Thermospheric NO Research Articles

Thermospheric NO Cooling During 2003 October “Halloween Storm”: Revisited

Thermospheric NO Cooling During 2003 October “Halloween Storm”: Revisited

Seasonal variation in nighttime NO radiative cooling as observed by TIMED/SABER in lower thermosphere during solar maximum and solar minimum

Both composition and temperature play a crucial role in determining the NO radiative cooling in lower thermosphere as observed by TIMED/SABER. In this work, we present a detailed investigation of seasonal variation in thermospheric NO radiative cooling. We have carried forward the investigation of Li et al. (2018) regarding the variations in local nighttime peak NO radiative cooling and its altitude during solar maximum and solar minimum conditions. By analyzing latitudinal changes over quiet times for each month in year 2018, it is evident that both the investigated parameters exhibit summer-winter variability. The qualitative contribution of different species (i.e., NO, and O), and temperatures in determining the vertical profile of NO radiative cooling for different latitudes is investigated by utilizing the NRLMSISE-00 estimated parameters, and SNOE observed NO density. The temperature, NO density, and compositional variations due to asymmetrical solar heating and associated summer-to-winter circulation in both the hemispheres during solar minimum conditions seem to be the dominating factor in controlling the NO radiative cooling during different seasons. The altitudes at which maximum cooling by NO occurs exhibits an inverse correlation with the amount of radiative cooling. The region of enhanced NO densities (polar and summer hemispheric low-mid latitude regions) have larger NO radiative cooling with lower peak altitudes in comparison to other regions (equatorial to winter hemispheric low-mid latitude regions), where NO radiative cooling is low with higher peak altitude values.

Thermospheric NO Cooling during an Unusual Geomagnetic Storm of 21–22 January 2005: A Comparative Study between TIMED/SABER Measurements and TIEGCM Simulations

The geomagnetic storm is the manifestation of the solar wind–magnetosphere interaction. It deposits huge amount of the solar energy into the magnetosphere–ionosphere–thermosphere (MIT) system. This energy creates global perturbations in the chemistry, dynamics, and energetics of the MIT system. The high latitude energy deposition results in the Joule and particle heating that subsequently increases the thermospheric temperature. The thermospheric temperature is effectively regulated by the process of thermospheric cooling emission by nitric oxide via 5.3 µm. A peculiar, intense geomagnetic storm (Dst = −105 nT) occurred during 21–22 January 2005, where the main phase developed during the northward orientation of the z-component of interplanetary magnetic field. We utilized the nitric oxide 5.3 µm infrared emission from the NCAR’s Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM) simulation and the Sounding of Atmosphere using Broadband Emission Radiometry (SABER) onboard the thermosphere–ionosphere–mesosphere energetic and dynamics satellite to investigate its response to this anomalous geomagnetic storm. We compared the model results with the observations on both the local and global scales. It is observed that the model results agree very well with the observations during quiet times. However, the model severely underestimates the cooling emission by one-fourth of the observations, although it predicts an enhancement in the thermospheric temperature and densities of atomic oxygen and nitric oxide during the geomagnetic storm.

Distinctive response of thermospheric cooling to ICME and CIR-driven geomagnetic storms

The temporal response of thermospheric CO2 and NO cooling emissions is investigated during ICME and CIR-driven geomagnetic storms by using data from the SABER instrument onboard the TIMED, GRACE, and DMSP satellites. The superposed epoch analysis reveals that the cooling emissions experience a strong enhancement and quick recovery to pre-event value within 3–4 days during CME storms. Whereas, it shows slower recovery that lasts for more than 6–7 days during CIR-driven storms. We performed detailed study of NO cooling emission owing to the fact that the production of NO depends on the external energy input. The different response of thermospheric NO cooling during CME and CIR storms can be attributed to differences in precipitation of particle (electron and ion) fluxes. A strong correlation with a positive timelag is observed between NO cooling emission and Dst index, coupling functions and particle flux. Further, the correlation between NO cooling flux and particle flux displays a distinct and stronger correlation during CIR storms as compared to CME. This study also shows that the Newell coupling function (normalized cross-correlation, r = 0.90 for CME and r = 0.92 for CIR) and the Akasofu parameter (r = 0.92 for CME, r = 0.76 for CIR) are better correlated with NO cooling flux, respectively, during CIR- and ICME-driven storms.

