scholarly journals Variações de intensidade do campo geomagnético em Santa Maria (Brasil) para os últimos 3 mil anos

2018 ◽  
Vol 40 ◽  
pp. 7
Author(s):  
Everton Frigo ◽  
Gelvam Hartmann
Keyword(s):  
Geomagnetic Field ◽  
Climate Changes ◽  
Internal Field ◽  
Outer Core ◽  
The South ◽  
The Past ◽  
Earth Magnetic Field ◽  
Electrically Charged ◽  
Santa Maria ◽  
Magnetic Field Variations

Earth magnetic field variations at secular scales and at hundred quilometers have internal origin at the outer core. The most important feature associated with this internal field is the South Atlantic Magnetic Anomaly (SAMA), which covers the South America and it is characterized by the lowest total field intensity at the surface. Here, we investigate the geomagnetic field variations in Santa Maria (Brazil) over the past 3 ka. Results indicate that the intensities observed in Santa Maria are the lowest of the geomagnetic field over the past 3 ka. The consequences of these field features could be the increase in the electrically charged particles reaching the low Earth atmosphere that may generate problems in the communications systems or climate changes.

scholarly journals Persistent westward drift of the geomagnetic field at the core–mantle boundary linked to recurrent high-latitude weak/reverse flux patches

2020 ◽  
Vol 222 (2) ◽  
pp. 1423-1432
Author(s):  
Andreas Nilsson ◽  
Neil Suttie ◽  
Monika Korte ◽  
Richard Holme ◽  
Mimi Hill
Keyword(s):  
Northern Hemisphere ◽  
High Latitude ◽  
Geomagnetic Field ◽  
Outer Core ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
The Past ◽  
Convection Rolls ◽  
Westward Drift

SUMMARY Observations of changes in the geomagnetic field provide unique information about processes in the outer core where the field is generated. Recent geomagnetic field reconstructions based on palaeomagnetic data show persistent westward drift at high northern latitudes at the core–mantle boundary (CMB) over the past 4000 yr, as well as intermittent occurrence of high-latitude weak or reverse flux patches. To further investigate these features, we analysed time-longitude plots of a processed version of the geomagnetic field model pfm9k.1a, filtered to remove quasi-stationary features of the field. Our results suggest that westward drift at both high northern and southern latitudes of the CMB have been a persistent feature of the field over the past 9000 yr. In the Northern Hemisphere we detect two distinct signals with drift rates of 0.09° and 0.25° yr−1 and dominant zonal wavenumbers of m = 2 and 1, respectively. Comparisons with other geomagnetic field models support these observations but also highlight the importance of sedimentary data that provide crucial information on high-latitude geomagnetic field variations. The two distinct drift signals detected in the Northern Hemisphere can largely be decomposed into two westward propagating waveforms. We show that constructive interference between these two waveforms accurately predicts both the location and timing of previously observed high-latitude weak/reverse flux patches over the past 3–4 millennia. In addition, we also show that the 1125-yr periodicity signal inferred from the waveform interference correlates positively with variations in the dipole tilt over the same time period. The two identified drift signals may partially be explained by the westward motion of high-latitude convection rolls. However, the dispersion relation might also imply that part of the drift signal could be caused by magnetic Rossby waves riding on the mean background flow.

scholarly journals Patterns of Atmospheric 14C Changes

Radiocarbon ◽  
1980 ◽  
Vol 22 (2) ◽  
pp. 166-176 ◽  
Author(s):  
Minze Stuiver ◽  
Paul D Quay
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Cosmic Ray ◽  
Solar Modulation ◽  
Production Rates ◽  
Climatic Fluctuation ◽  
The Past ◽  
Earth Magnetic Field ◽  
Carbon Reservoir ◽  
Cosmic Ray Flux

