Bibliography
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Notice:
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Found 2276 entries in the Bibliography.
Showing entries from 201 through 250
| 2021 |
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Non-storm time thermospheric O/N 2 depletion and NO enhancement Zhang, Yongliang; Paxton, Larry; Wang, Wenbin; Huang, Chaosong; Published by: Published on: |
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Investigating Geocoronal Absorption for Wavelength Calibration of Sounding Rockets Donders, Nicolas; Winebarger, Amy; Kankelborg, Charles; Vigil, Genevieve; Paxton, Larry; Zank, Gary; Published by: Published on: |
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Liang, Jun; Sydorenko, Dmytro; Donovan, Eric; Rankin, Robert; Published by: Published on: |
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Progresses and Challenges to specifying the IT system during weak storms Deng, Yue; Heelis, Roderick; Paxton, Larry; Lyons, Larry; Nishimura, Toshi; Zhang, Shunrong; Bristow, Bill; Maute, Astrid; Sheng, Cheng; Zhu, Qingyu; , others; Published by: Published on: |
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Space Physics and Aeronomy: Space Physics and Aeronomy, Solar Physics and Solar Wind Raouafi, Nour; Vourlidas, Angelos; Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Signatures of conjugate photoelectrons in the ionosphere and thermosphere Kil, Hyosub; Paxton, Larry; Schaefer, Robert; Huba, Joseph; Published by: Published on: |
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Solar, auroral, and radiation belt electrons enter the atmosphere at polar regions leading to ionization and affecting its chemistry. Climate models usually parametrize this ionization and the related changes in chemistry based on satellite particle measurements. Precise measurements of the particle and energy influx into the upper atmosphere are difficult because they vary substantially in location and time. Widely used particle data are derived from the POES and GOES satellite measurements which provide electron and proton spectra. We present the electron energy and flux measurements from the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instruments on board the Defense Meteorological Satellite Program (DMSP) satellites. This formation of now three operating satellites observes the auroral zone in the UV from which electron energies and fluxes are inferred in the range from 2 keV to 20 keV. We use these observed electron energies and fluxes to calculate ionization rates and electron densities in the upper mesosphere and lower thermosphere (≈ 80–200 km). We present our validation study of the SSUSI-derived electron densities to those measured by the ground-based EISCAT radar stations. We find that with the current standard parametrizations, the SSUSI-derived auroral electron densities (90–150 km) agree well with EISCAT measurements, with differences between +/- 20% for F18, and +/- 50 % for F17. The largest differences are at the lower end of the altitude range because there the electron densities decline very rapidly. Bender, Stefan; Espy, Patrick; Paxton, Larry; Published by: Earth and Space Science Open Archive ESSOAr Published on: YEAR: 2021 DOI: 10.1002/essoar.10506056.1 |
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Validation of SSUSI-derived auroral electron densities: comparisons to EISCAT data Bender, Stefan; Espy, Patrick; Paxton, Larry; Published by: Published on: |
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Recently, citizen scientist photographs led to the discovery of a new auroral form called “the dune aurora” which exhibits parallel stripes of brighter emission in the green diffuse aurora at about 100 km altitude. This discovery raised several questions, such as (i) whether the dunes are associated with particle precipitation, (ii) whether their structure arises from spatial inhomogeneities in the precipitating fluxes or in the underlying neutral atmosphere, and (iii) whether they are the auroral manifestation of an atmospheric wave called a mesospheric bore. This study investigates a large-scale dune aurora event on 20 January 2016 above Northern Europe. The dunes were observed from Finland to Scotland, spanning over 1,500 km for at least 4 h. Spacecraft observations indicate that the dunes are associated with particle precipitation and reveal the presence of a temperature inversion layer below the mesopause during the event, creating suitable conditions for mesospheric bore formation. The analysis of a time lapse of pictures by a citizen scientist from Scotland leads to the estimate that, during this event, the dunes propagate toward the west-southwest direction at about 200 m s−1, presumably indicating strong horizontal winds near the mesopause. These results show that citizen science and dune aurora studies can fill observational gaps and be powerful tools to investigate the least-known region of near-Earth space at altitudes near 100 km. Grandin, Maxime; Palmroth, Minna; Whipps, Graeme; Kalliokoski, Milla; Ferrier, Mark; Paxton, Larry; Mlynczak, Martin; Hilska, Jukka; Holmseth, Knut; Vinorum, Kjetil; , others; Published by: AGU Advances Published on: YEAR: 2021 DOI: https://doi.org/10.1029/2020AV000338 |
