Observations and Models of the Long-Term Evolution of Earth’s Magnetic Field

2010 ◽  
pp. 337-370
Author(s):  
Julien Aubert ◽  
John A. Tarduno ◽  
Catherine L. Johnson
Keyword(s):  
Magnetic Field ◽  
Long Term Evolution ◽  
Earth’S Magnetic Field ◽  
Term Evolution ◽  
Earth's Magnetic Field

Observations and Models of the Long-Term Evolution of Earth’s Magnetic Field

2010 ◽  
Vol 155 (1-4) ◽  
pp. 337-370 ◽  
Author(s):  
Julien Aubert ◽  
John A. Tarduno ◽  
Catherine L. Johnson
Keyword(s):  
Magnetic Field ◽  
Long Term Evolution ◽  
Earth’S Magnetic Field ◽  
Term Evolution ◽  
Earth's Magnetic Field

scholarly journals Long-term evolution of the heliospheric magnetic field inferred from cosmogenic 44Ti activity in meteorites

2018 ◽  
Vol 610 ◽  
pp. A28 ◽  
Author(s):  
S. Mancuso ◽  
C. Taricco ◽  
P. Colombetti ◽  
S. Rubinetti ◽  
N. Sinha ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Ice Cores ◽  
Long Term Evolution ◽  
Galactic Cosmic Rays ◽  
Sunspot Activity ◽  
Cosmogenic Isotopes ◽  
Heliospheric Magnetic Field ◽  
The Past ◽  
Term Evolution

Typical reconstructions of historic heliospheric magnetic field (HMF) BHMF are based on the analysis of the sunspot activity, geomagnetic data or on measurement of cosmogenic isotopes stored in terrestrial reservoirs like trees (14C) and ice cores (10Be). The various reconstructions of BHMF are however discordant both in strength and trend. Cosmogenic isotopes, which are produced by galactic cosmic rays impacting on meteoroids and whose production rate is modulated by the varying HMF convected outward by the solar wind, may offer an alternative tool for the investigation of the HMF in the past centuries. In this work, we aim to evaluate the long-term evolution of BHMF over a period covering the past twenty-two solar cycles by using measurements of the cosmogenic 44Ti activity (τ1∕2 = 59.2 ± 0.6 yr) measured in 20 meteorites which fell between 1766 and 2001. Within the given uncertainties, our result is compatible with a HMF increase from 4.87-0.30+0.24 nT in 1766 to 6.83-0.11+0.13 nT in 2001, thus implying an overall average increment of 1.96-0.35+0.43 nT over 235 years since 1766 reflecting the modern Grand maximum. The BHMF trend thus obtained is then compared with the most recent reconstructions of the near-Earth HMF strength based on geomagnetic, sunspot number, and cosmogenic isotope data.

scholarly journals Long-term Evolution of the Sun’s Magnetic Field during Cycles 15–19 Based on Their Proxies from Kodaikanal Solar Observatory

2020 ◽  
Vol 902 (1) ◽  
pp. L15
Author(s):  
Alexander V. Mordvinov ◽  
Bidya Binay Karak ◽  
Dipankar Banerjee ◽  
Subhamoy Chatterjee ◽  
Elena M. Golubeva ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Long Term Evolution ◽  
Solar Observatory ◽  
Term Evolution

scholarly journals Slow variations of the Earth’s magnetic field: technical, methodological and organizational features of measurements

2019 ◽  
Vol 127 ◽  
pp. 02026
Author(s):  
Sergey Y. Khomutov
Keyword(s):  
Magnetic Field ◽  
Global Network ◽  
Earth’S Magnetic Field ◽  
Measurement Systems ◽  
Long Term Stability ◽  
Earth's Magnetic Field ◽  
Methodological Problems ◽  
Organizational Features ◽  
Magnetic Observatories

Variations of the Earth’s magnetic field with times of several years or more reflect the processes within the planet and cause great scientific interest. Over the past 100 years the regular observations at magnetic observatories (MOs) and repeat stations are the only experimental basis for studying such variations. In recent decades, satellite measurements have complemented ground-based measurements, thus partially solving the problems of spatially highly heterogeneous global network of magnetic observatories. Absolute observations are made at MOs to get the total field intensity vector. Until now, these measurements are performed manually, they are labor intensity and subject to many factors, that are often poorly controlled and reduce the reliability of the results, especially over long periods of time (years and decades), including (1) systematic errors of used magnetometers; (2) magnetic pollution of the absolute pavilion and its surroundings (at a distance of the first hundred meters); (3) instability of the pillars and remote target required to determine magnetic declination; (4) changes of observers and their weak qualification. Significant methodological problems arise if MO is moved to new location without special activity or infrastructure of MO (pavilions or pillars) is changed without careful control. For long-term stability and reliability of measurements, magnetic observatories were joined in IAGA network and then INTERMAGNET. Within these networks, requirements and standards have been defined, absolute magnetometers are compared every two years and observers are being trained. Modern hardware technologies allow to solve partially problems the automation of absolute observations, the self-calibration of the magnetometers, the checking of the MO’s magnetic environment, etc. Fully automated measurement systems help to expand the MO network.

scholarly journals Reconstructing solar magnetic fields from historical observations

2019 ◽  
Vol 627 ◽  
pp. A11
Author(s):  
I. O. I. Virtanen ◽  
I. I. Virtanen ◽  
A. A. Pevtsov ◽  
L. Bertello ◽  
A. Yeates ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Active Regions ◽  
Long Term Evolution ◽  
Photospheric Magnetic Field ◽  
Solar Magnetic Fields ◽  
Term Evolution ◽  
Large Scale Field

