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.

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 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 Ambiguities in the classification of Cochin Estuary, West Coast of India

2013 ◽  
Vol 10 (3) ◽  
pp. 3595-3628 ◽  
Author(s):  
A. Shivaprasad ◽  
J. Vinita ◽  
C. Revichandran ◽  
N. T. Manoj ◽  
K. V. Jayalakshmy ◽  
...  
Keyword(s):  
Data Sets ◽  
Dry Period ◽  
Cochin Estuary ◽  
Short Term ◽  
Classification Schemes ◽  
Biological Features ◽  
High Runoff ◽  
Long Term Variations

Abstract. Cochin Estuary is a unique complex system along Indian coastline with a widespread area at the upstream. The fluctuations in salinity are of extreme kind ranging from entirely riverine to entirely saline. The high runoff months are characterized by monsoonal spells causing intense flushing. During the peak dry period, the runoff is less but steady providing a stable environment. River runoff is controlled by short term variations rather than long term variations. Using large comprehensive data sets, an attempt is made to evaluate several classification schemes for the estuary. The existing methods proved to be insufficient to represent the real salient features of this typical estuary. Arguments are also presented to illustrate the confusion in the names by which the estuary is commonly known. Therefore, a new nomenclature is proposed as "Cochin Monsoonal Estuarine Bay" embodying the physiographic, hydrographic and biological features of the estuary.

scholarly journals The dawn–dusk asymmetry of ion density in the dayside magnetosheath and its annual variability measured by THEMIS

2016 ◽  
Vol 34 (5) ◽  
pp. 511-528 ◽  
Author(s):  
Andrew P. Dimmock ◽  
Tuija I. Pulkkinen ◽  
Adnane Osmane ◽  
Katariina Nykyri
Keyword(s):  
Mach Number ◽  
Data Sets ◽  
Solar Cycles ◽  
Plasma Properties ◽  
Data Set ◽  
Ion Density ◽  
Physical Mechanisms ◽  
The Asymmetry ◽  
Coupling Processes

Abstract. The local and global plasma properties in the magnetosheath play a fundamental role in regulating solar wind–magnetosphere coupling processes. However, the magnetosheath is a complex region to characterise as it has been shown theoretically, observationally and through simulations that plasma properties are inhomogeneous, non-isotropic and asymmetric about the Sun-Earth line. To complicate matters, dawn–dusk asymmetries are sensitive to various changes in the upstream conditions on an array of timescales. The present paper focuses exclusively on dawn–dusk asymmetries, in particularly that of ion density. We present a statistical study using THEMIS data of the dawn–dusk asymmetry of ion density in the dayside magnetosheath and its long-term variations between 2009 and 2015. Our data suggest that, in general, the dawn-side densities are higher, and the asymmetry grows from noon towards the terminator. This trend was only observed close to the magnetopause and not in the central magnetosheath. In addition, between 2009 and 2015, the largest asymmetry occurred around 2009 decreasing thereafter. We also concluded that no single parameter such as the Alfvén Mach number, plasma velocity, or the interplanetary magnetic field strength could exclusively account for the observed asymmetry. Interestingly, the dependence on Alfvén Mach number differed between data sets from different time periods. The asymmetry obtained in the THEMIS data set is consistent with previous studies, but the solar cycle dependence was opposite to an analysis based on IMP-8 data. We discuss the physical mechanisms for this asymmetry and its temporal variation. We also put the current results into context with the existing literature in order to relate THEMIS era measurements to those made during earlier solar cycles.

scholarly journals Twenty Years of Atmospheric 14Co2 Observations At Schauinsland Station, Germany

Radiocarbon ◽  
1997 ◽  
Vol 39 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Ingeborg Levin ◽  
Bernd Kromer
Keyword(s):  
Northern Hemisphere ◽  
Seasonal Variations ◽  
Fossil Fuel ◽  
Data Sets ◽  
Black Forest ◽  
European Continent ◽  
Northern Latitudes ◽  
Single Exponential Function ◽  
Single Exponential

