Bibliography

Statistical Analysis of Throat Aurora Using Long Term DMSP/SSUSI Observation

Throat aurora is believed to be associated with magnetopause indentations and has direct implications on magnetopause reconnection. In this study, for the first time, we use Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations over ∼14 years to characterize the throat aurora occurrence, latitudinal extent, seasonal, and its solar cycle dependence. We identified 386 throat aurora cases during the different passes of the satellite over the northern hemisphere. The latitudinal extent of these throat aurorae are estimated and are divided into small, medium, and large categories. The small and medium latitudinal extent throat aurorae account for about 91\% of the total cases. The throat aurorae are found to occur most frequently in the post-noon hours. The throat aurorae were also observed more frequently during winter, likely due to summer-winter asymmetry in the ionospheric conductance. The occurrence of the throat aurora is also found to be anti-correlated with the solar cycle, likely because low solar activity gives good chances for sporadic reconnection that favors the occurrence of throat aurora. The dependence on interplanetary magnetic field reveals positive Bx favoring the occurrence of throat aurora. It also shows positive Bx (negative By) supports pre-noon (post-noon) occurrence. The difference in the trend and average values of background interplanetary magnetic field conditions with the throat aurora confirms the favorable conditions for the occurrence of throat aurora.

Selvakumaran, R.; Han, De-Sheng; Gokani, Sneha; Zhang, Y.;

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

YEAR: 2021     DOI: 10.1029/2021JA029164

auroral oval; magnetopause indentations; throat aurora

Non-storm time thermospheric O/N2 depletion and NO enhancement

It is well known that significant thermospheric O/N2 depletion and nitric oxide (NO) enhancement is a storm-time phenomenon. However, TIMED/GUVI observed events with a

Zhang, Yongliang; Paxton, Larry; Wang, Wenbin; Huang, Chaosong;

Published by:       Published on:

YEAR: 2021     DOI:

Ionosphere and Thermosphere Coupling at Mid- and Subauroral Latitudes

This chapter addresses the ionosphere–thermosphere (I/T) coupling phenomena. We define I/T coupling as the dynamical interaction between plasma and neutral particles in the upper atmosphere. This interaction involves the ionosphere response to changes in the thermospheric wind, composition, and temperature, and how the thermosphere dynamics and thermal state are affected by plasma electrodynamics, which may well be under the influence of magnetosphere–ionosphere coupling. It has been the main research focus for decades and will continue to be the center of aeronomy study. The ultimate sources driving dynamical I/T variations may be classified into origins from “above” (the sun, interplanetary, and magnetosphere) and from “below” (the low atmosphere, solid earth surface, and beneath). The cause-effect pathways have been presented in many previous studies covering broad research topics. here we provide only a few I/T coupling phenomena with a focus primarily on mid- and subauroral latitude processes to demonstrate recent progress and new understanding in several research frontiers. Topics covered include specifically ionospheric longitudinal variation morphology (from continental to global scales); neutral wind (especially zonal wind) effects on ionospheric longitudinal variations; important processes for the summer nighttime ionosphere; typical stormtime I/T coupling processes; high latitude winds; and stormtime subauroral I/T coupling phenomena.

Zhang, Shun-Rong;

Published by:       Published on:

YEAR: 2021     DOI: 10.1002/9781119815617.ch15

ionosphere–thermosphere coupling; ionospheric dynamics; ionospheric responses; subauroral latitudes; thermospheric neutral winds; thermospheric variations

Toward a Next Generation Particle Precipitation Model: Mesoscale Prediction Through Machine Learning (a Case Study and Framework for Progress)

We advance the modeling capability of electron particle precipitation from the magnetosphere to the ionosphere through a new database and use of machine learning (ML) tools to gain utility from those data. We have compiled, curated, analyzed, and made available a new and more capable database of particle precipitation data that includes 51 satellite years of Defense Meteorological Satellite Program (DMSP) observations temporally aligned with solar wind and geomagnetic activity data. The new total electron energy flux particle precipitation nowcast model, a neural network called PrecipNet, takes advantage of increased expressive power afforded by ML approaches to appropriately utilize diverse information from the solar wind and geomagnetic activity and, importantly, their time histories. With a more capable representation of the organizing parameters and the target electron energy flux observations, PrecipNet achieves a \textgreater50\% reduction in errors from a current state-of-the-art model oval variation, assessment, tracking, intensity, and online nowcasting (OVATION Prime), better captures the dynamic changes of the auroral flux, and provides evidence that it can capably reconstruct mesoscale phenomena. We create and apply a new framework for space weather model evaluation that culminates previous guidance from across the solar-terrestrial research community. The research approach and results are representative of the “new frontier” of space weather research at the intersection of traditional and data science-driven discovery and provides a foundation for future efforts.

