SPARX: A modeling system for Solar Energetic Particle Radiation Space Weather forecasting

M S Marsh,N B Crosby,M Dierckxsens,S Dalla,T Laitinen

doi:10.1002/2014sw001120

Abstract

AbstractThe capability to predict the parameters of an SEP event such as its onset, peak flux, and duration is critical to assessing any potential space weather impact. We present a new flexible modeling system simulating the propagation of Solar Energetic Particles (SEPs) from locations near the Sun to any given location in the heliosphere to forecast the SEP flux profiles. Solar Particle Radiation SWx (SPARX) uses an innovative methodology that allows implementation within an operational framework to overcome the time constraints of test particle modeling of SEP profiles, allowing the production of near‐real‐time SEP nowcasts and forecasts, when paired with appropriate near‐real‐time triggers. SPARX has the capability to produce SEP forecasts within minutes of being triggered by observations of a solar eruptive event. The model is based on the test particle approach and is spatially 3‐D, thus allowing for the possibility of transport in the direction perpendicular to the magnetic field. The model naturally includes the effects of perpendicular propagation due to drifts and drift‐induced deceleration. The modeling framework and the way in which parameters of relevance for Space Weather forecasting are obtained are described. The first results from the modeling system are presented. These results demonstrate that corotation and drift of SEP streams play an important role in shaping SEP flux profiles.

Highlights

In recent years, much work within Space Weather (SWx) has focused on the problem of forecasting Solar Energetic Particle (SEP) intensities near Earth and at other locations in the heliosphere, following the observation of a solar eruptive event, such as a solar flare or coronal mass ejection (CME).The flux of ionizing radiation due to Solar Energetic Particles (SEPs) may increase significantly within regions of space, following a solar event
In this paper we describe the methodology behind the model and forecasting system, an example of how the test particle approach has been implemented in an operational context, within the COronal Mass Ejections and Solar Energetic Particles (COMESEP) Alert System, and present examples of its output
We term this a Corotating Solar Energetic Particle Stream (CSEPS) which evolves over time, with the edges of the stream “softening” from a steep density gradient at the beginning of the event, to a more diffuse boundary of the particle stream as the event evolves

Summary

Introduction

Much work within Space Weather (SWx) has focused on the problem of forecasting Solar Energetic Particle (SEP) intensities near Earth and at other locations in the heliosphere, following the observation of a solar eruptive event, such as a solar flare or coronal mass ejection (CME). Particles are injected into the simulation at r = 2 solar radii, with a power law energy spectrum E−γ over the energy range 10–400 MeV, where the spectral index γ may be selected Their initial velocity vectors are randomly distributed in a semihemisphere and oriented outward from the Sun. Concerning the spatial distribution of the injected particles, to enhance computational efficiency, an extended injection region is constructed as a composite of smaller injection region “tiles.” The size of the extended injection region can vary between a minimum size of 6∘ ×6∘ and a larger size that is derived by combining multiple 6∘ ×6∘ injection tiles, with the aim of representing a CME-driven shock region at the Sun. During the simulation, each time a particle crosses a sphere of radius 1 AU its parameters at this time are output such as time, longitude, latitude, kinetic energy, and pitch angle.

Operational Running

Output

Results

Summary and Conclusion