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Space Physics and Aeronomy, Ionosphere Dynamics and Applications Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Exploring the Upper Atmosphere: Using Optical Remote Sensing Paxton, Larry; Zhang, Yongliang; Kil, Hyosub; Schaefer, Robert; Published by: Upper Atmosphere Dynamics and Energetics Published on: |
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Inversion of Ionospheric O/N-2 by Using FY-3D Ionospheric Photometer Data Da-xin, Wang; Li-ping, Fu; Fang, Jiang; Nan, Jia; Tian-fang, Wang; Shuang-tuan, Dou; Published by: SPECTROSCOPY AND SPECTRAL ANALYSIS Published on: |
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Space Physics and Aeronomy, Upper Atmosphere Dynamics and Energetics Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Space Physics and Aeronomy, Magnetospheres in the Solar System Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Space Physics and Aeronomy, Solar Physics and Solar Wind Zhang, Yongliang; Paxton, Larry; Published by: Published on: |
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Carter, Jennifer; Samsonov, Andrey; Milan, Stephen; Branduardi-Raymont, Graziella; Ridley, Aaron; Paxton, Larry; Anderson, Brian; Waters, Colin; Edwards, Thomas; Published by: Earth and Space Science Open Archive ESSOAr Published on: |
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Goncharenko, Larisa; Harvey, Lynn; Greer, Katelynn; Zhang, Shun-Rong; Coster, Anthea; Paxton, Larry; Published by: Geophysical Research Letters Published on: |
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Smith, Todd; Hacala, Ryan; Hohlfeld, Erik; Edens, Weston; Hibbitts, Charles; Paxton, Larry; Arnold, Steven; Westlake, Joseph; Rymer, Abigail; Chacos, Al; , others; Published by: Gravitational and Space Research Published on: |
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Transpolar arcs: Seasonal dependence identified by an automated detection algorithm Bower, Gemma; Milan, Stephen; Paxton, Larry; Published by: Earth and Space Science Open Archive ESSOAr Published on: |
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Ionospheric and thermospheric contributions in TIMED/GUVI O 135.6 nm radiances Zhang, Yongliang; Paxton, Larry; Schaefer, Robert; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Schaefer, Robert; Paxton, Larry; Zhang, Yongliang; Kil, Hyosub; Romeo, Giuseppe; Wolven, Brian; Yonker, Justin; Published by: Published on: |
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Dual-lobe reconnection and cusp-aligned auroral arcs Milan, Stephen; Bower, Gemma; Carter, Jennifer; Paxton, Larry; Anderson, Brian; Hairston, Marc; Published by: Published on: |
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The Universal Time Variations of the Intensity of Afternoon Aurora in Equinoctial Seasons The afternoon auroral emissions are investigated in the equinoxes for geomagnetically quiet conditions (Kp = 1) using auroral images from ultraviolet imager (UVI) aboard the Polar satellite. They are compared with solar illumination effects (the solar zenith angle [SZA] and the consequent ionospheric conductivity) and the dipole tilt angle, as well as the observational region 1 upward field-aligned currents (FACs) from AMPERE data. The averaged afternoon auroral emissions have pronounced universal time (UT) variations with valley (2.8 photons/cm2/s) at around 01:00–03:00 UT and peak (4.7 photons/cm2/s) at around 17:00–19:00 UT. They generally vary with the solar illumination, the dipole tilt angle and the observed region 1 upward FACs as a function of UT. The afternoon auroral intensity is anticorrelated with the SZA and positively proportional to the solar EUV-produced Pedersen conductivity, region 1 upward FACs and dipole tilt angle. Additionally, they depend weakly on solar flux under geomagnetically quiet conditions. These results suggest that in the afternoon auroral region, the peak auroral emissions are closely associated with the peak conductivity and the maximum upward FACs. Other mechanisms, such as the dipole tilt angle, may also contribute. Further comparison between the northern afternoon aurora and the FACs in the two conjugate hemispheres suggests little contributions on the auroral UT variations from the interhemispheric FACs in the equinoxes. Wang, Lingmin; Luan, Xiaoli; Lei, Jiuhou; Lynch, Kristina; Zhang, Binzheng; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028504 afternoon auroral emissions; auroral hot spots; dipole tilt angle; region 1 upward FACs; solar zenith angle; UT variations |
