scholarly journals Ionospheric trends in Southern Hemisphere stations due to the increasing greenhouse gases concentration

2015 ◽  
Vol 58 (3) ◽  
Author(s):  
José V. Venchiarutti ◽  
Blas F. de Haro ◽  
Ana G. Elías
Keyword(s):  
Greenhouse Gases ◽  
Southern Hemisphere ◽  
Middle Atmosphere ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Anthropogenic Sources ◽  
Solar Cycles ◽  
Critical Frequency Fof2 ◽  
Long Term Variations

<p>The lower and middle atmosphere present long-term variations in temperature and other parameters linked to anthropogenic sources, such as the increase in greenhouse gases concentration since the start of the industrial era. Some examples are the well known temperature increase in the troposphere and stratosphere cooling. Upper atmosphere parameters also present long-term variations. While in the case of the middle and lower atmosphere it is debated whether the origin of the trends is primarily anthropogenic or solar, in the upper atmosphere other sources are also able to induce long-term changes, such as long-term variations in geomagnetic activity and secular variations of the Earth’s magnetic field. In this paper, trends of the F2 layer critical frequency, foF2, measured at three Southern Hemisphere stations (Brisbane, Canberra and Christchurch) are analyzed to determine the importance of increasing greenhouse gases concentration effect. According to our results for the period covering solar cycles 18 to 21 (period 1944-1986), it is more important than natural forcings. Update estimates including solar cycle 23 are presented although the difficulty due to two of the three stations present big data gaps during cycle 22 and traditional ionospheric filtering is no longer entirely reliable for cycle 23. The aim of this study is to contribute both to an active area of aeronomy as is the study of trends in the upper atmosphere, and to the understanding of climate change.</p>

scholarly journals Nocturnal Sporadic-E Activity at Two Southern Hemisphere Stations over Three Solar Cycles

1984 ◽  
Vol 37 (2) ◽  
pp. 231
Author(s):  
WJ Baggaley
Keyword(s):  
Southern Hemisphere ◽  
Sunspot Number ◽  
High Latitude ◽  
Seasonal Variations ◽  
Data Sets ◽  
Solar Cycles ◽  
Geomagnetic Index ◽  
Sporadic E ◽  
Long Term Variations

Analyses are presented of monthly values of the occurrence of the ionospheric parameters j~ E; and foE; for the South Pacific stations Christchurch and Rarotonga over three complete solar cycles. For each station both pre-midnight and post-midnight data show seasonal variations similar to daytime with the high latitude station showing a winter enhancement. Data fluctuations of scales longer than a year are very pronounced compared with variations in other ionospheric parameters. No correlations exist between any of the data sets and either the sunspot number Rz or geomagnetic index. Long-term variations in fi.E, and fo E; are uncorrelated at a particular station.

Long-term variations of the oxygen red 630 nm line nightglow intensity

2007 ◽  
Vol 85 (2) ◽  
pp. 189-198 ◽  
Author(s):  
N B Gudadze ◽  
G G Didebulidze ◽  
G Sh. Javakhishvili ◽  
M G Shepherd ◽  
M V Vardosanidze
Keyword(s):  
Line Intensity ◽  
Peak Height ◽  
Mean Value ◽  
Lower Atmosphere ◽  
Data Set ◽  
Term Trend ◽  
Long Term Trend ◽  
Long Term Variations ◽  
Red Line

The long-term data set of total nightglow intensity of the oxygen red 630.0~nm line observed at Abastumani (41.8°N, 42.8°E) between 1957–1993 is investigated. The long-term trend and characteristic variations in solar radiation during an 11 year cycle of the red-line intensity are different after astronomical twilight (premidnight) and at midnight. The amplitude of deviation of the red-line intensity from its mean value at solar maximum and (or) minimum phase is greatest after astronomical twilight and decreases toward midnight. The long-term trend of these variations changes from its value about 0.74 R/year premidnight to its minimum negative value of about –1.92 R/year at and after midnight. This behavior of the long-term trend is considered as a possible result of an increase in electron density below the peak height (hmF2) of the ionospheric F2 layer and lowering of the height hmF2 after midnight predicted by the TIME-GCM model on the assumption of an increase in density of greenhouse gases in the lower atmosphere. The third-order regression equation (with different solar activity indices) is considered to be convenient for describing long-term variations in the mean annual red-line intensity.PACS Nos.: 94.10.Rk, 94.20.Ji, 92.60.Vb

scholarly journals Large-Scale Patterns of Prominences in the Global Solar Cycles During 1880–1995

1998 ◽  
Vol 167 ◽  
pp. 442-445
Author(s):  
Dirk K. Callebaut ◽  
Valentine I. Makarov ◽  
Ksenia S. Tavastsherna
Keyword(s):  
Large Scale ◽  
Wolf Number ◽  
Solar Cycles ◽  
Zonal Distribution ◽  
Periodic Oscillations ◽  
Period 1880 ◽  
Latitude Distribution ◽  
The Mean ◽  
Long Term Variations

AbstractThe zonal distribution of prominences, their poleward migration from the sunspot zone to the poles, the polar magnetic field reversals and a correlation of the mean latitude of filament bands at minimum activity with the maximum of Wolf number in the next cycle are briefly discussed for the period 1880–1995. The need for research on the longterm latitude distribution of the prominences is emphasized. New results concerning long-term variations of the torsional oscillations of the Sun and quasi-periodic oscillations of the latitude zonal boundaries from an analysis of Hα charts (1915–1990) are given.

