References of "Lo, D. Y"
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See detailUV Study of the Fourth Positive Band System of CO and OI 135.6 nm From Electron Impact on CO and CO2
Ajello, J. M.; Malone, C. P.; Evans, J. S. et al

in Journal of Geophysical Research: Space Physics (2019), 124

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A 1 Π → X 1 Σ + ) of CO and the optically forbidden O (5S ... [more ▼]

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A 1 Π → X 1 Σ + ) of CO and the optically forbidden O (5S  →  3P) 135.6 nm atomic transition by electron-impact-induced-fluorescence of CO and CO2 . We present a model excitation cross section from threshold to high energy for the A 1Π state, including cascade by electron impact on CO. The A 1Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO2 , an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total OI ( 5S o ) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of O i (135.6 nm) from dissociative excitation of CO and CO 2 indicates that the OI (5 S) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the OI (5 S) stat. [less ▲]

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See detailUnveiling Mars nightside mesosphere dynamics by IUVS/MAVEN global images of NO nightglow
Stiepen, Arnaud ULiege; Jain, S. K.; Schneider, N. M. et al

Conference (2017, September 01)

We analyze the morphology of the ultraviolet nightglow in the Martian upper atmosphere through Nitric Oxide (NO) δ and γ bands emissions observed by the Imaging Ultraviolet Spectrograph instrument on the ... [more ▼]

We analyze the morphology of the ultraviolet nightglow in the Martian upper atmosphere through Nitric Oxide (NO) δ and γ bands emissions observed by the Imaging Ultraviolet Spectrograph instrument on the Mars Atmosphere and Volatile EvolutioN spacecraft. The seasonal dynamics of the Martian thermosphere-mesosphere can be constrained based on the distribution of these emissions. We show evidence for local (emission streaks and splotches) and global (longitudinal and seasonal) variability in brightness of the emission and provide quantitative comparisons to GCM simulations. [less ▲]

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See detailTwilight Limb Observations of Aerosols in the Martian Atmosphere by MAVEN IUVS
Lo, D. Y.; Yelle, R. V.; Schneider, N. M. et al

in Lunar and Planetary Science Conference (2016, March 01)

We make use of a single-scattering model to investigate aerosol scattering of sunlight observed by MAVEN IUVS in the nightside atmospheric limb.

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See detailDiscovery of diffuse aurora on Mars
Schneider, N. M.; Deighan, J. I.; Jain, S. K. et al

in Science (2015), 350(6261),

Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment.We report the discovery of low-Altitude, diffuse auroras spanning much of Mars' northern ... [more ▼]

Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment.We report the discovery of low-Altitude, diffuse auroras spanning much of Mars' northern hemisphere, coincident with a solar energetic particle outburst. The Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, detected auroral emission in virtually all nightside observations for ~5 days, spanning nearly all geographic longitudes. Emission extended down to ~60 kilometer (km) altitude (1 microbar), deeper than confirmed at any other planet. Solar energetic particles were observed up to 200 kilo-electron volts; these particles are capable of penetrating down to the 60 km altitude. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit auroras more globally than Earth. [less ▲]

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See detailNew observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN
Stevens, M. H.; Evans, J. S.; Schneider, N. M. et al

in Geophysical Research Letters (2015)

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report ... [more ▼]

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report the first observations of the N2 Lyman-Birge-Hopfield (LBH) bands at Mars and confirm the tentative identification of the N2 Vegard-Kaplan (VK) bands. We retrieve N2 density profiles from the VK limb emissions and compare calculated limb radiances between 90 and 210km against both observations and predictions from a Mars general circulation model (GCM). Contrary to earlier analyses using other satellite data, we find that N2 abundances exceed GCM results by about a factor of 2 at 130km but are in agreement at 150km. The analysis and interpretation are enabled by a linear regression method used to extract components of UV spectra from IUVS limb observations. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailNonmigrating tides in the Martian atmosphere as observed by MAVEN IUVS
Lo, D. Y.; Yelle, R. V.; Schneider, N. M. et al

in Geophysical Research Letters (2015)

Using the Mars Atmospheric and Volatile EvolutioN mission (MAVEN) Imaging Ultraviolet Spectrograph (IUVS), we found periodic longitudinal variations in CO2 density in the Martian atmosphere. These density ... [more ▼]

Using the Mars Atmospheric and Volatile EvolutioN mission (MAVEN) Imaging Ultraviolet Spectrograph (IUVS), we found periodic longitudinal variations in CO2 density in the Martian atmosphere. These density variations are derived from observations of the CO2+ (B2Σ+→X2Π) emission from limb scans in the 100-190 km altitude range. The variations exhibit significant structure with longitudinal wave numbers 1, 2, and 3 in an effectively constant local solar time frame, and we attribute this structure to nonmigrating tides. The wave-2 component is dominated by the diurnal eastward moving DE1 tide at the equator and the semidiurnal stationary S0 tide at the midlatitudes. Wave-3 is dominated by the diurnal eastward moving DE2 tide, with possibly the semidiurnal eastward moving SE1 tide causing an amplitude increase at the midlatitudes. Structure in the wave-1 component can be explained by the semidiurnal westward moving SW1 tide. ©2015. American Geophysical Union. [less ▲]

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See detailThe structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations
Jain, S. K.; Stewart, A. I. F.; Schneider, N. M. et al

in Geophysical Research Letters (2015)

We report a comprehensive study of Mars dayglow observations focusing on upper atmospheric structure and seasonal variability. We analyzed 744 vertical brightness profiles comprised of ∼109,300 spectra ... [more ▼]

We report a comprehensive study of Mars dayglow observations focusing on upper atmospheric structure and seasonal variability. We analyzed 744 vertical brightness profiles comprised of ∼109,300 spectra obtained with the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite. The dayglow emission spectra show features similar to previous UV measurements at Mars. We find a significant drop in thermospheric scale height and temperature between LS = 218° and LS = 337-352°, attributed primarily to the decrease in solar activity and increase in heliocentric distance. We report the detection of a second, low-altitude peak in the emission profile of OI 297.2 nm, confirmation of the prediction that the absorption of solar Lyman alpha emission is an important energy source there. The CO2+ UV doublet peak intensity is well correlated with simultaneous observations of solar 17-22 nm irradiance at Mars. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailRetrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN
Evans, J. S.; Stevens, M. H.; Lumpe, J. D. et al

in Geophysical Research Letters (2015)

We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the ... [more ▼]

We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the Imaging Ultraviolet Spectrograph on board NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We use retrieved CO2 densities to derive temperature variability between 170 and 220km. Analysis of the data shows (1) low-mid latitude northern hemisphere CO2 densities at 170km vary by a factor of about 2.5, (2) on average, the N2/CO2 increases from 0.042±0.017 at 130km to 0.12±0.06 at 200km, and (3) the mean upper atmospheric temperature is 324±22K for local times near 14:00. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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