McGranaghan, Ryan; Ziegler, Jack; Bloch, Téo; Hatch, Spencer; Camporeale, Enrico; Lynch, Kristina; Owens, Mathew; Gjerloev, Jesper; Zhang, Binzheng; Skone, Susan;

Published by: Space Weather      Published on:

YEAR: 2021     DOI: 10.1029/2020SW002684

space weather; magnetosphere-ionosphere coupling; data science; evaluation; machine learning; particle precipitation

Corotation of ring current auroral spots at sub-auroral latitudes

We report observations of auroral spots s at sub-auroral latitudes. The auroral spots occurred during storm-recovery phases and corotated with the Earth at a speed either higher (super-rotation) or lower (sub-rotation) than the Earth\textquoterights rotation rate. In the dawn side, the spots have a slightly higher probability of super-rotation than that of the duskside auroral spots. The super- and sub-rotation is likely due to dynamics of the plasmasphere that is controlled by both drag (sub-rotation) and solar wind driven plasma convection.

Zhang, Yongliang; Paxton, Larry;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: Jan-02-2020

YEAR: 2020     DOI: 10.1016/j.jastp.2020.105195

Auroral spots; Corotation; Sub-auroral latitude

A method to derive global O/N2 ratios from SSUSI/DMSP based on Re-AURIC algorithm

Global thermospheric O/N₂ column density ratios are obtained using the SSUSI/DMSP far-ultraviolet (FUV) dayglow data and the Re-AURIC simulation results. The Re-AURIC is derived from the AURIC algorithm after some old modules are updated. The calculation processes of O/N₂ ratio are then established using the simulations of Re-AURIC to calibrate the ratios of the OI 135.6\ nm emission and N₂ LBHS emission from SSUSI observations. The standard deviation (1σ) and correlation coefficient are 0.045 and 0.769 compared with the O/N₂ ratios provided by the SSUSI EDR data. The statistical errors between the calculated ratios and the EDR references are generally less than 0.2 with 96.40\% at 2σ (95.44\%) and less than 0.1 with 60.51\% at about 1σ (68.26\%). Two global O/N₂ ratio maps are obtained using this method to study its variations when the magnetic storm occurs. The significant O/N₂ depletion can be seen in one O/N₂ ratio map whose Kp index is 6. Also, the depletion is not uniform at different longitudes and the scales extend from high latitude to low latitude during magnetic storm. This proposed method provides us with a simple and useful tool to obtain the global O/N₂ distribution and even the future modeling from the observations on satellites.

Ding, GuangXing; Chen, Bo; Zhang, Xiaoxin; He, Fei;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 03/2020

YEAR: 2020     DOI: 10.1016/j.jastp.2020.105196

FUV dayglow; Magnetic storm; O/N2 ratio; Re-AURIC

Dynamical Properties of Peak and Time-Integrated Geomagnetic Events Inferred From Sample Entropy

We provide a comprehensive statistical analysis of the sample entropy of peak and time-integrated geomagnetic events in 2001\textendash2017, considering different measures of event strength, different geomagnetic indices, and a simplified solar wind-magnetosphere coupling function . Our investigations reveal the existence of significant correlations between the entropies of , , and , and between such entropies and event strengths, as well as good correlations between peak levels of solar wind-magnetosphere coupling and ring current ( ) and entropies, suggesting a potential predictability of significant and events on the basis of appropriate functions of . Sensibly weaker correlations are found with entropy. We further show the presence of several significant entropy correlations between geomagnetic indices, solar wind-magnetosphere coupling, and trapped or precipitated energetic electron and ion fluxes measured by geostationary and low Earth orbit satellites in the outer radiation belt during the same periods. Entropy correlations between and trapped or precipitated 30- to 80-keV ion fluxes at low and between and trapped 40-keV electron fluxes at geostationary orbit correspond well with ring current properties and substorm-induced injections, respectively. Entropy correlations between and precipitation rates of energetic ion and electron fluxes demonstrate the sensibility of index entropy to both low-energy (5\textendash30 keV) electron injections and ring current. The stronger entropy correlation between solar wind-magnetosphere coupling and than likely stems from the more stochastic behavior of electron injections and fast losses near geostationary orbit.

