This study analyzed the Doppler shift in the solar spectrum using the Interface Region Imaging Spectrograph (IRIS). Two types of oscillations were investigated: long period damp and short period damp. The researchers observed periodic perturbations in the Doppler velocity oscillations of bright points (BPs) in the chromosphere and transition region (TR). Deep learning techniques were used to examine the statistical properties of damping in different solar regions. The results showed variations in damping rates, with higher damping in coronal hole areas. The study provided insights into the damping behavior of BPs and contributed to our understanding of energy dissipation processes in the solar chromosphere and TR.

Flares on the Sun are often associated with ejected plasma: these events are known as coronal mass ejections (CMEs). These events, although are studied in detail on the Sun, have only a few dozen known examples on other stars, mainly detected using the Doppler-shifted absorption/emission features in Balmer lines and tedious manual analysis. We present a possibility to find stellar CMEs with the help of high-resolution solar spectra.

A comparative analysis of sub-THz emission of stellar flares from red dwarfs has been carried out. ALMA observations indicate that the sub-THz emission flux from stellar flares with a duration of 10 s is an order of magnitude greater than for solar flares. The sub-THz emission is linearly polarized and decreases with frequency. The degree of polarization can reach tens of percent. We show that these types of spectrum slopes and linear polarization can be caused by the synchrotron emission of ultrarelativistic electrons. The origin of the observed relationships between sub-THz, low frequency radio, and X-ray emissions of stellar flares are discussed.

Coronal rain is formed in the post-impulsive phase of solar flares due to the thermal instability of coronal plasma in EUV loops. As a result, the sub-terahertz (sub-THz) emission flux in the post-impulsive phase of solar flares can be increased due to the increasing of the optical thickness of the thermal source. This suggests that sub-THz observations can be used as a diagnostic tool for coronal rain.

This work is aimed to analyse the relationship between the sub-THz radiation and variations of the temperature and the emission measure of the EUV coronal plasma during the post-impulsive phase of the SOL2022-05-04T08:45 solar flare.

Based on the two-dimensional temperature and emission measure distributions obtained from the AIA/SDO EUV intensity data, it was found that the temperature decreases whereas the emission measure reaches the maximum near the sub-THz flare peak. This circumstance and peculiarities of the radiation time profiles in different wave ranges show evidence in favor of the significant contribution of the thermal coronal loop plasma to the flare sub-THz radiation at least for some flare events. The sub-THz emission may be associated with a coronal condensation, accompanied by the formation of coronal rain.

The origin of the sub-terahertz (sub-THz) component of radio emission from solar flares, which is characterized by the increase flux with frequency in the 100-400 GHz range, is considered. On the basis of equations of 1D non-LTE radiation hydrodynamics we simulated the altitude distribution of the plasma density and temperature inside the flare loop caused by the interaction of non-stationary beam of accelerated electrons in the form of a triangular pulse with the chromospheric plasma. The FLARIX numerical code was used to calculate the dynamics of the flare plasma parameters at different heights which are compared with the RADYN numerical code. We found that the characteristic heights of the formation of sub-THz emission vary over a wide range with time for both codes. The main contribution to the sub-THz emission comes from the chromospheric and transition region plasma with temperatures of 104–105K.

Solar-type stars, including the Sun, have magnetic fields that extend from their interiors to the surface and beyond, influencing both the stellar activity and interplanetary medium. Magnetic activity phenomena, such as coronal mass ejections (CMEs), significantly impacts space weather. These CMEs, composed of plasma clouds with magnetic fields ejected from the stellar corona, pose a potential threat to planets by affecting their magnetosphere and atmosphere. Despite advancements in detecting stellar CMEs, detection remains limited. We focus on understanding CME propagation by analyzing key parameters like position, velocities, and the configuration of stellar magnetic fields. Using spot transit mapping, we reconstruct magnetograms for Kepler-63 and Kepler-411, employing the ForeCAT model to simulate CME trajectories from these stars. Results indicate that CME deflections generally decrease with radial velocity and increase with ejection latitude. Additionally, stars with stronger magnetic fields, such as Kepler-63, tend to cause more significant CME deflections.

Stellar activity depends on multiple parameters one of which is the age of the star. The members of open clusters are good targets to observe the activity at a given age of the stars since their ages are more precisely determined than that of field stars. Choosing multiple clusters, each with different age, gives us insight to the change in activity during the lifetime of stars. With the analysis of these stars we can also refine the parameters of gyrochronology (Barnes 2003), which is a method for estimating the age of low-mass, main sequence stars from their rotation periods.