The Downturn in Solar Activity during Solar Cycles 5 and 6

1991 ◽  
Vol 9 (2) ◽  
pp. 330-331 ◽  
Author(s):  
J. O. Murphy
Keyword(s):  
Solar Activity ◽  
Radial Growth ◽  
High Solar Activity ◽  
Data Sets ◽  
Solar Cycles ◽  
Reservoir Model ◽  
Proxy Data ◽  
Annual Index ◽  
Carbon Reservoir ◽  
Lagged Correlation

AbstractThe atmospheric 14C record, the corresponding WM values derived from a carbon reservoir model, auroral numbers and the Zurich relative annual sunspot numbers all demonstrate a substantial downturn in solar activity for the duration of solar cycles 5 and 6. This reduction is also imbedded in some dendrochronological proxy data sets, which describe an annual index radial growth rate for trees at high-altitude sites. A significant lagged correlation can exist between tree-ring indices and the 11–year solar cycle during periods of high solar activity, a feature which is not evident during quiescent periods.

scholarly journals On the Prediction of Solar Cycles

Solar Physics ◽  
2021 ◽  
Vol 296 (1) ◽  
Author(s):  
V. Courtillot ◽  
F. Lopes ◽  
J. L. Le Mouël
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Transfer Function ◽  
Singular Spectrum Analysis ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Planetary Motion ◽  
Data Sets ◽  
Solar Cycles ◽  
Jovian Planets

AbstractThis article deals with the prediction of the upcoming solar activity cycle, Solar Cycle 25. We propose that astronomical ephemeris, specifically taken from the catalogs of aphelia of the four Jovian planets, could be drivers of variations in solar activity, represented by the series of sunspot numbers (SSN) from 1749 to 2020. We use singular spectrum analysis (SSA) to associate components with similar periods in the ephemeris and SSN. We determine the transfer function between the two data sets. We improve the match in successive steps: first with Jupiter only, then with the four Jovian planets and finally including commensurable periods of pairs and pairs of pairs of the Jovian planets (following Mörth and Schlamminger in Planetary Motion, Sunspots and Climate, Solar-Terrestrial Influences on Weather and Climate, 193, 1979). The transfer function can be applied to the ephemeris to predict future cycles. We test this with success using the “hindcast prediction” of Solar Cycles 21 to 24, using only data preceding these cycles, and by analyzing separately two 130 and 140 year-long halves of the original series. We conclude with a prediction of Solar Cycle 25 that can be compared to a dozen predictions by other authors: the maximum would occur in 2026.2 (± 1 yr) and reach an amplitude of 97.6 (± 7.8), similar to that of Solar Cycle 24, therefore sketching a new “Modern minimum”, following the Dalton and Gleissberg minima.

scholarly journals A Neural Network-Based TEC Model Capable of Reproducing Nighttime Winter Anomaly

2021 ◽  
Vol 13 (22) ◽  
pp. 4559
Author(s):  
Marjolijn Adolfs ◽  
Mohammed Mainul Hoque
Keyword(s):  
Neural Network ◽  
Solar Activity ◽  
Geomagnetic Latitude ◽  
Machine Learning Techniques ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Total Electron ◽  
The Neural Network ◽  
Winter Anomaly

With the availability of fast computing machines, as well as the advancement of machine learning techniques and Big Data algorithms, the development of a more sophisticated total electron content (TEC) model featuring the Nighttime Winter Anomaly (NWA) and other effects is possible and is presented here. The NWA is visible in the Northern Hemisphere for the American sector and in the Southern Hemisphere for the Asian longitude sector under solar minimum conditions. During the NWA, the mean ionization level is found to be higher in the winter nights compared to the summer nights. The approach proposed here is a fully connected neural network (NN) model trained with Global Ionosphere Maps (GIMs) data from the last two solar cycles. The day of year, universal time, geographic longitude, geomagnetic latitude, solar zenith angle, and solar activity proxy, F10.7, were used as the input parameters for the model. The model was tested with independent TEC datasets from the years 2015 and 2020, representing high solar activity (HSA) and low solar activity (LSA) conditions. Our investigation shows that the root mean squared (RMS) deviations are in the order of 6 and 2.5 TEC units during HSA and LSA period, respectively. Additionally, NN model results were compared with another model, the Neustrelitz TEC Model (NTCM). We found that the neural network model outperformed the NTCM by approximately 1 TEC unit. More importantly, the NN model can reproduce the evolution of the NWA effect during low solar activity, whereas the NTCM model cannot reproduce such effect in the TEC variation.

