Bibliography
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Found 494 entries in the Bibliography.
Showing entries from 51 through 100
| 2021 |
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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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Observations showing the development of Subauroral Longitudinally Extended Emigerssions on a global scale are presented. It is demonstrated that they occur as a separation of an east-west arc-like band of luminosity that detaches away from the equatorward edge of the auroral distribution following episodes of auroral streamer production. They persist for time intervals on the order of ∼30 min and devolve into patchy disjointed segments before they fade. Emissions are seen in both 557.7 nm OI and 391.4 nm 1NG lines, and 630.0 nm emissions are often observed equatorward. The 391.4 nm emissions are typically weaker and fade away more quickly than the 557.7 nm emissions, suggesting that an auroral precipitation source is initially present but is rapidly depleted as the forms age. All cases are associated with enhanced Subauroral Polarization Stream (SAPS) flows, and one event shows clear association with large-scale Giant Undulations (GUs) and the formation of spur-like forms that fold equatorward under the main oval. A model is proposed for the production of subauroral longitudinally extended forms in which nonlinear growth of SAPS-induced surface waves on the plasmapause results in a disruption of the boundary. It is suggested that hot plasma of plasma sheet origin becomes entrained in the plasmasphere to produce transient precipitation-associated auroral emissions that may decay into STEVE emissions and that cold dense plasma from the plasmasphere becomes entrained onto open drift paths to feed long-lived drainage plumes. This process may occur quasi periodically during intense substorms and storm-time conditions. Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028556 Giant Undulations; STEVE; streamers; Subauroral Bands; Subauroral Polarization Streams; substorms |
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The geomagnetic storm that occurred on 25 August 25 2018, that is, during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo-Electromagnetic Satellite (CSES-01). By integrating the in situ measurements provided by CSES-01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca., 460 km) with ground-based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower- and mid-latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the equatorial electrojet (EEJ). Our proposed multisensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between prompt penetrating electric fields and disturbance dynamo electric fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES-01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter-EEJ during both 25 and 26 August at Braziliian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES-01/Swarm altitudes integrated with the ground-based observation recorded signatures of equatorial ionospheric anomaly crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude. Spogli, L.; Sabbagh, D.; Regi, M.; Cesaroni, C.; Perrone, L.; Alfonsi, L.; Di Mauro, D.; Lepidi, S.; Campuzano, S.; Marchetti, D.; De Santis, A.; Malagnini, A.; Scotto, C.; Cianchini, G.; Shen, Xu; Piscini, A.; Ippolito, A.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028368 Geomagnetic storms; Equatorial Electrojet; in situ plasma density; ionospheric elctroduamics; Ionospheric storms; low-latitude ionosphere |
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The geomagnetic storm that occurred on 25 August 25 2018, that is, during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo-Electromagnetic Satellite (CSES-01). By integrating the in situ measurements provided by CSES-01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca., 460 km) with ground-based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower- and mid-latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the equatorial electrojet (EEJ). Our proposed multisensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between prompt penetrating electric fields and disturbance dynamo electric fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES-01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter-EEJ during both 25 and 26 August at Braziliian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES-01/Swarm altitudes integrated with the ground-based observation recorded signatures of equatorial ionospheric anomaly crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude. Spogli, L.; Sabbagh, D.; Regi, M.; Cesaroni, C.; Perrone, L.; Alfonsi, L.; Di Mauro, D.; Lepidi, S.; Campuzano, S.; Marchetti, D.; De Santis, A.; Malagnini, A.; Scotto, C.; Cianchini, G.; Shen, Xu; Piscini, A.; Ippolito, A.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028368 Geomagnetic storms; Equatorial Electrojet; in situ plasma density; ionospheric elctroduamics; Ionospheric storms; low-latitude ionosphere |