scholarly journals Emerging pattern of global change in the upper atmosphere and ionosphere

2008 ◽  
Vol 26 (5) ◽  
pp. 1255-1268 ◽  
Author(s):  
J. Laštovička ◽  
R. A. Akmaev ◽  
G. Beig ◽  
J. Bremer ◽  
J. T. Emmert ◽  
...  
Keyword(s):  
Global Change ◽  
Greenhouse Gases ◽  
Greenhouse Gas ◽  
Large Body ◽  
Upper Atmosphere ◽  
Anthropogenic Emissions ◽  
Model Predictions ◽  
First Time ◽  
Emerging Pattern

Abstract. In the upper atmosphere, greenhouse gases produce a cooling effect, instead of a warming effect. Increases in greenhouse gas concentrations are expected to induce substantial changes in the mesosphere, thermosphere, and ionosphere, including a thermal contraction of these layers. In this article we construct for the first time a pattern of the observed long-term global change in the upper atmosphere, based on trend studies of various parameters. The picture we obtain is qualitative, and contains several gaps and a few discrepancies, but the overall pattern of observed long-term changes throughout the upper atmosphere is consistent with model predictions of the effect of greenhouse gas increases. Together with the large body of lower atmospheric trend research, our synthesis indicates that anthropogenic emissions of greenhouse gases are affecting the atmosphere at nearly all altitudes between ground and space.

scholarly journals Effects of Latitude-Dependent Gravity Wave Source Variations on the Middle and Upper Atmosphere

2021 ◽  
Vol 7 ◽  
Author(s):  
Erdal Yiğit ◽  
Alexander S. Medvedev ◽  
Manfred Ern
Keyword(s):  
General Circulation ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Three Dimensional ◽  
Circulation Model ◽  
Wave Activity ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Boreal Summer ◽  
Wave Source

Atmospheric gravity waves (GWs) are generated in the lower atmosphere by various weather phenomena. They propagate upward, carry energy and momentum to higher altitudes, and appreciably influence the general circulation upon depositing them in the middle and upper atmosphere. We use a three-dimensional first-principle general circulation model (GCM) with implemented nonlinear whole atmosphere GW parameterization to study the global climatology of wave activity and produced effects at altitudes up to the upper thermosphere. The numerical experiments were guided by the GW momentum fluxes and temperature variances as measured in 2010 by the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument onboard NASA’s TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite. This includes the latitudinal dependence and magnitude of GW activity in the lower stratosphere for the boreal summer season. The modeling results were compared to the SABER temperature and total absolute momentum flux and Upper Atmosphere Research Satellite (UARS) data in the mesosphere and lower thermosphere. Simulations suggest that, in order to reproduce the observed circulation and wave activity in the middle atmosphere, GW fluxes that are smaller than observed fluxes have to be used at the source level in the lower atmosphere. This is because observations contain a broader spectrum of GWs, while parameterizations capture only a portion relevant to the middle and upper atmosphere dynamics. Accounting for the latitudinal variations of the source appreciably improves simulations.

1. What is special about Earth’s atmosphere?

2017 ◽  
pp. 1-19
Author(s):  
Paul I. Palmer
Keyword(s):  
Middle Atmosphere ◽  
Outer Space ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Earth’S Atmosphere ◽  
Relative Proximity ◽  
Earth's Atmosphere ◽  
Different Characteristics

‘What is special about Earth’s atmosphere?’ describes the several interconnected layers that make up Earth’s atmosphere before considering the atmospheres of other planets. Each layer has different characteristics determined by the density of air and their relative proximity to Earth’s surface and outer space. The lower atmosphere consists of the troposphere, which extends from the surface to the tropopause at 10–15 km. The middle atmosphere is comprised of the stratosphere, extending to the stratopause at 50 km, and the mesosphere that stretches to the mesopause at 100 km. Above this is the upper atmosphere divided into the thermosphere, which takes us to 500–1,000 km, and the exosphere, which extends to the near vacuum of outer space.

scholarly journals The impact of CMEs on the critical frequency of F2-layer ionosphere (foF2)

2019 ◽  
Vol 15 (S356) ◽  
pp. 400-402
Author(s):  
Alene Seyoum ◽  
Nat Gopalswamy ◽  
Melessew Nigussie ◽  
Nigusse Mezgebe
Keyword(s):  
Critical Frequency ◽  
Angular Width ◽  
High Latitudes ◽  
Solar Cycles ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Critical Frequency Fof2 ◽  
The Impact ◽  
Very High

AbstractThe ionospheric critical frequency (foF2) from ionosonde measurements at geographic high, middle, and low latitudes are analyzed with the occurrence of coronal mass ejections (CMEs) in long term variability of the solar cycles. We observed trends of monthly maximum foF2 values and monthly averaged values of CME parameters such as speed, angular width, mass, and kinetic energy with respect to time. The impact of CMEs on foF2 is very high at high latitudes and low at low latitudes. The time series for monthly maximum foF2 and monthly-averaged CME speed are moderately correlated at high and middle latitudes.

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