Reply to Comments by Lei et al. on the Paper “Poststorm Thermospheric NO Overcooling?” by A.V. Mikhailov and L. Perrone (2020)

AbstractRecently, our paper “Poststorm Thermospheric NO Overcooling?” has been published in JGR. Lei with colleagues (2012) who have proposed the “NO overcooling” concept have written Comments on this paper. Below is given our reply. Everywhere MP20 means the reference to the paper by Mikhailov and Perrone (2020). In the beginning to avoid misunderstanding, it is necessary to stress that in MP20 we did not touch on the well‐documented process of the thermosphere NO cooling (e.g., Gordiets et al., 1982; Maeda et al., 1989; Mlynczak et al., 2018; Prölss, 2004, 2011; Roble, 1995; Weimer et al., 2011) which mainly takes place in the lower thermosphere. We only explained a decrease of neutral gas density at F2‐layer heights during the recovery storm phase. The effect manifests seasonal dependence which is not explained by the “NO overcooling” mechanism.

Comments on “Poststorm Thermospheric NO Overcooling?” by Mikhailov and Perrone (2020)

AbstractRecently Mikhailov and Perrone (2020, https://doi.org/10.1029/2019ja027122) proposed the mechanism of neutral atomic oxygen reduction, which is associated with the upper atmospheric circulation, to explain the reduction of total thermospheric mass density during the storm recovery phase. The authors further concluded arbitrarily that there is no need to introduce the storm‐time overcooling concept. However, their methodology is fundamentally flawed and their results and conclusions are incorrect. Instead, the overcooling scenario remains a viable concept in understanding thermospheric variations in the storm recovery phase.

Poststorm Thermospheric NO Overcooling?

AbstractA mechanism of the neutral gas density decrease at middle latitudes during the recovery storm phase is discussed. The recently proposed method to retrieve thermospheric parameters from ionospheric observations is used for the analysis of equinoctial, summer, and winter severe magnetic storms. CHAllenging Minisatellite Payload and Swarm neutral gas density observations are used for a comparison. It is shown that storm‐induced atomic oxygen variation is the controlling process. Well‐known F2‐layer storm morphology and the poststorm decrease of neutral gas density reflect the same storm‐induced variations of atomic oxygen abundance in the upper atmosphere. There is no need to attract a new “poststorm NO overcooling” concept to explain the decrease of neutral gas density.

Observations and Modeling of Increased Nitric Oxide in the Antarctic Polar Middle Atmosphere Associated With Geomagnetic Storm‐Driven Energetic Electron Precipitation

AbstractNitric oxide (NO) produced in the polar middle and upper atmosphere by energetic particle precipitation depletes ozone in the mesosphere and, following vertical transport in the winter polar vortex, in the stratosphere. Medium‐energy electron (MEE) ionization by 30–1,000 keV electrons during geomagnetic storms may have a significant role in mesospheric NO production. However, questions remain about the relative importance of direct NO production by MEE at altitudes ~60–90 km versus indirect NO originating from auroral ionization above 90 km. We investigate potential drivers of NO variability in the southern‐hemisphere mesosphere and lower thermosphere during 2013–2014. Contrasting geomagnetic activity occurred during the two austral winters, with more numerous moderate storms in the 2013 winter. Ground‐based millimeter‐wave observations of NO from Halley, Antarctica, are compared with measurements by the Solar Occultation For Ice Experiment (SOFIE) spaceborne spectrometer. NO partial columns over the altitude range 65–140 km from the two observational data sets show large day‐to‐day variability and significant disagreement, with Halley values on average 49% higher than the corresponding SOFIE data. SOFIE NO number densities, zonally averaged over geomagnetic latitudes −59° to −65°, are up to 3 × 108/cm3 higher in the winter of 2013 compared to 2014. Comparisons with a new version of the Whole Atmosphere Community Climate Model, which includes detailed D‐region ion chemistry (WACCM‐SIC) and MEE ionization rates, show that the model underestimates NO in the winter lower mesosphere whereas thermospheric abundances are too high. This indicates the need to further improve and verify WACCM‐SIC with respect to MEE ionization, thermospheric NO chemistry, and vertical transport.