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The delayed ionospheric response is analyzed for two well-defined 27-day solar rotation periods in the year 2019 with solar radio flux index F10.7 and Global-scale Observations of the Limb and Disk (GOLD) data, like solar extreme ultraviolet (EUV) flux proxy, O/N2 column density ratio and peak electron density, as well as International Global Navigation Satellite System Service rapid high-rate total electron content (TEC) map data. Although the correlation between GOLD solar EUV flux proxy and TEC is similar to the correlation between F10.7 and TEC, it is shown that the estimated delays based on GOLD data are in much better agreement with recent studies using EUV measurements compared to the delays based on F10.7 data. The GOLD peak electron density correlates well with TEC and allows insight to a local time interval when the ionosphere is not controlled by solar activity changes (17:00 LT to 21:00 LT). The present study investigates the impact of the solar activity (F10.7, GOLD EUV flux proxy) and O/N2 column density ratio on the ionospheric delay for two representative solar rotation periods. The capabilities of GOLD data for future research on the ionospheric response to the 27-day solar rotation period are demonstrated and discussed. These results are crucial information for precise ionospheric models and forecasts. Schmölter, Erik; Berdermann, Jens; Codrescu, Mihail; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028861 Ionosphere; solar proxies; time delay; total electron content |
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MLT science enabled by atmospheric lidars With the pioneering development and deployment of different types of narrowband sodium fluorescence lidars in Europe (1985) and North America (1990) along with subsequent potassium and iron lidars, temperature and wind profilers have been observed to investigate atmospheric dynamics in the mesosphere and lower thermosphere (MLT) in midlatitude, polar and equatorial regions. Their achieved resolution allows investigation ranging from small-scale gravity waves to long-term global change. This chapter highlights MLT science enabled by resonance fluorescence lidars in the past 30 years, divided into sections on climatology and long-term change of the atmospheric (background) state; MLT responses to external forcings that lead to atmospheric tides, the global-scale impacts of sudden stratospheric warming as well as geomagnetic storms; gravity wave dynamics and their fluxes; synergistic campaigns with lidars serving as a central instrument, and lidar observation of metal layers in the thermosphere at ever-higher altitudes. Recent advances in maintenance-free resonance lidars will increase the time and duration of lidar observation as well as their ease of operation. These should lead to more coherent multiple-day continuous observations of the MLT. Continued efforts to increase lidar signal/noise and to extend measurements from the main metal layers (80–110 km) into the lower thermosphere (up to 150 km) are ongoing. Further technology developments will also enable more lidar deployment on airplanes and in space to study the MLT over the oceans and other remote areas. She, Chiao-Yao; Liu, Alan; Yuan, Tao; Yue, Jia; Li, Tao; Ban, Chao; Friedman, Jonathan; Published by: Published on: YEAR: 2021 DOI: 10.1002/9781119815631.ch20 Geomagnetic storms; atmospheric stabilities; atmospheric state; climatology; clustered instrumentation; gravity wave dynamics; MLT science; resonance fluorescence lidars; sporadic metal layers; thermospheric metal layers |
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Impact of Storm-Enhanced Density (SED) on Ion Upflow Fluxes During Geomagnetic Storm The impact of the dynamic evolution of the Storm-Enhanced Density (SED) on the upward ion fluxes during the March 06, 2016 geomagnetic storm is studied using comprehensive multi-scale datasets. This storm was powered by a Corotating Interaction Region (CIR), and the minimum Sym-H reached ∼−110 nT. During the ionospheric positive storm phase, the SED formed and the associated plume and polar cap patches occasionally drifted anti-sunward across the polar cap. When these high-density structures encountered positive vertical flows, large ion upward fluxes were produced, with