High-Altitude Instrumentation for Infrared Observations of the Solar Corona

The solar magnetic field stores the energy that heats the sun’s corona to over one million degrees and powers dynamic, potentially earth-effective events like solar flares and coronal mass ejections. High-altitude infrared remote sensing is a promising new method for measuring coronal magnetic fields, which are weak and notoriously difficult to observe, and characterizing the surrounding plasma environment. In this talk, I describe recent insights provided by a new CfA airborne spectrometer and outline our plans for future airborne and balloon-borne spectrometers and magnetometers.
Our instrumentation program began with the development of an Airborne InfraRed Spectrometer (AIR-Spec) to measure infrared coronal emission lines during total solar eclipses. AIR-Spec made its commissioning observation from the NSF’s Gulfstream V research jet during the 2017 eclipse, when it measured all five of its target lines. These magnetically sensitive emission lines are promising candidates for future observations of the coronal magnetic field, and their characterization was an important first step toward developing the next generation of coronal magnetometers. The second AIR-Spec research flight took place during the 2019 eclipse across the south Pacific. Higher sensitivity and reduced jitter enabled more precise measurements of plasma density, temperature, and line-of-sight velocity further from the solar limb. AIR-Spec will fly for the third time during the December 14, 2020 South American eclipse, as one of two focal plane instruments on our new large-aperture solar tracking platform. The Airborne Stabilized Platform for InfraRed Experiments (ASPIRE) will enable even more sensitive measurements of the AIR-Spec lines, and the second focal plane instrument will provide 2D images of the corona at two temperatures. During the 2024 North American eclipse, ASPIRE will feed a new imaging Fourier transform spectrometer that will survey a much wider infrared window to look for new lines for plasma and magnetic field diagnostics. In parallel with that instrument, we plan to develop a balloon-borne coronagraph and spectropolarimeter that will observe the sun continuously for up to two weeks from above Antarctica. The CORonal Spectropolarimeter for Airborne Infrared Research (CORSAIR) will measure the magnetic and thermodynamic evolution of the corona and is a pathfinder for a future space mission.