Transfer Learning Aurora Image Classification and Magnetic Disturbance
Evaluation
Abstract
We develop an open source algorithm to apply Transfer learning to Aurora
image classification and Magnetic disturbance Evaluation (TAME). For
this purpose, we evaluate the performance of 80 pretrained neural
networks using the Oslo Auroral THEMIS (OATH) data set of all-sky
images, both in terms of runtime and their features’ predictive
capability. From the features extracted by the best network, we retrain
the last neural network layer using the Support Vector Machine (SVM)
algorithm to distinguish between the labels “arc”, “diffuse”,
“discrete”, “cloud”, “moon” and “clear sky / no aurora”. This
transfer learning approach yields 73% accuracy in the six classes; if
we aggregate the 3 auroral and 3 non-aurora classes, we achieve up to
91% accuracy. We apply our classifier to a new dataset of 550,000
images and evaluate the classifier based on these previously unseen
images. To show the potential usefulness of our feature extractor and
classifier, we investigate two test cases: First, we compare our
predictions for the “cloudy” images to meteorological data and second
we train a linear ridge model to predict perturbations in Earth’s
locally measured magnetic field. We demonstrate that the classifier can
be used as a filter to remove cloudy images from datasets and that the
extracted features allow to predict magnetometer measurements. All
procedures and algorithms used in this study are publicly available, and
the code and classifier are provided, which opens possibility for large
scale studies of all-sky images.