J. S. Evans

Computational Physics (United States)

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W. E. McClintock

Laboratory for Atmospheric and Space Physics

Sonal Jain

Laboratory for Atmospheric and Space Physics

J. Deighan

Laboratory for Atmospheric and Space Physics

R. Eastes

Laboratory for Atmospheric and Space Physics

N. M. Schneider

Laboratory for Atmospheric and Space Physics

J. Correira

Computational Physics (United States)

Michael Chaffin

University of Colorado Boulder

M. H. Stevens

United States Naval Research Laboratory

G. M. Holsclaw

University of Colorado Boulder

J. D. Lumpe

Computational Physics (United States)

Cooperative Institutions

Laboratory for Atmospheric and Space Physics

University of Colorado Boulder

University of California, Berkeley

Goddard Space Flight Center

University of Colorado System

Computational Physics (United States)

United States Naval Research Laboratory

NSF National Center for Atmospheric Research

Planetary Science Institute

Johns Hopkins University Applied Physics Laboratory

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A new technique for remote sensing of O₂ density from 140 to 180 km

Geophysical Research Letters (2014)

J. H. Hecht A. B. Christensen J. Yee G. Crowley R. L. Bishop

Abstract Observations of molecular oxygen are difficult to make in the Earth's atmosphere between 140 and 200 km altitude. Perhaps the most accurate measurements to date have been obtained from satellite instruments that measure solar occultations of the limb. These do provide height‐resolved O 2 density measurements, but the nature of this technique is such that the temporal/spatial distribution of the measurements is uneven. Here a new space‐based technique is described that utilizes two bright dayglow emissions, the (0,0) transition of the O 2 atmospheric band and the O I (630 nm), to derive the height‐resolved O 2 density from 140 to 180 km. Data from the Remote Atmospheric and Ionospheric Detection System, which was placed on the International Space Station in late 2009, are used to illustrate this technique. The O 2 density results for periods in May 2010 that were geomagnetically quiet and disturbed are compared to model predictions.

Airglow

QUIET

10.1002/2014gl062355

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Citations (4)

GOLD observations of the thermospheric response to the 10-12 May 2024 geomagnetic storm

Authorea (Authorea) (2024)

J. S. Evans J. Correira J. D. Lumpe R. Eastes Quan Gan

After days of intense solar activity, active region AR3664 launched seven CMEs towards Earth producing an extreme G5 geomagnetic storm commencing at 16:45 UT on Saturday May 10, 2024. The storm impacted power grids, disrupted precision navigational systems used by farming equipment, and generated aurora seen around the globe. The storm produced remarkable effects on composition, temperature, and dynamics in the Earth’s thermosphere that were observed by NASA’s Global-scale Observations of the Limb and Disk (GOLD) mission and are reported here for the first time. We use synoptic disk images of ΣO/N2 and neutral temperature (at ~160 km) measured by GOLD to directly link dynamics resulting from the storm with dramatic changes in thermospheric composition and temperature. We observe an apparent rotation simultaneously in ΣO/N2, neutral temperature, and total electron content. Equator-to-pole temperature differences reach 400 K with peak neutral temperatures near 160 km exceeding 1400 K at high latitudes.

10.22541/essoar.171865398.83614867/v1

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Citations (0)

New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Geophysical Research Letters (2015)

M. H. Stevens J. S. Evans N. M. Schneider A. I. F. Stewart J. Deighan

Abstract We identify molecular nitrogen (N 2 ) 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 N 2 Lyman‐Birge‐Hopfield (LBH) bands at Mars and confirm the tentative identification of the N 2 Vegard‐Kaplan (VK) bands. We retrieve N 2 density profiles from the VK limb emissions and compare calculated limb radiances between 90 and 210 km against both observations and predictions from a Mars general circulation model (GCM). Contrary to earlier analyses using other satellite data, we find that N 2 abundances exceed GCM results by about a factor of 2 at 130 km but are in agreement at 150 km. The analysis and interpretation are enabled by a linear regression method used to extract components of UV spectra from IUVS limb observations.

Atmosphere of Mars

10.1002/2015gl065319

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Citations (45)

UV Study of the Fourth Positive Band System of CO and Oi135.6 nm From Electron Impact on CO and CO₂

Journal of Geophysical Research Space Physics (2019)

J. M. Ajello C. P. Malone J. S. Evans G. M. Holsclaw Alan Hoskins

Abstract 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 ( 5 S o → 3 P) 135.6 nm atomic transition by electron‐impact‐induced‐fluorescence of CO and CO 2 . We present a model excitation cross section from threshold to high energy for the A 1 Π state, including cascade by electron impact on CO. The A 1 Π 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 CO 2 , 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 O i ( 5 S 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 O i ( 5 S o ) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the O i ( 5 S o ) state.

Electron excitation

Metastability

Glow discharge

10.1029/2018ja026308

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Citations (15)

Combined Analysis of Hydrogen and Oxygen 102.6 nm Emission at Mars

Geophysical Research Letters (2022)

Michael Chaffin J. Deighan Sonal Jain Greg Holsclaw Hoor AlMazmi

Abstract Water is lost from the Mars upper atmosphere to space as hydrogen and oxygen, both of which can be observed in scattered ultraviolet sunlight at 102.6 nm. We present Emirates Mars Mission Emirates Mars Ultraviolet Spectrometer (EMM/EMUS) insertion orbit observations of this airglow, resolving the independent altitude contributions of H and O for the first time. We present the first airglow modeling of the complete H and O 102.6 nm system and the first 3D azimuthally symmetric modeling of the O emission, retrieving temperatures and densities typical of northern spring. Our model reproduces the emission well above 200 km, but does not incorporate partial frequency redistribution needed to reproduce the observed O brightness at lower altitudes and on the disk. These results support future EMM/EMUS science orbit retrievals of H loss and the use of 102.6 nm observations to constrain planetary atmospheres across the solar system.

