Bibliography
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Found 44 entries in the Bibliography.
Showing entries from 1 through 44
| 2022 |
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Neutral composition information in ICON EUV dayglow observations Since the earliest space‐based observations of Earth s atmosphere, ultraviolet (UV) airglow has proven a useful resource for remote sensing of the ionosphere and thermosphere. The Tuminello, Richard; England, Scott; Sirk, Martin; Meier, Robert; Stephan, Andrew; Korpela, Eric; Immel, Thomas; Mende, Stephen; Frey, Harald; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2022JA030592 |
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Following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter. The EIA crests variations and associated ionosphere-thermosphere disturbances were investigated using Global Navigation Satellite System total electron content data, Global-scale Observations of the Limb and Disk ultraviolet images, Ionospheric Connection Explorer wind data, and ionosonde observations. The main results are as follows: (a) Following the eastward passage of expected eruption-induced atmospheric disturbances, daytime EIA crests, especially the southern one, showed severe suppression of more than 10 TEC Unit and collapsed equatorward over 10° latitudes, forming a single band of enhanced density near the geomagnetic equator around 14–17 UT, (b) Evening EIA crests experienced a drastic deformation around 22 UT, forming a unique X-pattern in a limited longitudinal area between 20 and 40°W. (c) Thermospheric horizontal winds, especially the zonal winds, showed long-lasting quasi-periodic fluctuations between ±200 m/s for 7–8 hr after the passage of volcano-induced Lamb waves. The EIA suppression and X-pattern merging was consistent with a westward equatorial zonal dynamo electric field induced by the strong zonal wind oscillation with a westward reversal. Aa, Ercha; Zhang, Shun-Rong; Wang, Wenbin; Erickson, Philip; Qian, Liying; Eastes, Richard; Harding, Brian; Immel, Thomas; Karan, Deepak; Daniell, Robert; Coster, Anthea; Goncharenko, Larisa; Vierinen, Juha; Cai, Xuguang; Spicher, Andres; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2022 DOI: 10.1029/2022JA030527 EIA suppression and X-pattern; Equatorial ionization anomaly; GNSS TEC; GOLD UV images; ICON MIGHTI neutral wind; Tonga volcano eruption |
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Time Delay Integration Imaging of the Nighttime Ionosphere from the ICON Observatory TIMED GUVI was on a high inclination orbit changing local time relatively slowly and missing a great deal of the equatorward low latitude regions at the wrong local times. Mende, SB; Frey, HU; England, SL; Immel, TJ; Eastes, RW; Published by: Space Science Reviews Published on: YEAR: 2022 DOI: 10.1007/s11214-022-00928-w |
| 2021 |
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In near-Earth space, variations in thermospheric composition have important implications for thermosphere-ionosphere coupling. The ratio of O to N2 is often measured using far-UV airglow observations. Taking such airglow observations from space, looking below the Earth s limb allows for the total column of O and N2 in the ionosphere to be determined. While these observations have enabled many previous studies, determining the impact of nonmigrating tides on thermospheric composition has proved difficult, owing to a small contamination of the signal by recombination of ionospheric O+. New ICON observations of far-UV are presented here, and their general characteristics are shown. Using these, along with other observations and a global circulation model, we show that during the morning hours and at latitudes away from the peak of the equatorial ionospheric anomaly, the impact of nonmigrating tides on thermospheric composition can be observed. During March–April 2020, the column O/N2 ratio was seen to vary by 3–4\% of the zonal mean. By comparing the amplitude of the variation observed with that in the model, both the utility of these observations and a pathway to enable future studies is shown. England, Scott; Meier, R.; Frey, Harald; Mende, Stephen; Stephan, Andrew; Krier, Christopher; Cullens, Chihoko; Wu, Yen-Jung; Triplett, Colin; Sirk, Martin; Korpela, Eric; Harding, Brian; Englert, Christoph; Immel, Thomas; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2021 DOI: 10.1029/2021JA029575 airglow; atmospheric composition; Atmospheric tides; thermosphere |