the largest upward flux reaching 3 × 1014 m−2s−1. These upflows were either the type-1 ion upflow associated with fast flow channels, such as the subauroral polarization stream (SAPS) channel, or the type-2 ion upflow due to soft particle precipitations in the cusp region. The total SED-associated upflow flux in the dayside cusp can be comparable to the total upflow flux in the nightside auroral zone despite the much smaller cusp area compared with the auroral zone. During the ionospheric negative storm phase, the ionospheric densities within the SED and plume decreased significantly and thus led to largely reduced upward fluxes. This event analysis demonstrates the critical role of the ionospheric high-density structures in creating large ion upward fluxes. It also suggests that the dynamic processes in the coupled ionosphere-thermosphere system and the resulting state of the ionospheric storm are crucial for understanding the temporal and spatial variations of ion upflow fluxes and thus should be incorporated into coupled geospace models for improving our holistic understanding of the role of ionospheric plasma in the geospace system. Zou, Shasha; Ren, Jiaen; Wang, Zihan; Sun, Hu; Chen, Yang; Published by: Frontiers in Astronomy and Space Sciences Published on: |
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Evaluating Auroral Forecasts Against Satellite Observations The aurora is a readily visible phenomenon of interest to many members of the public. However, the aurora and associated phenomena can also significantly impact communications, ground-based infrastructure, and high-altitude radiation exposure. Forecasting the location of the auroral oval is therefore a key component of space weather forecast operations. A version of the OVATION-Prime 2013 auroral precipitation model (Newell et al., 2014, https://doi.org/10.1002/2014sw001056) was used by the UK Met Office Space Weather Operations Centre (MOSWOC). The operational implementation of the OVATION-Prime 2013 model at the UK Met Office delivered a 30-min forecast of the location of the auroral oval and the probability of observing the aurora. Using weather forecast evaluation techniques, we evaluate the ability of the OVATION-Prime 2013 model forecasts to predict the location and probability of the aurora occurring by comparing the forecasts with auroral boundaries determined from data from the IMAGE satellite between 2000 and 2002. Our analysis shows that the operational model performs well at predicting the location of the auroral oval, with a relative operating characteristic (ROC) score of 0.82. The model performance is reduced in the dayside local time sectors (ROC score = 0.59) and during periods of higher geomagnetic activity (ROC score of 0.55 for Kp = 8). As a probabilistic forecast, OVATION-Prime 2013 tends to underpredict the occurrence of aurora by a factor of 1.1–6, while probabilities of over 90\% are overpredicted. Mooney, M.; Marsh, M.; Forsyth, C.; Sharpe, M.; Hughes, T.; Bingham, S.; Jackson, D.; Rae, I.; Chisham, G.; Published by: Space Weather Published on: YEAR: 2021 DOI: 10.1029/2020SW002688 AURORA; auroral forecasting; forecast verification; OVATION-Prime 2013; ROC scores; space weather |
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Assimilative Mapping of Electron Flux Using SSUSI Lyman-Birge-Hopfield Emissions Far ultraviolet (FUV) imaging of the aurora from space provides great insight into the dynamic coupling of the Earth’s atmosphere, ionosphere and magnetosphere on global scales. To gain quantitative understanding of these coupling processes, the global distribution of auroral energy flux is required, but the inversion of FUV emission to derive precipitating auroral particles’ energy flux is not straightforward. Furthermore, the spatial coverage of FUV imaging from LEO altitudes is often insufficient to achieve global mapping of this important parameter. This study seeks to fill these gaps left by the current geospace observing system using a combination of data assimilation and machine learning techniques. Specifically, this paper presents a new data-driven modeling approach to create instantaneous, global assimilative mappings of auroral electron total energy flux from Lyman-Birge-Hopfield (LBH) emission data from the Defense Meteorological System Program (DMSP) Special Sensor Ultraviolet Spectrographic Imager (SSUSI). The approach takes a two-step approach; the creation of assimilative maps of LBH emission using optimal interpolation, followed by the conversion to energy flux using a neural network model trained with conjunction observations of in-situ auroral particles and LBH emission from the DMSP SSJ and SUSSI instruments. We demonstrate the feasibility of this approach with a model prototype built with DMSP data from February 17-23 2014. This study serves as a blueprint for a future comprehensive data-driven modeling of auroral energy flux that is complimentary to traditional inversion techniques to take advantage of FUV imaging from LEO platforms for global assimilative mapping of auroral energy flux. Published by: Published on: Assimilative mapping; Electron flux; Far ultraviolet imaging; Lyman-Birge-Hopfield emission |
