Dynamics of the lower thermosphere consistent with satellite observations of 5577 Å airglow: I. Method of analysis

1984 ◽  
Vol 62 (4) ◽  
pp. 370-381 ◽  
Author(s):  
J. S. Murphree ◽  
R. D. Elphinstone ◽  
L. L. Cogger
Keyword(s):  
Atomic Oxygen ◽  
Molecular Diffusion ◽  
Numerical Solutions ◽  
Lower Thermosphere ◽  
Transport Processes ◽  
Physical Parameters ◽  
Dynamical Processes ◽  
Altitude Profile ◽  
Oxygen Profile

Numerical solutions of the continuity equation for atomic oxygen in the altitude range 80 to 120 km have been obtained for the purpose of investigating the various possible causes of latitudinal and seasonal variation in the atomic oxygen layer. The calculations take into account both photochemical and dynamical processes. Included in the dynamical processes are transport due to molecular diffusion, eddy turbulence, and time-independent macroscopic winds. The model allows the influence of these transport processes on the atomic oxygen altitude profile to be quantitatively evaluated. It is designed to provide a method to characterize the atomic oxygen profile by physical parameters for subsequent use in the interpretation of long-term temporal and latitudinal variation of 5577 Å airglow observations.

scholarly journals Change in turbopause altitude at 52 and 70° N

2016 ◽  
Vol 16 (4) ◽  
pp. 2299-2308 ◽  
Author(s):  
Chris M. Hall ◽  
Silje E. Holmen ◽  
Chris E. Meek ◽  
Alan H. Manson ◽  
Satonori Nozawa
Keyword(s):  
Time Series ◽  
Atomic Oxygen ◽  
Molecular Diffusion ◽  
Temporal Evolution ◽  
Molecular Mixing ◽  
Trace Species ◽  
Term Change ◽  
Meteor Trail ◽  
Altitude Estimation

Abstract. The turbopause is the demarcation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution that may be responsible for redistribution of atmospheric constituents. The general region of transition between turbulent and molecular mixing coincides with the base of the ionosphere, the lower region in which molecular oxygen is dissociated, and, at high latitude in summer, the coldest part of the whole atmosphere. This study updates previous reports of turbopause altitude, extending the time series by half a decade, and thus shedding new light on the nature of change over solar-cycle timescales. Assuming there is no trend in temperature, at 70° N there is evidence for a summer trend of  ∼  1.6 km decade−1, but for winter and at 52° N there is no significant evidence for change at all. If the temperature at 90 km is estimated using meteor trail data, it is possible to estimate a cooling rate, which, if applied to the turbopause altitude estimation, fails to alter the trend significantly irrespective of season. The observed increase in turbopause height supports a hypothesis of corresponding negative trends in atomic oxygen density, [O]. This supports independent studies of atomic oxygen density, [O], using mid-latitude time series dating from 1975, which show negative trends since 2002.

scholarly journals Effects of the planetary waves on the MLT airglow

2017 ◽  
Vol 35 (5) ◽  
pp. 1023-1032 ◽  
Author(s):  
Fabio Egito ◽  
Hisao Takahashi ◽  
Yasunobu Miyoshi
Keyword(s):  
General Circulation ◽  
Atomic Oxygen ◽  
Lower Thermosphere ◽  
Lower Boundary ◽  
Circulation Model ◽  
Vertical Transport ◽  
Transport Processes ◽  
Planetary Waves ◽  
Emission Rates ◽  
Middle Latitudes