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Global Effects of a Polar Solar Eclipse on the Coupled Magnetosphere-Ionosphere System It is well-known that solar eclipses can significantly impact the ionosphere and thermosphere, but how an eclipse influences the magnetosphere-ionosphere system is still unknown. Using a coupled magnetosphere-ionosphere-thermosphere model, we examined the impact on geospace of the northern polar-region eclipse that occurred on June 10, 2021. The simulations reveal that the eclipse-induced reduction in polar ionospheric conductivity causes large changes in field-aligned current, cross-polar cap potential and auroral activity. While such effects are expected in the northern hemisphere where solar obscuration occurred, they also occurred in the southern hemisphere through electrodynamic coupling. Eclipse-induced changes in monoenergetic auroral precipitation differ significantly between the northern hemisphere and southern hemisphere while diffuse auroral precipitation is interhemispherically symmetric. This study demonstrates that the geospace response to a polar-region solar eclipse is not limited just to the eclipse region but has global implications. Chen, Xuetao; Dang, Tong; Zhang, Binzheng; Lotko, William; Pham, Kevin; Wang, Wenbin; Lin, Dong; Sorathia, Kareem; Merkin, Viacheslav; Luan, Xiaoli; Dou, Xiankang; Luo, Bingxian; Lei, Jiuhou; Published by: Geophysical Research Letters Published on: YEAR: 2021 DOI: 10.1029/2021GL096471 auroral activity; magnetosphere-ionosphere coupling; polar solar eclipse |
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Precipitation flux and mean energy are then modeled based on TIMED GUVI-and DMSP SSUSI-inferred precipitation characteristics. Beginning with an overview of how the Themens, David; Jayachandran, Thayyil; McCaffrey, Anthony; Reid, Benjamin; Watson, Chris; Published by: 43rd COSPAR Scientific Assembly. Held 28 January-4 February Published on: |
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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: |
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explanation, that the lower summer measurements were the result of atmospheric composition change, based on the change of [O/N2] observed during the Boston summer by the GUVI Shepherd, Gordon; Cho, Young-Min; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028715 |
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Geomagnetic Pulsations Driving Geomagnetically Induced Currents Geomagnetically induced currents (GICs) are driven by the geoelectric field induced by fluctuations of Earth s magnetic field. Drivers of intense GICs are often associated with large impulsive events such as coronal mass ejections. To a lesser extent fluctuations from regular oscillations of the geomagnetic field, or geomagnetic pulsations, have also been identified as possible drivers of GICs. In this work we show that these low-frequency pulsations are directly observed in measured GIC data from power networks. Due to the low-pass nature of GICs, Pc5 and lower-frequency pulsations drive significant GICs for an extended duration even at midlatitudes. Longer-period Ps6-type disturbances apparently not typical of midlatitudes are seen with GIC amplitudes comparable to the peak GIC at storm sudden commencement. The quasi-ac (alternating current) nature of the sustained pulsation driving affects the power system response and cannot be properly modeled using only direct current (dc) models. A further consideration is that the often used dB/dt GIC proxy is biased to the sampling rate of the geomagnetic field measurements used. The dB/dt metric does not adequately characterize GIC activity at frequencies in the low ultralow-frequency (ULF) range, and a frequency-weighted proxy akin to geoelectric field should be used instead. Heyns, M.; Lotz, S.; Gaunt, C.; Published by: Space Weather Published on: YEAR: 2021 DOI: 10.1029/2020SW002557 space weather; geomagnetic pulsations; geomagnetically induced currents |
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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 |