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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 of far-ultraviolet (FUV) dayglow by the Global-scale Observations of Limb and Disk (GOLD) mission provide a new opportunity to monitor relative composition changes in the upper atmosphere as well as solar extreme ultraviolet (EUV) variability. Relative composition changes are quantified by ΣO/N2, the column density ratio of atomic oxygen to molecular nitrogen, while QEUV provides a measure of the solar EUV energy flux from 1 to 45 nm into the upper atmosphere. This spectral range provides the ionizing radiation which ultimately results in FUV airglow emission produced by photodissociation and photoelectron impact. The quantities ΣO/N2 and QEUV are derived from GOLD FUV observations through lookup tables that are constructed using a first-principles photoelectron transport model. The two FUV emissions used are O I 135.6 nm and the N2 Lyman-Birge-Hopfield (LBH) bands. We present an overview of the theoretical basis for the algorithms and practical considerations for application to GOLD data. The effects of uncertainties in electron impact cross sections, off-nadir viewing, and instrument artifacts are reviewed. We also discuss GOLD Level 1C DAY, Level 2 data products ON2 and QEUV, and present representative samples of each. Correira, J.; Evans, J.; Lumpe, J.; Krywonos, A.; Daniell, R.; Veibell, V.; McClintock, W.; Eastes, R.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029517 GOLD; neutral composition; ON2; QEUV; radiative recombination; thermosphere |
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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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Traveling ionospheric disturbances (TIDs) and their neutral counterparts known as traveling atmospheric disturbances (TADs) are believed to play a role in communicating inputs to other locations in the fluid. While these two phenomena are believed to be connected, they may not have a one-to-one correspondence as the geomagnetic field influences the TID but has no direct impact on the TAD. The relative amplitudes of the perturbations seen in the ionosphere and atmosphere have been observed but rarely together. This study reports results from a 3-day campaign to observe TIDs and TADs simultaneously over a broad latitudinal region over the eastern United States using a combination of Global-scale Observations of the Limb and Disk (GOLD) and a distributed network of ground-based Global Navigation Satellite System (GNSS) receivers. These results demonstrate that GOLD and the ground-based total electron content (TEC) observations can see the atmospheric and ionospheric portions of a large-scale traveling disturbance. The phase difference in the perturbations to the GOLD airglow brightness, O/N2 and thermospheric disk temperature are consistent with an atmospheric gravity wave moving through this region. The ionospheric signatures move at the same rate as those in the atmosphere, but their amplitudes do not have a simple correspondence to the amplitude of the signal seen in the atmosphere. This campaign demonstrates a proof-of-concept that this combination of observations is able to provide information on TIDs and TADs, including quantifying their impact on the temperature and chemical composition of the upper atmosphere. England, Scott; Greer, Katelynn; Zhang, Shun-Rong; Evans, Scott; Solomon, Stanley; Eastes, Richard; McClintock, William; Burns, Alan; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029248 |