High solar activity predictions through an artificial neural network

2017 ◽  
Vol 28 (06) ◽  
pp. 1750075 ◽  
Author(s):  
M. G. Orozco-Del-Castillo ◽  
J. C. Ortiz-Alemán ◽  
C. Couder-Castañeda ◽  
J. J. Hernández-Gómez ◽  
A. Solís-Santomé
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Solar Activity ◽  
Outer Space ◽  
High Energy ◽  
High Solar Activity ◽  
Solar Cycles ◽  
The Neural Network ◽  
Space Electronics ◽  
Artificial Neural

The effects of high-energy particles coming from the Sun on human health as well as in the integrity of outer space electronics make the prediction of periods of high solar activity (HSA) a task of significant importance. Since periodicities in solar indexes have been identified, long-term predictions can be achieved. In this paper, we present a method based on an artificial neural network to find a pattern in some harmonics which represent such periodicities. We used data from 1973 to 2010 to train the neural network, and different historical data for its validation. We also used the neural network along with a statistical analysis of its performance with known data to predict periods of HSA with different confidence intervals according to the three-sigma rule associated with solar cycles 24–26, which we found to occur before 2040.

scholarly journals Observations of Hysteresis Between Flare Index and Some Solar Indices

2001 ◽  
Vol 203 ◽  
pp. 125-128
Author(s):  
A. Özgüç ◽  
T. Ataç
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Sunspot Area ◽  
Saturation Effect ◽  
Hysteresis Phenomenon ◽  
Data Sets ◽  
Solar Cycles ◽  
Index Data ◽  
The Past ◽  
Flare Index

Using flare index data sets for solar cycles 21 and 22 we find that flare index and some solar activity indicators show a hysteresis phenomenon. It is observed that total sunspot area, mean magnetic field and coronal index follow different paths for the ascending and descending phases of the solar cycles while saturation effect exists at the extreme phases. However, we notice that the separations between the paths are not the same during the past two cycles of 21 and 22.

scholarly journals Long term ionospheric electron content variations over Delhi

2000 ◽  
Vol 18 (12) ◽  
pp. 1635-1644 ◽  
Author(s):  
J. K. Gupta ◽  
L. Singh
Keyword(s):  
Solar Activity ◽  
Magnetic Activity ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Positive Correlation ◽  
Radio Science ◽  
Ionospheric Physics ◽  
Winter Anomaly ◽  
Ionospheric Electron Content

Abstract. Ionospheric electron content (IEC) observed at Delhi (geographic co-ordinates: 28.63°N, 77.22°E; geomagnetic co-ordinates: 19.08°N, 148.91°E; dip Latitude 24.8°N), India, for the period 1975–80 and 1986–89 belonging to an ascending phase of solar activity during first halves of solar cycles 21 and 22 respectively have been used to study the diurnal, seasonal, solar and magnetic activity variations. The diurnal variation of seasonal mean of IEC on quiet days shows a secondary peak comparable to the daytime peak in equinox and winter in high solar activity. IECmax (daytime maximum value of IEC, one per day) shows winter anomaly only during high solar activity at Delhi. Further, IECmax shows positive correlation with F10.7 up to about 200 flux units at equinox and 240 units both in winter and summer; for greater F10.7 values, IECmax is substantially constant in all the seasons. IECmax and magnetic activity (Ap) are found to be positively correlated in summer in high solar activity. Winter IECmax shows positive correlation with Ap in low solar activity and negative correlation in high solar activity in both the solar cycles. In equinox IECmax is independent of Ap in both solar cycles in low solar activity. A study of day-to-day variations in IECmax shows single day and alternate day abnormalities, semi-annual and annual variations controlled by the equatorial electrojet strength, and 27-day periodicity attributable to the solar rotation.Key words: Ionosphere (equatorial ionosphere) · Magnetospheric physics (magnetosphere · ionosphere interactions) · Radio science (ionospheric physics)

scholarly journals Lonosphere-thermosphere Relation as Seen in Measured and Modeled Electron and Neutral Densities

2021 ◽  
Author(s):  
Kristin Vielberg ◽  
Armin Corbin ◽  
Jürgen Kusche ◽  
Chao Xiong ◽  
Claudia Stolle
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Geomagnetic Latitude ◽  
High Solar Activity ◽  
Data Sets ◽  
Electron Densities ◽  
Good Opportunity ◽  
Density Anomaly ◽  
The Difference ◽  
Correlation Properties

Abstract The availability of in-situ neutral and electron densities along the orbit of the satellite missions GRACE and CHAMP provide a good opportunity to study the ionosphere-thermosphere (IT) system. The aim of this paper is (1) to use these data sets, to study the IT density relation empirically via correlation properties for different conditions depending on solar activity, geomagnetic latitude, and local time and (2) to verify whether these relations are consistent with the output of the TIE-GCM model of the thermosphere and ionosphere. Our results show that the correlations of electron and neutral densities strongly depend on magnetic local time (MLT) with a minimal correlation between 6-9h MLT, e.g., every 131 days for CHAMP around 400km altitude and every 160 days for GRACE around 500km. During low solar activity, the correlation of modeled and measured densities agrees well for both satellites. On the contrary, we note that the correlations between the modeled values are higher, especially during high solar activity, where the difference between correlations of modeled and measured densities is about 0.2. We suggest that the reason for this misalignment might be related to the poor representation of the equatorial density anomaly in the model especially during high solar activity. We believe our results will be useful for studies that aim at assimilating electron densities into a physical model to improve the prediction of neutral densities, since the skill of data assimilation depends to a large extent on the representation of the correlation between both densities.