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Recent attention has been given to mesoscale phenomena across geospace (∼10 s km to 500 km in the ionosphere or ∼0.5 RE to several RE in the magnetosphere), as their contributions to the system global response are important yet remain uncharacterized mostly due to limitations in data resolution and coverage as well as in computational power. As data and models improve, it becomes increasingly valuable to advance understanding of the role of mesoscale phenomena contributions—specifically, in magnetosphere-ionosphere coupling. This paper describes a new method that utilizes the 2D array of Time History of Events and Macroscale Interactions during Substorms (THEMIS) white-light all-sky-imagers (ASI), in conjunction with meridian scanning photometers, to estimate the auroral scale sizes of intense precipitating energy fluxes and the associated Hall conductances. As an example of the technique, we investigated the role of precipitated energy flux and average energy on mesoscales as contrasted to large-scales for two back-to-back substorms, finding that mesoscale aurora contributes up to ∼80\% (∼60\%) of the total energy flux immediately after onset during the early expansion phase of the first (second) substorm, and continues to contribute ∼30–55\% throughout the remainder of the substorm. The average energy estimated from the ASI mosaic field of view also peaked during the initial expansion phase. Using the measured energy flux and tables produced from the Boltzmann Three Constituent (B3C) auroral transport code (Strickland et al., 1976; 1993), we also estimated the 2D Hall conductance and compared it to Poker Flat Incoherent Scatter Radar conductance values, finding good agreement for both discrete and diffuse aurora. Gabrielse, Christine; Nishimura, Toshi; Chen, Margaret; Hecht, James; Kaeppler, Stephen; Gillies, Megan; Reimer, Ashton; Lyons, Larry; Deng, Yue; Donovan, Eric; Evans, Scott; Published by: Frontiers in Physics Published on: |
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Recent attention has been given to mesoscale phenomena across geospace (∼10 s km to 500 km in the ionosphere or ∼0.5 RE to several RE in the magnetosphere), as their contributions to the system global response are important yet remain uncharacterized mostly due to limitations in data resolution and coverage as well as in computational power. As data and models improve, it becomes increasingly valuable to advance understanding of the role of mesoscale phenomena contributions—specifically, in magnetosphere-ionosphere coupling. This paper describes a new method that utilizes the 2D array of Time History of Events and Macroscale Interactions during Substorms (THEMIS) white-light all-sky-imagers (ASI), in conjunction with meridian scanning photometers, to estimate the auroral scale sizes of intense precipitating energy fluxes and the associated Hall conductances. As an example of the technique, we investigated the role of precipitated energy flux and average energy on mesoscales as contrasted to large-scales for two back-to-back substorms, finding that mesoscale aurora contributes up to ∼80\% (∼60\%) of the total energy flux immediately after onset during the early expansion phase of the first (second) substorm, and continues to contribute ∼30–55\% throughout the remainder of the substorm. The average energy estimated from the ASI mosaic field of view also peaked during the initial expansion phase. Using the measured energy flux and tables produced from the Boltzmann Three Constituent (B3C) auroral transport code (Strickland et al., 1976; 1993), we also estimated the 2D Hall conductance and compared it to Poker Flat Incoherent Scatter Radar conductance values, finding good agreement for both discrete and diffuse aurora. Gabrielse, Christine; Nishimura, Toshi; Chen, Margaret; Hecht, James; Kaeppler, Stephen; Gillies, Megan; Reimer, Ashton; Lyons, Larry; Deng, Yue; Donovan, Eric; Evans, Scott; Published by: Frontiers in Physics Published on: |
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TIMED/Global Ultraviolet Imager (GUVI) limb measurements of far-ultraviolet airglow emission have been used to investigate middle-low latitude thermospheric composition and neutral temperature responses to the 20 and 21 November 2003 (day of year [DOY] 324 and 325) superstorm. Altitude profiles of O, N2 number densities and temperature, as well as O/N2 column density ratio (∑O/N2), on the storm days along the GUVI limb tracks are compared with those on DOY 323 (quiet time). The storm-time composition and temperature responses were global and evolved continuously as the storm progressed. Specially, N2 and temperature increased almost globally at all altitudes during the storm and their perturbation structures were similar. The magnitudes of their enhancements both increased with altitude and latitude. The storm-induced O perturbations decreased in the lower thermosphere but increased in the upper thermosphere. Transition heights of O perturbations from decrease to increase changed with latitude and time. During the storm main and recovery phases, the storm-induced ∑O/N2 decreases were mostly related to the O depletion in the low-middle thermosphere, whereas ∑O/N2 increases during the storm were primarily caused by N2 depletion. There was a remarkable hemispheric asymmetry in composition responses as they have different morphologies and lifetime, especially during the storm recovery phase. Yu, Tingting; Wang, Wenbin; Ren, Zhipeng; Yue, Jia; Yue, Xinan; He, Maosheng; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028427 neutral composition; altitude profile; hemispheric asymmetry in composition responses; neutral temperature; superstorm; transition heights of O responses |