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We analyze horizontal plasma drifts measured by the Defense Meteorological Satellite Program satellites during two intense magnetic storms. It is found, for the first time, that westward plasma flows associated with subauroral polarization streams (SAPS) in the dusk-evening sector penetrate continuously to equatorial latitudes. The westward ion drifts between subauroral and equatorial latitudes occur nearly simultaneously. The latitudinal profile of the westward ion drifts at low latitudes (approximately within ±30° magnetic latitude [MLat]) is relatively flat, and the westward ion drifts at the magnetic equator reach 200–300 m s−1. In the dawn-morning sector, eastward ion drifts at subauroral latitudes are also SAPS. The storm-time dawnside auroral boundary moves to ∼±55° MLat, and the dawnside SAPS penetrate to ∼±20° MLat at 0930 local time. A dawnside SAPS flow channel appears to exist, although it is not as well defined as the duskside SAPS flow channel. Thermospheric wind data measured by the Challenging Minisatellite Payload satellite are analyzed, and zonal disturbance winds are derived. Disturbance winds can reach equatorial latitudes rapidly near midnight but are limited to ±40° geographic latitude or higher near noon. The effects of disturbance winds on the zonal ion drifts at middle and low latitudes are discussed. It is suggested that both the westward ion drifts at middle and low latitudes in the dusk-evening sector and the eastward ion drifts at middle and lower latitudes in the dawn-morning sector are caused primarily by penetration of the SAPS and auroral electric fields. Huang, Chao-Song; Zhang, Yongliang; Wang, Wenbin; Lin, Dong; Wu, Qian; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA030001 Electric field; Ionosphere; ionospheric plasma drift; penetration electric field; Subauroral Polarization Streams; thermospheric wind |
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Equatorial Ionization Anomaly Variations During Geomagnetic Storms The equatorial ionization anomaly (EIA) was discovered in the 1940s. Since then, the research on ionospheric storm effects at the equatorial and low latitudes has become one of the hottest topics in the ionospheric community. During the past 2 decades, large amounts of ionospheric and thermospheric data from the ground-based and satellite-borne observations and also from the novel capability of three-dimensional numerical models stimulated the ionospheric weather studies. Recent scientific progresses on the EIA response to geomagnetic storms are briefly described here, together with some suggestions for the future research directions of the EIA storm effects. Published by: Published on: YEAR: 2021 DOI: 10.1002/9781119815617.ch13 Geomagnetic storms; Equatorial ionization anomaly; equatorial ionospheric response; equatorial regions; low latitude regions; physical mechanisms |
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We present new measurements of the vertical density profile of the Earth s atmosphere at altitudes between 70 and 200 km, based on Earth occultations of the Crab Nebula observed with the X-ray Imaging Spectrometer onboard Suzaku and the hard X-ray Imager onboard Hitomi. X-ray spectral variation due to the atmospheric absorption is used to derive tangential column densities of the absorbing species, that is, N and O including atoms and molecules, along the line of sight. The tangential column densities are then inverted to obtain the atmospheric number density. The data from 219 occultation scans at low latitudes in both hemispheres from September 15, 2005 to March 26, 2016 are analyzed to generate a single, highly averaged (in both space and time) vertical density profile. The density profile is in good agreement with the Naval-Research-Laboratory s-Mass-Spectrometer-Incoherent-Scatter-Radar-Extended (NRLMSISE-00) model, except for the altitude range of 70–110 km, where the measured density is ∼50\% smaller than the model. Such a deviation is consistent with the recent measurement with the SABER aboard the TIMED satellite (Cheng et al., 2020, https://doi.org/10.3390/atmos11040341). Given that the NRLMSISE-00 model was constructed some time ago, the density decline could be due to the radiative cooling/contracting of the upper atmosphere as a result of greenhouse warming in the troposphere. However, we cannot rule out a possibility that the NRL model is simply imperfect in this region. We also present future prospects for the upcoming Japan-US X-ray astronomy satellite, X-Ray Imaging and Spectroscopy Mission (XRISM), which will allow us to measure atmospheric composition with unprecedented spectral resolution of ΔE ∼ 5 eV in 0.3–12 keV. Katsuda, Satoru; Fujiwara, Hitoshi; Ishisaki, Yoshitaka; Yoshitomo, Maeda; Mori, Koji; Motizuki, Yuko; Sato, Kosuke; Tashiro, Makoto; Terada, Yukikatsu; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2020JA028886 Crab Nebula; Hitomi; occultation; Suzaku; upper atmosphere; X-rays |