We present and discuss quasi-continuous long-term 14CO2 observations from the continental background station Schauinsland (48°N, 8°E, 1205 m asl, Black Forest, southern Germany). The observed steady decline of atmospheric 14CO2 from 1977 to 1996 can be described by a single exponential function with an e-folding time of (16.3 ± 0.2) yr. Summer means (May to August) in atmospheric 14CO2 at Schauinsland compare within Δ14C = ±4‰ with measurements made on individual rings from a tree grown in the near vicinity of the Schauinsland site. Both data sets are slightly depleted by up to 5‰ if compared to maritime background measurements of atmospheric 14CO2 made at Izaña, Tenerife. This is due to the influence of fossil fuel CO2 emissions over the European continent as well as generally in mid latitudes of the Northern Hemisphere. δ13C analyses from the Schauinsland samples show mean seasonal variations with an amplitude of ±0.4‰, caused by atmosphere-biosphere exchange, and a mean decrease from 1977 to 1996 of δ13C = −0.017‰ yr−1. This trend is mainly due to an increasing quantity of fossil fuel CO2 in the atmosphere, depleted in 13C/12C ratio, and compares well to trends measured at other stations in mid-to-high northern latitudes.

Nonlinear Prediction of Solar Cycle 25

2018 ◽  
Vol 13 (S340) ◽  
pp. 321-322
Author(s):  
Volkan Sarp ◽  
Ali Kılçık
Keyword(s):  
Solar Activity ◽  
Sunspot Number ◽  
Prediction Method ◽  
Solar Cycles ◽  
Nonlinear Prediction ◽  
Cycle 24 ◽  
And Performance ◽  
Prediction Approach ◽  
Good Agreement

AbstractSolar activity is a chaotic process and there are various approximations to forecast its long term and short term variations. But there is no prediction method that predicts the solar activity exactly. In this study, a nonlinear prediction approach was applied to international sunspot numbers and performance of predictions was tested for the last 5 solar cycles. These predictions are in good agreement with observed values of the tested solar cycles. According to these results, end of cycle 24 is expected at February, 2020 with 7.7 smoothed monthly mean sunspot number and maximum of cyle 25 is expected at May, 2024 with 119.6 smoothed monthly mean sunspot number.

scholarly journals Nature of the unusually long solar cycles

2010 ◽  
Vol 6 (S273) ◽  
pp. 169-173
Author(s):  
Nadezhda Zolotova ◽  
Dmitri Ponyavin
Keyword(s):  
Solar Cycles ◽  
Butterfly Diagram ◽  
Low Activity ◽  
Long Term Variations ◽  
Phase Differences

AbstractThe evolution of prolonged and unusually long solar cycles such as 23rd, 20th, and especially 4th is considered. Why the length of the 4th cycle was exceptionally large or really composed of two short cycles? Are the prolonged solar minima can be considered as precursor of low activity of the next cycles? Resolving these puzzles seems to be very important for dynamo theories trying to explain the solar long-term variations. We propose a possible model of the butterfly diagram during unusually long and prolonged cycles, based on (i) the Gnevyshev idea of sunspot distribution over the latitudes, and (ii) the phase differences of the northern and southern hemispheric activities.

scholarly journals Long-term variations in the neutral gas composition of the thermosphere over Norilsk (2003–2013)

2016 ◽  
Vol 2 (4) ◽  
pp. 92-97
Author(s):  
Галина Кузнецова ◽  
Galina Kuznetsova ◽  
Ольга Яковлева ◽  
Olga Yakovleva ◽  
Галина Кушнаренко ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Gas Composition ◽  
Ionospheric Layer ◽  
Neutral Gas ◽  
Different Seasons ◽  
Long Term Variations

Seasonal variations in relative values of the main gas components of the thermosphere [O]/[N2] and [O2]/[O] were received at the station Norilsk during the period 2003–2013. Estimates were made using a technique the authors developed and data from the Norilsk digisonde (69° N, 88° E) for heights below the ionospheric layer F1 maximum under quiet and disturbed geomagnetic conditions in different seasons. We established that the [O2]/[O] ratio in the quiet and disturbed geomagnetic conditions in all seasons by the end of 2013 decreased from 10 to 20 % relative to the values of 2003. The [O]/[N2] ratio for the same conditions increased to 17 %.

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