Long-term variations in geomagnetic and solar activities and secular variations of the geomagnetic field components

1991 ◽  
Vol 35 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Jaroslav Střeštík
Keyword(s):  
Geomagnetic Field ◽  
Secular Variations ◽  
Long Term Variations

scholarly journals Solar Modulation Effects in Terrestrial Production of Carbon-14

Radiocarbon ◽  
1980 ◽  
Vol 22 (2) ◽  
pp. 133-158 ◽  
Author(s):  
Giuliana Castagnoli ◽  
Devendra Lal
Keyword(s):  
Solar Activity ◽  
Cosmic Ray ◽  
Solar Modulation ◽  
Carbon 14 ◽  
Cosmic Ray Modulation ◽  
The Earth ◽  
Secular Variations ◽  
Galactic Cosmic Ray ◽  
Long Term Variations

This paper is concerned with the expected deviations in the production rate of natural 14C on the earth due to changes in solar activity. We review the published estimates of the global production rates of 14C due to galactic and solar cosmic ray particles, and present new estimates of the expected secular variations in 14C production, taking into account the latest information available on galactic cosmic ray modulation and long-term variations in solar activity.

Paleomagnetism of Late Archean metavolcanics and metasediments, Abitibi orogen, Canada: tholeiites of the Kinojevis Group

1983 ◽  
Vol 20 (3) ◽  
pp. 436-461 ◽  
Author(s):  
John Wm. Geissman ◽  
David W. Strangway ◽  
Ann M. Tasillo-Hirt ◽  
Larry S. Jensen
Keyword(s):  
Geomagnetic Field ◽  
Regional Metamorphism ◽  
Natural Remanent Magnetization ◽  
Blocking Temperature ◽  
High Coercivity ◽  
Polar Wander ◽  
Magnetic Viscosity ◽  
Secular Variations ◽  
Temperature Time

Iron-rich and magnesium-rich basaltic tholeiites of the latest Archean Kinojevis Group, central Abitibi Belt, northeastern Ontario, contain a natural remanent magnetization that is generally multivectorial. The components in all units reside in essentially pure magnetite, not the original titanomagnetites (where x for Fe3−xTixO4 probably was 0.60–0.65). Any original TRM was lost by chemical reconstitution of the magnetic oxides in response to primary deuteric conditions, long-term burial, regional metamorphism to prehnite–pumpellyite facies, and possibly intrusion by Matachewan dikes. Data from contact tests with Matachewan dikes indicate that the units are indeed capable of retaining a very latest Archean – earliest Proterozoic field (e.g., D = 194.9°, I = −14.3°, k = 8.1, α95 = 7.9°; n = 45 vectors, 38 samples). High-coercivity, high-blocking-temperature directions from samples from other flows, corrected for nearly penecontemporaneous downwarping, are in only crude agreement with those of Matachewan dikes, possibly suggesting that these components reflect a general Late Archean – Early Proterozoic field for the Superior Province. The paleomagnetic data from Kinojevis tholeiites indicate the emplacement, burial, and tight downwarping of the 10 km or so of Kinojevis stratigraphy were nearly synchronous with Matachewan intrusion. The Kinojevis data by themselves cannot be taken as statistically reliable indicators of the pre- (or immediately post-) Matachewan geomagnetic field nor can temperature–time relations for magnetic viscosity be used to predict the preservation of a statistically reliable TRM in any of these units. Individual magnetization components were blocked over geologically short periods of time, whereas the ensemble of data from discrete flows must record secular variations, field excursions, and possibly long-term polar wander.

Length of day fluctuations at long and short timescales. Geomagnetic drivers

2020 ◽  
Author(s):  
Crisan Demetrescu ◽  
Venera Dobrica
Keyword(s):  
Time Series ◽  
Geomagnetic Field ◽  
Ring Current ◽  
Outer Core ◽  
Length Of Day ◽  
Direct Control ◽  
Torsional Oscillations ◽  
Decadal Variations ◽  
Long Term Variations

<p>We decompose the well known LOD time series provided by IERS, that shows so-called decadal variations, in fluctuations at several timescales, namely: sub-centennial (60-90 years), inter-decadal (20-35 years), decennial (~11 years) and intra-decennial (~6 years). A Hodrick and Prescott (1977) type of analysis is used, followed by the decomposition of the trend and oscillatory parts at the mentioned timescales using Butterworth filtering. Comparing the results to previously (e.g. Dobrica et al., 2018) known oscillations of the geomagnetic field (dD/dt), and carrying out a similar analysis for parameters describing the evolution of the magnetospheric ring current, suggest the latter is the ultimate driver of both geomagnetic and LOD variations. The probable mechanisms are discussed as well: Alfvén torsional oscillations in the outer core, triggered by variations in the magnetospheric ring current, or a direct control of geomagnetic declination by variations in the magnetospheric ring current. While the first one is long accepted for the long-term variations in D and LOD, a similar possibility for the 6-year variation is out of question due to the implied value of the geomagnetic field within the outer core (Gillet et al., 2010); for the latter we suggest the second mechanism.       </p>