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Conjugate Photoelectron Energy Spectra Derived From Coincident FUV and Radio Measurements We present a method for estimating incident photoelectrons energy spectra as a function of altitude by combining global scale far-ultraviolet (FUV) and radio-occultation (RO) measurements. This characterization provides timely insights important for accurate interpretation of ionospheric parameters inferred from the recently launched Ionospheric Connection Explorer (ICON) observations. Quantification of photoelectron impact is enabled by the fact that conjugate photoelectrons (CPEs) directly affect FUV airglow emissions but not RO measurements. We demonstrate a technique for estimation of photoelectron fluxes and their spectra by combining coincident ICON and COSMIC2 measurements and show that a significant fraction of ICON-FUV measurements is affected by CPEs during the winter solstice. A comparison of estimated photoelectron fluxes with measured photoelectron spectra is used to gain further insights into the estimation method and reveals consistent values within 10–60 eV. Urco, J.; Kamalabadi, F.; Kamaci, U.; Harding, B.; Frey, H.; Mende, S.; Huba, J.; England, S.; Immel, T.; Published by: Geophysical Research Letters Published on: YEAR: 2021 DOI: 10.1029/2021GL095839 airglow; conjugate photolectrons; COSMIC2; energy spectra; ICON |
| 2020 |
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Immel, Thomas; Greer, Katelynn; Lieberman, Ruth; Paxton, Larry; Published by: Published on: |
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Immel, Thomas; Greer, Katelynn; Lieberman, Ruth; Paxton, Larry; Published by: Published on: |
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A comparison of thermospheric FUV radiance and composition from TIMED, GOLD and ICON Zhang, Y; Paxton, LJ; Schaefer, RK; Eastes, R; McClintock, WE; Immel, TJ; Published by: Published on: |
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Daily Variability in the Terrestrial UV Airglow New capability for observing conditions in the upper atmosphere comes with the implementation of global ultraviolet (UV) imaging from geosynchronous orbit. Observed by the NASA Immel, Thomas; Eastes, Richard; McClintock, William; Mende, Steven; Frey, Harald; Triplett, Colin; England, Scott; Published by: Atmosphere Published on: YEAR: 2020 DOI: 10.3390/atmos11101046 |
| 2019 |
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The National Aeronautics and Space Administration Ionospheric Connection Explorer (ICON) mission will study the close relationship between the ionosphere, the atmospheric weather, and space weather using in situ and remote sensing instruments proving plasma density, temperature, ion drift velocity, and thermospheric wind velocity over the equatorial region. In particular, the far ultraviolet (FUV) instrument will image the terrestrial limb in two wavelength channels. During nighttime, only the channel characterizing the bright 135.6-nm emission of atomic oxygen will be used. The purpose of this study is to simulate FUV nightglow measurements under quiet as well as disturbed ionospheric conditions. Classical medium-scale traveling ionospheric disturbances (MSTIDs), which are understood as the ionospheric signature of atmospheric gravity waves, are one of the main sources of ionospheric variability. Here, we simulate their potential appearance in the FUV instrument data. The simulation model produces FUV images used as input to identify and characterize MSTIDs. MSTID propagation parameters can be retrieved under specific geometrical configurations between the FUV lines of sight and propagation direction of the MSTID, which differs depending on the limb or sublimb observing geometry. The largest MSTID signature is expected during equinoxes under solar maximum periods, for MSTID periods of less than 30\ min. The weak brightness of the 135.6-nm multiplet under solar minimum conditions is the main limitation to the MSTID detection on the nightside. Future MSTID detection algorithms would have to cope with very low signal-to-noise ratio, in particular during solstices and under solar minimum conditions. Wautelet, G.; Hubert, B.; erard, J.-C.; Immel, T.; Published by: Journal of Geophysical Research: Space Physics Published on: 08/2019 YEAR: 2019 DOI: 10.1029/2019JA026930 |
