Abstract
The Sun Coronal Ejection Tracker (SunCET) is an extreme ultraviolet imager and spectrograph instrument concept for tracking coronal mass ejections through the region where they experience the majority of their acceleration: the difficult-to-observe middle corona. It contains a wide field of view (0–4 R⊙) imager and a 1 Å spectral-resolution-irradiance spectrograph spanning 170–340 Å. It leverages new detector technology to read out different areas of the detector with different integration times, resulting in what we call “simultaneous high dynamic range”, as opposed to the traditional high dynamic range camera technique of subsequent full-frame images that are then combined in post-processing. This allows us to image the bright solar disk with short integration time, the middle corona with a long integration time, and the spectra with their own, independent integration time. Thus, SunCET does not require the use of an opaque or filtered occulter. SunCET is also compact – ~15 × 15 × 10 cm in volume – making it an ideal instrument for a CubeSat or a small, complementary addition to a larger mission. Indeed, SunCET is presently in a NASA-funded, competitive Phase A as a CubeSat and has also been proposed to NASA as an instrument onboard a 184 kg Mission of Opportunity.
Highlights
Introduction and science driversThe primary science question that the Sun Coronal Ejection Tracker (SunCET) instrument concept is designed to address is: What are the dominant physical mechanisms for coronal mass ejection acceleration as a function of altitude and time?In the standard model configuration of a coronal mass ejection (CME; Fig. 1), a CME must overcome the constraint of overlying field in order to escape
The Sun Coronal Ejection Tracker (SunCET) is an extreme ultraviolet imager and spectrograph instrument concept for tracking coronal mass ejections through the region where they experience the majority of their acceleration: the difficult-to-observe middle corona
These effects are primarily due to vignetting (e.g. Koutchmy, 1988; Aime et al, 2019). This is not the case with SunCET as it does not require an occulter to observe the CMEs in the low- and middle-corona, so its spatial resolution is not diffraction limited and is superior even in the field of view (FOV) region that overlaps with the coronagraphs
Summary
SunCET observations can discriminate between single-peak versus doublepeak CME acceleration profiles, which determines the duration of a velocity perturbation in the torus instability model. Another CME initiation mechanism arises from the magnetic field topology of the flux rope. SunCET will be the first mission that allows continuous measurements of CMEs during their initial acceleration phase using only a single instrument This is advantageous compared to currently used instruments, where, e.g. EUV imagers in the low corona are combined with white-light coronagraphs higher up to track this phase. The same challenges with different CME structures in EUV versus white light will be present, but SunCET’s broader temperature response should mitigate this somewhat
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