Abstract DGP2026-116

The solar corona is the extension of the solar atmosphere away from the Sun, and the source of the solar wind, which shapes the environments of all objects in interplanetary space. In particular, it is also the source of dynamic events such as Coronal Mass Ejections (CMEs) and solar flares, which can have a significant  impact on magnetic fields for Earth-orbiting satellites and other planets. At present, total solar eclipses (TSEs) offer the best platform to observe the solar corona in the visible wavelength range. Like all astronomical observations, imaging and spectroscopy are the main remote sensing tools for exploring the physical properties of the corona.

This talk will focus on spectra obtained during TSEs using a novel design, namely a partially multiplexed high-resolution spectrometer to obtain high-resolution spectra (λ/∆λ ≤ 20000, slit-width dependent) in the wavelength range from the UV to the near IR (300 to 1100 nm). This spectrometer enabled the investigation of the elemental composition of the corona, the ionic temperature of its different species through spectral line widths and the dynamics of the coronal plasma through Doppler shifts.

The instrument is a grating spectrometer using a mirror slit with a slit width below 100 µm for the incoming light. The exit plane is monitored using a low noise CCD or CMOS camera with the appropriate pixel density. Several such devices (1 …3) are used simultaneously to span the desired wavelength range using specially corrected lens or mirror optics and appropriate filters. The slit mirror deflects the incoming light such that the position of the Sun with respect to the slit can be monitored with a separate camera. The spectrometers are operated in very high order (> 40). This has the advantage that the spectral resolution is larger by a factor of the order number compared to a standard spectrometer in first order using an identical slit width. Since the spectra consist of groups of lines containing multiple (3 …6) spectral orders, their analysis is significantly more difficult than that of a standard spectrometer. The assignment of the order number is performed using a special algorithm.

During totality the entrance slit of the spectrometer (in the focus of the entrance optics) is scanned over the corona, either by computer-controlled programming of the mount or by stopping the tracking of the mount during totality. Consequently, the different slit positions across the corona can be combined to generate a the 2D distribution of elemental composition, ionic temperatures and velocities, of the coronal area scanned.

Examples from TSE observations in Svalbard (2015), the USA (2017, 2024) and Western Australia (2023) will be presented. The 2023 TSE was observed with a spectrometer airborne to approx. 450 m by a kite, the 2024 TSE was observed using spectrometers mounted on a high-altitude aircraft (WB57) research aircraft operated by NASA. The application of such devices for planetary research will also be discussed.