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The Response of Middle Thermosphere (∼160 km) Composition to the November 20 and 21, 2003 Superstorm TIMED/GUVI limb measurements and first-principles simulations from the Thermosphere Ionosphere Electrodynamics Global Circulation Model (TIEGCM) are used to investigate thermospheric atomic oxygen (O) and molecular nitrogen (N2) responses in the middle thermosphere on a constant pressure surface (∼160 km) to the November 20 and 21, 2003 superstorm. The consistency between GUVI observations and TIEGCM simulated composition changes allows us to utilize TIEGCM outputs to investigate the storm-time behaviors of O and N2 systematically. Diagnostic analysis shows that horizontal and vertical advection are the two main processes that determine the storm-induced perturbations in the middle thermosphere. Molecular diffusion has a relatively smaller magnitude than the two advection processes, acting to compensate for the changes caused by the transport partly. Contributions from chemistry and eddy diffusion are negligible. During the storm initial and main phases, composition variations at high latitudes are determined by both horizontal and vertical advection. At middle-low latitudes, horizontal advection is the main driver for the composition changes where O mass mixing ratio decreases (N2 mass mixing ratio increases); whereas horizontal and vertical advection combined to dominate the changes in the regions where increases ( decreases). Over the entire storm period, horizontal advection plays a significant role in transporting high-latitude composition perturbations globally. Our results also demonstrate that storm-time temperature changes are not the direct cause of the composition perturbations on constant pressure surfaces. Yu, Tingting; Wang, Wenbin; Ren, Zhipeng; Cai, Xuguang; Yue, Xinan; He, Maosheng; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029449 atomic oxygen; GUVI limb observations; middle thermosphere; molecular nitrogen; storm-time perturbations; TIEGCM |
| 2020 |
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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 |
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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 |
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Auroral Structure and Dynamics From GOLD The Global-scale Observations of the Limb and Disk (GOLD) mission data contain significant quantitative information about the aurora on a global scale. Here we present techniques for quantifying such information, including the temporal development of the structure within the auroral oval using the GOLD images. These techniques are applied to auroral observations in the GOLD data, in particular showing an example of how the longitudinal structure within the aurora varies over the course of six consecutive days with differing levels of geomagnetic activity. A simple model of the solar-induced airglow is presented that is used to remove the sunlight contamination from the dayside auroral observations. Comparisons to ground-based auroral imaging are used for the overall auroral context and to make estimates of the proportionality between the intensities of the green line (557.7\ nm) emission in the visible and the 135.6\ nm emissions in the GOLD data. These observations are consistent with the intensity of the 135.6\ nm auroral emission being on the same order as the intensity of the 557.7\ nm auroral emission. They were both found to be around 1\ kR for a stable auroral arc on a day with low geomagnetic activity (3 November 2018) and around 10\ kR for an active auroral display on a day with higher levels of geomagnetic activity (5 November 2018). This could have important implications for making direct comparisons between space-based ultraviolet auroral imaging and ground-based visible-light auroral imaging and the total energy input estimates that are derived from them. Published by: Journal of Geophysical Research: Space Physics Published on: 02/2020 YEAR: 2020 DOI: 10.1029/2019JA027650 |