| 2018 |
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Daytime O/N2 Retrieval Algorithm for the Ionospheric Connection Explorer (ICON) The NASA Ionospheric Connection Explorer Far-Ultraviolet spectrometer, ICON FUV, will measure altitude profiles of the daytime far-ultraviolet (FUV) OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) band emissions that are used to determine thermospheric density profiles and state parameters related to thermospheric composition; specifically the thermospheric column O/N2 ratio (symbolized as ΣO/N2). This paper describes the algorithm concept that has been adapted and updated from one previously applied with success to limb data from the Global Ultraviolet Imager (GUVI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. We also describe the requirements that are imposed on the ICON FUV to measure ΣO/N2 over any 500-km sample in daytime with a precision of better than 8.7\%. We present results from orbit-simulation testing that demonstrates that the ICON FUV and our thermospheric composition retrieval algorithm can meet these requirements and provide the measurements necessary to address ICON science objectives. Stephan, Andrew; Meier, R.; England, Scott; Mende, Stephen; Frey, Harald; Immel, Thomas; Published by: Space Science Reviews Published on: 01/2018 YEAR: 2018 DOI: 10.1007/s11214-018-0477-6 |
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The ionospheric connection explorer mission: Mission goals and design The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection Immel, Thomas; England, SL; Mende, SB; Heelis, RA; Englert, CR; Edelstein, J; Frey, HU; Korpela, EJ; Taylor, ER; Craig, WW; , others; Published by: Space Science Reviews Published on: YEAR: 2018 DOI: 10.1007/s11214-017-0449-2 |
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The Ionospheric Connection Explorer (ICON) Far Ultraviolet (FUV) imager, ICON FUV, will measure altitude profiles of OI 135.6 nm emissions to infer nighttime ionospheric parameters. Kamalabadi, Farzad; Qin, Jianqi; Harding, Brian; Iliou, Dimitrios; Makela, Jonathan; Meier, RR; England, Scott; Frey, Harald; Mende, Stephen; Immel, Thomas; Published by: Space science reviews Published on: |
| 2017 |
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Daytime Ionosphere Retrieval Algorithm for the Ionospheric Connection Explorer (ICON) The NASA Ionospheric Connection Explorer Extreme Ultraviolet spectrograph, ICON EUV, will measure altitude profiles of the daytime extreme-ultraviolet (EUV) OII emission near 83.4 and 61.7\ nm that are used to determine density profiles and state parameters of the ionosphere. This paper describes the algorithm concept and approach to inverting these measured OII emission profiles to derive the associated O+ density profile from 150\textendash450\ km as a proxy for the electron content in the F-region of the ionosphere. The algorithm incorporates a bias evaluation and feedback step, developed at the U.S. Naval Research Laboratory using data from the Special Sensor Ultraviolet Limb Imager (SSULI) and the Remote Atmospheric and Ionospheric Detection System (RAIDS) missions, that is able to effectively mitigate the effects of systematic instrument calibration errors and inaccuracies in the original photon source within the forward model. Results are presented from end-to-end simulations that convolved simulated airglow profiles with the expected instrument measurement response to produce profiles that were inverted with the algorithm to return data products for comparison to truth. Simulations of measurements over a representative ICON orbit show the algorithm is able to reproduce hmF2 values to better than 5\ km accuracy, and NmF2 to better than 12\% accuracy over a 12-second integration, and demonstrate that the ICON EUV instrument and daytime ionosphere algorithm can meet the ICON science objectives which require 20\ km vertical resolution in hmF2 and 18\% precision in NmF2. Stephan, Andrew; Korpela, Eric; Sirk, Martin; England, Scott; Immel, Thomas; Published by: Space Science Reviews Published on: 10/2017 YEAR: 2017 DOI: 10.1007/s11214-017-0385-1 |
