Magnetic fields are an essential constituent of our Universe and their manifestations on
Earth were recognized a long time ago: from loadstones found in the ancient Greece in the …

The current state of our knowledge, and ignorance, of the nature of oscillations in sunspots
is surveyed. An effort is made to summarize the robust aspects of both the observational and …

Recent observational evidence for magnetic field direction effects on helioseismic signals in
sunspot penumbrae is suggestive of magnetohydrodynamic (MHD) mode conversion …

We have modeled numerically the propagation of waves through magnetic structures in a
stratified atmosphere. We first simulate the propagation of waves through a number of …

Magnetic fields are the cause of almost all forms of solar activity. Near the solar surface, and
possibly in the entire convection zone, these fields occur in the form of isolated flux tubes. In …

This review on some aspects of waves in gases concentrates first (Part I) on modern
research in the acoustics of fluids at rest or in steady or turbulent motion, in free space, in the …

Context. The chromosphere is a partially ionized layer of the solar atmosphere that mediates
the transition between the photosphere where the gas motion is determined by the gas …

Local helioseismology seeks to probe the near surface regions of the Sun, and in particular
of active regions. These are distinguished by their strong magnetic fields, yet current local …

Velocity oscillations" measured" simultaneously at the photosphere and the chromosphere—
from time series of spectropolarimetric data in the 10830 Å region—of different solar …

Context. In the solar atmosphere, the acoustic cutoff frequency is a local quantity that
depends on atmospheric height. It separates low-frequency evanescent waves from high …