Bibliography

Simultaneous Detection of Signatures of Conjugate Photoelectrons in the Ionosphere and Thermosphere

We investigate the impact of conjugate photoelectrons (CPEs) on the topside (∼600 km altitude) ionosphere at low and midlatitudes using measurements of the ion temperature, density, and composition from the first Republic of China satellite during a period of the high to moderate solar activity (March 1999 to June 2004). Elevated ion temperatures and densities are observed in the dark Northern American-Atlantic sector during the December solstice and in the Australian sector during the June solstice. The oxygen ion fraction and density are also elevated at these locations. These observations indicate that photoelectrons from the conjugate hemisphere heat the local ionospheric plasma. The morphology of the ion temperature in the winter hemisphere is well represented by the solar zenith angle in the sunlit conjugate hemisphere. The CPE hypothesis for the observed ionospheric heating is confirmed by coincident nighttime enhancements of the far ultraviolet airglow measured by the Global Ultraviolet Imager onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite.

Kil, Hyosub; Paxton, Larry; Schaefer, Robert;

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

YEAR: 2022     DOI: 10.1029/2021JA030121

airglow; conjugate photoelectron; ion density; ion temperature

First Comparison of Traveling Atmospheric Disturbances Observed in the Middle Thermosphere by Global-Scale Observations of the Limb and Disk to Traveling Ionospheric Disturbances Seen in Ground-Based Total Electron Content Observations

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

Ionosphere; thermosphere; airglow; atmospheric waves

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

First Results From the Retrieved Column O/N2 Ratio From the Ionospheric Connection Explorer (ICON): Evidence of the Impacts of Nonmigrating Tides

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

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

Deducing Non-Migrating Diurnal Tides in the Middle Thermosphere With GOLD Observations of the Earth's far Ultraviolet Dayglow From Geostationary Orbit

The global-scale observations of the limb and disk (GOLD) Mission images middle thermosphere temperature and the vertical column density ratio of oxygen to molecular nitrogen (O/N2) using its far ultraviolet imaging spectrographs in geostationary orbit. Since GOLD only measures these quantities during daylight, and only over the ∼140° of longitude visible from geostationary orbit, previously developed tidal analysis techniques cannot be applied to the GOLD data set. This paper presents a novel approach that deduces two specified non-migrating diurnal tides using simultaneous measurements of temperature and O/N2. DE3 (diurnal eastward propagating wave 3) and DE2 (diurnal eastward propagating wave 2) during October 2018 and January 2020 are the focus of this paper. Sensitivity analyses using TIE-GCM simulations reveal that our approach reliably retrieves the true phases, whereas a combination of residual contributions from secondary tides, the restriction in longitude, and random uncertainty can lead to ∼50\% error in the retrieved amplitudes. Application of our approach to GOLD data during these time periods provides the first observations of non-migrating diurnal tides in measurements taken from geostationary orbit. We identify discrepancies between GOLD observations and TIE-GCM modeling. Retrieved tidal amplitudes from GOLD observations exceed their respective TIE-GCM amplitudes by a factor of two in some cases.

Krier, Christopher; England, Scott; Greer, Katelynn; Evans, Scott; Burns, Alan; Eastes, Richard;

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

YEAR: 2021     DOI: 10.1029/2021JA029563

airglow; composition; temperature; thermosphere; tides

Limb Viewing Hyper Spectral Imager (LiVHySI) for airglow measurements onboard YOUTHSAT-1

Bisht, R.S.; Hait, A.K.; Babu, P.N.; Sarkar, S.S.; Benerji, A.; Biswas, A.; Saji, A.K.; Samudraiah, D.R.M.; Kirankumar, A.S.; Pant, T.K.; Parimalarangan, T.;

Published by: Advances in Space Research      Published on: 08/2014

YEAR: 2014     DOI: 10.1016/j.asr.2014.01.016

airglow; Electron density; Ionosphere; Rayleigh; thermosphere; Volume emission

Remote sensing of neutral temperatures in the Earth\textquoterights thermosphere using the Lyman-Birge-Hopfield bands of N ₂ : Comparisons with satellite drag data

This paper presents remotely sensed neutral temperatures obtained from ultraviolet observations and compares them with temperatures from the NRLMSISE-00 version of the Mass Spectrometer and Incoherent Scatter (MSIS) model (unconstrained and constrained to match the total densities from satellite drag). Latitudinal profiles of the temperatures in the Earth\textquoterights thermosphere are obtained by inversion of high-resolution (\~1.3\ \r A) observations of the (1,1) and (5,4) Lyman-Birge-Hopfield (LBH) bands of N₂. The spectra are from the High resolution Ionospheric and Thermospheric Spectrograph (HITS) instrument aboard the Advanced Research and Global Observation Satellite (ARGOS). The results indicate that on each day examined there was consistency between the remotely sensed thermospheric temperatures, the densities from coincident satellite drag measurements at adjacent altitudes, and the NRLMSISE-00 model.