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The Far Ultra-Violet Imager on the Icon Mission ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a Czerny\textendashTurner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to overcome the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft. Mende, S.; Frey, H.; Rider, K.; Chou, C.; Harris, S.; Siegmund, O.; England, S.; Wilkins, C.; Craig, W.; Immel, T.; Turin, P.; Darling, N.; Loicq, J.; Blain, P.; Syrstad, E.; Thompson, B.; Burt, R.; Champagne, J.; Sevilla, P.; Ellis, S.; Published by: Space Science Reviews Published on: 10/2017 YEAR: 2017 DOI: 10.1007/s11214-017-0386-0 |
| 2016 |
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Using a three-dimensional nonhydrostatic general circulation model, we investigate the response of the thermosphere–ionosphere system to the 5–6 August 2011 major geomagnetic Yi\ugit, Erdal; Frey, Harald; Moldwin, Mark; Immel, Thomas; Ridley, Aaron; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: YEAR: 2016 DOI: 10.1016/j.jastp.2015.10.002 |
| 2015 |
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The August 2011 URSI World Day campaign: Initial results During a 10-day URSI World Day observational campaign beginning on August 1, 2011, an isolated, major geomagnetic storm occurred. On August 5,\ Kp\ reached values of 8-and\ Dst\ dropped to -113\ nT. The occurrence of this isolated storm in the middle of a 10-day URSI World Day campaign provides and unprecedented opportunity to observe the coupling of solar wind energy into the magnetosphere and to evaluate the varied effects that occur in the coupled magnetosphere\textendashionosphere\textendashthermosphere system. Dramatic changes in the ionosphere are seen at every one of the active radar stations, extending from Greenland down to equatorial Peru in the American sector and at middle latitudes in Ukraine. Data from TIMED and THEMIS are shown to support initial interpretations of the observations, where we focus on processes in the middle latitude afternoon sector during main phase, and the formation of a dense equatorial ionosphere during storm recovery. The combined measurements strongly suggest that the changes in ionospheric conditions observed after the main storm phase can be attributed in large part to changes in the stormtime thermosphere. This is through the generation of disturbance dynamo winds and also global neutral composition changes that either reduce or enhance plasma densities in a manner that depends mainly upon latitude. Unlike larger storms with possibly more sustained forcing, this storm exhibits minimal effects of persistent meridional stormtime wind drag, and little penetration of solar wind electric potentials to low latitudes. It is, therefore, an outstanding example of an impulsive event that exhibits longer-term effects through modification of the background atmosphere. Immel, Thomas; Liu, Guiping; England, Scott; Goncharenko, Larisa; Erickson, Philip; Lyashenko, Mykhaylo; Milla, Marco; Chau, Jorge; Frey, Harald; Mende, Stephen; Zhou, Qihou; Stromme, Anja; Paxton, Larry; Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: 11/2015 YEAR: 2015 DOI: 10.1016/j.jastp.2015.09.005 |
| 2013 |
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Impacts of atmospheric ultrafast Kelvin waves on radio scintillations in the equatorial ionosphere We present a statistical analysis of the amplitudes of GPS scintillations (S4 index) observed throughout 2008\textendash2010 using the satellite radio occultation measurements of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). Here, for the first time, periodic variability in the occurrence of S4 is investigated using these data. Significant variations of S4 with periods of 2.5\textendash4 days (quasi-3 days) are identified from the observations during postsunset hours (1900\textendash2400 local time) between 15\textdegreeS\textendash 15\textdegreeN magnetic latitude during this 3 year interval. Coherence analyses of these variations with the geomagnetic Ap index, solar EUV irradiance, and atmospheric wind measurements from an equatorial mesosphere meteor radar at Thumba, India ( 8.5\textdegreeN, 77\textdegreeE) are performed, providing a measure of the relationship between variations in the scintillations and potential drivers. The quasi-3 day variations in S4 are found to covary with the