LONG-TERM TRENDS IN COSMIC RAYS AND GEOMAGNETIC FIELD SECULAR VARIATIONS

2021 ◽  
Vol 44 ◽  
pp. 79-80
Author(s):  
A.G. Elias ◽  
◽  
B.S. Zossi ◽  
A.R. Gutierrez Falcon ◽  
E.S. Comedi ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Data Center ◽  
Geomagnetic Field ◽  
The Earth ◽  
Geomagnetic Cutoff Rigidity ◽  
Secular Variations ◽  
Geomagnetic Cutoff ◽  
Long Term Trends ◽  
Long Term Trend

Cosmic rays are modulated by solar and geomagnetic activity. In addition, the flux that arrives to the Earth is sensitive to the inner geomagnetic field through its effect on the geomagnetic cutoff rigidity, Rc. This field has been decaying globally at a rate of ~5% per century from at least 1840. However, due to its configuration and non-uniform trend around the globe, its secular variation during the last decades has induced negative and positive Rc trends depending on location. In the present work, the database from the World Data Center for Cosmic Rays (WDCCR) is used to analyze long-term trend variations linked to geomagnetic secular variations. This database includes more than 100 stations covering, some of them, almost seven decades since the 1950’s. Those stations spanning more than 20 years of data are selected for the present study in order to adequately filter solar activity effects.

scholarly journals Review of Long-Term Trends in the Equatorial Ionosphere Due the Geomagnetic Field Secular Variations and Its Relevance to Space Weather

Atmosphere ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 40
Author(s):  
Ana G. Elias ◽  
Blas F. de Haro Barbas ◽  
Bruno S. Zossi ◽  
Franco D. Medina ◽  
Mariano Fagre ◽  
...  
Keyword(s):  
Space Weather ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Upper Atmosphere ◽  
Anthropogenic Activity ◽  
Weather Forecasts ◽  
Term Change ◽  
Secular Variations ◽  
Long Term Trends

The Earth’s ionosphere presents long-term trends that have been of interest since a pioneering study in 1989 suggesting that greenhouse gases increasing due to anthropogenic activity will produce not only a troposphere global warming, but a cooling in the upper atmosphere as well. Since then, long-term changes in the upper atmosphere, and particularly in the ionosphere, have become a significant topic in global change studies with many results already published. There are also other ionospheric long-term change forcings of natural origin, such as the Earth’s magnetic field secular variation with very special characteristics at equatorial and low latitudes. The ionosphere, as a part of the space weather environment, plays a crucial role to the point that it could certainly be said that space weather cannot be understood without reference to it. In this work, theoretical and experimental results on equatorial and low-latitude ionospheric trends linked to the geomagnetic field secular variation are reviewed and analyzed. Controversies and gaps in existing knowledge are identified together with important areas for future study. These trends, although weak when compared to other ionospheric variations, are steady and may become significant in the future and important even now for long-term space weather forecasts.

Fluvial magnetic susceptibility as a proxy for long‐term variations of mountain permafrost development in the Alp‐Carpathian region

Boreas ◽  
2021 ◽  
Author(s):  
Zoltán Püspöki ◽  
Philip Leonard Gibbard ◽  
Annamária Nádor ◽  
Edit Thamó‐Bozsó ◽  
Pál Sümegi ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Carpathian Region ◽  
Mountain Permafrost ◽  
Long Term Variations

Long-term variations of C1–C5 alkyl nitrates and their sources in Hong Kong

2021 ◽  
Vol 270 ◽  
pp. 116285
Author(s):  
Lewei Zeng ◽  
Hai Guo ◽  
Xiaopu Lyu ◽  
Beining Zhou ◽  
Zhenhao Ling ◽  
...  
Keyword(s):  
Hong Kong ◽  
Alkyl Nitrates ◽  
Long Term Variations

Application of singular spectrum analysis in reconstruction of the annual signal from GRACE

2020 ◽  
Vol 14 (3) ◽  
pp. 295-302
Author(s):  
Chuandong Zhu ◽  
Wei Zhan ◽  
Jinzhao Liu ◽  
Ming Chen
Keyword(s):  
Time Series ◽  
Spectrum Analysis ◽  
Singular Spectrum Analysis ◽  
Mixture Effect ◽  
Singular Spectrum ◽  
Grace Data ◽  
Terrestrial Water ◽  
Annual Signal ◽  
Long Term Variations

AbstractThe mixture effect of the long-term variations is a main challenge in single channel singular spectrum analysis (SSA) for the reconstruction of the annual signal from GRACE data. In this paper, a nonlinear long-term variations deduction method is used to improve the accuracy of annual signal reconstructed from GRACE data using SSA. Our method can identify and eliminate the nonlinear long-term variations of the equivalent water height time series recovered from GRACE. Therefore the mixture effect of the long-term variations can be avoided in the annual modes of SSA. For the global terrestrial water recovered from GRACE, the peak to peak value of the annual signal is between 1.4 cm and 126.9 cm, with an average of 11.7 cm. After the long-term and the annual term have been deducted, the standard deviation of residual time series is between 0.9 cm and 9.9 cm, with an average of 2.1 cm. Compared with the traditional least squares fitting method, our method can reflect the dynamic change of the annual signal in global terrestrial water, more accurately with an uncertainty of between 0.3 cm and 2.9 cm.

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