Hydrocarbon species, and in particular CH4, play a key role in the stratosphere-thermosphere boundary of Jupiter, which occurs around the μ-bar pressure level. Previous analyses of solar occultation, ...He and Ly-α airglow, and ISO/SWS measurements of the radiance around 3.3 μm have inferred significantly different methane concentrations. Here we aim to accurately model the CH4 radiance at 3.3 μm measured by ISO/SWS by using a comprehensive non-local thermodynamic equilibrium model and the most recent collisional rates measured in the laboratory for CH4 to shed new light onto the methane concentration in the upper atmosphere of Jupiter. These emission bands have been shown to present a peak contribution precisely at the μ-bar level, hence directly probing the region of interest. We find that a high CH4 concentration is necessary to explain the data, in contrast with the most recent analyses, and that the observations favour the lower limit of the latest laboratory measurements of the CH4 collisional relaxation rates. Our results provide precise constraints on the composition and dynamics of the lower atmosphere of Jupiter.
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Retrieval of abundances of atmospheric species from limb infrared emission spectra requires accurate knowledge of the pointing of the instrument in terms of elevation, as well as temperature and ...pressure profiles. An optimal estimation‐based method is presented to infer these quantities from measured spectra. The successful and efficient joint retrieval of these largely correlated quantities depends strongly on the proper selection of the retrieval space, the selection of spectral microwindows, and the choice of reasonable constraints which force the solution to be stable. The proposed strategy was applied to limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Envisat research satellite in order to validate the instrument pointing information based on the satellite's orbit and attitude control system which uses star tracker information as a reference. Both systematic and periodic pointing calibration errors were detected, which meanwhile have been corrected to a major part. Furthermore, occasional pitch jumps were detected, which could be assigned to parameter uploads to the satellite's orbit and attitude control system. It has been shown that in general, it is justified to assume local thermodynamic equilibrium below 60 km for these purposes. The retrieval method presented has been proven to be suitable for independent monitoring of MIPAS line‐of‐sight pointing.
The vast set of near‐global and continuous atmospheric measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument since 2002, including daytime and ...nighttime kinetic temperature (Tk) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 μm CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non‐LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2(υ2) by N2, O2 and O, and the CO2(υ2) vibrational‐vibrational exchange to estimate their impact on SABER Tk for different atmospheric conditions. The Tk is more sensitive to the uncertainty in the latter two, and their effects depend on altitude. The Tk combined systematic error due to non‐LTE kinetic parameters does not exceed ±1.5 K below 95 km and ±4–5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is ±3 K at 80 km, ±6 K at 84 km and ±18 K at 100 km under the less favorable polar summer conditions. For strong temperature inversion layers, the errors reach ±3 K at 82 km and ±8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to ±3 K.
In this paper, we analyze the strong unidentified emission near 3.28 micron in Titan's upper daytime atmosphere recently discovered by Dinelli et al.We have studied it by using the NASA Ames PAH IR ...Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 micron. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 10(exp 4) particles / cubic cm. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is approx 430 u; the mean area is about 0.53 sq. nm; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.
The large solar storms in October–November 2003 produced enormous solar proton events (SPEs) where high energetic particles reached the Earth and penetrated into the middle atmosphere in the polar ...regions. At this time, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) was observing the atmosphere in the 6–68 km altitude range. MIPAS observations of NOx (NO + NO2) and O3 of the period from 25 October to 14 November 2003 are the first global measurements of NOx species, covering both the summer (daylight) and winter (dark) polar regions during an SPE. Very large values of NOx in the upper stratosphere of 180 ppbv (parts per billion by volume) have been measured, and a large asymmetry in northern and southern polar cap NOx enhancements was found. Arctic mean polar cap (>60°) NOx enhancements of 20 to 70 ppbv between 40 to 60 km lasted for at least 2 weeks, while the Antarctic mean NOx enhancement was between 10 and 35 ppbv and was halved after 2 weeks. Ozone shows depletion signatures associated with both HOx (H + OH + HO2) and NOx enhancements but at different timescales. Arctic lower mesospheric (upper stratospheric) ozone is reduced by 50–70% (30–40%) for about 2 weeks after the SPEs. A smaller ozone depletion signal was observed in the Antarctic atmosphere. After the locally produced Arctic middle and upper stratospheric as well as mesospheric NOx enhancement, large amounts of NOx were observed until the end of December. These are explained by downward transport processes. These enhancements drastically declined with the mid‐December stratospheric warming. Significant O3 depletion was observed inside the polar vortex in a wide altitude range during this period. From mid‐January until the end of March 2004, MIPAS observed extraordinary high values of NO2 in the upper stratosphere of the northern polar region (mean in‐vortex values up to 350 ppbv at ∼54 km), which seem to be caused by the unusually strong vortex and downward transport at that time together with an uncommonly large auroral activity starting with the solar storms in October–November and continuing over the winter. In‐vortex ozone was observed to significantly decline in the mid‐February to late March period above the 1750 K potential temperature level.