Mourenas, D.; Artemyev, A.; Zhang, X.-J.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2020

YEAR: 2020     DOI: 10.1029/2019JA027599

Dynamical complexity; Entropy; geomagnetic indices; Geomagnetic storms; Solar wind magnetosphere coupling

Modeled IMF B _y Effects on the Polar Ionosphere and Thermosphere Coupling

There is still an inadequate understanding of how the interplanetary magnetic field (IMF) east-west component (B_y) affects thermospheric composition, and other ionospheric and thermospheric fields in a systematic way. Utilizing the state-of-art first-principles Coupled Magnetosphere Ionosphere Thermosphere (CMIT) modeling and TIMED/Global Ultraviolet Imager (GUVI)-observed ΣO/N₂ covering an entire solar cycle (year 2002\textendash2016), as well as a neutral parcel trajectory tracing technique, we emphasize that not only the direction of B_y, but also its strength relative to the IMF north-south component (B_z) that has important effects on high latitude convection, Joule heating, electron density, neutral winds, and neutral composition patterns in the upper thermosphere. The Northern Hemisphere convection pattern becomes more twisted for positive B_y cases than negative cases: the dusk cell becomes more rounded compared with the dawn cell. Consequently, equatorward neutral winds are stronger during postmidnight hours in negative B_y cases than in positive B_y cases, creating a favorable condition for neutral composition disturbances (characterized by low ΣO/N₂) to expand to lower latitudes. This may lead to a more elongated ΣO/N₂ depletion area along the morning-premidnight direction for negative B_y conditions compared with the positive B_y conditions. Backward neutral parcel trajectories indicate that a lower ΣO/N₂ parcel in negative B_y cases comes from lower altitudes, as compared with that for positive B_y cases, leading to larger enhancements of N₂ in the former case.

Liu, Jing; Burns, Alan; Wang, Wenbin; Zhang, Yongliang;

Published by: Journal of Geophysical Research: Space Physics      Published on: 02/2020

YEAR: 2020     DOI: 10.1029/2019JA026949

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

Estimation of solar EUV flux from TIMED/GUVI data

Zhang, Yongliang; Paxton, Larry; Schaefer, Robert;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2020     DOI:

Case Study of Asymmetries in Polar Rain Aurora

Herschbach, Dennis; Zhang, Yongliang;

Published by:       Published on:

YEAR: 2020     DOI:

Persistence of the long-duration daytime TEC enhancements at different longitudinal sectors during the August 2018 geomagnetic storm

Li, Qiaoling; Huang, Fuqing; Zhong, Jiahao; Zhang, Ruilong; Kuai, Jiawei; Lei, Jiuhou; Liu, Libo; Ren, Dexin; Ma, Han; Yoshikawa, Akimasa; , others;

Published by: Journal of geophysical research: space physics      Published on:

YEAR: 2020     DOI:

Dataset for Multi-scale observations of two polar cap arcs occuring on different magnetic field topologies

Reidy, Jade; Fear, Robert; Whiter, Daniel; Lanchester, Betty; Kavanagh, AJ; Price, David; Chadney, Joshua; Zhang, Yongliang; Paxton, Larry; , others;

Published by:       Published on:

YEAR: 2020     DOI:

Multiscale observation of two polar cap arcs occurring on different magnetic field topologies

Reidy, JA; Fear, RC; Whiter, DK; Lanchester, BS; Kavanagh, AJ; Price, David; Chadney, Joshua; Zhang, Y; Paxton, LJ;

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

YEAR: 2020     DOI:

A comparison of thermospheric FUV radiance and composition from TIMED, GOLD and ICON

Zhang, Y; Paxton, LJ; Schaefer, RK; Eastes, R; McClintock, WE; Immel, TJ;

Published by:       Published on:

YEAR: 2020     DOI:

Modeled IMF By effects on the polar ionosphere and thermosphere coupling

Liu, Jing; Burns, Alan; Wang, Wenbin; Zhang, Yongliang;

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

YEAR: 2020     DOI:

Prominent daytime TEC enhancements under the quiescent condition of January 2017

UltraViolet Imager (GUVI) for the longitude and latitude bins of 30 and 10, respectively. However, as shown in Figure 3c, the O/N 2 ratio from Global UltraViolet Imager (GUVI) had no

Huang, Fuqing; Lei, Jiuhou; Zhang, Ruilong; Li, Na; Gu, Shengyang; Yu, You; Liu, Libo; Owolabi, Charles; Ning, Baiqi; Li, Guozhu; , others;

Published by: Geophysical Research Letters      Published on:

YEAR: 2020     DOI: 10.1029/2020GL088398

The day-glow data application of FY-3D IPM in monitoring O/N2

The Ionosphere Photometer (IPM) is a far ultraviolet nadir-viewing photometer that flew aboard the second-generation, polar-orbiting Chinese meteorological satellite FY-3D, which was

Jiang, Fang; Mao, Tian; Zhang, Xiaoxin; Wang, Yungang; Fu, Liping; Hu, Xiuqing; Wang, DaXin; Jia, Nan; Wang, Tianfang; Sun, YueQiang;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2020     DOI: 10.1016/j.jastp.2020.105309

