High Resolution Imaging Spectroscopy of a Tiny Sigmoidal Mini-filament Eruption

Minifilament (MF) eruption producing small jets and micro-flares is regarded as an important source for coronal heating and the solar wind transients through studies mostly based on coronal observations in the extreme ultraviolet (EUV) and X-ray wavelengths. In this study, we focus on the chromospheric plasma diagnostics of a tiny minifilament in quiet Sun located at [71'', 450''] on 2021--08--07 at 19:11 UT observed as part of the ninth encounter of the PSP campaign. Main data obtained are the high cadence, high resolution spectroscopy from the Fast Imaging Solar Spectrograph (FISS) and high-resolution magnetograms from the Near InfraRed Imaging Spectropolarimeter (NIRIS) on the 1.6~m Goode Solar Telescope (GST) at Big Bear Solar Observatory (BBSO). The mini-filament with size ~1''×5'' and a micro-flare are detected in both the Hα line center and SDO/AIA 193, 304~\ images. On the NIRIS magnetogram, we found that the cancellation of a magnetic bipole in the footpoints of the minifilament triggered its eruption in a sigmoidal shape. By inversion of the \ and Ca { ii} spectra under the embedded cloud model, we found a temperature increase of 3,800 K in the brightening region, associated with rising speed average of MF increased by 18~km~s⁻¹. This cool plasma is also found in the EUV images. We estimate the kinetic energy change of the rising filament as 1.5×10²⁵$~ergs, and thermal energy accumulation in the MF, 1.4$×10²⁵~ergs. From the photospheric magnetograms, we find the magnetic energy change is 1.6×10²⁶$~ergs across the PIL of converging opposite magnetic elements, which amounts to the energy release in the chromosphere in this smallest two-ribbon flare ever observed.