Τhe observational and empirical thermospheric CO2 and NO power do not exhibit power-law behavior; an indication of their reliability

In this paper we investigate the evolution of the energy emitted by CO2 and NO from the Earth's thermosphere on a global scale using both observational and empirically derived data. In the beginning, we analyze the daily power observations of CO2 and NO received from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) equipment on the NASA Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite for the entire period 2002–2016. We then perform the same analysis on the empirical daily power emitted by CO2 and NO that were derived recently from the infrared energy budget of the thermosphere during 1947–2016. The tool used for the analysis of the observational and empirical datasets is the detrended fluctuation analysis, in order to investigate whether the power emitted by CO2 and by NO from the thermosphere exhibits power-law behavior. The results obtained from both observational and empirical data do not support the establishment of the power-law behavior. This conclusion reveals that the empirically derived data are characterized by the same intrinsic properties as those of the observational ones, thus enhancing the validity of their reliability.

Global observations of thermospheric temperature and nitric oxide from MIPAS spectra at 5.3μm

[1] We present vertically resolved thermospheric temperatures and NO abundances in terms of volume mixing ratio retrieved simultaneously from spectrally resolved 5.3 μm emissions recorded by the Michelson Interferometer for Passive Atmospheric Spectroscopy (MIPAS) in its upper atmospheric observation mode during 2005–2009. These measurements are unique since they represent the first global observations of temperature and NO for both day and night conditions taken from space. A retrieval scheme has been developed which accounts for vibrational, rotational and spin-orbit non-LTE distributions of NO. Retrieved polar temperature and NO profiles have a vertical resolution of 5–10 km for high Ap values, and degrade to 10–20 km for low Ap conditions. Though retrieved NO abundances depend strongly on the atomic oxygen profile used in the non-LTE modeling, observations can be compared to model results in a consistent manner by applying a simple correction. Apart from this, total retrieval errors are dominated by instrumental noise. The typical single measurement precision of temperature and NO abundances are 5–40 K and 10–30%, respectively, for high Ap values, increasing to 30–70 K for Tk and 20–50% for NO VMR for low Ap conditions. Temperature and NO profiles observed under auroral conditions are rather insensitive to smoothing errors related to the mapping of a priori profile shapes. However, for extra-polar and low Ap conditions, a potential systematic bias in the retrieved nighttime temperature and NO profiles related to smoothing errors has been identified from a comparison to Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) simulations. We have constructed a solar minimum monthly climatology of thermospheric temperature and NO from MIPAS observations taken during 2008–2009. MIPAS temperature distributions agree well, on average, with the Mass Spectrometer and Incoherent Scatter radar model (NRLMSISE-00), but some systematic differences exist. MIPAS temperatures are generally colder than NRLMSISE-00 in the polar middle thermosphere (mainly in the summer polar region) by up to 40 K; and are warmer than NRLMSISE-00 in the lower thermosphere around 120–125 km by 10–40 K. Thermospheric NO daytime distributions agree well with the Nitric Oxide Empirical Model (NOEM), based on Student Nitric Oxide Explorer (SNOE) observations. A comparison of MIPAS NO number density with the previous climatology for the declining phases of the solar cycle based on HALOE and SME data shows that MIPAS is generally larger with values ranging from 10 to 40%, except in the auroral region and at the equatorial latitudes above 130 km where the MIPAS/HALOE+SME ratio varies from 1.6 to 2. Day-night differences in MIPAS NO show daytime enhancements of up to 140% in the tropical and midlatitudes middle thermosphere. In the lower thermosphere, the diurnal amplitude is smaller and NO concentrations are generally higher during night by about 10–30%, particularly in the auroral regions.

Energetic particle precipitation effects on the Southern Hemisphere stratosphere in 1992–2005

Measurements from several different satellite instruments are used to estimate effects of energetic particle precipitation (EPP) on NOx (NO + NO2) in the Southern Hemisphere stratosphere from 1992 to 2005. The focus is the EPP Indirect Effect (IE), whereby NOx produced in the mesosphere or thermosphere via EPP (EPP‐NOx) descends to the stratosphere during the polar winter, where it can participate in catalytic ozone destruction. EPP‐NOx entering the stratosphere is found to vary in magnitude from 0.1 to 2.6 gigamoles per year, with maximum values occurring in 1994 and 2003. The interannual variation correlates strongly with several measures of EPP activity, including auroral and medium energy electron hemispheric power, and satellite measurements of thermospheric NO. This represents the first estimation of EPP‐NOx contributions to the stratospheric odd nitrogen budget using observations over an entire solar cycle. The results will be useful for evaluating and constraining global models to investigate coupling of the upper and lower atmosphere by the EPP IE, including any influences this might have on ozone trends and possibly on climate.

