Constraining the pass-band of future space-based coronagraphs for observations of solar eruptions in the FeXIV 530.3 nm “green line”

Abstract

Constraining the pass-band of future space-based Coronagraphs for observations of solar eruptions in the FeXIV 530.3nm "green line"-Manuscript Draft-Manuscript Number: EXPA-D-16-00027R1 Full Title: Constraining the pass-band of future space-based Coronagraphs for observations of solar eruptions in the FeXIV 530.3nm "green line"

CME-induced Thermodynamic Changes in the Corona as Inferred from Fe xi and Fe xiv Emission Observations during the 2017 August 21 Total Solar Eclipse

“…Even in a small bandpass, the continuum radiation constitutes a substantial fraction of the emission at optical wavelengths. We thus caution the 'spectral purity' arguments of Bemporad et al (2017), who state that correction for the continuum is not necessary. Indeed, using an on-band observation alone will not produce physically meaningful results (especially for Fe xiv, see Section 3.1).…”

“…In the coronal holes, Fe xiv is far less abundant, going down to around 1 % that of the continuum. Fe xi emission is stronger than the continuum emission throughout the entire corona, and is strongest in the western limb active region (see Section 2.3) where it is as much as six times the continuum intensity (note that the scale in The low intensity of Fe xiv relative to the local continuum is quite a bit lower than what is predicted by Bemporad et al (2017), who argue that a single observation of the Fe xiv emission without a continuum subtraction can give useful results. We are finding that in fact, the 'spectral purity' of Fe xiv is less than 50% in our 0.5 nm bandpasses almost everywhere in the corona, which is more similar to the spectral purity that Bemporad et al (2017) predicts for a 1 or 2 nm bandpass.…”

“…Fe xi emission is stronger than the continuum emission throughout the entire corona, and is strongest in the western limb active region (see Section 2.3) where it is as much as six times the continuum intensity (note that the scale in The low intensity of Fe xiv relative to the local continuum is quite a bit lower than what is predicted by Bemporad et al (2017), who argue that a single observation of the Fe xiv emission without a continuum subtraction can give useful results. We are finding that in fact, the 'spectral purity' of Fe xiv is less than 50% in our 0.5 nm bandpasses almost everywhere in the corona, which is more similar to the spectral purity that Bemporad et al (2017) predicts for a 1 or 2 nm bandpass. Observation and subtraction of the continuum subtraction is absolutely essential to infer any physical properties of the corona other than morphological structure (see Section 2.1).…”

Comparison of the Coronal Green-line Intensities with the EUV Measurements from SDO/AIA

“…Finally, we must admit that due to the small aperture of the Lijiang coronagraph, some conclusions made in this work are very preliminary and need to be further confirmed and improved by future higher-resolution observations for corona. Therefore, the development of the next-generation instruments, such as the large coronagraph of 1 m aperture in the project of CGST (Chinese Giant Solar Telescope) (Fang 2011;Liu 2014;Deng et al 2016;Liu et al 2016Liu et al , 2021 and the space coronagraph of ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) (Bemporad et al 2017), are highly awaited in this rapidly developing area.…”