Detection of kink oscillations in solar coronal loops by a CNN-LSTM neural network

Abstract

A hybrid machine learning model which combines a shallow convolutional neural network and a long short-term memory network (CNN--LSTM), has been developed to automate the detection of kink oscillations in coronal plasma loops within large volumes of high-cadence sequences of imaging data. The network was trained on a set of 10,000 synthetic data cubes designed to mimic sequences of coronal images, achieving an accuracy greater than 98\% on this synthetic dataset. The model was then applied to detect kink oscillations in real data cubes of coronal active regions observed with SDO/AIA in the 171~\AA\ channel. This dataset consisted of 50 samples with visually detected kink oscillations and 128 samples without. Each sample covered an area of 260$\times$260~pixels in the spatial domain and a duration of 30~min with a 12~s cadence in the time domain. Both off-limb and on-disk regions of interest were used. The data were pre-processed by median filtering in the time domain, and Gaussian smoothing and Contrast Limited Adaptive Histogram Equalization in the spatial domain. In the real dataset, the performance of the model was 83.7\%.The model is fully available in open access. We regard the CNN--LSTM model developed as a first step toward creating robust tools for routine solar coronal data mining in the context of coronal oscillation study.