Aims. The evolution of the photospheric magnetic field has only been regularly observed since the 1970s. The absence of earlier observations severely limits our ability to understand the long-term evolution of solar magnetic fields, especially the polar fields that are important drivers of space weather. Here, we test the possibility to reconstruct the large-scale solar magnetic fields from Ca II K line observations and sunspot magnetic field observations, and to create synoptic maps of the photospheric magnetic field for times before modern-time magnetographic observations. Methods. We reconstructed active regions from Ca II K line synoptic maps and assigned them magnetic polarities using sunspot magnetic field observations. We used the reconstructed active regions as input in a surface flux transport simulation to produce synoptic maps of the photospheric magnetic field. We compared the simulated field with the observed field in 1975−1985 in order to test and validate our method. Results. The reconstruction very accurately reproduces the long-term evolution of the large-scale field, including the poleward flux surges and the strength of polar fields. The reconstruction has slightly less emerging flux because a few weak active regions are missing, but it includes the large active regions that are the most important for the large-scale evolution of the field. Although our reconstruction method is very robust, individual reconstructed active regions may be slightly inaccurate in terms of area, total flux, or polarity, which leads to some uncertainty in the simulation. However, due to the randomness of these inaccuracies and the lack of long-term memory in the simulation, these problems do not significantly affect the long-term evolution of the large-scale field.

Long-term variations of the external and internal components of the Earth's magnetic field

1986 ◽  
Vol 91 (B5) ◽  
pp. 4787 ◽  
Author(s):  
J. Gavoret ◽  
D. Gibert ◽  
M. Menvielle ◽  
J. L. Le Mouël
Keyword(s):  
Magnetic Field ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field ◽  
Long Term Variations

scholarly journals Drivers of Upper Atmosphere Climate Change

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Sarah Stanley
Keyword(s):  
Climate Change ◽  
Magnetic Field ◽  
Carbon Dioxide ◽  
Upper Atmosphere ◽  
Earth’S Magnetic Field ◽  
Temperature Trends ◽  
Earth's Magnetic Field ◽  
New Research

New research confirms the influence of carbon dioxide on long-term temperature trends in the upper atmosphere, but changes in Earth’s magnetic field also play a key role.

scholarly journals Long-term changes in solar quiet (Sq) geomagnetic variations related to Earth's magnetic field secular variation

2013 ◽  
Vol 118 (6) ◽  
pp. 3712-3718 ◽  
Author(s):  
Blas F. de Haro Barbas ◽  
Ana G. Elias ◽  
Ingrid Cnossen ◽  
Marta Zossi de Artigas
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Earth’S Magnetic Field ◽  
Geomagnetic Variations ◽  
Long Term Changes ◽  
Earth's Magnetic Field

scholarly journals Long-term evolution of magnetic fields in flaring Active Region NOAA 12673

2022 ◽  
Vol 21 (12) ◽  
pp. 312
Author(s):  
Johan Muhamad ◽  
Muhamad Zamzam Nurzaman ◽  
Tiar Dani ◽  
Arun Relung Pamutri
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Flares ◽  
Long Term Evolution ◽  
Solar Dynamics Observatory ◽  
Active Longitude ◽  
Term Evolution ◽  
Solar Dynamics ◽  
Different Characteristics

Abstract During the lifetime of AR 12673, its magnetic field evolved drastically and produced numerous large flares. In this study, using full maps of the Sun observed by the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory, we identified that AR 12673 emerged in decayed AR 12665, which had survived for two solar rotations. Although both ARs emerged at the same location, they possessed different characteristics and different flare productivities. Therefore, it is important to study the long-term magnetic evolution of both ARs to identify the distinguishing characteristics of an AR that can produce large solar flares. We used the Space-weather Helioseismic and Magnetic Imager Active Region Patch data to investigate the evolution of the photospheric magnetic field and other physical properties of the recurring ARs during five Carrington rotations. All these investigated parameters dynamically evolved through a series of solar rotations. We compared the long-term evolution of AR 12665 and AR 12673 to understand the differences in their flare-producing properties. We also studied the relation of the long-term evolution of these ARs with the presence of active longitude. We found that the magnetic flux and complexity of AR 12673 developed much faster than those of AR 12665. Our results confirmed that a strong emerging flux that emerged in the pre-existing AR near the active longitude created a very strong and complex AR that produced large flares.

Long time convergence of magnetohydrodynamic flows to alfvénic states

2007 ◽  
Vol 73 (6) ◽  
pp. 947-955
Author(s):  
MANUEL NÚÑEZ
Keyword(s):  
Magnetic Field ◽  
Long Term Evolution ◽  
Static Equilibrium ◽  
Transient Processes ◽  
Term Evolution ◽  
Magnetohydrodynamic Flows ◽  
Long Time ◽  
Simple Class ◽  
Turbulent Plasmas

AbstractAlfvénic states of a plasma, where velocity and magnetic field coincide, form a particular simple class of ideal equilibria and are also found in certain astrophysical phenomena. While transient processes of alignment in turbulent plasmas are well known and due to preferential spectral transfer, the possible long-term evolution of a magnetohydrodynamic plasma towards an alfvénic state has been rarely studied. It is shown that this tendency does not exist: neither specific ideal alfvénic equilibria nor the whole set of such states attract trajectories in any functional sense. Another possibility is that the perturbations of a static equilibrium could tend to become alfvénic, such as the classical Alfvén waves. We find that if these equilibria are current free, when a perturbation approaches an alfvénic state it immediately bounces away from it.

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