Prediction and variation of the auroral oval boundary based on a deep learning model and space physical parameters

The auroral oval boundary represents an important physical process with implications for the ionosphere and magnetosphere. An automatic auroral oval boundary prediction method

Han, Yiyuan; Han, Bing; Hu, Zejun; Gao, Xinbo; Zhang, Lixia; Yang, Huigen; Li, Bin;

Published by: Nonlinear Processes in Geophysics      Published on:

YEAR: 2020     DOI: 10.5194/npg-27-11-2020

Observation of thermosphere and ionosphere using the ionosphere PhotoMeter (IPM) on the Chinese meteorological satellite FY-3D

The Ionosphere PhotoMeter (IPM) is a far ultraviolet nadir-viewing photometer that flew aboard the second-generation, polar-orbiting Chinese meteorological satellite Feng-Yun 3D (FY-3D), which was launched on November 25th, 2017.

Jiang, Fang; Mao, Tian; Zhang, Xiaoxin; Wang, Yun-Gang; Hu, Xiuqing; Wang, DaXin; Jia, Nan; Wang, Tianfang; Sun, YueQiang; Fu, Li-Ping;

Published by: Advances in Space Research      Published on:

YEAR: 2020     DOI: 10.1016/j.asr.2020.07.027

New Aspects of the Ionospheric Behavior Over Millstone Hill During the 30-Day Incoherent Scatter Radar Experiment in October 2002

The geomagnetic storm-driven ionospheric changes and the involved processes are interesting and challenging topics in understanding and predicting the ionosphere. In this study we investigate the response of the ionosphere to geomagnetic disturbances during the 30-day incoherent scatter radar measurements conducted at Millstone Hill (42.6\textdegreeN, 71.5\textdegreeW) from 4 October to 4 November 2002. During geomagnetically disturbed periods, while the peak electron density of the F2 layer (NmF2) and total electron content deviate remarkably from the quiet time ones in a similar way, the incoherent scatter radar measurements reveal that the changes in electron density are frequently different between low and high altitudes. The electron density is significantly depleted at low altitudes; however, at topside it either changes slightly or sometime is enhanced. The enhanced vertical scale height around 600 km under geomagnetically active conditions implies that the topside electron density profiles become much steeper. The increase in the peak height of F2 layer (hmF2) indicates the upward motions under the action of the storm-driven dynamic processes. Further, sometimes strong differences are shown in total electron content between Millstone Hill and longitude 100\textdegreeW. The competing contributions from dynamic processes and disturbance composition to the storm-time ionospheric changes over Millstone Hill are indicated in the different responses in electron density at the bottomside and topside of the ionosphere.

Liu, Libo; Le, Huijun; Chen, Yiding; Zhang, Ruilong; Wan, Weixing; Zhang, Shun-Rong;

Published by: Journal of Geophysical Research: Space Physics      Published on: 07/2019

YEAR: 2019     DOI: 10.1029/2019JA026806

New Aspects of the Ionospheric Behavior Over Millstone Hill During the 30-Day Incoherent Scatter Radar Experiment in October 2002

The geomagnetic storm-driven ionospheric changes and the involved processes are interesting and challenging topics in understanding and predicting the ionosphere. In this study we investigate the response of the ionosphere to geomagnetic disturbances during the 30-day incoherent scatter radar measurements conducted at Millstone Hill (42.6\textdegreeN, 71.5\textdegreeW) from 4 October to 4 November 2002. During geomagnetically disturbed periods, while the peak electron density of the F2 layer (NmF2) and total electron content deviate remarkably from the quiet time ones in a similar way, the incoherent scatter radar measurements reveal that the changes in electron density are frequently different between low and high altitudes. The electron density is significantly depleted at low altitudes; however, at topside it either changes slightly or sometime is enhanced. The enhanced vertical scale height around 600 km under geomagnetically active conditions implies that the topside electron density profiles become much steeper. The increase in the peak height of F2 layer (hmF2) indicates the upward motions under the action of the storm-driven dynamic processes. Further, sometimes strong differences are shown in total electron content between Millstone Hill and longitude 100\textdegreeW. The competing contributions from dynamic processes and disturbance composition to the storm-time ionospheric changes over Millstone Hill are indicated in the different responses in electron density at the bottomside and topside of the ionosphere.