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In this work, we evaluated the quasi-realistic ionosphere forecasting capability by an ensemble Kalman filter (EnKF) ionosphere and thermosphere data assimilation algorithm. The National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model is used as the background model in the system. The slant total electron contents (TECs) from global International Global Navigation Satellite Systems Service ground-based receivers and from the Constellation Observing System for Meteorology, Ionosphere and Climate are assimilated into the system, and the ionosphere is then predicted in advance during the quiet interval of 23 to 27 March 2010. The predicted ionosphere vertical TEC (VTEC) and the critical frequency foF2 are validated by the Massachusetts Institute of Technology VTEC and global ionosondes network, respectively. We found that the ionosphere forecast quality could be enhanced by optimizing the thermospheric neutral components via the EnKF method. The ionosphere electron density forecast accuracy can be improved by at least 10\% for 24 hr. Furthermore, the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) [O/N2] observations are used to validate the predicted thermosphere [O/N2]. The validation shows that the [O/N2] optimized by EnKF has better agreement with the TIMED/GUVI observation. This study further demonstrates the validity of EnKF in enhancing the ionospheric forecast capability in addition to our previous observing system simulation experiments by He et al. (2019, https://doi.org/10.1029/2019JA026554). He, Jianhui; Yue, Xinan; Le, Huijun; Ren, Zhipeng; Wan, Weixing; Published by: Space Weather Published on: 02/2020 YEAR: 2020 DOI: 10.1029/2019SW002410 |
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Traits of sub-kilometre F-region irregularities as seen with the Swarm satellites During the night, in the F-region, equatorial ionospheric irregularities manifest as plasma depletions observed by satellites, and they may cause radio signals to fluctuate. In this study, the distribution characteristics of ionospheric F-region irregularities in the low latitudes were investigated using 16 Hz electron density observations made by a faceplate which is a component of the electric field instrument (EFI) onboard Swarm satellites of the European Space Agency (ESA). The study covers the period from October\ 2014 to October\ 2018 when the 16 Hz electron density data were available. For comparison, both the absolute (dNe) and relative (dNe/Ne) density perturbations were used to quantify the level of ionospheric irregularities. The two methods generally reproduced the local-time (LT), seasonal and longitudinal distribution of equatorial ionospheric irregularities as shown in earlier studies, demonstrating the ability of Swarm 16 Hz electron density data. A difference between the two methods was observed based on the latitudinal distribution of ionospheric irregularities where (dNe) showed a symmetrical distribution about the magnetic equator, while dNe/Ne showed a magnetic-equator-centred Gaussian distribution. High values of dNe and dNe/Ne were observed in spatial bins with steep gradients of electron density from a longitudinal and seasonal perspective. The response of ionospheric irregularities to geomagnetic and solar activities was also investigated using Kp index and solar radio flux index (F10.7), respectively. The reliance of dNe/Ne on solar and magnetic activity showed little distinction in the correlation between equatorial and off-equatorial latitudes, whereas dNe showed significant differences. With regard to seasonal and longitudinal distribution, high dNe and dNe/Ne values were often found during quiet magnetic periods compared to magnetically disturbed periods. The dNe increased approximately linearly from low to moderate solar activity. Using the high-resolution faceplate data, we were able to identify ionospheric irregularities on the scale of only a few hundred of metres. Aol, Sharon; Buchert, Stephan; Jurua, Edward; Published by: Annales Geophysicae Published on: 02/2020 YEAR: 2020 DOI: 10.5194/angeo-38-243-2020 |
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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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This chapter reviews fundamental properties and recent advances of diffuse and pulsating aurora. Diffuse and pulsating aurora often occurs on closed field lines and involves energetic electron precipitation by wave-particle interaction. After summarizing the definition, large-scale morphology, types of pulsation, and driving processes, we review observation techniques, occurrence, duration, altitude, evolution, small-scale structures, fast modulation, relation to high-energy precipitation, the role of ECH waves, reflected and secondary electrons, ionosphere dynamics, and simulation of wave-particle interaction. Finally we discuss open questions of diffuse and pulsating aurora. Nishimura, Yukitoshi; Lessard, Marc; Katoh, Yuto; Miyoshi, Yoshizumi; Grono, Eric; Partamies, Noora; Sivadas, Nithin; Hosokawa, Keisuke; Fukizawa, Mizuki; Samara, Marilia; Michell, Robert; Kataoka, Ryuho; Sakanoi, Takeshi; Whiter, Daniel; Oyama, Shin-ichiro; Ogawa, Yasunobu; Kurita, Satoshi; Published by: Space Science Reviews Published on: 01/2020 YEAR: 2020 DOI: 10.1007/s11214-019-0629-3 |