During the last three decades, it has become increasingly clear that atmospheric modelling and remote sounding of the atmosphere from space, to name just two important application areas, are affected ...by non-equilibrium processes which have not been incorporated into traditional radiative transfer calculations. These processes, dubbed "non-LTE", are therefore the subject of growing interest among scholars and researchers dealing with the upper atmosphere. This important book provides the first comprehensive and "global" description of non-LTE infrared emissions in the atmosphere of the Earth and other planets, starting with the theoretical foundations and progressing to the most important applications. Besides giving an introduction to this complex subject, it is a guide to the state-of-the-art in incorporating non- LTE processes into radiative transfer algorithms and computer models of the atmosphere. Numerous examples are presented of the application of these methods to (a) atmospheric remote sensing, (b) atmospheric energy budget (cooling and heating rate) calculations, and (c) atmospheres other than the Earth's.
Hydrogen and helium transmission signals trace the upper atmospheres of hot gas-giant exoplanets, where the incoming stellar extreme ultraviolet and X-ray fluxes are deposited. Further, for the ...hottest stars, the near-ultraviolet excitation of hydrogen in the Balmer continuum may play a dominant role in controlling the atmospheric temperature and driving photoevaporation. KELT-9 b is the archetypal example of such an environment as it is the hottest gas-giant exoplanet known to date (
T
eq
∼ 4500 K) and orbits an A0V-type star. Studies of the upper atmosphere and escaping gas of this ultra-hot Jupiter have targeted the absorption in the Balmer series of hydrogen (
n
1
= 2 →
n
2
> 2). Unfortunately, the lowermost metastable helium state that causes the triplet absorption at 1083 Å is not sufficiently populated for detection. This is due to the low extreme-ultraviolet and X-ray fluxes from the host star, and to its high near-ultraviolet flux, which depopulates this metastable state. Here, we present evidence of hydrogen absorption in the Paschen series in the transmission spectrum of KELT-9 b observed with the high-resolution spectrograph CARMENES. Specifically, we focus on the strongest line covered by its near-infrared channel, Pa
β
at 12 821.6 Å (
n
1
= 3 →
n
2
= 5). The observed absorption shows a contrast of (0.53
−0.13
+0.12
)%, a blueshift of −14.8
−3.2
+3.5
km s
−1
, and a full width at half maximum of 31.9
−8.3
+11.8
km s
−1
. The observed blueshift in the absorption feature could be explained by day-to-night circulation within the gravitationally bound atmosphere or, alternatively, by Pa
β
absorption originating in a tail of escaping gas moving toward the observer as a result of extreme atmospheric evaporation. This detection opens a new window for investigating the atmospheres of ultra-hot Jupiters, providing additional constraints of their temperature structure, mass-loss rates, and dynamics for future modeling of their scorching atmospheres.
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We have analyzed limb daytime observations of Titan's upper atmosphere at 3.3 μm, acquired by the visual‐infrared mapping spectrometer (VIMS) on Cassini. They were previously studied by García‐Comas ...et al. (2011) to derive CH4 densities. Here, we report an unidentified emission peaking around 3.28 μm, hidden under the methane R branch. This emission is very strong, with intensity comparable to the CH4 bands located in the same spectral region. It presents a maximum at about 950 km and extends from 600 km up to 1250 km. It is definitely pumped by solar radiation since it vanishes at night. Our analysis shows that neither methane nor the major hydrocarbon compounds already discovered in Titan's upper atmosphere are responsible for it. We have discarded many other potential candidates and suggest that the unidentified emission might be caused by aromatic compounds.
