Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995mnras.273..187s&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 273, Issue 1, pp. 187-200.
Astronomy and Astrophysics
Astronomy
12
Polarization - Ism Clouds - Dust, Extinction - Ism: Magnetic Fields
Scientific paper
It is unlikely that Davis-Greenstein alignment of non-spherical dust grains is achieved by ordinary paramagnetic relaxation. A new model is outlined in which the magnetic relaxation mechanism is enhanced by superparamagnetism in non-spherical pinwheel grains having a classical core-mantle structure. The model is applied to the magnetic (Davis-Greenstein) alignment problem for pinwheels producing interstellar polarization in dense clouds, as well as the diffuse cloud medium. It is shown that the magnetic alignment efficiency for polarizing pin wheels is independent of grain size, and therefore insensitive to mantle growth and erosion processes. This makes it possible to understand why dust grains are aligned in cold molecular clouds where icy mantle growth occurs. It is also shown that the combination of suprathermal rotation and superparamagnetism produces perfect Davis-Greenstein alignment for interstellar magnetic fields as weak as B ≍3 × 10-7 G. As the mean interstellar magnetic field is 10 times stronger than this value, it is concluded that the magnetic alignment efficiency for pinwheel grains is saturated in clouds where interstellar optical and infrared polarizations are observed. As a consequence, polarization-to-extinction ratios P/Av are independent of magnetic field strength. It is therefore misleading to determine the strengths of cloud magnetic fields on the basis of polarization measurements. Variations of the P/Av ratio from one cloud to another are mainly caused by variations in the magnetic field geometry.
No associations
LandOfFree
Interstellar polarization and magnetic alignment of pinwheel dust grains - II. Grain alignment efficiency does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Interstellar polarization and magnetic alignment of pinwheel dust grains - II. Grain alignment efficiency, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interstellar polarization and magnetic alignment of pinwheel dust grains - II. Grain alignment efficiency will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-848504