Bibliography

Pronounced Suppression and X-Pattern Merging of Equatorial Ionization Anomalies After the 2022 Tonga Volcano Eruption

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

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

A Comparative Analysis of the OI 130.4-nm Emission Observed by NASA's TIMED Mission Using a Monte Carlo Radiative Transfer Model

Remote sensing of the OI 130.4-nm emission is potentially a useful means for routine monitoring of the atomic oxygen abundance in the upper atmosphere, especially for altitudes above urn:x-wiley:jgra:media:jgra55449:jgra55449-math-0001300 km where the OI 135.6-nm emission becomes too dim to be useful. However, to date, the interpretation of the OI 130.4-nm emission as a proxy for the O density remains ambiguous in that the relative contribution of the external and internal sources to the production of this emission has not been fully understood. In this study, we perform a comparative analysis of the OI 130.4-nm dayglow observed by NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission using a Monte Carlo radiative transfer model to investigate the consistency between models and the TIMED/Global UltraViolet Imager (GUVI) data. T

Qin, Jianqi; Harding, Brian;

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

YEAR: 2020     DOI: 10.1029/2019JA027520

First radiative transfer analysis of the OI 130.4-nm emission observed by NASA's TIMED mission

observed by the Global UltraViolet Imager (GUVI) aboard NASA s TIMED mission. The solar O densities, and/or that the GUVI and SEE calibrations may need to be revisited. We will

Qin, Jianqi; Harding, Brian;

Published by:       Published on:

YEAR: 2019     DOI:

Nonparametric H Density Estimation Based on Regularized Nonlinear Inversion of the Lyman Alpha Emission in Planetary Atmospheres

Inversion of space-borne remote sensing measurements of the resonantly scattered solar Lyman alpha (121.6-nm) emission in planetary atmospheres is the most promising means of quantifying the H density in a vast volume of space near terrestrial planets. Owing to the highly nonlinear nature of the inverse problem and the lack of sufficient data constraints over the large volume of space where H atoms are present, previous inversion methods relied on physics-based parametric formulations of the H density distributions to guarantee solution uniqueness. Those physical formulations, such as the Chamberlain model, were developed with simple assumptions of the atmospheric conditions. The use of such formulations as constraints significantly limits the range of possible solutions, which might lead to large errors in the case when those assumptions are invalid. In this study, we demonstrate for the first time the feasibility of estimating the H density through regularized nonlinear inversion of the Ly-α emission in an optically thick atmosphere, without using parametric formulations. Specifically, Occam\textquoterights inversion algorithm is used to demonstrate that the H density can be estimated in a large volume of space near the planet, with accuracy in different atmospheric regions depending on the observation scheme. Two distinctly different schemes are examined, including a low-Earth orbit and a geostationary orbit. Modeling results show that the low-Earth orbit is better for H density estimation in the thermosphere, while the high-altitude orbit is better for estimation in the exosphere. Our results could provide useful information for designing the observation schemes of future missions.

Qin, Jianqi; Harding, Brian; Waldrop, Lara;

Published by: Journal of Geophysical Research: Space Physics      Published on: 09/2018

YEAR: 2018     DOI: 10.1029/2018JA025954

Inferring nighttime ionospheric parameters with the far ultraviolet imager onboard the ionospheric connection explorer

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:

YEAR: 2018     DOI: