Emission of Hydromagnetic Waves from Sunspot Umbras.

The Structure of Hydromagnetic Shock Waves

Es werden Wellen in einem quasi-neutralen Gas untersucht, das Ionen und Elektronen enthält und genügend kalt ist, so daß die thermischen Bewegungen vernachlässigt werden können. Außerdem werden Zusammenstöße zwischen den Teilchen vernachlässigt, jedoch nicht die Trägheitseffekte des elektrischen Stromes. Die nicht-linearen Gleichungen für unendlich ausgedehnte, ebene Kompressionswellen, die sic...

The Rotation of Hydromagnetic Waves by the Ionosphere

We show that the Doppler shift on whistler mode signals from VLF transmitters may be used to infer the magnetic field of an hydromagnetic wave above the ionosphere in the magnetosphere. This inferred field can then be compared with that measured on the ground. We examine one event in detail and show the data imply that a it/2 rotation of the orientation of the wave ellipse has occurred between ...

Interaction of Energetic Ring Current Protons with Magnetospheric Hydromagnetic Waves

Can Nonlinear Hydromagnetic Waves Support a Self-Gravitating Cloud?

Using self-consistent magnetohydrodynamic (MHD) simulations, we explore the hypothesis that nonlinear MHD waves dominate the internal dynamics of galactic molecular clouds. Our models employ an isothermal equation of state and allow for self-gravity. We adopt “slab-symmetry,” which permits motions v⊥ and fields B⊥ perpendicular to the mean field, but permits gradients only parallel to the mean ...

Observations of Running Waves in a Sunspot Chromosphere

Spectropolarimetric time series data of the primary spot of active region NOAA 9448 were obtained in the Si i 10827 Å line and the He i 10830 Å multiplet with the Tenerife Infrared Polarimeter. Throughout the time series the spectrograph slit was fixed over a region covering umbra, a light bridge, penumbra, and quiet sun. We present speeds of running penumbral waves in the chromosphere, their r...