variations of the three drivers examined. In particular, the S4 signatures are found to be coherent with the atmospheric ultrafast Kelvin (UFK) planetary waves characterized by the zonal wind measurements of the radar. This study shows that these UFK waves are as important as the solar and geomagnetic drivers in forcing the day-to-day variations of the occurrence of equatorial spread F. Liu, Guiping; Immel, Thomas; England, Scott; Frey, Harald; Mende, Stephen; Kumar, Karanam; Ramkumar, Geetha; Published by: Journal of Geophysical Research: Space Physics Published on: 02/2013 YEAR: 2013 DOI: 10.1002/jgra.50139 day-to-day variability; Equatorial ionosphere; scintillation; Ultra Fast Kelvin planetary wave |
| 2012 |
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An empirical model of the drift velocity of equatorial plasma depletions The Far-Ultraviolet Imager on the IMAGE spacecraft (IMAGE-FUV) has been used to observe O+plasma depletions in the post-sunset equatorial ionosphere. Small-scale density irregularities associated with such depletions are believed to adversely affect trans-ionospheric radio signals such as GPS. Prediction of the motion of these plasma depletions is a necessary component of the ability to forecast the occurrence of such radio signal interference. An automated method has recently been developed to identify and track the position and zonal drift velocity of these depletions. Here we use this method to create a large database of the zonal drift velocities of these depletions. We present an empirical model based on these observations that describes the observed drift velocities as a function of both local time and magnetic latitude, which is essential to represent their behavior. A comparison of the observed drift velocities with zonal winds from both an empirical model (Horizontal Wind Model; HWM07) and a first-principles model (the TIEGCM) reveals that the plasma depletions\textquoteright drift velocities have a latitudinal gradient that cannot be explained solely by the F-region dynamo in the post-sunset period, at least by these climatological models. This suggests that these plasma depletions may not simply drift with the background F-region plasma. It has previously been suggested that vertical polarization electric fields associated with the plasma depletions are responsible for their zonal drifts exceeding the background flow, which may explain the previously-observed discrepancy in the drift velocities and the discrepancy in their gradients reported here. Published by: Journal of Geophysical Research: Space Physics Published on: 12/2012 YEAR: 2012 DOI: 10.1029/2012JA018091 |
| 2010 |
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England, S.; Immel, T.; Huba, J.; Hagan, M.; Maute, A.; DeMajistre, R.; Published by: Journal of Geophysical Research Published on: Jan-01-2010 YEAR: 2010 DOI: 10.1029/2009JA014894 |
| 2009 |
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England, Scott; Zhang, Xiaoli; Immel, Thomas; Forbes, Jeffrey; DeMajistre, Robert; Published by: Earth Planets Space Published on: |
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Upward propagating tidal effects across the E-and F-regions of the ionosphere Immel, Thomas; England, Scott; Zhang, Xiaoli; Forbes, Jeffrey; DeMajistre, Robert; Published by: Earth, planets and space Published on: |
| 2008 |
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Neutral composition and density effects in the October-November 2003 Magnetic Storms Immel, TJ; Crowley, Geoff; Forbes, JM; Nerem, RS; Sutton, EK; Published by: Midlatitude Ionospheric Dynamics and Disturbances Published on: |
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England, SL; Immel, TJ; Huba, JD; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2007 |
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Lin, C.; Wang, W.; Hagan, M.; Hsiao, C.; Immel, T.; Hsu, M.; Liu, J; Paxton, L.; Fang, T.; Liu, C.; Published by: Geophysical Research Letters Published on: Jan-01-2007 YEAR: 2007 DOI: 10.1029/2007GL029265 |
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Park, SH; England, SL; Immel, TJ; Frey, HU; Mende, SB; Published by: Journal of Geophysical Research: Space Physics Published on: |
| 2006 |
