Near Infrared Imaging Magnetometry

Abstract

Infrared array detectors are a new and promising tool for investigating the properties of magnetic field concentrations in the solar photosphere. Array measurements provide large statistical samples of polarized line profiles and display the spatial organization of the magnetic field. The wavelength region near 1.6 μm has important advantages for magnetometry: spectral lines with magnetic sensitivites ranging from low to very high; low continuum opacity; high continuum flux; and the possibility of sub-arcsecond angular resolution with existing telescopes. Initial results have extended earlier work on the distribution of field strength and flux in plages and revealed new properties specifically connected with spatial structure. The quality and flexibility of near infrared magnetographs can be expected to improve rapidly.

Infrared Solar Physics

“…While reading John Jefferies’ introduction to the 1992 IAU Symposium (Jefferies, 1994 ), it is inspirational to see how much real progress has been made over the past 20 years. The initial magnetic field measurements with an infrared array detector observing the highly advantageous Fe I 1564.8 nm spectral line were being made at the time of that meeting (Rabin, 1994 ), and now they are routine (Jaeggli et al , 2010 ). Observations of the solar corona, including the potential for magnetic field measurements, were just being discussed (Kumar and Davila, 1994 ), and now coronal magnetic field measurements are made using the favorable 1074.7 nm emission line on a regular basis (Tomczyk et al , 2008 ).…”

“…Instruments using grating spectropolarimeters with arrays include the NIM (Rabin et al , 1992 ), the TIP (Mártinez Pillet et al , 1999 ), and the NAC (Plymate and Penn, 2007 ). Imaging Fabry-Perot spectropolarimeters include the NIM-2 (Rabin et al , 1996 ) and IRIM (Cao et al , 2004 ). And, finally, a new facility-class instrument at the NSO/DST is the FIRS instrument, a multi-slit grating spectropolarimeter with a 1024 × 1024 HgCdTe detector (Jaeggli et al , 2010 ).…”