Liu, Libo; Le, Huijun; Chen, Yiding; Zhang, Ruilong; Wan, Weixing; Zhang, Shun-Rong;

Published by: Journal of Geophysical Research: Space Physics      Published on: 07/2019

YEAR: 2019     DOI: 10.1029/2019JA026806

Deriving Thermospheric Temperature From Observations by the Global Ultraviolet Imager on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics Satellite

This paper reports a preliminary result for estimating thermospheric temperature around 155 km from the N₂ Lyman-Birge-Hopfield bands observed by TIMED/Global Ultraviolet Imager (GUVI). Atmospheric Ultraviolet Radiance Integrated Code model (Strickland et al., 1999, https://doi.org/10.1016/S0022-4073(98)00098-3) calculations indicate that the intensity ratio in the N₂ Lyman-Birge-Hopfield (0,0) and (1,0) bands at 144.5- to 145.5- and 141.0- to 142.0-nm quasi-linearly depend on N₂ rotational temperature. The observed ratios and the Atmospheric Ultraviolet Radiance Integrated Code results are used together to specify the thermospheric temperature around 155 km under sunlit conditions. The estimated temperature agrees fairly well with the neutral temperature at 155 km from WACCM-X model. The estimated temperature is also higher over the auroral oval and O/N₂ depleted regions. Furthermore, meridional wave-like structures were clearly seen in the derived temperature and were likely caused by traveling atmospheric disturbances.

Zhang, Yongliang; Paxton, Larry; Schaefer, Robert;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2019

YEAR: 2019     DOI: 10.1029/2018JA026379

Wide-field auroral imager onboard the Fengyun satellite

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N₂ LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68\textdegree in the along-track direction and 10\textdegree in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130\textdegree \texttimes 10\textdegree. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF₂ filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth\textquoterights surface. The sensitivity is \>0.01 counts s^-1 Rayleigh^-1 pixel^-1 (140\textendash180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

Zhang, Xiao-Xin; Chen, Bo; He, Fei; Song, Ke-Fei; He, Ling-Ping; Liu, Shi-Jie; Guo, Quan-Feng; Li, Jia-Wei; Wang, Xiao-Dong; Zhang, Hong-Ji; Wang, Hai-Feng; Han, Zhen-Wei; Sun, Liang; Zhang, Pei-Jie; Dai, Shuang; Ding, Guang-Xing; Chen, Li-Heng; Wang, Zhong-Su; Shi, Guang-Wei; Zhang, Xin; Yu, Chao; Yang, Zhong-Dong; Zhang, Peng; Wang, Jin-Song;

Published by: Light: Science \& Applications      Published on: 05/2019

YEAR: 2019     DOI: 10.1038/s41377-019-0157-7

Wide-field auroral imager onboard the Fengyun satellite

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N₂ LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68\textdegree in the along-track direction and 10\textdegree in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130\textdegree \texttimes 10\textdegree. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF₂ filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth\textquoterights surface. The sensitivity is \>0.01 counts s^-1 Rayleigh^-1 pixel^-1 (140\textendash180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

Zhang, Xiao-Xin; Chen, Bo; He, Fei; Song, Ke-Fei; He, Ling-Ping; Liu, Shi-Jie; Guo, Quan-Feng; Li, Jia-Wei; Wang, Xiao-Dong; Zhang, Hong-Ji; Wang, Hai-Feng; Han, Zhen-Wei; Sun, Liang; Zhang, Pei-Jie; Dai, Shuang; Ding, Guang-Xing; Chen, Li-Heng; Wang, Zhong-Su; Shi, Guang-Wei; Zhang, Xin; Yu, Chao; Yang, Zhong-Dong; Zhang, Peng; Wang, Jin-Song;

Published by: Light: Science \& Applications      Published on: 05/2019

YEAR: 2019     DOI: 10.1038/s41377-019-0157-7

Wide-field auroral imager onboard the Fengyun satellite

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N₂ LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68\textdegree in the along-track direction and 10\textdegree in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130\textdegree \texttimes 10\textdegree. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF₂ filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth\textquoterights surface. The sensitivity is \>0.01 counts s^-1 Rayleigh^-1 pixel^-1 (140\textendash180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

Zhang, Xiao-Xin; Chen, Bo; He, Fei; Song, Ke-Fei; He, Ling-Ping; Liu, Shi-Jie; Guo, Quan-Feng; Li, Jia-Wei; Wang, Xiao-Dong; Zhang, Hong-Ji; Wang, Hai-Feng; Han, Zhen-Wei; Sun, Liang; Zhang, Pei-Jie; Dai, Shuang; Ding, Guang-Xing; Chen, Li-Heng; Wang, Zhong-Su; Shi, Guang-Wei; Zhang, Xin; Yu, Chao; Yang, Zhong-Dong; Zhang, Peng; Wang, Jin-Song;