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England, S.; Immel, T.; Sagawa, E.; Henderson, S.; Hagan, M.; Mende, S.; Frey, H.; Swenson, C.; Paxton, L.; Published by: Journal of Geophysical Research Published on: Jan-01-2006 YEAR: 2006 DOI: 10.1029/2006JA011795 |
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Longitudinal variation of the E-region electric fields caused by atmospheric tides England, S.; Maus, S.; Immel, T.; Mende, S.; Published by: Geophysical Research Letters Published on: Jan-01-2006 YEAR: 2006 DOI: 10.1029/2006GL027465 |
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Effect of IMF By on thermospheric composition at high and middle latitudes: 2. Data comparisons Immel, Thomas; Crowley, Geoff; Hackert, Chris; Craven, John; Roble, Ray; Published by: Journal of Geophysical Research: Space Physics Published on: |
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Immel, Thomas; Crowley, Geoff; Craven, John; Published by: Adv. Space Res Published on: |
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Effect of IMF BY on thermospheric composition at high and middle latitudes: 1. Numerical experiments Magnetic storms and their effects on the thermosphere and ionosphere have been studied for many years, yet there are many aspects of the thermospheric and ionospheric responses that are not understood. The purpose of this paper is to show how the high-latitude composition depends on the sign of the IMF BY component, using controlled simulations with a global first principles model. Because the high-latitude convection and neutral wind systems are strongly controlled by the IMF BY component, it seems likely that the compositional response that is driven by high-latitude forcing should also be sensitive to the BY component. To date, no first-principles modeling has been performed to test the idea of IMF BY effects on composition. Numerical experiments using model simulations provide insight into this important scientific question, since the thermospheric compositional response to the convection patterns for different IMF BZ and BY can be studied in isolation in a model. In this paper we use a first-principles model to determine the effect of the IMF BY component on the compositional response of the high-latitude thermosphere. We show for the first time that a clockwise rotation of the potential pattern resulting from a change from BY-negative to BY-positive drives a corresponding rotation in the wind, neutral density, and composition distributions. BY control of thermospheric composition has been invoked in the literature to explain an apparent variability in the effectiveness of auroral activity in causing thermospheric storm effects at middle latitudes, as observed in global images of the far-ultraviolet (FUV) OI 130.4-nm emission from the DE-1 auroral imager. However, the effect in the simulations presented here is opposite from that suggested by earlier work based on DE data, indicating another explanation must be sought for the DE results. These simulations are highly relevant for interpreting data being provided by more modern UV imaging instruments on the DMSP, TIMED, and IMAGE satellites. Crowley, G.; Immel, T.; Hackert, C.; Craven, J.; Roble, R.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2006 DOI: https://doi.org/10.1029/2005JA011371 |
| 2005 |
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DeMajistre, R.; Brandt, P.; Immel, T.; Yee, J.-H.; Dalgarno, A.; Paxton, L.; Kharchenko, V.; Published by: Geophysical Research Letters Published on: Jan-01-2005 YEAR: 2005 DOI: 10.1029/2005GL023059 |
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Some of the most intense solar flares measured in 0.1 to 0.8 nm x-rays in recent history occurred near the end of 2003. The Nov 4 event is the largest in the NOAA records (X28) and the Oct 28 flare was the fourth most intense (X17). The Oct 29 flare was class X7. These flares are compared and contrasted to the July 14, 2000 Bastille Day (X10) event using the SOHO SEM 26.0 to 34.0 nm EUV and TIMED SEE 0.1\textendash194 nm data. High time resolution, \~30s ground-base GPS data and the GUVI FUV dayglow data are used to examine the flare-ionosphere relationship. In the 26.0 to 34.0 nm wavelength range, the Oct 28 flare is found to have a peak intensity greater than twice that of the Nov 4 flare, indicating strong spectral variability from flare-to-flare. Solar absorption of the EUV portion of the