Key Points
We observe an unknown emission in VIMS spectra of Titan's upper atmosphere
The feature is persistent, very strong, present at daytime and peaks at 950 km
Not caused by known Titan gases, aromatic hydrocarbons are likely carriers
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Solar eruptions in early 2005 led to a substantial barrage of charged particles on the Earth's atmosphere during the 16–21 January period. Proton fluxes were greatly increased during these several ...days and led to the production of HOx (H, OH, HO2) and NOx (N, NO, NO2), which then caused the destruction of ozone. We focus on the Northern polar region, where satellite measurements and simulations with the Whole Atmosphere Community Climate Model (WACCM3) showed large enhancements in mesospheric HOx and NOx constituents, and associated ozone reductions, due to these solar proton events (SPEs). The WACCM3 simulations show enhanced short-lived OH and HO2 concentrations throughout the mesosphere in the 60–82.5° N latitude band due to the SPEs for most days in the 16–21 January 2005 period, somewhat higher in abundance than those observed by the Aura Microwave Limb Sounder (MLS). These HOx enhancements led to huge predicted and MLS-measured ozone decreases of greater than 40 % throughout most of the northern polar mesosphere during the SPE period. Envisat Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measurements of hydrogen peroxide (H2O2) show increases throughout the stratosphere with highest enhancements of about 60 pptv in the lowermost mesosphere over the 16–18 January 2005 period due to the solar protons. WACCM3 predictions indicate H2O2 enhancements over the same time period of about three times that amount. Measurements of nitric acid (HNO3) by both MLS and MIPAS show an increase of about 1 ppbv above background levels in the upper stratosphere during 16–29 January 2005. WACCM3 simulations show only minuscule HNO3 increases (<0.05 ppbv) in the upper stratosphere during this time period. Polar mesospheric enhancements of NOx are computed to be greater than 50 ppbv during the SPE period due to the small loss rates during winter. Computed NOx increases, which were statistically significant at the 95 % level, lasted about a month past the SPEs. The SCISAT-1 Atmospheric Chemistry Experiment Fourier Transform Spectrometer NOx measurements and MIPAS NO2 measurements for the polar Northern Hemisphere are in reasonable agreement with these predictions. An extremely large ground level enhancement (GLE) occurred during the SPE period on 20 January 2005. We find that protons of energies 300 to 20 000 MeV, associated with this GLE, led to very small enhanced lower stratospheric odd nitrogen concentrations of less than 0.1 % and ozone decreases of less than 0.01 %.
Ultra-hot Jupiters are highly irradiated gas giant exoplanets on close-in orbits around their host stars. The dayside atmospheres of these objects strongly emit thermal radiation due to their ...elevated temperatures, making them prime targets for characterization by emission spectroscopy. We analyzed high-resolution spectra from CARMENES, HARPS-N, and ESPaDOnS taken over eight observation nights to study the emission spectrum of WASP-33b and draw conclusions about its atmosphere. By applying the cross-correlation technique, we detected the spectral signatures of Ti
i
, V
i
, and a tentative signal of Ti
ii
for the first time via emission spectroscopy. These detections are an important finding because of the fundamental role of Ti- and V-bearing species in the planetary energy balance. Moreover, we assessed and confirm the presence of OH, Fe
i
, and Si
i
from previous studies. The spectral lines are all detected in emission, which unambiguously proves the presence of an inverted temperature profile in the planetary atmosphere. By performing retrievals on the emission lines of all the detected species, we determined a relatively weak atmospheric thermal inversion extending from approximately 3400 to 4000 K. We infer a supersolar metallicity close to 1.5 dex in the planetary atmosphere, and find that its emission signature undergoes significant line broadening with a Gaussian full width at half maximum of about 4.5 km s
−1
. Also, we find that the atmospheric temperature profile retrieved at orbital phases far from the secondary eclipse is about 300 to 700 K cooler than that measured close to the secondary eclipse, which is consistent with different day- and nightside temperatures. Moreover, retrievals performed on the emission lines of the individual chemical species lead to consistent results, which gives additional confidence to our retrieval method. Increasing the number of species included in the retrieval and expanding the set of retrieved atmospheric parameters will further advance our understanding of exoplanet atmospheres.
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