Determination of Prominence Plasma β from the Dynamics of Rising Plumes

Abstract

Observations by the Hinode satellite show in great detail the dynamics of rising plumes, dark in chromospheric lines, in quiescent prominences that propagate from large (~10 Mm) bubbles that form at the base of the prominences. These plumes present a very interesting opportunity to study magnetohydrodynamic (MHD) phenomena in quiescent prominences, but obstacles still remain. One of the biggest issues is that of the magnetic field strength, which is not easily measurable in prominences. In this paper we present a method that may be used to determine a prominence's plasma β when rising plumes are observed. Using the classic fluid dynamic solution for flow around a circular cylinder with an MHD correction, the compression of the prominence material can be estimated. This has been successfully confirmed through simulations; application to a prominence gave an estimate of the plasma β as β = 0.47 ± 0.079 to 1.13 ± 0.080 for the range γ = 1.4-1.7. Using this method it may be possible to estimate the plasma β of observed prominences, therefore helping our understanding of a prominence's dynamics in terms of MHD phenomena.