Nov 4 limb event is a possible cause. The dayside ionosphere responds dramatically (\~2.5 min 1/e rise time) to the x-ray and EUV input by an abrupt increase in total electron content (TEC). The Oct 28 TEC ionospheric peak enhancement at the subsolar point is \~25 TECU (25 \texttimes 1012 electrons/cm2) or 30\% above background. In comparison, the Nov 4, Oct 29 and the Bastille Day events have \~5\textendash7 TECU peak enhancements above background. The Oct 28 TEC enhancement lasts \~3 hrs, far longer than the flare duration. This latter ionospheric feature is consistent with increased electron production in the middle altitude ionosphere, where recombination rates are low. It is the EUV portion of the flare spectrum that is responsible for photoionization of this region. Further modeling will be necessary to fully understand the detailed physics and chemistry of flare-ionosphere coupling. Tsurutani, B.; Judge, D.; Guarnieri, F.; Gangopadhyay, P.; Jones, A.; Nuttall, J.; Zambon, G.A.; Didkovsky, L.; Mannucci, A.J.; Iijima, B.; Meier, R.; Immel, T.J.; Woods, T.; Prasad, S.; Floyd, L.; Huba, J.; Solomon, S.; Straus, P.; Viereck, R.; Published by: Geophysical Research Letters Published on: 02/2005 YEAR: 2005 DOI: 10.1029/2004GL021475 |
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Earth FUV Dayglow Response to the 20 January 2005 Solar Flare: TIMED and IMAGE Observations Retherford, KD; Gladstone, R; Solomon, SC; Immel, TJ; Published by: Published on: |
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England, SL; Immel, TJ; Sagawa, E; Henderson, S; Hagan, ME; Mende, SB; Frey, HU; Swenson, C; Paxton, LJ; Published by: Published on: |
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We compare, for the first time, geomagnetically-conjugate plasma bubbles observed by ground-based OI 630.0-nm all-sky imagers at Shigaraki, Japan (34.8◦ N, 136.1◦ E; magnetic Ogawa, Tadahiko; Sagawa, Eiichi; Otsuka, Yuichi; Shiokawa, Kazuo; Immel, Thomas; Published by: Earth, planets and space Published on: YEAR: 2005 DOI: 10.1186/BF03351822 |
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Tsurutani, BT; Judge, DL; Meier, RR; Immel, TJ; Woods, TN; Published by: Geophysical research letters Published on: |
| 2004 |
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O/N 2 changes during 1--4 October 2002 storms: IMAGE SI-13 and TIMED/GUVI observations Thermospheric O/N2 column density ratios referenced at a N2 column density of 1017 cm-2 are obtained using the IMAGE SI-13 and TIMED/GUVI far-ultraviolet (FUV) dayglow data, AURIC simulation results, and MSIS86 model. Each of the magnetic storms occurring during a 4-day period (1\textendash4 October 2002) caused significant O/N2 depletion that was detected by both of the IMAGE SI-13 and GUVI instruments. The depletion extended down to latitudes of 10\textdegree and -5\textdegree in the Northern and Southern Hemispheres, respectively. Simultaneous measurements show an excellent agreement between the SI-13 and GUVI O/N2 on both global and local scales. The IMAGE SI-13 O/N2 data provide direct optical evidence that the O/N2 depletion corotates with the Earth. The GUVI O/N2 indicate the depletion in both of the hemispheres is not symmetric owing to the seasonal effect and differences in heating and convection induced winds. Both the IMAGE SI-13 and GUVI O/N2 maps also provide a good opportunity for future modeling efforts. Zhang, Y.; Paxton, L.; Morrison, D.; Wolven, B.; Kil, H.; Meng, C.-I.; Mende, S.; Immel, T.; Published by: Journal of Geophysical Research Published on: 10/2004 YEAR: 2004 DOI: 10.1029/2004JA010441 |
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IMAGE-FUV observations of the October-November 2003 flare and magnetic storm effects on Earth Immel, TT; Ostgaard, N; Strickland, DJ; Frey, HU; Mende, SB; Lu, G; Published by: Published on: |
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The Global Ionosphere Thermosphere Model results of the April 2002 storm Ridley, AJ; oth, G; Deng, Y; Kozyra, J; Immel, T; Paxton, L; Published by: Published on: |
| 2003 |
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Zhang, Y; Paxton, LJ; Immel, TJ; Frey, HU; Mende, SB; Published by: Journal of geophysical research Published on: |