Abstract. The planetary-wave-induced airglow variability in the mesosphere and lower thermosphere (MLT) is investigated using simulations with the general circulation model (GCM) of Kyushu University. The model capabilities enable us to simulate the MLT OI557.7 nm, O2b(0–1), and OH(6–2) emissions. The simulations were performed for the lower-boundary meteorological conditions of 2005. The spectral analysis reveals that at middle latitudes, oscillations of the emission rates with the period of 2–20 days appear throughout the year. The 2-day oscillations are prominent in the summer and the 5-, 10-, and 16-day oscillations dominate from the autumn to spring equinoxes. The maximal amplitude of the variations induced by the planetary waves was 34 % in OI557.7 nm, 17 % in O2b(0–1), and 8 % in OH(6–2). The results were compared to those observed in the middle latitudes. The GCM simulations also enabled us to investigate vertical transport processes and their effects on the emission layers. The vertical transport of atomic oxygen exhibits similar periodic variations to those observed in the emission layers induced by the planetary waves. The results also show that the vertical advection of atomic oxygen due to the wave motion is an important factor in the signatures of the planetary waves in the emission rates.

Interference filter spectral imaging of twilight O<sup>+</sup>(<sup>2</sup>P-<sup>2</sup>D) emission

1995 ◽  
Vol 13 (2) ◽  
pp. 189-194
Author(s):  
Y. Ma ◽  
R. N. Peterson ◽  
S. P. Zhang ◽  
I. C. McDade ◽  
R. H. Wiens ◽  
...  
Keyword(s):  
Atomic Oxygen ◽  
Emission Rate ◽  
Narrow Band ◽  
Rotational Temperature ◽  
Model Atmosphere ◽  
Interference Filter ◽  
Oxygen Profile ◽  
Spectral Imager ◽  
Good Agreement

Abstract. A spectral imager specifically designed to measure the O+(2P-2D) emission in the thermosphere during twilight has been constructed and tested in Toronto (43.8°N, 79.3°W), and found to show promise for long-term and campaign-mode operations. A modification of the mesopause oxygen rotational temperature imager (MORTI), it consists basically of a narrow-band interference filter (0.14 nm bandwidth) to separate wavelengths as a function of off-axis angle, a lens to focus the spectrum into a series of concentric rings, and a focal plane array (CCD) to record the spectral images in digital form. The instrument was built with two fields of view, one for the zenith and one for 20° above the horizon, movable to track the azimuth of the Sun, in order to provide appropriate data for inversion. Data gathered during June 1991 provided measurements of the column-integrated emission rate with a precision of about 3%. An atomic oxygen profile was deduced that showed good agreement with that predicted by the MSIS-90 model atmosphere. Geomagnetically induced variations of the O+ lines, calcium spectra resulting from meteor showers, and OH nightglow were also observed.

Thermospheric composition response to Sudden Stratospheric Warmings observed by the Global-Scale Observations of the Limb and Disk (GOLD) instrument

2020 ◽  
Author(s):  
Jens Oberheide ◽  
Nicholas Pedatella ◽  
Quan Gan ◽  
Komal Kumari ◽  
Alan Burns ◽  
...  
Keyword(s):  
Atomic Oxygen ◽  
Ionospheric Plasma ◽  
Molecular Diffusion ◽  
Lower Thermosphere ◽  
Density Ratio ◽  
Polar Vortex ◽  
Global Scale ◽  
Mean Circulation ◽  
The Impact ◽  
Composition Changes

&lt;p&gt;Observations from the recently launched Global-Scale Observations of the Limb and Disk (GOLD) instrument on the geostationary SES-14 communications satellite provide the first observational proof for the impact of stratospheric weather, that is, polar vortex dynamics during a Sudden Stratospheric Warming (SSW), on the composition of the thermosphere. During the early January 2019 SSW, GOLD observes a &gt;10% O/N2 column density ratio depletion in both hemispheres unrelated to geomagnetic activity. The data and supporting TIE-GCM and WACCM-X simulations show that enhanced global-scale wave activity during the SSW causes an enhanced wave driving of the lower thermosphere zonal mean circulation that leads to a reduction in lower thermosphere atomic oxygen, which then propagates through molecular diffusion into the upper thermosphere. The observed composition changes will likely impact Earth's ionospheric plasma environment as well and imply another pathway for SSW impacts on space weather, in addition to dynamo processes.&lt;/p&gt;

scholarly journals Numerical Investigation of Natural Convection Viscoelastic Jeffrey’s Nanofluid Flow from a Vertical Permeable Flat Plate with Heat Generation, Thermal Radiation, and Chemical Reaction

