Dipole model of the Earth's magnetic field

About: Dipole model of the Earth's magnetic field is a research topic. Over the lifetime, 2756 publications have been published within this topic receiving 83021 citations.

Bounce‐averaged diffusion coefficients due to resonant interaction of the outer radiation belt electrons with oblique chorus waves computed in a realistic magnetic field model

Abstract: [1] We present the results of calculations of the bounce-averaged pitch angle, mixed, and momentum diffusion coefficients in a dipole and two realistic field models (the T01s model for quiet and storm conditions). We consider resonant interactions of the outer radiation belt electrons with oblique chorus waves. We demonstrate that on the dayside, the use of a realistic magnetic field versus a dipole field only makes a significant difference for small equatorial pitch angles at energies larger than E = 1 MeV. On the nightside, the differences between the scattering rates calculated in the Tsyganenko and dipole models can reach several orders of magnitude at various equatorial pitch angles for electrons with E ≥ 0.5 MeV. The most significant changes in the scattering rates computed in the realistic and dipole magnetic fields occur during the geomagnetically active conditions. On the nightside, for E ≥ 0.5 MeV, the diffusion coefficients calculated in the Tsyganenko field show significant scattering near the edge of the loss cone that can produce loss of electrons to the atmosphere, while in the dipole model there is no scattering at small equatorial pitch angles. Our computations in the realistic field show that resonant interactions between electrons with E ≤ 1 MeV and chorus waves can be an effective net loss mechanism on both the dayside and the nightside. To explain the differences in the scattering rates associated with a change in the magnetic field model, we present the contribution of various resonant harmonics to the diffusion and examine the changes in the resonance condition.

Transient electromagnetic fields of a vertical magnetic dipole on a two-layer earth

Abstract: The transient fields of a vertical magnetic dipole on a two-layer earth model are expressed in analytical form using two different approaches. In the first, the fields in the time domain are obtained as the inverse Laplace transforms of derived full wave time-harmonic solutions, while in the second, the concept of natural frequencies of the stratified earth is utilized. Comparison with a previously obtained approximate solution reveals that the latter is the late time part of the present solution. Important features in the waveforms of the surface fields due to step and pulsed current excitations are demonstrated by a variety of numerical examples. These features provide diagnostic means of sensing the earth's stratification, overburden thickness, and the ratio of conductivities of the layers.

Probability distribution functions of microscale magnetic fluctuations during quiet conditions

Abstract: A statistical study of microscale magnetic fluctuations in the interplanetary and magnetosheath region during quiet conditions is approached from the concept of probability distribution function. Magnetic field data from Explorer 34 were used to reconstruct the distribution functions and to calculate some of their moments. The distribution functions are found to be nearly tri-Maxwellian as the background field is relatively quiet. The direction of maximum fluctuations is found to be nearly perpendicular to that of the background magnetic field, but the fluctuations are rarely circularly polarized. Across the Earth's bow shock, the degree of fluctuation anisotropy increases, but no noticeable change in relative fluctuation intensity has been observed.

Corrections to the azimuthal component of the interplanetary magnetic field due to meridional flow in the solar wind

Abstract: Stellar-wind models which incorporate meridional flows, open magnetic flux tubes in the equatorial plane of the star. The transport of magnetic field to higher latitudes is accompanied by an increase in the azimuthal velocity, increasing the corotation of the plasma at all latitudes. The percentage correction to the azimuthal magnetic field compared to classical models is a 10-- 20 percent effect at 5 AU and theta=90degree, whereas the azimuthal velocity correction is a 20--40 percent effect. The model is compared with recent observations from Pioneer 10 which may indicate that the azimuthal magnetic field is not as large near Jupiter as suggested by classical two-dimensional models. (AIP)

Solar wind electrons as tracers of the Martian magnetotail topology

Abstract: Simultaneous measurements of electrons and magnetic field are used to study the topology of the Martian magnetosphere Halo solar wind electrons streaming along magnetic field lines replicate variations of the Bx component, thus tracing the interplanetary magnetic field draping in most parts of the Martian tail This suggests that the magnetic field observed near the equatorial plane of Mars is mainly induced However, there are regions where this perfect tracing is violated This could be considered as evidence for an intrinsic planetary field An alternative interpretation involves the relationship between these regions and ionospheric holes