IR spectroscopy of COmosphere dynamics with the CO first overtone band

TL;DR

This paper presents observations of the CO first overtone band near 2300 nm to diagnose lower atmospheric dynamics, revealing shock wave behavior and p-mode oscillations, emphasizing the need for advanced mid-infrared instrumentation in solar studies.

Contribution

It demonstrates the use of the CO first overtone band as a diagnostic tool for solar atmospheric dynamics and discusses the importance of improved mid-infrared instruments for future research.

Findings

Center-to-limb increase in CO line width supports shock wave presence.

Detection of five-minute oscillations in line strength and Doppler shifts.

Highlighting the necessity of large telescopes with advanced mid-infrared capabilities.

Abstract

We discuss observations of the weak first overtone CO absorption band near 2300 nm with the U.S. National Solar Observatory Array Camera (NAC), a modern mid-infrared detector. This molecular band provides a thermal diagnostic that forms lower in the atmosphere than the stronger fundamental band near 4600 nm. The observed center-to-limb increase in CO line width qualitatively agrees with the proposed higher temperature shocks or faster plasma motions higher in the COmosphere. The spatial extent of chromospheric shock waves is currently at or below the diffraction limit of the available C0 lines at existing telescopes. Five minute period oscillations in line strength and measured Doppler shifts are consistent with the p-mode excitation of the photospheric gas. We also show recent efforts at direct imaging at 4600 nm. We stress that future large-aperture solar telescopes must be teamed with improved, dynamic mid-infrared instruments, like the NAC, to capitalize on the features that motivate such facilities.