Natural atmospheric 14C changes are caused by fluctuations in upper atmospheric 14C production rates (Q) that are related to earth geomagnetic field variations and changes in solar wind magnetic shielding properties. Climate variability may also be responsible for some of the changes because it influences exchange rates of 14C between the various terrestrial carbon reservoirs.Upper atmospheric 14C production rates QM, in at/sec cm2 (earth), were calculated for the past 1200 years from the atmospheric 14C record and a carbon reservoir model. The changes in QM are compared in detail with the predicted Q variability derived from an Aa solar modulation mechanism and 20th century neutron flux observations. The influence of earth geomagnetic field changes on the magnitude of the solar wind modulation is discussed, and it is shown that the variations in this magnitude agree with the known differences in earth magnetic field intensity during the past 1200 years. The larger calculated QM oscillations during the sixth millennium bp also agree with this concept.Solar wind magnetic as well as geomagnetic forces modulate the incoming cosmic ray flux and explain the main features of the atmospheric 14C record. It is argued that climatic fluctuation is not a dominant cause.The oscillations between 3200 and 3700 BC, as measured by de Jong, Mook, and Becker, differ in rise time from those found for the current millennium.

scholarly journals The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Christopher C. Finlay ◽  
Clemens Kloss ◽  
Nils Olsen ◽  
Magnus D. Hammer ◽  
Lars Tøffner-Clausen ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Field Model ◽  
Internal Field ◽  
South Atlantic ◽  
Time Dependent ◽  
The South ◽  
Spherical Harmonic Degree ◽  
Core Mantle Boundary ◽  
The Pacific ◽  
Harmonic Degree

Abstract We present the CHAOS-7 model of the time-dependent near-Earth geomagnetic field between 1999 and 2020 based on magnetic field observations collected by the low-Earth orbit satellites Swarm, CryoSat-2, CHAMP, SAC-C and Ørsted, and on annual differences of monthly means of ground observatory measurements. The CHAOS-7 model consists of a time-dependent internal field up to spherical harmonic degree 20, a static internal field which merges to the LCS-1 lithospheric field model above degree 25, a model of the magnetospheric field and its induced counterpart, estimates of Euler angles describing the alignment of satellite vector magnetometers, and magnetometer calibration parameters for CryoSat-2. Only data from dark regions satisfying strict geomagnetic quiet-time criteria (including conditions on IMF $$B_z$$ B z and $$B_y$$ B y at all latitudes) were used in the field estimation. Model parameters were estimated using an iteratively reweighted regularized least-squares procedure; regularization of the time-dependent internal field was relaxed at high spherical harmonic degree compared with previous versions of the CHAOS model. We use CHAOS-7 to investigate recent changes in the geomagnetic field, studying the evolution of the South Atlantic weak field anomaly and rapid field changes in the Pacific region since 2014. At Earth’s surface a secondary minimum of the South Atlantic Anomaly is now evident to the south west of Africa. Green’s functions relating the core–mantle boundary radial field to the surface intensity show this feature is connected with the movement and evolution of a reversed flux feature under South Africa. The continuing growth in size and weakening of the main anomaly is linked to the westward motion and gathering of reversed flux under South America. In the Pacific region at Earth’s surface between 2015 and 2018 a sign change has occurred in the second time derivative (acceleration) of the radial component of the field. This acceleration change took the form of a localized, east–west oriented, dipole. It was clearly recorded on ground, for example at the magnetic observatory at Honolulu, and was seen in Swarm observations over an extended region in the central and western Pacific. Downward continuing to the core–mantle boundary, we find this event originated in field acceleration changes at low latitudes beneath the central and western Pacific in 2017.

scholarly journals ORBITAL NOISE OF THE EARTH CAUSES INTENSITY FLUCTUATION IN THE GEOMAGNETIC FIELD

2003 ◽  
Vol 03 (01) ◽  
pp. L63-L72 ◽  
Author(s):  
H. S. LIU ◽  
R. KOLENKIEWLCZ ◽  
C. WADE
Keyword(s):  
Geomagnetic Field ◽  
Noise Spectrum ◽  
Outer Core ◽  
The Past ◽  
The Earth ◽  
Spectral Peaks ◽  
Relative Paleointensity ◽  
Intensity Fluctuations ◽  
Composite Curve ◽  
Insight Into

Orbital noise of Earth's obliquity can provide an insight into the core of the Earth that causes intensity fluctuations in the geomagnetie field. Here we show that noise spectrum of the obliquity frequency have revealed a series of frequency periods centered at 250-, 100-, 50-, 41-, 30-, and 26-kyr which are almost identical with the observed spectral peaks from the composite curve of 33 records of relative paleointensity spanning the past 800 kyr (Sint–800 data). A continuous record for the past two million years also reveals the presence of the major 100 kyr periodicity in obliquity noise and geomagnetic intensity fluctuations. These results of correlation suggest that obliquity noise may power the dynamo, located in the liquid outer core of the Earth, which generates the geomagnetic field.

