Magnetic fields, pressures, and thermally unstable gas in prominent \hi shells
C. Heiles;
ApJ, 1989, 336, 808
ABSTRACT:B(parallel) from the Zeeman effect has been measured for the 21 cm line in emission in a number of morphologically prominent H I shells.
The H I structures are in fact filamentary instead of sheetlike.
B(parallel) is typically about 6.4 micro-G.
If estimates of n(H I) are correct, magnetic
pressure dominates thermal gas pressure by a factor of about 67, and linewidths
are somewhat smaller than the Alfven velocity.
B(parallel) as derived
from the Zeeman effect does not correlate with Faraday rotation.
A similar lack of correlation is found when comparing optical and diffuse
synchrotron polarization in the North Polar Spur.
Thus, the magnetic field is oriented differently in different types of region,
with little if any correlation.
KEYWORDS: h i regions, interstellar gas, interstellar magnetic fields, emission spectra, faraday effect, gas pressure, signal to noise ratios, thermal stability, zeeman effect
PERSOKEY:h_i, ,
CODE: heiles89