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A Synoptic-Scale Wavelike Structure in the Nighttime Equatorial Ionization Anomaly Both ground- and satellite-based airglow imaging have significantly contributed to understanding the low-latitude ionosphere, especially the morphology and dynamics of the equatorial ionization anomaly (EIA). The NASA Global-scale Observations of the Limb and Disk (GOLD) mission focuses on far-ultraviolet airglow images from a geostationary orbit at 47.5°W. This region is of particular interest at low magnetic latitudes because of the high magnetic declination (i.e., about -20°) and proximity of the South Atlantic magnetic anomaly. In this study, we characterize an exciting feature of the nighttime EIA using GOLD observations from October 5, 2018 to June 30, 2020. It consists of a wavelike structure of a few thousand kilometers seen as poleward and equatorward displacements of the EIA-crests. Initial analyses show that the synoptic-scale structure is symmetric about the dip equator and appears nearly stationary with time over the night. In quasi-dipole coordinates, maxima poleward displacements of the EIA-crests are seen at about ± 12° latitude and around 20 and 60° longitude (i.e., in geographic longitude at the dip equator, about 53°W and 14°W). The wavelike structure presents typical zonal wavelengths of about 6.7 × 103 km and 3.3 × 103 km. The structure s occurrence and wavelength are highly variable on a day-to-day basis with no apparent dependence on geomagnetic activity. In addition, a cluster or quasi-periodic wave train of equatorial plasma depletions (EPDs) is often detected within the synoptic-scale structure. We further outline the difference in observing these EPDs from FUV images and in situ measurements during a GOLD and Swarm mission conjunction. Rodríguez-Zuluaga, J.; Stolle, C.; Yamazaki, Y.; Xiong, C.; England, S.; Published by: Earth and Space Science Published on: YEAR: 2021 DOI: 10.1029/2020EA001529 equatorial plasma bubbles; Equatorial ionization anomaly; Equatorial ionosphere; forcing from below; wave structure |
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This paper reports that plasma density depletions appearing at middle latitudes near sunrise survived until afternoon on 29 May 2017 during the recovery phase of a geomagnetic storm. By analyzing GPS data collected in Japan, we investigate temporal variations in the horizontal two-dimensional distribution of total electron content (TEC) during the geomagnetic storm. The SYM-H index reached −142 nT around 08 UT on 28 May 2017. TEC depletions extending up to approximately 38°N along the meridional direction appeared over Japan around 05 LT (LT = UT + 9 hours) on 29 May 2017, when TEC rapidly increased at sunrise due to the solar extreme ultraviolet (EUV) radiation. The TEC depletions appeared sequentially over Japan for approximately 8 hours in sunlit conditions. At 06 LT on 29 May, when the plasma depletions first appeared over Japan, the background TEC was enhanced to approximately 17 TECU, and then decreased to approximately 80\% of the TEC typical of magnetically quiet conditions. We conclude that this temporal variation of background plasma density in the ionosphere was responsible for the persistence of these plasma depletions for so long in daytime. By using the Naval Research Laboratory: Sami2 is Another Model of the Ionosphere (SAMI2), we have evaluated how plasma production and ambipolar diffusion along the magnetic field may affect the rate of plasma depletion disappearance. Simulation shows that the plasma density increases at the time of plasma depletion appearance; subsequent decreases in the plasma density appear to be responsible for the long-lasting persistence of plasma depletions during daytime. The plasma density depletion in the top side ionosphere is not filled by the plasma generated by the solar EUV productions because plasma production occurs mainly at the bottom side of the ionosphere. Otsuka, Yuichi; Shinbori, Atsuki; Sori, Takuya; Tsugawa, Takuya; Nishioka, Michi; Huba, Joseph; Published by: Earth and Planetary Physics Published on: YEAR: 2021 DOI: 10.26464/epp2021046 Ionosphere; GPS; ionospheric irregularity; plasma bubble; SAMI2 |
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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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We describe a long-term data set of global average thermospheric mass density derived from orbit data on ∼7,700 objects in low Earth orbit, via the effect of atmospheric drag. The data cover the years 1967–2019 and altitudes 250–575 km, and the temporal resolution is 3–4 days for most years. The data set is an extension and revision of a previous version. The most important change is the use of more precise orbit data: special perturbation state vectors are now used starting in 2001, instead of mean Keplerian orbital elements. The data are suitable for climatological studies of thermospheric variations and trends, and for space weather studies on time scales longer than 3 days. Emmert, J.; Dhadly, M.; Segerman, A.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029455 |
