Earth's magnetic field

About: Earth's magnetic field is a research topic. Over the lifetime, 20360 publications have been published within this topic receiving 446747 citations. The topic is also known as: magnetic field of Earth & geomagnetic field.

The cosmic‐ray flare effect: 1. Some new methods of analysis

Abstract: A systematic method for determining the angular dependence of the cosmic radiation in the vicinity of the earth during a cosmic-ray solar flare effect and a method for determing the rigidity spectrum of the radiation during the anisotropic phase of a flare effect are dcscribed. Calculations of the asymptotic directions of approach of particles using a simulation of the geomagnetic field which includes spherical surface harmonics up to the sixth degree, a method of correcting flare observations to a given atmospheric pressure level which takes into account the short attenuation length of the flare radiation, and a comparison which shows that a number of high-latitude sea-level neutron monitors are strictly comparable despite differences in their geometries are presented. (auth) Observations of the iiarc cffccts of Mlay 4 and Novem

A three-dimensional kinematic dynamo

Abstract: A number of steady (marginal) solutions of the induction equation governing the magnetic field created by a particular class of threedimensional flows in a sphere of conducting fluid surrounded by an insulator are derived numerically. These motions possess a high degree of symmetry which can be varied to confirm numerically that the corresponding asymptotic limit of Braginsky is attained. The effect of altering the spatial scale of the motions without varying their vigour can also be examined, and it is found that dynamo action is at first eased by decreasing their characteristic size. There are, however, suggestions that the regenerative efficiency does not persistently increase to very small length scales, but ultimately decreases. It is further shown that time varying motions, in which the asymmetric components of flow travel as a wave round lines of latitude, can sustain fields having co-rotating asymmetric parts. It is demonstrated that, depending on their common angular velocity, these may exist at slightly smaller magnetic Reynolds numbers than the corresponding models having steady flows and fields. The possible bearing of the integrations on the production of the magnetic field of the Earth is considered, and the implied ohmic dissipation of heat in the core of the Earth is estimated for different values of the parameters defining the model.

Horizontal Wind Systems in the Ionospheric E region Deduced from the Dynamo Theory of the Geomagnetic Sq variation Part II. Rotating Earth

Abstract: Horizontal wind systems in the ionospheric E region are deduced from the dynamo theory by using the same total electric field as in Part I. [1] In Part II the effect of the Coriolis force is taken into consideration and a further study is made about the wind motion in the E region. The wind velocity is obtained by solving the equation of motion of the atmosphere for the rotating earth simultaneously with the dynamo equation.It is shown as in Part I that the diurnal wind motion predominates over the semi-diurnal one in the E region and the semi-diurnal pressure variation is almost in phase with that observed at the ground.The conspicious differences in the results between Part I and Part II are: (1) The diurnal pressure variation in the E region reaches its maximum value at about 7p.m. local solar time in Part II instead of at 9a.m. as in Part I. (2) Amplification of the semi-diurnal pressure variation in the E region is estimated to be 25-30 at low latitudes in Part II instead of 50 as in Part I.The vertical drift velocity in the F2 region is calculated by using our wind-systems.In Appendices the mathematical consideration is given to our treatment.

International Geomagnetic Reference Field Revision 1985

Abstract: The International Association of Geomagnetism and Aeronomy (IAGA) Division I, Working Group 1, deals with the topic “Analysis of the Main Field and Secular Variations.” One of the more important functions of the working group is the periodic revision of the International Geomagnetic Reference Field (IGRF). The 13 members of the working group have professional interests covering a broad spectrum of geomagnetic science, including the theory and practice of geomagnetic analysis and modeling, the theory of the origin of the magnetic fields of the earth and other bodies, the theory of geomagnetic secular variation, the application of field models in magnetic survey data processing, and geomagnetic charting.

The diamagnetic effect of the equatorial Appleton anomaly: Its characteristics and impact on geomagnetic field modeling

Abstract: [1] The diamagnetic effect generally reduces the magnetic field inside a plasma. Its importance is appreciated in regions like the magnetosphere and the solar wind. In the ionosphere, depletions of the geomagnetic field have up to now been considered negligible. The CHAMP satellite provides for the first time the combination of high-resolution magnetic field measurements and plasma density observations on the same spacecraft in low-Earth orbit. We show the typical distribution of electron density at the altitude of about 430 km for various local times. Particularly prominent features are the density enhancements north and south of the dip equator. As expected, the magnetic field intensity is depressed in the crest region by an amount of more than 5 nT. The diamagnetic effect is strongest from sunset to midnight and thus causes errors in global geomagnetic field models which are usually computed from data sampled at all night-time hours.