scholarly journals Atmospheric tides in the ionosphere - I. Solar tides in the F 2 region

1947 ◽  
Vol 189 (1017) ◽  
pp. 241-260 ◽  
Keyword(s):  
Magnetic Field ◽  
Vertical Component ◽  
Vertical Motion ◽  
Atmospheric Tides ◽  
Recombination Coefficient ◽  
Earth’S Magnetic Field ◽  
Dynamo Theory ◽  
Night Time ◽  
Geographical Variations ◽  
Earth's Magnetic Field

A theory, based on solar tides, is advanced to explain the anomalous seasonal, diurnal and geographical variations of F 2 region ionization. It is shown that the horizontal winds due to these tides must cause electrons to move along the lines of the earth’s magnetic field. The resultant motion has a vertical component. Account is taken of polarization of the medium by the ‘dynamo’ electric forces. Owing to viscosity the vertical motion decreases upwards in the F 2 region. Application of the equation of continuity shows that the F 2 region becomes greatly distorted. A ‘longitude effect’ is found to arise by reason of the asymmetry of the earth’s magnetic field. The theory is used to explain the high F 2 ionization densities found in low latitudes, and the high values of h' F 2 at noon near the equator. It is also used to explain the afternoon and night-time increases in ionization found at certain locations. It is suggested that the effective recombination coefficient in F 2 is much lower than the generally accepted values. It is shown that Appleton & Weekes’s evidence of lunar tidal effects in the E region does not conflict with the ‘dynamo’ theory of magnetic variations or with Pekeris’s calculations. Observational evidence of the existence of solar tides in the F 2 region is presented.

scholarly journals Night-time Sferic Propagation at Frequencies Below 10 KHz

1967 ◽  
Vol 20 (1) ◽  
pp. 101 ◽  
Author(s):  
KJW Lynn ◽  
J Crouchley
Keyword(s):  
Magnetic Field ◽  
Geographic Distribution ◽  
Angle Of Incidence ◽  
European Studies ◽  
Earth’S Magnetic Field ◽  
Night Time ◽  
The West ◽  
Earth's Magnetic Field ◽  
Effective Angle

Results of a study at Brisbane of individual night-time sferics of known origin are described. A propagation attenuation minimum was observed in the 3-6 kHz range. The geographic distribution of sferic types was also examined. Apparent propagation asynunetries were observed, since sferics were detected at greater ranges to the west than to the east at 10 kHz, whilst the number of tweek-sferics arising from the east was about four times that arising from the west. Comparison with European studies suggest that these asymmetries are general. These results are then " interpreted in terms of an ionospheric reflection cgefficient which is a function of the effective angle of incidence of the wave on the ionosphere and of orientation with respect to the Earth's magnetic field within the ionosphere.

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.

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 A theory of the Earth's magnetic field and of sunspots, based on a self-excited dynamo incorporating the Hall effect

2001 ◽  
Vol 8 (4/5) ◽  
pp. 265-279 ◽  
Author(s):  
A. de Paor
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Energy Coupling ◽  
Order System ◽  
Sunspot Activity ◽  
Earth’S Magnetic Field ◽  
Dynamo Theory ◽  
Field Reversal ◽  
Geophysical Processes ◽  
Earth's Magnetic Field

Abstract. A new viewpoint on the generation and maintenance of the Earth's magnetic field is put forward, which integrates self-exciting dynamo theory with the possibility of energy coupling along orthogonal axes provided by the Hall effect. A nonlinear third-order system is derived, with a fourth equation serving as an observer of unspecified geophysical processes which could result in field reversal. Lyapunov analysis proves that chaos is not intrinsic to this system. Relative constancy of one of the variables produces pseudo equilibrium in a second order subsystem and allows for self-excitation of the geomagnetic field. Electromagnetic analysis yields expressions for key parameters. Models for secular variations recorded at London, Palermo and at the Cape of Good Hope over the past four hundred years are offered. Offset of the Earth's magnetic axis from the geographic axis is central to time-varying declination, but its causes have not yet been established. Applicability of the model to the explanation of sunspot activity is outlined. A corroborating experiment published by Peter Barlow in 1831 is appended.

Broad-scale magnetic anomalies over central and eastern Canada: a discussion

1981 ◽  
Vol 18 (3) ◽  
pp. 657-661 ◽  
Author(s):  
R. L. Coles ◽  
G. V. Haines ◽  
W. Hannaford
Keyword(s):  
Magnetic Field ◽  
Sea Level ◽  
Vertical Component ◽  
Magnetic Anomalies ◽  
Superior Province ◽  
The South ◽  
Earth’S Magnetic Field ◽  
Eastern Canada ◽  
Earth's Magnetic Field ◽  
Broad Scale

Profiles of anomalies in the vertical component of the Earth's magnetic field over central and eastern Canada, observed at an average altitude of 4 km above sea level, show broad regions with distinctive anomaly character. These subdivisions indicate major differences in the evolutions of regions within individual structural provinces. Particularly notable is a region of intense anomalies in the northern part of the Superior Province in Quebec, contrasting with much weaker anomaly relief to the south and east.

Geomagnetic dynamos

1958 ◽  
Vol 250 (986) ◽  
pp. 543-583 ◽  
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Equations Of Motion ◽  
Conducting Fluid ◽  
Earth’S Magnetic Field ◽  
Dynamo Theory ◽  
Dynamo Action ◽  
Earth’S Core ◽  
Earth's Core ◽  
Earth's Magnetic Field

The ‘dynamo theory’ ascribes the origin of the earth’s magnetic field to the dynamo action of motions in the conducting fluid of the earth’s core. This paper supports the theory by proving rigorously that it is possible to postulate a pattern of motions in a sphere filled with conducting fluid in such a way that the arrangement acts as a dynamo producing a magnetic field extending outside the conductor. The equations of motion of the fluid are ignored. The proof is given for a model consisting of two eddies in the earth’s core, and does no more than demonstrate that motions in a sphere filled with conducting fluid can act as a steady dynamo. It is certainly not suggested that the motions in the earth’s core are so simple. There is nothing pathological about the relative orientations of the angular velocity vectors of the two eddies which lead to dynamo action; in fact about half of the possible relative orientations work.

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