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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 |
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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 |
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Ionospheric parameters in the European sector during the magnetic storm of August 25—26, 2018 Blagoveshchensky, DV; Sergeeva, MA; Published by: Advances in Space Research Published on: |
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Chernigovskaya, MA; Shpynev, BG; Yasyukevich, AS; Khabituev, DS; Published by: Published on: |
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Hemispheric asymmetry of the dayside aurora due to imbalanced solar insolation Liou, Kan; Mitchell, Elizabeth; Published by: Scientific Reports Published on: |
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Published by: Chinese Journal of Geophysics Published on: |
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Case Study of Asymmetries in Polar Rain Aurora Herschbach, Dennis; Zhang, Yongliang; Published by: Published on: |
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Oberheide, J; Pedatella, NM; Gan, Q; Kumari, K; Burns, AG; Eastes, RW; Published by: Geophysical Research Letters Published on: |
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Reidy, Jade; Fear, Robert; Whiter, Daniel; Lanchester, Betty; Kavanagh, AJ; Price, David; Chadney, Joshua; Zhang, Yongliang; Paxton, Larry; , others; Published by: Published on: |
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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: |
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Ionospheric parameters in the European sector during the magnetic storm of August 25—26, 2018 The GUVI data used here are provided through support from the NASA MO&DA program. The GUVI instrument was designed and built by The Aerospace Corporation and The Johns Blagoveshchensky, DV; Sergeeva, MA; Published by: Advances in Space Research Published on: YEAR: 2020 DOI: 10.1016/j.asr.2019.07.044 |
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Climatology characteristics of ionospheric irregularities described with GNSS ROTI the Global Ultraviolet Imager (GUVI) settled on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission spacecraft. The GUVI-based model is completely Kotulak, Kacper; Zakharenkova, Irina; Krankowski, Andrzej; Cherniak, Iurii; Wang, Ningbo; Fron, Adam; Published by: Remote Sensing Published on: YEAR: 2020 DOI: 10.3390/rs12162634 |
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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 |
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First results of UV radiation measurements made by AURA detector onboard VDNH-80 cubesat GUVI experiment data Chernov, DV; Glinkin, EV; Klimov, PA; Murashov, AS; Published by: Advances in the Astronautical Sciences Published on: |
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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 |
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This paper focuses on unique aspects of the ionospheric response at conjugate locations over Europe and South Africa during the 7–8 September 2017 geomagnetic storm including Habarulema, John; Katamzi-Joseph, Zama; a, Dalia; Nndanganeni, Rendani; Matamba, Tshimangadzo; Tshisaphungo, Mpho; Buchert, Stephan; Kosch, Michael; Lotz, Stefan; Cilliers, Pierre; , others; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2020 DOI: 10.1029/2020JA028307 |
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In this article, we present a study of the perturbations occurring in the Earth’s environment on 7 October 2015. We use a multi-instrument approach, including space and ground Molina, Maria; Dasso, S; Mansilla, G; Namour, Jorge; Cabrera, Miguel; Zuccheretti, Enrico; Published by: Solar Physics Published on: YEAR: 2020 DOI: 10.1007/s11207-020-01728-7 |
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Global navigation satellite system (GNSS) precise positioning performance will be strongly affected under severe ionospheric anomaly conditions. The combination of multi-GNSS can increase the available observations and improve the geometry of continuously tracked satellites. This paper focuses on assessing the positioning performance with the combination of Global Positioning System (GPS), Global naya Navigatsionnaya Sputnikova Sistema (GLONASS), and BeiDou System (BDS) around the St. Patrick s Day geomagnetic storm (9–18 March) in 2015 in Hong Kong. The rate of total electron content (TEC) index (ROTI) indicates severe ionospheric anomalies before the superstorm, while it was absent during the main