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Auroral Energy Flux and Joule Heating Derived From Global Maps of Field-Aligned Currents We calculate auroral energy flux and Joule heating in the high-latitude ionosphere for 27 geomagnetically active days using two-dimensional maps of field-aligned currents determined by the Active Magnetosphere and Planetary Response Experiment. The energy input to the ionosphere due to Joule heating increases more rapidly with geomagnetic activity than that due to precipitating particles. The energy flux varies more smoothly with time than Joule heating, which is impulsive in nature on time scales from minutes to tens of minutes. These impulsive events correlate well with recoveries in the Sym-H index, with the maximum correlation when compared to Sym-H recoveries 70 min later. Because of prior studies that have associated transient recoveries of Sym-H with substorm expansions, the delay found here suggests that dissipation of energy in the ionosphere occurs during the substorm growth phase prior to the release of magnetic energy caused by diversion of tail currents. Published by: Geophysical Research Letters Published on: YEAR: 2021 DOI: 10.1029/2020GL091527 Geomagnetic storms; Auroral energy flux; auroral energy input; auroral substorms; Joule heating; ring current |
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SuperHAPI: SuperMAG and TIMED/GUVI Data-agnostic Delivery Using HAPI We implemented an extensible Python server for the HAPI (Heliophysics Application Programmers Interface) specification to serve time series data from multiple missions that store their Antunes, Alex; Vandegriff, Jon; Published by: Published on: |
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The dominant composition on the O/N2 responses during a geomagnetic storm Here, TIMED/GUVI limb measurements and TIEGCM simulations were used to investigate The consistency of O/N2 variations between GUVI observations and TIEGCM predictions Yu, Tingting; Wang, Wenbin; Ren, Zhipeng; Cai, Xuguang; Published by: Published on: |
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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 |
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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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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: |
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Neutral Hydrogen in the Terrestrial Thermosphere and Exosphere The exosphere is the interface between the Earth s neutral atmosphere and interplanetary space. Our understanding of this important interface, through observations of its mean state and its response to external forcing, will provide important constraints as we seek to develop a complete picture of our complicated space-atmosphere system. This chapter will highlight the contributions of ground-based geocoronal hydrogen observations to our understanding of this system. Observations are made throughout the night; the base of the Earth s shadow is used as a first-order probe of the exosphere s altitude structure. Major areas of scientific focus include (1) high resolution observations of the geocoronal hydrogen Balmer α line profile and its relation to excitation mechanisms, effective temperature, and exospheric physics; (2) retrieval of geocoronal hydrogen parameters such as the hydrogen column abundance [H], the hydrogen density profile [H]( z ), and the photochemically initiated hydrogen flux ϕ (H); and (3) long-term observations of the geocoronal hydrogen column emission intensity for the investigation of natural variability, such as solar cycle trends, and of potential anthropogenic change due to increases in atmospheric concentrations of greenhouse gases. Published by: Published on: YEAR: 2021 DOI: 10.1002/9781119815631.ch8 Fabry-Perot spectrometer; geocoronal Balmer; ground-based geocoronal hydrogen observations; hydrogen density profile; hydrostatic equilibrium; neutral hydrogen; terrestrial exosphere; terrestrial thermosphere |
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On the relationship between traveling atmospheric and ionospheric disturbances The simulations are also compared with observations of neutral density from the Swarm satellite, the O/N2 column density ratio from TIMED/GUVI, and TEC from global GPS network as Published by: Published on: |
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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. 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 |
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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: |