References of "Jain, S. K"
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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 detailMAVEN IUVS Remote Sensing Highlights Relevant to Upcoming TGO Observations
Chaffin, M.; Schneider, N. M.; Deighan, J. et al

in From Mars Express to ExoMars (2018, February 01)

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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 detailMAVEN IUVS Observations of the Aftermath of the Comet Siding Spring Meteor Shower on Mars
Schneider, N. M.; Crismani, M.; Deighan, J. I. et al

Conference (2017, September 01)

A comet's close passage by Mars deposited an unprecedented amount of vaporized dust whose elements were detected by the MAVEN spacecraft.

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See detailGlobal Simulation of UV Atmospheric Emissions
González-Galindo, F.; López-Valverde, M. A.; Forget, F. et al

Conference (2017, January 17)

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See detailDetection of a persistent meteoric metal layer in the Martian atmosphere
Crismani, M. M. J.; Schneider, N. M.; Plane, J. M. C. et al

in Nature Geoscience (2017), 10(6), 401-404

Interplanetary dust particles sporadically enter planetary atmospheres at orbital velocities and ablate as collisions occur with ambient gases to produce a persistent layer of metallic atoms (for example ... [more ▼]

Interplanetary dust particles sporadically enter planetary atmospheres at orbital velocities and ablate as collisions occur with ambient gases to produce a persistent layer of metallic atoms (for example, Fe, Mg, Na) in their upper atmospheres. Such layers are well studied at Earth, but have not been directly detected elsewhere in the Solar System. Here we report the detection of a meteoric layer consisting of Mg+ ions near an altitude of 90 km in the Martian atmosphere from ultraviolet remote sensing observations by NASA's MAVEN spacecraft. We observe temporal variability in the Mg+ layer over the course of a Martian year, moving up and down in altitude seasonally and in response to dust storms, and displaying diurnal fluctuations in density. We also find that most meteor showers do not significantly perturb this layer, which constrains the fluence of eleven observed Martian meteor showers to less than our estimated global dust flux. The persistence and variability of the Mg+ layer are difficult to explain with existing models and reconcile with other transient layers of ions observed in the Martian ionosphere. We suggest that the transient layers are not sourced from the persistent Mg+ layer and thus not derived from meteoric material, but are ambient ions produced by some unknown mechanism. © 2017 Macmillan Publishers Limited, part of Springer Nature. [less ▲]

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See detailThe structure and variability of Mars dayside thermosphere from MAVEN NGIMS and IUVS measurements: Seasonal and solar activity trends in scale heights and temperatures
Bougher, S. W.; Roeten, K. J.; Olsen, K. et al

in Journal of Geophysical Research. Space Physics (2017)

Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the ... [more ▼]

Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft. Average scale heights (over 150-180 km for solar zenith angles ≤75°) from several different sampling periods were obtained from each instrument. NGIMS and IUVS scale height trends were found to be in good agreement, with both showing scale heights decreasing after perihelion and reaching a low value near aphelion (13.6 to 9.4 km). Between these two seasonal extremes, the temperature decreased by ∼70 K (from 240 to 170 K). These trends were also analyzed with respect to the changing solar flux reaching the planet, using the Lyman alpha irradiance measured by the Extreme Ultraviolet Monitor (EUVM) on MAVEN. Scale heights responded strongly to the changing solar flux. During this part of the MAVEN mission (October 2014 to May 2016), it was concluded that over longer timescales (at least several months), dayside thermospheric temperatures are chiefly driven by changing solar forcing, although it is the effects of changing heliocentric distance rather than changing solar activity which seem to have the greatest impact. Furthermore, effects of solar forcing were not observed on shorter timescales (less than a month), suggesting local wave effects may dominate solar forcing on these timescales. Finally, temperatures from two NGIMS sampling periods were compared to temperatures from the Mars Global Ionosphere-Thermosphere Model (M-GITM) and found to be in good agreement. © 2017. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailVariability of D and H in the Martian Upper Atmosphere Observed with the MAVEN IUVS Echelle Channel
Clarke, J. T.; Mayyasi, M.; Bhattacharyya, D. et al

in Journal of Geophysical Research. Space Physics (2017)

The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions ... [more ▼]

The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions, which are produced by resonant scattering of solar emission, over the course of most of a martian year. The fundamental purpose of these measurements is to understand the physical principles underlying the escape of H and D from the upper atmosphere into space, and thereby to relate present-day measurements of an enhanced HDO/H2O ratio in the bulk atmosphere to the water escape history of Mars. Variations in these emissions independent of the solar flux reflect changes in the density and/or temperature of the species in the upper atmosphere. The MAVEN measurements show that the densities of both H and D vary by an order of magnitude over a martian year, and not always in synch with each other. This discovery has relevance to the processes by which H and D escape into space. One needs to understand the controlling factors to be able to extrapolate back in time to determine the water escape history from Mars at times when the atmosphere was thicker, when the solar flux and solar wind were stronger, etc. Further measurements will be able to identify the specific controlling factors for the large changes in H and D, which likely result in large changes in the escape fluxes of both species. [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 detailTwo Types of Aurora on Mars as Observed by MAVEN's Imaging UltraViolet Spectrograph
Schneider, Nicholas M.; Deighan, J.; Jain, S. K. et al

in AAS/Division for Planetary Sciences Meeting Abstracts (2015, November 01)

The Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft has detected two distinct types of auroral emission on Mars. First, we report the discovery of a low altitude, diffuse aurora spanning ... [more ▼]

The Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft has detected two distinct types of auroral emission on Mars. First, we report the discovery of a low altitude, diffuse aurora spanning much of Mars’ northern hemisphere coincident with a solar energetic particle outburst. IUVS observed northerly latitudes during late December 2014, detecting auroral emission in virtually all nightside observations for ~5 days spanning virtually all geographic longitudes. The vertical profile showed emission down to ~70 km altitude (1 microbar), deeper than confirmed at any other planet. The onset and duration of emission coincide with the observed arrival of solar energetic particles up to 200 keV precipitating directly and deeply into the atmosphere. Preliminary modeling of the precipitation, energy deposition and spectral line emission yields good matches to the observations. These observations represent a new class of planetary auroras produced in the Martian middle atmosphere. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit aurora more globally than Earth.Second, we confirm the existence of small patches of discrete aurora near crustal magnetic fields in Mars' southern hemisphere, as observed previously by SPICAM on Mars Express (Bertaux et al., Nature, 435, 790-794 (2005)). IUVS observed southern latitudes in July and August 2015, detecting discrete auroral emission in ~1% of suitable observations. Limb scans resolved both vertically and along-slit indicate this type of auroral emission was patchy on the scale of ~40 km, and located at higher altitudes ~140 km. The higher altitudes imply a lower energy of precipitating particles. The mix of spectral emissions also differed signficiantly from the diffuse aurora, indicating different excitation and quenching processes.We will discuss the observed properties of the aurora and associated charged particle precipitation, as well as the broader implications of this high-energy deposition into Mars' atmopshere. [less ▲]

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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 detailMAVEN observations of the response of Mars to an interplanetary coronal mass ejection
Jakosky, B. M.; Grebowsky, J. M.; Luhmann, J. G. et al

in Science (2015), 350(6261),

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ... [more ▼]

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-Term evolution of the Mars atmosphere. [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 detailProbing the Martian atmosphere with MAVEN/IUVS stellar occultations
Gröller, H.; Yelle, R. V.; Koskinen, T. T. et al

in Geophysical Research Letters (2015)

The first campaign of stellar occultations with the Imaging Ultraviolet Spectrograph (IUVS) instrument on board of Mars Atmosphere and Volatile EvolutioN (MAVEN) mission was executed between 24 and 26 ... [more ▼]

The first campaign of stellar occultations with the Imaging Ultraviolet Spectrograph (IUVS) instrument on board of Mars Atmosphere and Volatile EvolutioN (MAVEN) mission was executed between 24 and 26 March 2015. From this campaign 13 occultations are used to retrieve CO2 and O2 number densities in the altitude range between 100 and 150 km. Observations probe primarily the low-latitude regions on the nightside of the planet, just past the dawn and dusk terminator. Calculation of temperature from the CO2 density profiles reveals that the lower thermosphere is significantly cooler than predicted by the models in the Mars Climate Database. A systematically cold layer with temperatures of 105-120 K is seen in the occultations at a pressure level around 7 × 10-6 Pa. © 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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See detailMAVEN IUVS observation of the hot oxygen corona at Mars
Deighan, J.; Chaffin, M. S.; Chaufray, J.-Y. et al

in Geophysical Research Letters (2015)

Observation of the hot oxygen corona at Mars has been an elusive measurement in planetary science. Characterizing this component of the planet's exosphere provides insight into the processes driving loss ... [more ▼]

Observation of the hot oxygen corona at Mars has been an elusive measurement in planetary science. Characterizing this component of the planet's exosphere provides insight into the processes driving loss of oxygen at the current time, which informs understanding of the planet's climatic evolution. The Mars Atmosphere and Volatile EvolutioN (MAVEN) Imaging Ultraviolet Spectrograph (IUVS) instrument is now regularly collecting altitude profiles of the hot oxygen corona as part of its investigation of atmospheric escape from Mars. Observations obtained thus far have been examined and found to display the expected gross structure and variability with EUV forcing anticipated by theory. The quality and quantity of the data set provides valuable constraints for the coronal modeling community. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailUltraviolet observations of the hydrogen coma of comet C/2013 A1 (Siding Spring) by MAVEN/IUVS
Crismani, M. M. J.; Schneider, N. M.; Deighan, J. I. et al

in Geophysical Research Letters (2015)

We used the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiting spacecraft to construct images of the hydrogen coma of comet C/2013 A1 (Siding Spring ... [more ▼]

We used the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiting spacecraft to construct images of the hydrogen coma of comet C/2013 A1 (Siding Spring) days before its close encounter with Mars. We obtain a water production rate of 1.1 ± 0.5 × 1028 molecules/s and determine the total impacting fluence of atoms and molecules corresponding to the photodissociation of water and its daughter species to be 2.4 ± 1.2 × 104 kg. We use these observations to confirm predictions that the mass of delivered hydrogen is comparable to the existing reservoir above 150 km. Furthermore, we reconcile disparity between observations and predictions about the detectability of the hydrogen perturbation and thermospheric response. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailStudy of the Martian cold oxygen corona from the OI 130.4nm by IUVS/MAVEN
Chaufray, J. Y.; Deighan, J.; Chaffin, M. S. et al

in Geophysical Research Letters (2015)

First observations of the OI 130.4nm resonant line performed by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) are presented in this paper ... [more ▼]

First observations of the OI 130.4nm resonant line performed by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) are presented in this paper. This emission line is observed during the different orbit phases of MAVEN. The atomic oxygen density and the temperature at 200km are retrieved from an automatic pipeline using a radiative transfer model for resonant scattering lines for a selection of coronal profiles. These selected profiles are representative of the coronal scans done during the first months of the mission (from November 2014 to January 2015). The derived oxygen density and the temperature near the exobase are in the predicted range by the current thermospheric models of Mars for moderate solar activity, and some diurnal variations are observed. However, the absolute calibration of the instrument significantly limits the accuracy of density and temperature results. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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