We apply the method of MHD seismology to estimate the magnetic field in spicules using observed kink waves. We include the effects of gravitational stratification, the neglect of which leads to an error of around 30 % in the estimation of the magnetic field. With stratification included, we find the magnetic field in spicules in the range 8-16 G. We also estimate a density of 7.4*(10-10) kg m^-3 in spicules. The estimated values of magnetic field and density are in agreement with the available observations. Improved measurement of height, oscillation period, and plasma density in spicules will further enhance the precision of this method.
Authors: Singh, K.A.P. and Dwivedi, B.N.
Publication Status: accepted for publication in New Astronomy
Last Modified: 2007-06-11 02:29
Spatial Damping of Linear Compressional Magnetoacoustic Waves in Quiescent Prominences
We study the spatial damping of magnetoacoustic waves in an unbounded quiescent prominence invoking the technique of MHD seismology. We consider Newtonian radiation in the energy equation and derive a fourth order general dispersion relation in terms of wavenumber k. Numerical solution of dispersion relation suggests that slow mode is more affected by radiation. The high frequency waves have been found to be highly damped. The uncertainty in the radiative relaxation time, however, does not allow us to conclude if the radiation is a dominant damping mechanism in quiescent prominences.
Authors: K.A.P. Singh
Publication Status: Published in Journal of Astrophysics and Astronomy
Last Modified: 2006-11-07 07:24
Damping of Compressional MHD Waves in Quiescent Prominences and Prominence-Corona Transition Region (PCTR)
The effects of radiative losses due to Newtonian cooling and MHD turbulence have been considered to examine the spatial damping of linear compressional waves in quiescent prominences and prominence-corona transition region (PCTR). The radiative losses give acceptable damping lengths for the slow mode wave for the radiative relaxation times in the range (10-1000s). From prominence seismology, the values of opacity and turbulent kinematic viscosity have been inferred. It has been found that for a given value of radiative relaxation time, the high frequency slow mode waves are highly damped. We have also investigated the possible role of MHD turbulence in damping of MHD waves and found a turbulent viscosity can re-produce the observed damping time and damping length in prominences, especially in PCTR.
Authors: K.A.P. Singh
Publication Status: submitted to Astronomy and Astrophysics
Last Modified: 2006-09-11 10:01