A two-dimensional model of thermospheric nitric oxide sources and their contributions to the middle atmospheric chemical balance

The NASA/Goddard Space Flight Center two-dimensional (GSFC 2D) photochemical transport model has been used to study the influence of thermospheric NO on the chemical balance of the middle atmosphere. Lower thermospheric NO sources are included in the GSFC 2D model in addition to the sources that are relevant to the stratosphere. A time series of hemispheric auroral electron power has been used to modulate the auroral NO production in the auroral zone. A time series of the Ottawa 10.7-cm solar flux index has been used as a proxy to modulate NO production at middle and low latitudes by solar EUV and soft X-rays. An interhemispheric asymmetry is calculated for the amounts of odd nitrogen in the polar stratosphere. We compute a <∼3% enhancement in the odd nitrogen (NO y =N, NO, NO 2, NO 3, N 2O 5, BrONO 2, ClONO 2, HO 2NO 2, and HNO 3) budget in the north polar stratosphere (latitude > 50°) due to thermospheric sources, whereas we compute a <∼8% enhancement in the NO y budget in the south polar stratosphere (latitude > 50°).

Polar stratospheric descent of NOy and CO and Arctic denitrification during winter 1992–1993

Observations inside the November 1994 Antarctic stratospheric vortex and inside the April 1993 remnant Arctic stratospheric vortex by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer are reported. In both instances, elevated volume mixing ratios (VMRs) of carbon monoxide (CO) were measured. A peak Antarctic CO VMR of 60 ppbv (where 1 ppbv = 10−9 per unit volume) was measured at a potential temperature (Θ) of 710 K (∼27 km), about 1 km below the altitude of a pocket of elevated NOy (total reactive nitrogen) at a deep minimum in N2O (&lt;5 ppbv). The Arctic observations also show a region of elevated vortex CO with a peak VMR of 90 ppbv at 630–670 K (∼25 km) but no corresponding enhancement in NOy, perhaps because of stronger dynamical activity in the northern hemisphere polar winter and/or interannual variability in the production of mesospheric or lower thermospheric NO. By comparing vortex and extravortex observations of NOy obtained at the same N2O VMR, Arctic vortex denitrification of 5 ± 2 ppbv at 470 K (∼18 km) is inferred. We show that our conclusion of substantial Arctic winter 1992–1993 denitrification is robust by comparing our extravortex observations with previous polar measurements obtained over a wide range of winter conditions. Correlations of NOy with N2O measured at the same Θ by ATMOS in the Arctic vortex and at midlatitudes on board the ER‐2 aircraft several weeks later lie along the same mixing line. The result demonstrates the consistency of the two data sets and confirms that the ER‐2 sampled fragments of the denitrified Arctic vortex following its breakup. An analysis of the ATMOS Arctic measurements of total hydrogen shows no evidence for significant dehydration inside the vortex.

MAHRSI observations of nitric oxide in the mesosphere and lower thermosphere

In November, 1994, the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) observed the distribution of NO between the altitudes of 76 and 140 km by measuring limb intensity profiles of solar resonance fluorescence in the NO A ²Σ → X ²II (1,0) γ band near 215 nm. The observations were made from the ASTRO‐SPAS (Shuttle Pallet Satellite) spacecraft which was deployed and retrieved by the space shuttle. The data provided a seven hour snapshot of lower thermospheric and mesospheric NO from sunrise near 48°S to sunset near 61° N latitude following a period of low solar and high geomagnetic activity. Inferred peak lower thermospheric NO densities ranged from 3 × 107 cm−3 near the equator to 2 × 108 cm−3 at high northern latitudes, roughly consistent with previous observations for the same conditions. Individual vertical density profiles showed substantial structure and large orbit to orbit variations, suggesting that the distribution of mesospheric and lower thermospheric NO is dynamically influenced.

Precipitating electrons: Evidence for effects on mesospheric odd nitrogen

Observations of electron fluxes made by the PET and LICA instruments aboard SAMPEX have been used with NO measurements made by HALOE aboard UARS to provide evidence of mesospheric and lower thermospheric NO formation due to precipitating electrons. Results indicate significant NO increases from 70 to 120 km which are associated with the occurrence of enhanced electron populations in the outer trapping regions of the magnetosphere, 2.5 ≤ L ≤ 7, which precipitate into the atmosphere.

