Forecasting the geomagnetic e ects to technological systems on the ground requires rapid calculations of the electric and magnetic elds produced by the auroral electrojet. The electrojet is often modelled as a line current at a height of 100 km, but in reality it has a nite width and is typically spread over 5◦ or 6◦ of latitude. We show that the width of the electrojet can easily be included i...

The nature of our star, the Sun, is dominated by its complex and variable magnetic fields. It is the purpose of this paper to review the fundamental nature of our magnetic Sun by outlining the most basic principles behind the way the Sun works and how its fields are generated, and to examine not only the historical observations of our magnetic star, but, in particular, to study the wonderful ob...

A crucial remaining challenge in the development of the magnetic resonance force microscope (MRFM) is to place the magnetic probe on the mechanical resonator. Here we address the problem of spurious detector response arising from interactions between the magnetic tip and various external applied elds. Ferromagnetic resonance experiments on a microscopic, thin-lm yttrium iron garnet crystal moun...

The demagnetization processes and the magnetic viscosity have been studied on a bulk-amorphous Nd 60 Fe 30 Al 10 rod at room temperature. Many unique magnetic properties have been found in this novel hard magnetic material. A clear hysteresis was present on the minor loops, though the total and irreversible susceptibilities exhibited single-phase magnet behavior. A signi"cant magnetic viscosity...

Accretion discs are ubiquitous in astrophysics and in particular in accreting objects like cataclysmic variables, X-ray binaries or young stars. For many years magnetic ®elds have been included in models of such objects to be able to generate out ̄ows or jets or to explain accretion ofmatter on to the poles of the central objects. The interest in magnetic ®elds in accretion systems has been rece...

Time varying ionospheric currents caused by geomagnetic storms originating from the Sun induce electric currents in expansive technological networks located on the Earth’s surface. These so-called geomagnetically induced currents (GICs) can be damaging to the systems in which they 9ow. The ability to estimate the magnitude of GICs is, therefore, desirable in order to mitigate any serious e:ects...

A technique for analyzing multiple-time, single-point datasets is presented, which yields information about the (spectral) variation of MHD elds in directions perpendicular to the mean ow. The analysis can be performed for any homogeneous solenoidal elds, including magnetic and incompressible velocity uctuations. A summary of the associated theory is given, along with initial results obtained u...

Several coronal bright points identified in a quiet region of the Sun from SOHO/EIT Fe XII images are found to have a time evolution from birth to decay which is extremely well correlated with the rise and fall of magnetic flux as determined from photospheric magnetograms made with the SOHO/MDI instrument. Radiative losses of the bright points are found to be much less than conductive losses bu...

We develop a practical forward fitting method based on the SIMPLEX algorithm with shaking, which allows the derivation of the magnetic field and other parameters along a solar flaring loop using microwave imaging spectroscopy of gyrosynchrotron emission. We illustrate the method using a model loop with spatially varying magnetic field, filled with uniform ambient density and an evenly distribut...

We examine the observations of large-scale magnetic elds in the Universe. We begin at the largest scale with clusters of galaxies and work our way down through galaxies and nally to the Milky Way, on which we concentrate in detail. We examine the observations of the Galactic magnetic eld, and their interpretation, under the philosophy that the Galactic magnetic eld is like that in other spiral ...