A new method for estimating global coronal wave properties based on their interaction with solar coronal holes

Among the effects of interactions between global coronal waves (CWs) and coronal holes (CHs) is the formation of reflected and transmitted waves. Observations of such events provide us with measurements of different CW parameters, such as phase speed and intensity amplitudes. However, several of these parameters are provided with only intermediate observational quality, whereas other parameters, such as the phase speed of transmitted waves, can hardly be observed in general. We present a new method to estimate crucial CW parameters, such as density and phase speed of reflected as well as transmitted waves, Mach numbers and density values of the CH’s interior, by using analytical expressions in combination with the most basic and most accessible observational measurements available. The transmission and reflection coefficients were derived from linear theory and used to calculate estimations for phase speeds of incoming, reflected, and transmitted waves. The obtained analytical expressions were validated by performing numerical simulations of CWs interacting with CHs. This new method enables us to determine in a fast and straightforward way reliable CW and CH parameters from basic observational measurements which provides a powerful tool to better understand the observed interaction effects between CWs and CHs.

Single and Multiwavelength Detection of Coronal Dimming and Coronal Wave Using Faster R-CNN

Automatic detection of solar events, especially uncommon events such as coronal dimming (CD) and coronal wave (CW), is very important in solar physics research. The CD and CW are not only related to the detection of coronal mass ejections (CMEs) but also affect space weather. In this paper, we have studied methods for automatically detecting them. In addition, we have collected and processed a dataset that includes the solar images and event records, where the solar images come from the Atmospheric Imaging Assembly (AIA) of Solar Dynamics Observatory (SDO) and the event records come from Heliophysics Event Knowledgebase (HEK). Different from the methods used before, we introduce the idea of deep learning. We train single-wavelength and multiwavelength models based on Faster R-CNN. In terms of accuracy, the single-wavelength model performs better. The multiwavelength model has a better detection performance on multiple solar events than the single-wavelength model.

Propagation of a global coronal wave and its interaction with large-scale coronal magnetic structures

Context. Global coronal waves associated with solar eruptions (the so-called EIT waves) often encounter coronal holes and solar active regions and interact with these magnetic structures. This interaction leads to a number of observed effects such as wave reflection and transmission. Aims. We consider the propagation of a large-scale coronal shock wave and its interaction with large-scale non-uniformities of the background magnetic field and plasma parameters. Methods. Using the Lare2d code, we performed 2.5-dimensional simulations of the interaction of a large-scale single-pulse fast-mode magnetohydrodynamic shock wave of weak-to-moderate intensity with the region of enhanced Alfvén speed as well as with that of reduced Alfvén speed. We analysed simple models of non-uniformity and the surrounding plasma to understand the basic effects in wave propagation. Results. We found the reflected waves of plasma compression and rarefaction, transmitted waves that propagate behind or ahead of the main part of the wave, depending on properties of the plasma non-uniformity, and secondary wave fronts. The obtained results are important to the correct interpretation of the global coronal wave propagation in the solar corona, understanding of theoretical aspects of the interaction of large-scale coronal shock waves with large-scale coronal magnetic structures, and diagnostics of coronal plasma parameters.