卷 49, 编号 4 (2023)

We investigate the ionization sources of the diffuse gas at various galactic heights in galaxies with various stellar masses, H
 luminosities, and specific star formation rates. For this purpose, we use the SDSS-IV MaNGA DR16 data and the theoretical models of photoionization and shock ionization from the Mexican Million Models database (3MdB). Our final sample contains 239 edge-on galaxies, which makes the results statistically significant and allows even great galactic heights to be investigated using the spectra stacking procedure. Using diagnostic diagrams, we show that for galaxies of all the types being investigated the behavior of the diffuse ionized gas is adequately described by the models of photoionization by young OB stars and hot low-mass evolved stars. However, in galaxies with high stellar masses or passive star formation shocks can also contribute to the ionization. For galaxies of all the types being investigated we find that the flux from OB stars and the ionization parameter decrease with height, while the relative contribution of hot low-mass evolved stars to the ionization increases. The greatest difference of the contributions from these sources to the gas ionization is observed between galaxies with different specific star formation rates and different stellar masses: hot low-mass evolved stars are the main source of gas ionization in galaxies with passive star formation (and with high stellar masses), whereas in galaxies with active star formation (and with lower stellar masses) OB stars are a decisive factor of the diffuse gas ionization.

For both periods of the double-mode Cepheid V371 Per and for the Cepheid OGLE-LMC-CEP-2132 we have constructed 
 diagrams spanning a time interval of 126 and 119 years, respectively. The 
 diagrams have the shape of parabolas, which has allowed us for the first time to determine the quadratic light elements and to calculate the rates of evolutionary changes in their periods: @ s yr-1 and @ s yr-1 for the fundamental mode and the first overtone of V371 Per, @espectively, and @ s yr-1  for OGLE-LMC-CEP-2132, in agreement with the results of theoretical calculations for the first crossing of the instability strip. The pulsation stability test proposed by Lombard and Koen has confirmed that the increase in the periods is real.

Based on the model of a collapsing magnetic trap, we consider the influence of the temperature of a Maxwellian flare plasma on the efficiency of the betatron acceleration of quasi-thermal fast electrons in the cusp region of coronal loops. We show that an increase in the temperature causes a sharp growth (by 6–8 orders of magnitude) in the number density of quasi-thermal electrons which are capable of overcoming the ‘‘Coulomb loss barrier.’’ This suggests the necessity of background plasma preheating in the cusp region to 
 MK, for which the betatron mechanism can be responsible. We discuss the connection between the impulsive phase of flare energy release and the X-ray precursors of solar flares.