2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
T. M. Agbaje ◽  
P. G. L. Leach
Keyword(s):  
Boundary Layer ◽  
Thermal Radiation ◽  
Flat Plate ◽  
Chemical Reaction ◽  
Heat Generation ◽  
Numerical Solutions ◽  
Transport Processes ◽  
Physical Parameters ◽  
Nanoparticle Concentration ◽  
Suction Parameter

The boundary layer flow of an incompressible viscoelastic Jeffrey’s nanofluid from a vertical permeable flat plate is investigated. We consider the effects of heat generation, thermal radiation, and chemical reaction on the fluid flow. The nonlinear transformed coupled differential equations that describe the transport processes are solved numerically using a multidomain bivariate spectral quasilinearization method (MD-BSQLM). This innovative method involves blending the quasilinearization idea with the bivariate Lagrange interpolation. The solutions of the resulting system of equations are then obtained sequentially on multiple intervals using the Chebyshev spectral collocation method. The method is shown to give accurate solutions for boundary layer-type equations. The influence of various physical parameters on velocity, temperature, and nanoparticle concentration fields, as well as on the skin friction and heat and mass transfer coefficients, is shown and discussed in detail. The range of the values of the governing parameters considered in this study is between 0 , 4 . For qualitative validation of the results and the numerical method used, calculations were carried out to graphically obtain the velocity, temperature, and nanoparticle concentration fields for selected physical parameter values. The results obtained were found to correlate with the results from published literature. For quantitative verification of our findings, the MD-BSQLM numerical solutions were again confirmed against published results reported in the literature, and the results were observed to be in perfect agreement. This study’s findings indicate that the Deborah number and suction parameter have related effects on the velocity profile, which is to suppress both the flow velocity and the momentum boundary layer thickness. Increasing the heat generation and thermal radiation parameters enhances both the temperature and thermal boundary layer depths. In contrast, an increase in the chemical reaction parameter causes a decrease in the fluid concentration.

scholarly journals Change in turbopause altitude at 52 and 70° N

2015 ◽  
Vol 15 (14) ◽  
pp. 20287-20304
Author(s):  
C. M. Hall ◽  
S. E. Holmen ◽  
C. E. Meek ◽  
A. H. Manson ◽  
S. Nozawa
Keyword(s):  
Atomic Oxygen ◽  
Molecular Diffusion ◽  
Temporal Evolution ◽  
Molecular Mixing ◽  
Lower Region ◽  
Trace Species ◽  
Term Change ◽  
Meteor Trail ◽  
Altitude Estimation

Abstract. The turbopause is the demarkation between atmospheric mixing by turbulence (below) and molecular diffusion (above). When studying concentrations of trace species in the atmosphere, and particularly long-term change, it may be important to understand processes present, together with their temporal evolution, that may be responsible for redistribution of atmospheric constituents. The general region of transition between turbulent and molecular mixing coincides with the base of the ionosphere, the lower region in which molecular oxygen is dissociated, and, at high latitude in summer, the coldest part of the whole atmosphere. This study updates previous reports of turbopause altitude, extending the time series by half a decade, and thus shedding new light on the nature of change over solar-cycle timescales. Assuming there is no trend in temperature, at 70° N there is evidence for a summer trend of ~ 1.2 km decade−1, but for winter and at 52° N there is no significant evidence for change at all. If the temperature at 90 km is estimated using meteor trail data, it is possible to estimate a cooling rate, which, if applied to the turbopause altitude estimation, fails to alter the trend significantly irrespective of season. While studies of atomic oxygen density, [O], using mid-latitude timeseries dating from 1975, show positive trends which can be explained by a lowering of the turbopause, [O] exhibits negative trends since 2002 that, although at a different latitude, are compatible with the observed increase in turbopause height reported here.

