Abstract
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 pixels, focusing on the wavelengths in the range of 1.0;{-};1.6;~mu {text{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.
Highlights
Solar polarimetry is indispensable to determine solar magnetic fields governing a variety of phenomena in the solar atmosphere
Near-infrared polarimetry provides a new insight into the solar magnetic field study
Filaments occasionally erupt and become part of coronal mass ejections (CMEs), and the magnetic field in the filaments is the source of the magnetic field in the CME interplanetary flux ropes
Summary
Solar polarimetry is indispensable to determine solar magnetic fields governing a variety of phenomena in the solar atmosphere. Eruptive events occurring on the solar surface occasionally result in a harmful effect to the Earth, and the investigation of such phenomena and the magnetic field information on the Sun is crucially important. One of the reasons of the advantage of the near-infrared observations is that there are a number of rather informative absorption lines in the near-infrared range. One of these is the He I 1083.0-nm line, which is formed in the chromosphere (e.g., Lagg 2007; Penn 2014). From the viewpoint of space weather, the information on the magnetic field in the flux ropes arriving at the Earth is crucially important, because the orientation of the magnetic field in the flux ropes affects the severity of the resulting geomagnetic
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