Krywonos, Andrey; Murray, D.; Eastes, R.; Aksnes, A.; Budzien, S.; Daniell, R.;

Published by: Journal of Geophysical Research      Published on: 09/2012

YEAR: 2012     DOI: 10.1029/2011JA017226

airglow; N2; remote sensing; satellite drag; temperature; thermosphere

The Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite: A 20 year perspective

The Wind Imaging Interferometer (WINDII) was launched on the NASA\textquoterights Upper Atmosphere Research Satellite on 12 September 1991 and operated until 2003. Its role in the mission was to measure vector winds in the Earth\textquoterights atmosphere from 80 to 110 km, but its measurements extended to nearly 300 km. The approach employed was to measure Doppler shifts from a suite of visible region airglow lines emitted over this altitude range. These included atomic oxygen O(¹S) and O(¹D) lines, as well as lines in the OH Meinel (8,3) and O₂ Atmospheric (0,0) bands. The instrument employed was a Doppler Michelson Interferometer that measured the Doppler shift as a phase shift of the cosinusoidal interferogram generated by single airglow lines. An extensive validation program was conducted after launch to confirm the accuracy of the measurements. The dominant wind field, the first one observed by WINDII, was that of the migrating diurnal tide at the equator. The overall most notable WINDII contribution followed from this: determining the influence of dynamics on the transport of atmospheric species. Currently, nonmigrating tides are being studied in the thermosphere at both equatorial and high latitudes. Other aspects investigated included solar and geomagnetic influences, temperatures from atmospheric-scale heights, nitric oxide concentrations, and the occurrence of polar mesospheric clouds. The results of these observations are reviewed from a perspective of 20 years. A future perspective is then projected, involving more recently developed concepts. It is intended that this description will be helpful for those planning future missions.

Shepherd, G.; Thuillier, G.; Cho, Y.-M.; Duboin, M.-L.; Evans, W.; Gault, W.; Hersom, C.; Kendall, D.; Lathuillère, C.; Lowe, R.; McDade, I.; Rochon, Y.; Shepherd, M.; Solheim, B.; Wang, D.-Y.; Ward, W.;

Published by: Reviews of Geophysics      Published on: 06/2012

YEAR: 2012     DOI: 10.1029/2012RG000390

airglow; dynamics; interferometers; mesosphere; temperature; winds

Influence of systematic error on least squares retrieval of upper atmospheric parameters from the ultraviolet airglow

This paper investigates the effect of simple systematic error, or bias (i.e., in the magnitude of data or an associated model), on physical parameters retrieved by least squares algorithms from observations that are indexed by an independent variable. This factor is now of critical interest with the advent of global, space-based ultraviolet remote sensing of thermospheric and ionospheric composition by experimental and operational systems. A finite bias between an observed intensity profile and the parametric physical model used to compute a least squares solution will contaminate the values of retrieved physical parameters. The simplest mitigation method is to retrieve an additional bias adjustment parameter (additive or multiplicative) as part of the solution. The result is a measurably superior fit. The utility of this approach can depend on the particular spectral feature of interest. The discussion includes derivation of relevant equations and diagnostic tests. An illustrative application concerns recent observations of the dayside O II 834 A airglow, which contains information on O+, the dominant ion in the ionospheric F region.

Picone, J.;

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

YEAR: 2008     DOI: https://doi.org/10.1029/2007JA012831

systematic error; discrete inverse theory; airglow

Initial observations with the Global Ultraviolet Imager (GUVI) in the NASA TIMED satellite mission

The Global Ultraviolet Imager (GUVI) instrument carried aboard the NASA TIMED satellite measures the spectral radiance of the Earth\textquoterights far ultraviolet airglow in the spectral region from 120 to 180 nm using a cross-track scanning spectrometer design. Continuous operation of the instrument provides images of the Earth\textquoterights disk and limb in five selectable spectral bands. Also, spectra at fixed scanning mirror position can be obtained. Initial results demonstrate the quantitative functionality of the instrument for studies of the Earth\textquoterights dayglow, aurora, and ionosphere. Moreover, through forward modeling, the abundance of the major constituents of the thermosphere, O, N₂, and O₂\ and thermospheric temperatures can be retrieved from observations of the limb radiance. Variations of the column O/N₂\ ratio can be deduced from sunlit disk observations. In regions of auroral precipitation not only can the aurora regions be geographically located and the auroral boundaries identified, but also the energy flux Q, the characteristic energy E_o, and a parameter f_o\ that scales the abundance of neutral atomic oxygen can be derived. Radiance due to radiative recombination in the ionospheric F region is evident from both dayside and nightside observations of the Earth\textquoterights limb and disk, respectively. Regions of depleted F-region electron density are evident in the tropical Appleton anomaly regions, associated with so-called ionospheric \textquotedblleftbubbles.\textquotedblright Access to the GUVI data is provided through the GUVI website\ www.timed.jhuapl.edu\guvi.

Christensen, AB; Paxton, LJ; Avery, S; Craven, J; Crowley, G; Humm, DC; Kil, H; Meier, RR; Meng, C-I; Morrison, D; , others;

Published by: Journal of Geophysical Research: Space Physics (1978\textendash2012)      Published on:

YEAR: 2003     DOI: 10.1029/2003JA009918

airglow; AURORA; ultraviolet; imaging; satellite; atmosphere