Apparent effect of magnetic activity upon secular variation of the vertical component of the Earth's magnetic field

1934 ◽  
Vol 15 (1) ◽  
pp. 175
Author(s):  
A. G. McNish
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Vertical Component ◽  
Magnetic Activity ◽  
Apparent Effect ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field

The westward drift of the Earth's magnetic field

1950 ◽  
Vol 243 (859) ◽  
pp. 67-92 ◽  
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Outer Part ◽  
Earth’S Magnetic Field ◽  
Dynamo Theory ◽  
The Core ◽  
The Earth ◽  
Earth's Magnetic Field ◽  
Harmonic Analyses ◽  
Westward Drift

The westward drift of the non-dipole part of the earth’s magnetic field and of its secular variation is investigated for the period 1907-45 and the uncertainty of the results discussed. It is found that a real drift exists having an angular velocity which is independent of latitude. For the non-dipole field the rate of drift is 0.18 ± 0-015°/year, that for the secular variation is 0.32 ±0-067°/year. The results are confirmed by a study of harmonic analyses made between 1829 and 1945. The drift is explained as a consequence of the dynamo theory of the origin of the earth’s field. This theory required the outer part of the core to rotate less rapidly than the inner part. As a result of electromagnetic forces the solid mantle of the earth is coupled to the core as a whole, and the outer part of the core therefore travels westward relative to the mantle, carrying the minor features of the field with it.

Secular variation of the Earth's magnetic field revealed by Mexican Geomagnetic Repeat Stations during the last two centuries

2021 ◽  
pp. 103652
Author(s):  
Avto Goguitchaichvili ◽  
Esteban Hernández ◽  
Rafael García ◽  
Vadim Kravchinsky ◽  
Rubén Cejudo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field

scholarly journals A magnetometer for the measurement of the Earth's vertical magnetic intensity in C. G. S. measure

1928 ◽  
Vol 117 (777) ◽  
pp. 434-458 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vertical Component ◽  
Field Measurements ◽  
Horizontal Component ◽  
Magnetic Intensity ◽  
Earth’S Magnetic Field ◽  
Simple Operation ◽  
Horizontal Field ◽  
Earth's Magnetic Field

The measurement of the vertical component of the earth’s magnetic field is a less simple operation than that of the horizontal component. The horizontal field measurements are on a satisfactory basis, whether made by the swinging magnet method, or by the more recently developed electric magnetometers, in which known magnetic fields may be provided by means of known currents flowing through coils of known dimensions.

scholarly journals Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin

2018 ◽  
Vol 36 (1) ◽  
pp. 275-285 ◽  
Author(s):  
Enrique G. Cordaro ◽  
Patricio Venegas ◽  
David Laroze
Keyword(s):  
Magnetic Field ◽  
Vertical Component ◽  
Cutoff Rigidity ◽  
Earth’S Magnetic Field ◽  
Convergent Margin ◽  
Flat Slab ◽  
Geomagnetic Cutoff Rigidity ◽  
Geomagnetic Cutoff ◽  
Variation Rate ◽  
Earth's Magnetic Field

Abstract. We present a different view of secular variation of the Earth's magnetic field, through the variations in the threshold rigidity known as the variation rate of geomagnetic cutoff rigidity (VRc). As the geomagnetic cutoff rigidity (Rc) lets us differentiate between charged particle trajectories arriving at the Earth and the Earth's magnetic field, we used the VRc to look for internal variations in the latter, close to the 70° south meridian. Due to the fact that the empirical data of total magnetic field BF and vertical magnetic field Bz obtained at Putre (OP) and Los Cerrillos (OLC) stations are consistent with the displacement of the South Atlantic magnetic anomaly (SAMA), we detected that the VRc does not fully correlate to SAMA in central Chile. Besides, the lower section of VRc seems to correlate perfectly with important geological features, like the flat slab in the active Chilean convergent margin. Based on this, we next focused our attention on the empirical variations of the vertical component of the magnetic field Bz, recorded in OP prior to the Maule earthquake in 2010, which occurred in the middle of the Chilean flat slab. We found a jump in Bz values and main frequencies from 3.510 to 5.860 µHz, in the second derivative of Bz, which corresponds to similar magnetic behavior found by other research groups, but at lower frequency ranges. Then, we extended this analysis to other relevant subduction seismic events, like Sumatra in 2004 and Tohoku in 2011, using data from the Guam station. Similar records and the main frequencies before each event were found. Thus, these results seem to show that magnetic anomalies recorded on different timescales, as VRc (decades) and Bz (days), may correlate with some geological events, as the lithosphere–atmosphere–ionosphere coupling (LAIC).

scholarly journals Multipole Analysis. II. Geomagnetic Secular Variation

1969 ◽  
Vol 22 (4) ◽  
pp. 481 ◽  
Author(s):  
RW James
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Time Trends ◽  
Earth’S Magnetic Field ◽  
Geomagnetic Secular Variation ◽  
Rates Of Change ◽  
Multipole Analysis ◽  
Earth's Magnetic Field

The method of multipole analysis described in Part I is applied to the Earth's magnetic field for various epochs between 1845 and 1965, allowing the geomagnetic secular variation to be illustrated by time trends in the multipole parameters. The rates of change of the multipole parameters are used to separate the secular variation into non.drifting, meridional drifting, and longitudinal drifting components, which are discussed in detail for the epoch 1965.

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