Published by: Light: Science \& Applications      Published on: 05/2019

YEAR: 2019     DOI: 10.1038/s41377-019-0157-7

Wide-field auroral imager onboard the Fengyun satellite

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N₂ LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68\textdegree in the along-track direction and 10\textdegree in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130\textdegree \texttimes 10\textdegree. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF₂ filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth\textquoterights surface. The sensitivity is \>0.01 counts s^-1 Rayleigh^-1 pixel^-1 (140\textendash180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

Zhang, Xiao-Xin; Chen, Bo; He, Fei; Song, Ke-Fei; He, Ling-Ping; Liu, Shi-Jie; Guo, Quan-Feng; Li, Jia-Wei; Wang, Xiao-Dong; Zhang, Hong-Ji; Wang, Hai-Feng; Han, Zhen-Wei; Sun, Liang; Zhang, Pei-Jie; Dai, Shuang; Ding, Guang-Xing; Chen, Li-Heng; Wang, Zhong-Su; Shi, Guang-Wei; Zhang, Xin; Yu, Chao; Yang, Zhong-Dong; Zhang, Peng; Wang, Jin-Song;

Published by: Light: Science \& Applications      Published on: 05/2019

YEAR: 2019     DOI: 10.1038/s41377-019-0157-7

Wide-field auroral imager onboard the Fengyun satellite

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N₂ LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68\textdegree in the along-track direction and 10\textdegree in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130\textdegree \texttimes 10\textdegree. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF₂ filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth\textquoterights surface. The sensitivity is \>0.01 counts s^-1 Rayleigh^-1 pixel^-1 (140\textendash180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

Zhang, Xiao-Xin; Chen, Bo; He, Fei; Song, Ke-Fei; He, Ling-Ping; Liu, Shi-Jie; Guo, Quan-Feng; Li, Jia-Wei; Wang, Xiao-Dong; Zhang, Hong-Ji; Wang, Hai-Feng; Han, Zhen-Wei; Sun, Liang; Zhang, Pei-Jie; Dai, Shuang; Ding, Guang-Xing; Chen, Li-Heng; Wang, Zhong-Su; Shi, Guang-Wei; Zhang, Xin; Yu, Chao; Yang, Zhong-Dong; Zhang, Peng; Wang, Jin-Song;

Published by: Light: Science \& Applications      Published on: 05/2019

YEAR: 2019     DOI: 10.1038/s41377-019-0157-7

Observations of conjugated ring current auroras at subauroral latitudes

We report three ring current aurora events that are conjugated in the two hemispheres observed by satellite and ground imagers on May 16, 2005, August 26, 2018 and September 5, 2005. The ring current auroras appeared as auroral spots or arcs in the day, dusk or night side. These events confirm that the particle sources are in the equatorial ring current ions and pitch angle diffusion of the ions lead to the ion precipitation in the both hemisphere on the same field lines, thus the auroras are conjugated.

Zhang, Yongliang; Paxton, Larry;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 03/2019

YEAR: 2019     DOI: 10.1016/j.jastp.2019.01.005

Impact of nitric oxide, solar EUV and particle precipitation on thermospheric density decrease

Space Weather Modeling Capabilities Assessment: Auroral Precipitation and High-Latitude Ionospheric Electrodynamics

As part of its International Capabilities Assessment effort, the Community Coordinated Modeling Center initiated several working teams, one of which is focused on the validation of models and methods for determining auroral electrodynamic parameters, including particle precipitation, conductivities, electric fields, neutral density and winds, currents, Joule heating, auroral boundaries, and ion outflow. Auroral electrodynamic properties are needed as input to space weather models, to test and validate the accuracy of physical models, and to provide needed information for space weather customers and researchers. The working team developed a process for validating auroral electrodynamic quantities that begins with the selection of a set of events, followed by construction of ground truth databases using all available data and assimilative data analysis techniques. Using optimized, predefined metrics, the ground truth data for selected events can be used to assess model performance and improvement over time. The availability of global observations and sophisticated data assimilation techniques provides the means to create accurate ground truth databases routinely and accurately.

Robinson, Robert; Zhang, Yongliang; Garcia-Sage, Katherine; Fang, Xiaohua; Verkhoglyadova, Olga; Ngwira, Chigomezyo; Bingham, Suzy; Kosar, Burcu; Zheng, Yihua; Kaeppler, Stephen; Liemohn, Michael; Weygand, James; Crowley, Geoffrey; Merkin, Viacheslav; McGranaghan, Ryan; Mannucci, Anthony;

Published by: Space Weather      Published on: 01/2019

YEAR: 2019     DOI: 10.1029/2018SW002127

Addressing O2R with the SSUSI Operational Space Sensor: Lessons Learned

Schaefer, Robert; Paxton, Larry; Romeo, Giuseppe; Kil, Hyosub; Wolven, Brian; Zhang, Yongliang;

