Forecasting Solar Energetic Particle Fluence with Multi-Spacecraft Observations

TL;DR

This paper demonstrates that accounting for interplanetary magnetic field corotation significantly improves the accuracy of solar energetic particle fluence forecasts, which is crucial for space weather prediction and safety.

Contribution

It introduces a simple particle transport model that incorporates corotation effects and validates it against STEREO spacecraft observations.

Findings

Ignoring corotation can cause up to tenfold errors in fluence estimates.

The model aligns well with STEREO SEP observations.

Corotation effects are essential for accurate space weather forecasting.

Abstract

Forecasting Solar Energetic Particle (SEP) fluence, as integrated over an SEP event, is an important element when estimating the effect of solar eruptions on humans and technology in space. Current real-time estimates are based on SEP measurements at a single location in space. However, the interplanetary magnetic field corotates with the Sun approximately 13$^\circ$ each day with respect to Earth, thus in 4 days a near-Earth spacecraft will have changed their connection about 60$^\circ$ from the original SEP source. We estimate the effect of the corotation on particle fluence using a simple particle transport model, and show that ignoring corotation can cause up to an order of magnitude error in fluence estimations, depending on the interplanetary particle transport conditions. We compare the model predictions with STEREO observations of SEP events.