scholarly journals Monitoring of the geomagnetic field variations at the high- mountain biospheric station «Dzhuga» and forecasting of natural disasters and extreme weather

2017 ◽  
pp. 35-43
Author(s):  
A.N. Lukin ◽  
◽  
P.G. Rodimcev ◽  
N.B. Eskin ◽  
◽  
...  
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
High Sensitivity ◽  
High Mountain ◽  
Acoustic Fields ◽  
Experimental Systems ◽  
The Earth ◽  
Earth Magnetic Field ◽  
Physical Fields ◽  
Magnetic Field Variations

In the paper realization of the research project connected with monitoring of the Earth magnetic field variations at the high-mountain biosphere station «Dzuga» is considered. The acoustic channel of influence of the space weather and technologies of visualization of the geomagnetic and acoustic fields with use of high-sensitivity model experimental systems is considered. The new concept of forecasting of extreme natural events with use of the universal phenomenon of spacial self-synchronization of oscillations of geomagnetic and acoustic fields and on the basis of the analysis of the structure of holograms of physical fields is formulated.

scholarly journals Publisher Correction: Record warming at the South Pole during the past three decades

2021 ◽  
Author(s):  
Kyle R. Clem ◽  
Ryan L. Fogt ◽  
John Turner ◽  
Benjamin R. Lintner ◽  
Gareth J. Marshall ◽  
...  
Keyword(s):  
South Pole ◽  
The South ◽  
The Past

scholarly journals d4PDF: large-ensemble and high-resolution climate simulations for global warming risk assessment

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Masayoshi Ishii ◽  
Nobuhito Mori
Keyword(s):  
Risk Assessment ◽  
Global Warming ◽  
High Resolution ◽  
Climate Changes ◽  
Future Climate ◽  
Atmospheric Models ◽  
Large Ensemble ◽  
Past Climate ◽  
The Past ◽  
Climate Simulations

Abstract A large-ensemble climate simulation database, which is known as the database for policy decision-making for future climate changes (d4PDF), was designed for climate change risk assessments. Since the completion of the first set of climate simulations in 2015, the database has been growing continuously. It contains the results of ensemble simulations conducted over a total of thousands years respectively for past and future climates using high-resolution global (60 km horizontal mesh) and regional (20 km mesh) atmospheric models. Several sets of future climate simulations are available, in which global mean surface air temperatures are forced to be higher by 4 K, 2 K, and 1.5 K relative to preindustrial levels. Nonwarming past climate simulations are incorporated in d4PDF along with the past climate simulations. The total data volume is approximately 2 petabytes. The atmospheric models satisfactorily simulate the past climate in terms of climatology, natural variations, and extreme events such as heavy precipitation and tropical cyclones. In addition, data users can obtain statistically significant changes in mean states or weather and climate extremes of interest between the past and future climates via a simple arithmetic computation without any statistical assumptions. The database is helpful in understanding future changes in climate states and in attributing past climate events to global warming. Impact assessment studies for climate changes have concurrently been performed in various research areas such as natural hazard, hydrology, civil engineering, agriculture, health, and insurance. The database has now become essential for promoting climate and risk assessment studies and for devising climate adaptation policies. Moreover, it has helped in establishing an interdisciplinary research community on global warming across Japan.

scholarly journals Our New Cathedrals: Spirituality and Old-Growth Forests in Western Australia

2006 ◽  
Vol 3 (1) ◽  
Author(s):  
David Worth
Keyword(s):  
Social Movements ◽  
Western Australia ◽  
The State ◽  
The South ◽  
Old Growth ◽  
The Past ◽  
South West ◽  
Old Growth Forests ◽  
Heated Debate ◽  
Policy Proposals

Over the past 30 years in Western Australia (WA), there has been heated debate about the future use of the remaining karri and jarrah forests in the south-west of the State. This debate revolves around policy proposals from two social movements: one wants to preserve as much of the remaining old-growth forests as possible, and an opposing movement supports a continued

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