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Negative ionospheric storms seen by the IMAGE FUV instrument Data from the IMAGE SI-13 instrument are used to study depletions in the OI 135.6 nm dayglow intensity due to two magnetic storms observed on 8 June and 15 July 2000. Results show that the SI-13 instrument is sensitive to changes in the 135.6 nm dayglow caused by depletion of the O/N2\ column density ratio. It is found that depletion levels in the SI-13 images are weaker than those in the true O/N2\ values or electron density parameters, such as NmF2 (peak F2 electron density) due to the N2\ LBH contribution in the SI-13 intensities. A depletion of -20\% (8 June 2000) and -50\% (15 July 2000) in the SI-13 intensities corresponds to -50\% and -90\% reductions in NmF2, respectively. AURIC simulations indicate that -67\% is the maximum depletion level that can be seen in the SI-13 intensities. The Millstone radar, digisonde and DMSP observations reveal that the electron density depletion extended from the low F-layer altitudes up to 840 km. Owing to the prevailing thermospheric circulation pattern, the depletions cover a wide area (at least 1/8 Earth surface) over the Northern Hemisphere for both of the cases. A deep depletion was always seen first in the morning side and then at later local times. The atmosphere took about 12 hours (8 June case) and more than 24 hours (15 July case) to recover. The results from the SI-13 images are in a good agreement with digisonde, radar, and DMSP observations. The depletion in the SI-13 intensity can be explained by the Joule and particle heating in the high-latitude regions. The heating has two effects: (1) The heated air is nitrogen-rich/oxygen-depleted and (2) a wind surge created by the heating in the night side moves the oxygen-deplete air upward and transports it to lower latitudes together with the neutral wind. Corotation with the Earth brings the oxygen-depleted air to the dayside. Zhang, Y.; Paxton, L.J.; Kil, H.; Meng, C.-I.; Mende, S.~B.; Frey, H.~U.; Immel, T.~J.; Published by: Journal of Geophysical Research (Space Physics) Published on: YEAR: 2003 DOI: 10.1029/2002JA009797 Atmospheric Composition and Structure: Airglow and aurora; Atmospheric Composition and Structure: Thermosphere-composition and chemistry; atmospheric composition change; depletion of OI 135.6 nm dayglow; Ionosphere: Ionospheric disturbances; Ionosphere: Plasma temperature and density; Magnetospheric Physics: Storms and substorms; negative ionospheric storms |
| 2002 |
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Dayside detached auroras (DDA) refer to auroras observed separate from the equatorward edge of the main oval on the dayside. They are studied here using IMAGE FUV and DMSP particle data. Occurrence of these DDA appears to be correlated with sudden solar wind dynamic pressure enhancements and northward interplanetary magnetic field, as monitored by the Wind satellite. They are usually very dynamic and short-lived with a lifetime of the order of 10 minutes. Out of the three FUV instrument channels on IMAGE, DDA are best detected by the IMAGE FUV SI-12 instrument, which measures intensities of the Doppler red-shifted Hydrogen Lyman Alpha line. This indicates that energetic proton precipitation is the major component. Simultaneous DMSP particle observations confirm that energetic protons (\>10 keV) in the dayside inner magnetosphere are the primary source of those DDA detected by the SI-12 instrument. DMSP also detected significant electron fluxes associated with the DDA, but the electron precipitations have little or no contribution to the DDA intensities detected by the SI-12 instrument. Precipitations of energetic protons (electrons) which caused DDA could be explained by enhanced cyclotron instability which arose from adiabatic compression following sudden solar wind dynamic pressure enhancements. Zhang, Y.; Paxton, L.J.; Immel, T.; Frey, H.; Published by: Journal of Geophysical Research: Space Physics Published on: YEAR: 2002 DOI: 10.1029/2002JA009355 AURORA; dayside detached aurora; proton precipitation; solar wind pressure enhancement |
| 1994 |
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Variations in the FUV dayglow after intense auroral activity Craven, JD; Nicholas, AC; Frank, LA; Strickland, DJ; Immel, TJ; Published by: Geophysical research letters Published on: |
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