phase of the storm in Hong Kong. Furthermore, strong scintillation events on signal-to-noise ratio (SNR) and multipath (MP) observables are observed during ionospheric anomalies period. Then the performance of single-point positioning (SPP) and precise point positioning (PPP) with multi-GNSS is shown. The ionospheric scintillation events may reduce pseudorange accuracy but affect SPP performance a little in this study, while the PPP accuracy is vastly decreased due to the subsequent reconvergence caused by frequent cycle slip (CS). Compared to PPP solutions with GPS only, the accuracy is improved significantly with the combination of multi-GNSS. Lu, Yangwei; Wang, Zhenjie; Ji, Shengyue; Chen, Wu; Published by: Radio Science Published on: YEAR: 2020 DOI: 10.1029/2019RS007004 |
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Physical processes of meso-scale, dynamic auroral forms Meso-scale auroral forms, such as poleward boundary intensifications, streamers, omega bands, beads and giant undulations, are manifestations of dynamic processes in the magnetosphere driven, to a large part, by plasma instabilities in the magnetotail. New observations from ground- and space-based instrumentation and theoretical treatments are giving us a clearer view of some of the physical processes behind these auroral forms. However, questions remain as to how some of these observations should be interpreted, given uncertainties in mapping auroral features to locations in the magnetotatil and due to the significant overlap in the results from a variety of models of different plasma instabilities. We provide an overview of recent results in the field and seek to clarify some of the remaining questions with regards to what drives some of the largest and most dynamic auroral forms. Forsyth, C; Sergeev, VA; Henderson, MG; Nishimura, Y; Gallardo-Lacourt, B; Published by: Space Science Reviews Published on: YEAR: 2020 DOI: 10.1007/s11214-020-00665-y |
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Challenges to understanding the Earth s ionosphere and thermosphere We discuss, in a limited way, some of the challenges to advancing our understanding and description of the coupled plasma and neutral gas that make up the ionosphere and Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2020 DOI: 10.1029/2019JA027497 |
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Effects of the interplanetary magnetic field y component on the dayside aurora A dawn\textendashdusk asymmetry in many high-latitude ionospheric and magnetospheric phenomena, including the aurora, can be linked to the east\textendashwest (y) component of the interplanetary magnetic field (IMF). Owing to the scarcity of observations in the Southern Hemisphere, most of the previous findings are associated with the Northern Hemisphere. It has long been suspected that if the IMF By component also produces a dawn\textendashdusk asymmetry and/or a mirror image in the Southern Hemisphere as predicted by some theories. The present study explores the effect of the IMF By component on the dayside aurora from both hemispheres by analyzing the auroral emission data from the Global UltraViolet scanning spectrograph Imager on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission spacecraft from 2002 to 2007. The data set comprises 28,774 partial images of the northern hemispheric oval and 29,742 partial images of the southern hemispheric oval, allowing for a statistical analysis. It is found that even though auroras in different regions of the dayside oval respond differently to the orientation of the IMF By component, their responses are opposite between the two hemispheres. For example, at ~ 1400\textendash1600\ MLT in the Northern Hemisphere, where the so-called 1500\ MLT auroral hot spots occur, peak auroral energy flux is larger for negative IMF By comparing to positive IMF By. The response is reversed in the Southern Hemisphere. The present study also suggests that the total energy flux does not change with the IMF By orientation change. This result is consistent with a larger (smaller) convection vortex in the postnoon sector for IMF By \< 0 (By \> 0) resulting from anti-parallel merging. Published by: Geoscience Letters Published on: 11/2019 YEAR: 2019 DOI: 10.1186/s40562-019-0141-3 |
