-015-1088-7

asymmetry; Electron density; Ionosphere; irregularity; Pedersen conductivity

2014

Global distribution of atomic oxygen in the mesopause region as derived from SCIAMACHY O( ¹ S) green line measurements

A new data set of atomic oxygen abundance in the upper mesosphere and lower thermosphere is presented. The data are derived from the nighttime atomic oxygen green line limb emission measurements of the SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) instrument on the European Environmental Satellite. The temporal coverage is October 2002 until April 2012, and the latitudinal extent is 50\textdegreeS to 80\textdegreeN at 10 P.M. local time. This data set is compared to other satellite data sets, in particular to recently published data of SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and the Mass Spectrometer and Incoherent Scatter model. SCIAMACHY atomic oxygen peak abundances are typically 3\textendash6\texttimes10¹¹ mol/cm³ at the atomic oxygen maximum region, depending on latitude and season. These values are similar to previous values based on chemiluminescence measurements of the atomic oxygen three-body recombination reaction but at least 30\% lower than atomic oxygen abundances obtained from SABER.

Kaufmann, M.; Zhu, Y.; Ern, M.; Riese, M.;

Published by: Geophysical Research Letters Published on: 09/2014

YEAR: 2014 DOI: 10.1002/grl.v41.1710.1002/2014GL060574

atomic oxygen; energy balance; mesopause; remote sensing data; SCIAMACHY

2013

East-west differences in F -region electron density at midlatitude: Evidence from the Far East region

The global configuration of the geomagnetic field shows that the maximum east-west difference in geomagnetic declination of northern middle latitude lies in the US region (~32\textdegree), which produces the significant ionospheric east-west coast difference in terms of total electron content first revealed by Zhang et al. (2011). For verification, it is valuable to investigate this feature over the Far East area, which also shows significant geomagnetic declination east-west gradient but smaller (~15\textdegree) than that of the US. The current study provides evidence of the longitudinal change supporting the thermospheric zonal wind mechanism by examining the climatology of peak electron density (NmF2), electron density (Ne) of different altitudes in the Far East regions with a longitude separation of up to 40\textendash60\textdegree based on ground ionosonde and space-based measurements. Although the east-west difference (R_ew) over the Far East area displays a clear diurnal variation similar to the US feature, that is negative R_ew (West Ne \> East Ne) in the noon and positive at evening-night, the observational results reveal more differences including: (1) The noontime negative R_ew is most pronounced in April\textendashJune while in the US during February\textendashMarch. Thus, for the late spring and summer period negative R_ew over the Far East region is more significant than that of the US. (2) The positive R_ew at night is much less evident than in the US, especially without winter enhancement. (3) The magnitude of negative R_ew tends to enhance toward solar maximum while in the US showing anticorrelation with the solar activity. The altitude distribution of pronounced negative difference (300\textendash400 km) moves upward as the solar flux increases and hence produces the different solar activity dependence at different altitude. The result in the paper is not simply a comparison corresponding to the US results but raises some new features that are worth further studying and improve our current understanding of ionospheric longitude difference at midlatitude.

Zhao, Biqiang; Wang, Min; Wang, Yungang; Ren, Zhipeng; Yue, Xinan; Zhu, Jie; Wan, Weixing; Ning, Baiqi; Liu, Jing; Xiong, Bo;

Published by: Journal of Geophysical Research: Space Physics Published on: 01/2013

YEAR: 2013 DOI: 10.1029/2012JA018235

geomagnetic declination; longitudinal variation; midlatitude ionosphere

2012

Ensemble Modeling with Data Assimilation Models: A New Strategy for Space Weather Science, Specifications and Forecasts

Schunk, Robert; Scherliess, L; Eccles, JV; Gardner, LC; Sojka, JJ; Zhu, L; Pi, X; Mannucci, A; Wilson, BD; Komjathy, A; , others;