scholarly journals Equinoctial asymmetry in solar activity variations of <I>Nm</I>F2 and TEC

2012 ◽  
Vol 30 (3) ◽  
pp. 613-622 ◽  
Author(s):  
Y. Chen ◽  
L. Liu ◽  
W. Wan ◽  
Z. Ren
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
High Solar Activity ◽  
Solar Cycles ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Increase Rate ◽  
Dip Equator ◽  
The Difference

Abstract. The ionosonde NmF2 data (covering several solar cycles) and the JPL TEC maps (from 1998 through 2009) were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity. With solar activity increasing, the equinoctial asymmetry of noontime NmF2 increases at middle latitudes but decreases or changes little at low latitudes, while the equinoctial asymmetry of TEC increases at all latitudes. The latitudinal feature of the equinoctial asymmetry at high solar activity is different from that at low solar activity. The increases of NmF2 and TEC with the solar proxy P = (F10.7+F10.7A)/2 also show equinoctial asymmetries that depend on latitudes. The increase rate of NmF2 with P at March equinox (ME) is higher than that at September equinox (SE) at middle latitudes, but the latter is higher than the former at the EIA crest latitudes, and the difference between them is small at the EIA trough latitudes. The phenomenon of higher increase rate at SE than at ME does not appear in TEC. The increase rate of noontime TEC with P at ME is higher than that at SE at all latitudes, and the difference between them peaks at both sides of dip equator. It is mentionable that the equinoctial asymmetries of NmF2 and TEC increase rates present some longitudinal dependence at low latitude. The influences of equinoctial differences in the thermosphere and ionospheric dynamics processes on the equinoctial asymmetry of the electron density were briefly discussed.

scholarly journals Possible traces of solar activity effect on the surface air temperature of mid-latitudes

2009 ◽  
Vol 5 (S264) ◽  
pp. 343-349
Author(s):  
Ali Kilcik ◽  
Atila Özgüç ◽  
Jean-Pierre Rozelot
Keyword(s):  
Solar Activity ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Cyclic Behavior ◽  
Data Sets ◽  
Solar Cycles ◽  
Index Data ◽  
Activity Effect ◽  
European Part Of Russia ◽  
Flare Index

AbstractIn this study we investigate the effects of solar activity on the surface air temperature of mid-latitudes. This enables us to understand existence of solar activity effects on the temperature. We used surface air temperature and pressure data as climate parameters, and solar flare index data as solar activity indicator, for the 25 - 50 degree longitude and 30 - 70 degree latitude zone, including Turkey and European part of Russia. We considered the parameters temperature, pressure and flare index data for the period ranging from January 1975 to the end of December 2007, which covers almost three solar cycles, namely 21st, 22nd, and 23rd. We found some significant correlations between solar activity and surface air temperature for cycles 22 and 23 for some zones. We applied multitaper method to obtain the cyclic behavior of surface air temperature data sets. The most pronounced power peaks were found by this transform around 1.2 and 2.5 years which were reported earlier for some solar activity indicators. We concluded that signature of solar activity effect exists on surface air temperature of mid-latitudes where we studied.

scholarly journals A 22-year cycle in the F layer ionization of the ionosphere

1997 ◽  
Vol 15 (8) ◽  
pp. 1015-1027 ◽  
Author(s):  
E. Feichter ◽  
R. Leitinger
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Annual Variation ◽  
Sunspot Cycle ◽  
Statistical Processing ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Total Electron ◽  
Cycle Variation

Abstract. The double-sunspot-cycle variation in terrestrial magnetic activity has been well known for about 30 years. In 1990 we examined and compared the low-solar-activity (LSA) part of two consecutive cycles and predicted from this database and from published results the existence of a double-sunspot-cycle variation in total electron content (TEC) of the ionosphere too. This is restricted to noontime when the semi-annual component is well developed. Since 1995 we have had enough data for the statistical processing for high-solar-activity (HSA) conditions of two successive solar cycles. The results confirm the LSA findings. The annual variation of TEC shows a change from an autumn maximum in cycle 21 to a spring maximum during the next solar cycle. Similar to the aa indices for geomagnetic activity the TEC data show a phase change in the 1-year component of the Fourier transform of the annual variation. Additionally we found the same behaviour in the F-layer peak electron density (Nmax) over four solar cycles. This indicates that there exists a double-sunspot-cycle variation in the F-layer ionization over Europe too. It is very likely coupled with the 22-year cycle in geomagnetic activity.

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