The Spread of Pollutants from Harbour Sludge Depots

1984 ◽  
Vol 16 (3-4) ◽  
pp. 623-633
Author(s):  
M Loxham ◽  
F Weststrate
Keyword(s):  
Time Scales ◽  
Molecular Diffusion ◽  
Near Field ◽  
Parameter Analysis ◽  
Migration Patterns ◽  
Long Time ◽  
Dilution Effects ◽  
Short Time ◽  
Harbour Sludge

It is generally agreed that both the landfill option, or the civil techniques option for the final disposal of contaminated harbour sludge involves the isolation of the sludge from the environment. For short time scales, engineered barriers such as a bentonite screen, plastic sheets, pumping strategies etc. can be used. However for long time scales the effectiveness of such measures cannot be counted upon. It is thus necessary to be able to predict the long term environmenttal spread of contaminants from a mature landfill. A model is presented that considers diffusion and adsorption in the landfill site and convection and adsorption in the underlaying aquifer. From a parameter analysis starting form practical values it is shown that the adsorption behaviour and the molecular diffusion coefficient of the sludge, are the key parameters involved in the near field. The dilution effects of the far field migration patterns are also illustrated.

scholarly journals Study of the Synchrotron Photoionization Oxidation of Alpha-Angelica Lactone (AAL) Initiated by O(3P) at 298, 550, and 700 K

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4070
Author(s):  
Golbon Rezaei ◽  
Giovanni Meloni
Keyword(s):  
Atomic Oxygen ◽  
Fossil Fuels ◽  
Reaction Products ◽  
Photoionization Mass Spectrometry ◽  
Natural Substances ◽  
Primary Products ◽  
Major Reaction ◽  
Angelica Lactone ◽  
Significant Attention

In recent years, biofuels have been receiving significant attention because of their potential for decreasing carbon emissions and providing a long-term renewable solution to unsustainable fossil fuels. Currently, lactones are some of the alternatives being produced. Many lactones occur in a range of natural substances and have many advantages over bioethanol. In this study, the oxidation of alpha-angelica lactone initiated by ground-state atomic oxygen, O(3P), was studied at 298, 550, and 700 K using synchrotron radiation coupled with multiplexed photoionization mass spectrometry at the Lawrence Berkeley National Lab (LBNL). Photoionization spectra and kinetic time traces were measured to identify the primary products. Ketene, acetaldehyde, methyl vinyl ketone, methylglyoxal, dimethyl glyoxal, and 5-methyl-2,4-furandione were characterized as major reaction products, with ketene being the most abundant at all three temperatures. Possible reaction pathways for the formation of the observed primary products were computed using the CBS–QB3 composite method.

scholarly journals Perturbation of eigenvalues due to gaps in two-dimensional boundaries

2006 ◽  
Vol 463 (2079) ◽  
pp. 759-786 ◽  
Author(s):  
Anthony M.J Davis ◽  
Stefan G Llewellyn Smith
Keyword(s):  
Eigenvalue Problems ◽  
Numerical Solutions ◽  
Neumann Boundary ◽  
Diffusion Problem ◽  
Length Scale ◽  
Two Dimensional ◽  
Constructive Approach ◽  
Term Outcome ◽  
Long Term Outcome

Motivated by problems involving diffusion through small gaps, we revisit two-dimensional eigenvalue problems with localized perturbations to Neumann boundary conditions. We recover the known result that the gravest eigenvalue is O (|ln  ϵ | −1 ), where ϵ is the ratio of the size of the hole to the length-scale of the domain, and provide a simple and constructive approach for summing the inverse logarithm terms and obtaining further corrections. Comparisons with numerical solutions obtained for special geometries, both for the Dirichlet ‘patch problem’ where the perturbation to the boundary consists of a different boundary condition and for the gap problem, confirm that this approach is a simple way of obtaining an accurate value for the gravest eigenvalue and hence the long-term outcome of the underlying diffusion problem.

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