A New Setup for Ground‐based Measurements of Solar Activity at 10 μm

Abstract

Solar activity measurements in the far-to mid-IR range are receiving renewed interest as part of an effort to complement recent results obtained at submillimeter wavelengths. A new setup has been developed to measure solar activity in the infrared spectral region centered at 10 mm (30 THz) by means of a camera with focal plane array of uncooled microbolometers. An optical arrangement of concave-convex-concave mirrors magnifies and focuses the full-disk solar image to fit into the field of view of the camera. Techniques were developed to characterize the camera and calibrate the measurements in brightness temperature and flux units.

Association of Mid-Infrared Solar Plages with Calcium K Line Emissions and Magnetic Structures

“…Mid-IR continuum images can become an important complementary observational tool to describe spatial features of hot plasma above the photosphere in active regions. Bright mid-IR area surrounding a sunspot was recently reported, from observations made with a small-aperture telescope and wide photometric beam (25 arcseconds) (Melo et al 2006). They were suggested as equivalent to the previously found "plage-like" features (Gezari, Livingstone & Varosi 1999).…”

An Observational Overview of Solar Flares

“…No dedicated solar infrared observatories at wavelengths much longward of 1µm exist at present although developments are underway in imaging at 10 µm (e.g., Hudson 1975), with flares already having been detected (Melo et al 2006). Specific observations on the 1 m McMath Solar Telescope make use of the mid-infrared to study photospheric magnetic fields (Moran et al 2007), and at the 0.76 m Dunn Solar Telescope to probe flare activity at the "opacity minimum" spectral region around 1.5 µm .…”

Bright 30 THz impulsive solar bursts

“…The first setup designed to detect solar flares at 30 THz was initially tested at “Bernard Lyot” Solar Observatory, Campinas, Brazil, using a Hale‐type coelostat with two 20 cm flat mirrors, reflecting radiation into a 15 cm diameter Newtonian telescope, feeding an early type Wuhan IR928 30 THz uncooled camera amorphous silicon 320 × 240 microbolometer array sensitive to about 0.5 K. It has been later installed at El Leoncito Observatory, in Argentina Andes, utilizing a Jensch‐type coelostat with 30 cm flat mirrors, projecting radiation into a 15 cm diameter Newtonian telescope, for a number of observational campaigns [ Melo et al , , ; Marcon et al , ; Kaufmann et al , ; Cassiano et al , ]. The setup has been later modified, forming a solar image of nearly three fourths of the disk at the focal plane by afocal adjustment done by placement of a germanium lens in front of an uncooled vanadium oxide microbolometer array of a FLIR A20 8–15 µm (30 THz) 320 × 240 pixel camera, sensitive to about 0.1 K [ Marcon et al , ; Kaufmann et al , ].…”