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Variations of ionospheric parameters Total Electron Content (TEC) by GNSS, critical frequency (foF2) by vertical sounding and electron density (Ne) by low-altitude satellite were studied at high, mid and low latitudes of the European sector during the magnetic storm of August 25\textendash26, 2018. During the main phase of the storm the ionospheric F2-layer was under the positive disturbance at mid and low latitudes. Then the transition from the positive to negative ΔfoF2 values occurred at all latitudes. The recovery phase was characterized by negative ionospheric disturbance at all latitudes. This is due to the decrease of thermospheric O/N2 ratio during the recovery phase of the storm. The intense Es layers screened the reflections from the F2-layer on August 26th at high and at low latitudes but at different times. Some blackouts occurred due to the high absorption level at high latitudes. In general, foF2 and TEC data were highly correlated. The major Ne changes were at the low latitudes. In general, Ne data confirmed the ionospheric dynamics revealed with foF2 and TEC. Blagoveshchensky, D.V.; Sergeeva, M.A.; Published by: Advances in Space Research Published on: 08/2019 YEAR: 2019 DOI: 10.1016/j.asr.2019.07.044 |
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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 |
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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 |
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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 |
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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 |
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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 |
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It has been known for decades that the nightside aurora in the Northern Hemisphere (NH) tends to be brighter when the interplanetary magnetic field (IMF) measured at Earth has a dawnward (negative y) component compared to a duskward (positive y) component. This asymmetric response to the polarity of IMF By has been explained by an interhemispheric current flowing out of the NH due to a nonuniform \textquotedblleftpenetration\textquotedblright of IMF By onto the magnetotail. If such a hypothesis is correct, it should predict a brighter aurora in the nightside Southern Hemisphere (SH) for positive IMF By than negative IMF By. Here we investigate this hypothesis using Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics/Global Ultraviolet Imager data. The present study not only reproduces the result previously found in NH but also shows an opposite change to its Northern Hemispheric counterpart in SH in response to the different IMF By polarity. When comparing north to south, for negative IMF By, the premidnight auroral energy flux is greater in NH than that in SH. The result becomes opposite for positive IMF By. This result is consistent with the hypothesis of the existence of an interhemispheric field-aligned current. Published by: Journal of Geophysical Research: Space Physics Published on: 02/2019 YEAR: 2019 DOI: 10.1029/2018JA025953 |
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Longitudinal variations of the ionospheric trough position For the first time a comprehensive pattern of the longitudinal effect of the ionospheric trough position was obtained. We present new results with longitudinal variations of the winter trough position as a function of geomagnetic latitude for both hemispheres and conditions of high and low solar activity and all local time hours. We used a large observational data set obtained onboard the Kosmos-900, Interkosmos-19 and CHAMP satellites for quiet geomagnetic conditions. We found that a magnitude of the trough position longitudinal effect averaged for a fixed local time is greater in the daytime (6\textendash8\textdegree) than in the nighttime (3\textendash5\textdegree). The longitudinal effect magnitude reaches its maximum (16\textdegree) in the morning (at 08 LT) in the Southern hemisphere at high solar activity. But on certain days at any solar activity the longitudinal effect magnitude can reach 9\textendash10\textdegree even at night. The shape of the longitudinal effect was found to differ significantly in two hemispheres. In the Northern hemisphere the trough is usually closest to the pole in the eastern (American) longitudinal sector, and in the Southern hemisphere the trough is closest in the western (Eurasian) longitudinal sector. The magnitude and shape of the longitudinal effect is also different during low and high solar activity. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) simulations demonstrate that during low solar activity, the longitudinal variations of the daytime trough position is mainly determined by longitudinal variations of the ionization function, formed due to the longitudinal variations in the solar zenith angle and the atomic oxygen density distribution. The longitudinal variations of the nighttime trough position is formed by the longitudinal variations in ionization of precipitating auroral particles, neutral atmosphere composition, and electric field. Karpachev, A.T.; Klimenko, M.V.; Klimenko, V.V.; Published by: Advances in Space Research Published on: 01/2019 YEAR: 2019 DOI: 10.1016/j.asr.2018.09.038 |