Published by:       Published on:

YEAR: 2019     DOI:

Using Artificial Neural Network Training for Space Weather Products

Zhang, Yongliang; Paxton, Larry;

Published by:       Published on:

YEAR: 2019     DOI:

Sun-Induced Chlorophyll Fluorescence as a Proxy of Photosynthesis: Measurements, Modeling, and Applications from Field, Airborne, and Satellite Platforms II Posters

Zhang, Yongguang; Joiner, Joanna; Guan, Kaiyu; Yang, Xi;

Published by:       Published on:

YEAR: 2019     DOI:

Space weather modeling capabilities assessment: Auroral precipitation and high-latitude ionospheric electrodynamics

Robinson, Robert; Zhang, Yongliang; Garcia-Sage, Katherine; Fang, Xiaohua; Verkhoglyadova, Olga; Ngwira, Chigomezyo; Bingham, Suzy; Kosar, Burcu; Zheng, Yihua; Kaeppler, Stephen; , others;

Published by: Space Weather      Published on:

YEAR: 2019     DOI:

Detection of Land Surface Phenology from New Generation Geostationary Satellites and Its Compassion with Observations from Polar-Orbiting Satellites

Zhang, Xiaoyang; Ye, Yongchang; Wang, Weile; Wang, Yujie;

Published by:       Published on:

YEAR: 2019     DOI:

Storm-time variations in the thermsopheric density, composition and temperature.

Zhang, Yongliang; Paxton, Larry; Schaefer, Robert;

Published by:       Published on:

YEAR: 2019     DOI:

Anomaly distribution of ionospheric total electron content responses to some solar flares

Le, Huijun; Liu, Libo; Chen, Yiding; Zhang, Hui;

Published by: Earth and Planetary Physics      Published on:

YEAR: 2019     DOI:

Case Study of Dawn-Dusk Asymmetry in Polar Rain Aurora

Herschbach, Dennis; Zhang, Yongliang;

Published by:       Published on:

YEAR: 2019     DOI:

Equatorial ionospheric electrodynamics over Jicamarca during the 6—11 September 2017 space weather event

We use the observations from the incoherent scatter radar and the magnetometers over Jicamarca (11.95 S, 76.87 W) sector to investigate the equatorial ionospheric electrodynamics

Zhang, Ruilong; Liu, Libo; Le, Huijun; Chen, Yiding;

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

YEAR: 2019     DOI: 10.1029/2018JA026295

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

Ionosphere-thermosphere system heating and cooling during storms

Zesta, Eftyhia; Oliveira, Denny; Zhang, Yongliang; Dawkins, Erin; Panka, Peter;

Published by:       Published on:

YEAR: 2019     DOI:

Advances in Auroral Studies I

Zhang, Yongliang; Paxton, Larry; Robinson, Robert; MacDonald, Elizabeth; Mitchell, Elizabeth;

Published by:       Published on:

YEAR: 2019     DOI:

Composition Changes Around the Equinoxes

Burns, Alan; Cai, Xuguang; Wang, Wenbin; Qian, Liying; Zhang, Yongliang; Eastes, Richard; McClintock, William;

Published by:       Published on:

YEAR: 2019     DOI:

IMF B y Effects on the high-latitude Ionosphere and Thermosphere

Liu, Jing; Wang, Wenbin; Burns, Alan; Zhang, Yongliang;

Published by:       Published on:

YEAR: 2019     DOI:

A case study comparing citizen science aurora data with global auroral boundaries derived from satellite imagery and empirical models

Ionospheric and Thermospheric Responses to the Recent Strong Solar Flares on 6 September 2017

Two solar flares X2.2 and X9.3 erupted over the active region 2673 on 6 September 2017, and the second flare is the strongest since 2005. In order to investigate the ionospheric and thermospheric responses to the two solar flares, the global total electron content and the critical frequency of F2 layer obtained from GPS stations and ionosondes are used. The results indicate that the ionosphere in the sunlit hemisphere increased significantly with magnitudes of 0.1 and 0.5 total electron content units for the X2.2 and X9.3 solar flares, respectively. The electron density, thermospheric neutral density, and neutral temperature simulated by the Thermosphere-Ionosphere Electrodynamics Global Circulation Model show that the behavior of ionospheric and thermospheric responses is different. The ionospheric disturbances occurred at the altitude ranges of 150-300\ km, and the thermospheric responses occurred at the altitudes of 250-400\ km are caused by solar extreme ultraviolet and ultraviolet photons, respectively. Both ionospheric and thermospheric responses are proportional to the height within their corresponding altitude ranges. Observations and simulations reveal that the ionospheric and thermospheric responses are nonlinearly dependent on the solar zenith angle. The disturbances caused by the X2.2 solar flare are symmetric, but the X9.3 solar flare are not. The O/N₂ density ratio simulated by Thermosphere-Ionosphere Electrodynamics Global Circulation Model increases from lev0 to lev5.0 pressure surface with a magnitude of 0.1\textendash1.8, while the ratio decreases in the American sector with a magnitude of -0.6 to -0.3. The longitudinal asymmetry of O/N₂ density ratio is a major contributor to the longitudinal asymmetry of ionospheric and thermospheric responses.