Airglow

Ultraviolet

Atmosphere of Mars

Atmospheric models

10.1029/2022gl099851

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Citations (3)

Titan airglow during eclipse

Geophysical Research Letters (2012)

Robert A. West J. M. Ajello M. H. Stevens D. F. Strobel G. R. Gladstone

Solar XUV photons can provide enough energy to account for the observed nitrogen UV dayglow emissions above 800 km, but a small or sporadic contribution from energetic particles cannot be ruled out. Furthermore, ion production at altitudes deeper than 800 km as inferred from radio occultation cannot be produced by solar XUV stimulation and implies energy deposition from protons and oxygen ions. Here we examine UV spectra and visible‐wavelength images of Titan in Saturn's shadow, when XUV stimulation is absent. UV emissions are observed in one of the three sets of spectra, and the intensity of these emissions is about a factor of 10 less than the peak intensity reported on the dayside. We observe visible‐wavelength emissions for the first time. No horizontally resolved auroral structures are seen in the visible images. At visible wavelengths Titan has a global emission at the haze‐top level that is not understood, although cosmic ray ionization and chemiluminescence are candidates needing further investigation.

Airglow

Radio occultation

Extreme ultraviolet

Haze

Ultraviolet

Occultation

10.1029/2012gl053230

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Citations (15)

Seasonal and Latitudinal Variations of Dayside N₂/CO₂ Ratio in the Martian Thermosphere Derived From MAVEN IUVS Observations

Journal of Geophysical Research Planets (2020)

Nao Yoshida Hiromu Nakagawa Naoki Terada J. S. Evans N. M. Schneider

Abstract The dayside N 2 /CO 2 at 140 km altitude in the Martian thermosphere has been investigated by the imaging ultraviolet spectrograph (IUVS) aboard the Mars atmosphere and volatile evolution spacecraft during the period from October 2014 to May 2018. We find that N 2 /CO 2 at 140 km altitude varies significantly in the range of 0.02–0.20 and shows a seasonal sinusoidal trend. The higher value appears during aphelion and the lower value during perihelion. Variations of observed N 2 /CO 2 ratio at 140 km are mainly associated with CO 2 number density. Thus, while we found that N 2 /CO 2 varies at a given altitude, we could not identify variations at a given pressure level. In order to reveal the drivers of N 2 /CO 2 variations at 140 km, we examine the effects of surface N 2 /CO 2 , thermospheric temperature, and homopause altitude. The variations of homopause altitude could be the dominant driver of changes in N 2 /CO 2 . Inferred dayside homopause altitudes derived from IUVS observations show an anti‐correlation with the trend of N 2 /CO 2 at 140 km. Distributions of CO 2 density at the inferred homopause altitudes suggest that dayside homopause altitude is mainly controlled by inflation and contraction of the lower atmosphere. Additionally, N 2 /CO 2 shows a clear latitudinal dependence for L s = 80°–100°. Higher N 2 /CO 2 values appear in the southern winter hemisphere, corresponding to lower homopause altitude by ∼30 km. Meanwhile, the latitudinal dependence of both N 2 /CO 2 and homopause altitude disappears for L s = 340°–360°.

Atmosphere of Mars

10.1029/2020je006378

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Citations (8)

Thermal structure of Mars’ middle and upper atmospheres: Understanding the impacts of dynamics and solar forcing

Icarus (2021)

Sonal Jain Emmaris Soto J. S. Evans J. Deighan N. M. Schneider

Forcing (mathematics)

Solar variation

10.1016/j.icarus.2021.114703

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Citations (22)

Patchy Proton Aurora at Mars: A Global View of Solar Wind Precipitation Across the Martian Dayside From EMM/EMUS

Geophysical Research Letters (2022)

Michael Chaffin C. M. Fowler J. Deighan Sonal Jain Greg Holsclaw

Abstract Proton aurora at Mars are thought to form indirectly, as a result of solar wind proton charge exchange with planetary coronal hydrogen upstream of the bow shock. This charge exchange produces beamed energetic neutral atoms that bypass the induced magnetosphere and cause spatially uniform auroral emission when they collide with the thermosphere. Here we report multiple definitive observations of spatially localized “patchy” proton aurora at Mars using the Emirates Mars Ultraviolet Spectrometer on the Emirates Mars Mission, and characterize the plasma environment during these events using contemporaneous Mars Atmosphere and Volatile EvolutioN mission measurements. Multiple mechanisms are required to explain these observations, including at times the direct deposition of solar wind plasma into the thermosphere, particularly during radial interplanetary magnetic field conditions. Much future work will be needed to assess these mechanisms and understand the impact of these auroral events on Mars atmospheric evolution.

Atmosphere of Mars

Atmospheric escape

Exosphere

10.1029/2022gl099881

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Citations (16)

Discovery of a proton aurora at Mars

Nature Astronomy (2018)

J. Deighan Sonal Jain Michael Chaffin Xiaohua Fang J. S. Halekas

Atmosphere of Mars

Energetic neutral atom

Corona (planetary geology)

Atmospheric escape

Solar energetic particles

10.1038/s41550-018-0538-5

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Citations (74)