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Nanoflares are thought to be one of the prime candidates that can heat the solar corona to its multimillion kelvin temperature. Individual nanoflares are difficult to detect with the present generation of instruments, but their presence can be inferred by comparing simulated nanoflare-heated plasma emissions with the observed emission. Using HYDRAD coronal loop simulations, we model the emission from an X-ray bright point (XBP) observed by the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS), along with the nearest available observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) and the X-Ray Telescope (XRT) on board the Hinode observatory. The length and magnetic field strength of the coronal loops are derived from the linear force-free extrapolation of the observed photospheric magnetogram by the Helioseismic and Magnetic Imager on board SDO. Each loop is assumed to be heated by random nanoflares, whose magnitude and frequency are determined by the loop length and magnetic field strength. The simulation results are then compared and matched against the measured intensity from AIA, XRT, and MaGIXS. Our model results indicate the observed emission from the XBP under study could be well matched by a distribution of nanoflares with average delay times 1500–3000 s. Further, we demonstrate the high sensitivity of MaGIXS and XRT for diagnosing the heating frequency using this method, while AIA passbands are found to be the least sensitive.

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) sounding rocket experiment launched on 2021 July 30 from the White Sands Missile Range in New Mexico. MaGIXS is a unique solar observing telescope developed to capture X-ray spectral images of coronal active regions in the 6–24 Å wavelength range. Its novel design takes advantage of recent technological advances related to fabricating and optimizing X-ray optical systems, as well as breakthroughs in inversion methodologies necessary to create spectrally pure maps from overlapping spectral images. MaGIXS is the first instrument of its kind to provide spatially resolved soft X-ray spectra across a wide field of view. The plasma diagnostics available in this spectral regime make this instrument a powerful tool for probing solar coronal heating. This paper presents details from the first MaGIXS flight, the captured observations, the data processing and inversion techniques, and the first science results.

The Airborne Infrared Spectrometer (AIR-Spec) offers an unprecedented opportunity to explore the near-infrared (NIR) wavelength range. It has been flown at two total solar eclipses, in 2017 and 2019. The wavelength range of the much-improved instrument on the second flight (2019 July 2) was shifted to cover two density-sensitive lines from S xi . In this paper we study detailed diagnostics for temperature, electron density, and elemental abundances by comparing results from AIR-Spec slit positions above the east and west limbs with those from Hinode/EIS, the PolarCam detector, and SDO/AIA. We find very good agreement in the electron densities obtained from the EIS EUV line ratios, those from the NIR S xi ratio, and those obtained from the polarized brightness PolarCam measurements. Electron densities ranged from log N _e [cm ^−3 ] = 8.4 near the limb to 7.2 at R _0 = 1.3. EIS spectra indicate that the temperature distribution above the west limb is near isothermal at around 1.3 MK, while that on the east has an additional higher- T component. The AIR-Spec radiances in Si x and S xi , as well as the AIA data in the 171, 193, and 211 Å bands, are consistent with the EIS results. EIS and AIR-Spec data indicate that the sulfur abundance (relative to silicon) is photospheric in both regions, confirming our previous results of the 2017 eclipse. The AIA data also indicate that the absolute iron abundance is photospheric. Our analysis confirms the importance of the diagnostic potential of the NIR wavelength range and that this important wavelength range can be used reliably and independently to determine coronal plasma parameters.

Recent observations by the Interface Region Imaging Spectrograph (IRIS) have revealed pockets of hot gas (∼2–8 × 104 K) potentially resulting from magnetic reconnection in the partially ionized lower solar atmosphere (IRIS bombs; IBs). Using joint observations between IRIS and the Chinese New Vacuum Solar Telescope, we have identified 10 IBs. We find that 3 are unambiguously and 3 others are possibly connected to Ellerman bombs (EBs), which show intense brightening of the extended wings without leaving an obvious signature in the core. These bombs generally reveal the following distinct properties: (1) the O iv 1401.156 Å and 1399.774 Å lines are absent or very weak; (2) the Mn i 2795.640 Å line manifests as an absorption feature superimposed on the greatly enhanced Mg ii k line wing; (3) the Mg ii k and h lines show intense brightening in the wings and no dramatic enhancement in the cores; (4) chromospheric absorption lines such as Ni ii 1393.330 Å and 1335.203 Å are very strong; and (5) the 1700 Å images obtained with the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory reveal intense and compact brightenings. These properties support the formation of these bombs in the photosphere, demonstrating that EBs can be heated much more efficiently than previously thought. We also demonstrate that the Mg ii k and h lines can be used to investigate EBs similarly to , which opens a promising new window for EB studies. The remaining four IBs obviously have no connection to EBs and they do not have the properties mentioned above, suggesting a higher formation layer, possibly in the chromosphere. [ABSTRACT FROM AUTHOR]