Coupling between middle and upper atmospheric NO: Constraints from HALOE observations

Observations of NO, NO2, and CH4 from the HALOE instrument on the UARS satellite are used to investigate the transport of thermospheric NO into the middle atmosphere. By comparing the variation of NO and NO2 with simultaneous measurements of a long lived stratospheric tracer like CH4, regions of enhanced odd nitrogen can be quantified. Our results indicate substantial enhancement of NO in the high latitude winter mesosphere extending from thermospheric altitudes down to about 55–60 km. We also see evidence of substantial equator ward mixing of mesospheric NO. Occasional enhancements of NOx are seen extending down into the upper stratosphere in winter; however, they do not appear to persist. Observations by HALOE at latitudes up to 75–80 degrees in early spring show no evidence for enhanced NOx. This suggests that the effect of thermospheric NO on high latitude upper stratospheric O3 may be less than previously thought.

On the radiative coupling between mesospheric and thermospheric nitric oxide

A photochemical model of nitric oxide from 40 to 250 km has been used to study the distribution of NO in the mesosphere and lower thermosphere. The model includes a parameterization of NO photolysis that can account for the opacity of a varying thermospheric NO layer. This model is used to test the suggestion that increases in thermospheric NO which increase this opacity ”shield” NO at lower altitudes by decreasing the photolytic destruction rate. The model was ”tuned” to reproduce two recent observations of thermospheric NO, the high latitude rocket experiment of Eparvier and Barth [1992] and the midlatitude ground‐based microwave experiment of Clancy et al. [1992]. In the first case, the model indicated that the large thermospheric NO layer could have caused significant shielding and up to a factor of 2 effect on the mesospheric NO is seen. On the other hand, for the midlatitude observation the NO optical pathlength was too small to be significant. A time dependent version of the model was used to study the response of mesospheric NO to auroral energy input during winter. Under conditions which combine rapid transport and NO self‐shielding, the model suggests that NO density increases could propagate into the upper stratosphere.

Highly rotationally excited NO(υ,J) in the thermosphere from CIRRIS 1A limb radiance measurements

Earthlimb spectra of thermospheric NO fundamental band emissions, obtained in the CIRRIS 1A Space Shuttle experiment, have been analyzed using nonlinear least‐squares spectral fitting. Absolute NO(υ≥1,J) column densities have been determined in the 100 to 260‐km tangent height region and inverted to yield altitude‐dependent number densities for both a rotationally thermalized and a highly rotationally excited population component. Emissions from high‐J levels are predicted to dominate the Δυ=2 overtone bands during the daytime. The rotationally excited population is found to decrease more at night than the rotationally thermalized component. In addition, radiance from the CO υ=1→0 fundamental band is observed in the NO R‐branch band head region, with greater relative importance at night. The derived CO rotational temperatures are significantly greater than modeled local kinetic temperatures. These results provide important inputs to models of NO(υ,J) formation mechanisms, and of the chemistry, radiative processes, and energy budget of the thermosphere.

Analysis of selected nitric oxide observations in the lower thermosphere by HALOE on UARS

Measurements of nitric oxide mixing ratios have been made by the Halogen Occultation Experiment on the Upper Atmosphere Research Satellite over an altitude range extending from 15 to 130 km on every spacecraft sunrise and sunset event with the exception of about 8% downtime. Selected NO profiles from the first few months of observations were examined with emphasis on the relation between geomagnetic disturbances and enhanced NO in the lower thermosphere. During a large geomagnetic storm on November 8–9, 1991, HALOE obtained 15 NO sunrise profiles along the ∼50°N latitude circle. A factor of 3 increase in NO mixing ratio above ∼115 km at this latitude and a one to two day decay time were observed. The measured NO longitude/altitude cross section on this day shows a longitudinal asymmetry in the NO distribution with a maximum near the geomagnetic pole. From approximately one month's data, a latitude/altitude cross section of zonal mean NO mixing ratio was calculated. An example of such cross sections demonstrates a strong positive correlation between geomagnetic activity and thermospheric NO globally. This auroral forcing has a larger effect on increasing NO at high latitude than at low latitude.

Empirical correlations in thermospheric NO density measured from rockets and satellites

The diurnal, latitude, solar flux, and geomagnetic activity variations in thermospheric NO density measured at latitudes as high as 70° have been parameterized with a simple, empirical model. Consistent trends are found in both rocket and satellite measurements, although there are some differences that suggest the presence of systematic errors that add factor of 2 uncertainties to the model predictions. While NO measurements taken with IR emission and γ band fluorescence techniques are in reasonable agreement, evidence suggests that the ion composition and continuum chemiluminescence methods may be less accurate. The current model provides a convenient means for estimating daytime and nighttime NO densities for use in atmospheric chemistry and radiation studies.