A HAWAII-2RG infrared camera operated under fast readout mode for solar polarimetry

Polarimetry is a crucial method to investigate solar magnetic fields. From the viewpoint of space weather, the magnetic field in solar filaments, which occasionally erupt and develop into interplanetary flux ropes, is of particular interest. To measure the magnetic field in filaments, high-performance polarimetry in the near-infrared wavelengths employing a high-speed, large-format detector is required; however, so far, this has been difficult to be realized. Thus, the development of a new infrared camera for advanced solar polarimetry has been started, employing a HAWAII-2RG (H2RG) array by Teledyne, which has $$2048~\times 2048$$ 2048 × 2048 pixels, focusing on the wavelengths in the range of $$1.0\;{-}\;1.6\;~\mu {\text{m}} $$ 1.0 - 1.6 μ m . We solved the problem of the difficult operation of the H2RGs under “fast readout mode” synchronizing with high-speed polarization modulation by introducing a “MACIE” (Markury ASIC Control and Interface Electronics) interface card and new assembly codes provided by Markury Scientific. This enables polarization measurements with high frame-rates, such as 29–117 frames per seconds, using a H2RG. We conducted experimental observations of the Sun and confirmed the high polarimetric performance of the camera.

A HAWAII-2RG infrared camera operated under fast readout mode for solar polarimetry

Polarimetry is a crucial method to investigate solar magnetic fields. From the viewpoint of space weather, the magnetic field in solar laments, which occasionally erupt and develop into interplanetary flux ropes, is of particular interest. To measure the magnetic field in laments, high-performance polarimetry in the near-infrared wavelengths employing a high-speed, large-format detector is required; however, so far, this has been difficult to be realized. Thus, the development of a new infrared camera for advanced solar polarimetry has been started, employing a HAWAII-2RG (H2RG) array by Teledyne, which has 2048 x 2048 pixels, focusing on the wavelengths in the range of 1.0{1.6 um. We solved the problem of the difficult operation of the H2RGs under "fast readout mode" synchronizing with high-speed polarization modulation by introducing a "MACIE" (Markury ASIC Control and Interface Electronics) interface card and new assembly codes provided by Markury Scientific This enables polarization measurements with high frame-rates, such as 29{117 frames per seconds, using a H2RG. We conducted experimental observations of the Sun and confirmed the high polarimetric performance of the camera.

A HAWAII-2RG Infrared Camera Operated Under Fast Readout Mode for Solar Polarimetry

Polarimetry is a crucial method to investigate solar magnetic elds. From the viewpoint of space weather, the magnetic eld in solar laments, which occasionally erupt and develop into interplanetary ux ropes, is of particular interest. To measure the magnetic eld in laments, high-performance polarimetry in the near-infrared wavelengths employing a high-speed, large-format detector is required; however, so far, this has been difficult to be realized. Thus, the development of a new infrared camera for advanced solar polarimetry has been started, employing a HAWAII-2RG (H2RG) array by Teledyne, which has 2048 2048 pixels, focusing on the wavelengths in the range of 1.0{1.6 m. We solved the problem of the difficult operation of the H2RGs under \fast readout mode" synchronizing with high-speed polarization modulation by introducing a \MACIE" (Markury ASIC Control and Interface Electronics) interface card and new assembly codes provided by Markury Scientic. This enables polarization measurements with high frame-rates, such as 29{117 frames per seconds, using a H2RG. We conducted experimental observations of the Sun and conrmed the high polarimetric performance of the camera.

Solar polarimetry in the K I D2 line : A novel possibility for a stratospheric balloon

Of the two solar lines, K I D1 and D2, almost all attention so far has been devoted to the D1 line, as D2 is severely affected by an O2 atmospheric band. This, however, makes the latter appealing for balloon and space observations from above (most of) the Earth’s atmosphere. We estimate the residual effect of the O2 band on the K I D2 line at altitudes typical for stratospheric balloons. Our aim is to study the feasibility of observing the 770 nm window. Specifically, this paper serves as a preparation for the third flight of the Sunrise balloon-borne observatory. The results indicate that the absorption by O2 is still present, albeit much weaker, at the expected balloon altitude. We applied the obtained O2 transmittance to K I D2 synthetic polarimetric spectra and found that in the absence of line-of-sight motions, the residual O2 has a negligible effect on the K I D2 line. On the other hand, for Doppler-shifted K I D2 data, the residual O2 might alter the shape of the Stokes profiles. However, the residual O2 absorption is sufficiently weak at stratospheric levels that it can be divided out if appropriate measurements are made, something that is impossible at ground level. Therefore, for the first time with Sunrise III, we will be able to perform polarimetric observations of the K I D2 line and, consequently, we will have improved access to the thermodynamics and magnetic properties of the upper photosphere from observations of the K I lines.

Two Centuries of Solar Polarimetry

In 1811, François Arago observed the disk of the Sun with his “lunette polariscopique”. From the absence of detectable polarization compared with his laboratory observations of glowing solids, liquids, and flames he concluded that the Sun's visible surface is an incandescent gas. From this beginning, thanks to orders of magnitude technology improvements, a remarkable amount of what we know about the physics of the Sun has continued to flow from solar polarimetry. This short review compares some selected polarimetric discoveries with subsequent recent observations to illustrate the tremendous progress of solar polarimetry during the last two centuries.