Propagation of torsional Alfvén waves along magnetic flux tubes has been extensively studied for many years but no conclusive results regarding the existence of a cutoff frequency for these waves have been obtained. The main purpose of this paper is to derive new wave equations that describe the propagation of linear torsional Alfvén waves along thin and isothermal magnetic flux tubes, and use ...

The nonlinear three-wave interaction process at the heart of the parametric decay process is studied by launching counterpropagating Alfvén waves from antennas placed at either end of the Large Plasma Device. A resonance in the beat wave response produced by the two launched Alfvén waves is observed and is identified as a damped ion acoustic mode based on the measured dispersion relation. Other...

A case study of medium-scale travelling ionospheric disturbances (TIDs) that are correlated with solar wind Alfvén waves is presented. The HF radar groundscatter signatures of TIDs caused by atmospheric gravity waves with periods of 20–40 min are traced to a source at high latitudes, namely pulsed ionospheric flows (PIFs) due to bursts in the convection electric field and/or the associated iono...

Tokamak plasmas with reversed magnetic shear are prone to the excitation of Alfvén cascade !AC" eigenmodes by energetic particles. These modes exhibit a quasiperiodic pattern of predominantly upward frequency sweeping. Observations also reveal that the AC spectral lines sometimes bend at low frequencies, which is a significant deviation from the shear Alfvén wave dispersion relation. This paper...

We investigate how properties of the corona and solar wind in open coronal holes depend on properties of magnetic fields and their footpoint motions at the surface. We perform one-dimensional magnetohydrodynamical (MHD) simulations for the heating and the acceleration in coronal holes by low-frequency Alfvén waves from the photosphere to 0.3 or 0.1AU. We impose low-frequency ( < ∼ 0.05Hz) trans...

Analyses of the widths and shifts of optically thin emission lines in the ultraviolet spectrum of the active dwarf ǫ Eri (K2 V) are presented. The spectra were obtained using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. The line widths are used to find the nonthermal energy density and its variation with temperature from ...

Certain regions of the solar atmosphere are at sufficiently low temperatures to be only partially ionised. The lower chromosphere contains neutral atoms, the existence of which greatly increases the efficiency of the damping of waves due to collisional friction momentum transfer. More specifically the Cowling conductivity can be up to 12 orders of magnitude smaller than the Spitzer value, so th...

Perhaps the most intriguing result of Planck’s dust-polarization measurements is the observation that the power in the E-mode polarization is twice that in the B mode, as opposed to pre-Planck expectations of roughly equal dust powers in E and B modes. Here we show how the Eand Bmode powers depend on the detailed properties of the fluctuations in the magnetized interstellar medium. These fluctu...