Elliptically polarized transverse magnetohydrodynamic waves in quiet-region thread-like structures observed using the MiHI prototype

Transverse magnetohydrodynamic (MHD) waves are often observed in the solar chromosphere with two different methods, the imaging method and the spectroscopic method. The velocity amplitudes of line-of-sight (LOS) oscillations inferred from the spectroscopic method, however, are usually found to be much smaller than those of plane-of-sky (POS) oscillations inferred from the imaging method. In order to understand the nature of this discrepancy, we compared these two types of oscillations by applying both methods to the same features. Using the Microlensed Hyperspectral Imager (MiHI) prototype, which provides data with an unprecedentedly high spatial, spectral, and temporal resolution and enables simultaneous acquisition of images and spectra, we detected transverse waves in thread-like structures seen in a quiet-Sun region. To investigate the nature of these oscillations, we analyzed three distinct events. Our analysis revealed that the structures oscillate both in the POS and the LOS directions, with periods of about 2.3 minutes. Notably, the velocity amplitudes measured by the spectroscopic method tend to be smaller than those measured by the imaging method, with differences of up to a factor of 2.3. Moreover, the phase differences between the two types of velocity oscillations vary significantly, with values of 209°, –75°, and 84° for events 1, 2, and 3, respectively. These findings indicate that the transverse MHD waves are elliptically polarized, and that larger amplitude oscillations occur in the POS direction. Our simultaneous detection of transverse MHD waves in two directions suggests the possibility of additional energy transport that may previously have been overlooked.