Li, Wang; Yue, Jianping; Yang, Yang; He, Changyong; Hu, Andong; Zhang, Kefei;

Published by: Journal of Geophysical Research: Space Physics      Published on: 10/2018

YEAR: 2018     DOI: 10.1029/2018JA025700

On the Responses of Mesosphere and Lower Thermosphere Temperatures to Geomagnetic Storms at Low and Middle Latitudes

Observations from lidars and satellites have shown that large neutral temperature increases and decreases occur in the middle and low latitudes of the mesosphere and lower thermosphere region during geomagnetic storms. Here we undertake first-principles simulations of mesosphere and lower thermosphere temperature responses to storms using the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model to elucidate the nature and causes of these changes. Temperature variations were not uniform; instead, nighttime temperatures changed earlier than daytime temperatures, and temperatures changed earlier at high latitudes than at low ones. Furthermore, temperatures increased in some places/times and decreased in others. As the simulation behaves similar to observations, it provides an opportunity to understand physical processes that drive the observed changes. Our analysis has shown that they were produced mainly by adiabatic heating/cooling that was associated with vertical winds resulting from general circulation changes, with additional contributions from vertical heat advection.

Li, Jingyuan; Wang, Wenbin; Lu, Jianyong; Yuan, Tao; Yue, Jia; Liu, Xiao; Zhang, Kedeng; Burns, Alan; Zhang, Yongliang; Li, Zheng;

Published by: Geophysical Research Letters      Published on: 08/2019

YEAR: 2018     DOI: 10.1029/2018GL078968

On the Responses of Mesosphere and Lower Thermosphere Temperatures to Geomagnetic Storms at Low and Middle Latitudes

Observations from lidars and satellites have shown that large neutral temperature increases and decreases occur in the middle and low latitudes of the mesosphere and lower thermosphere region during geomagnetic storms. Here we undertake first-principles simulations of mesosphere and lower thermosphere temperature responses to storms using the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model to elucidate the nature and causes of these changes. Temperature variations were not uniform; instead, nighttime temperatures changed earlier than daytime temperatures, and temperatures changed earlier at high latitudes than at low ones. Furthermore, temperatures increased in some places/times and decreased in others. As the simulation behaves similar to observations, it provides an opportunity to understand physical processes that drive the observed changes. Our analysis has shown that they were produced mainly by adiabatic heating/cooling that was associated with vertical winds resulting from general circulation changes, with additional contributions from vertical heat advection.

Li, Jingyuan; Wang, Wenbin; Lu, Jianyong; Yuan, Tao; Yue, Jia; Liu, Xiao; Zhang, Kedeng; Burns, Alan; Zhang, Yongliang; Li, Zheng;

Published by: Geophysical Research Letters      Published on: 08/2019

YEAR: 2018     DOI: 10.1029/2018GL078968

Nighttime Enhancements in the Midlatitude Ionosphere and Their Relation to the Plasmasphere

In situ electron density measurements by the CHAllenging Minisatellite Payload and the Defense Meteorological Satellites Program F17 satellites show that the midlatitude ionization at altitudes of \~350 and 850\ km is enhanced in the late evening. The enhancements increase to maximum around midnight and are clearly observed till early morning as the equatorial ionization decays to minimal level. They appear in the winter hemisphere during June and December solstices and in both hemispheres during equinox. The enhancements are well confined between \textpm30\textdegree and \textpm50\textdegree magnetic latitude, with the magnetic flux tubes of L = 1.3 - 2.4 connecting to the plasmasphere. Furthermore, coincident longitudinal variations exist in both the ionospheric enhancements and the plasmaspheric total electron content, especially during the solstice months. The coincidence may suggest essential plasma transport between the ionosphere and the plasmasphere. These facts support the idea that the plasmasphere provides extra plasma to the midlatitude ionosphere through downward plasma influx along the magnetic field lines to form the nighttime ionization enhancements when the sunlight is absent.

Li, Quanhan; Hao, Yongqiang; Zhang, Donghe; Xiao, Zuo;

Published by: Journal of Geophysical Research: Space Physics      Published on: 08/2018

YEAR: 2018     DOI: 10.1029/2018JA025422