Prediction of Geomagnetic Auroral Electrojet Indices with Long
Short-Term Memory (LSTM) Recurrent Neural Network
Abstract
Space weather phenomena occur from the Sun to the Earth with damaging
impacts on ground-based and space-borne technological infrastructure.
The geomagnetic auroral electrojet indices, AU, AL, and AE, have been
widely used for monitoring space weather and geomagnetic activities
during space storms and substorms. The time series data of solar wind
monitored by upstream satellite and ground-based auroral electrojet
indices form the input-output system characterizing the dynamic coupling
among solar wind, Earth’s magnetosphere, and ionosphere. The data-driven
predictions of auroral electrojet indices during geomagnetic storms and
substorms face the challenges of capturing the variations of ionospheric
electrojet current driven by multiple solar wind variables and are
modeled as a coupled complex system with finite and variable memory. The
recurrent neural network (RNN) based Long Short-Term Memory (LSTM)
machine learning algorithm is well suited to classify, process, and make
predictions of the coupled solar wind-magnetosphere-ionosphere system by
preserving important information from earlier parts of the coupled time
series and carrying it forward. In this study, an RNN-based LSTM model
has been built to predict the time series of AE/AL indices with
multi-variate solar wind inputs. Both 5-minute and hourly long-term time
series data from the NASA OMNI database were used to drive the LSTM
model. The coupled time series data are divided into training and
testing datasets. The Root-Mean-Square-Error (RMSE) between the
predicted and actual AE/AL indices of the testing sets was used to
evaluate the roles of the number of layers in the LSTM, memory length of
the coupled system, prediction time, and different combinations of solar
wind input parameters (magnetic field, velocity, and density). The
performance of the LSTM model in predicting AL/AE indices during major
geomagnetic storm and substorm events is analyzed. The differences and
challenges of applying LSTM to predict 5-min and hourly AE/AL indices
are also discussed.