The ambient solar magnetic field plays a key role in heliophysics in general and in space weather in particular. It is especially important for the propagation of solar energetic particles (SEPs), guiding them along the magnetic field from their generation near the Sun to locations in the heliosphere. Solar Particle Events (SPEs), arising from SEPs produced by solar eruptions, represent a significant hazard for humans and technological infrastructure. Providing longer range (2-3 day) forecasts of SPEs and/or all-clear periods is highly desirable but difficult to achieve, because a forecast must occur prior to the start of the eruption. Given a flare/CME forecast, a major source of uncertainty in SPEs is the magnetic connectivity. The goal of our project is to develop CORHEL-E (CORHEL with Evolution). CORHEL-E will provide time-dependent coronal and solar wind solutions, driven by evolving boundary conditions provided by photospheric flux transport models. In phase I of our project, we will demonstrate time-dependent estimates of magnetic connectivity of Earth for specific time periods, using ensembles of solutions to assess variability and uncertainty. At the completion of phase II, we will provide CORHEL-E to the CCMC, capable of running continuously. Given a flare/eruption forecast from a threatening active region, CORHEL-E will allow the user to assess the regional connectivity and likelihood that SEPs can reach Earth or other heliospheric locations of interest. Using STAT, an eruption can actually be simulated and particle fluxes predicted. Longer term, our vision for an operational capability is a near-real time model of the solar corona and inner heliosphere, updated with new magnetic (and other) observations as they become available. CMEs would be initiated in the model after being observed, and then be simulated as part of the continuous solution. The development of CORHEL-E is a crucial next step towards this goal.
SPEs are of particular concern to NASA SRAG, which is responsible for ensuring that the radiation exposure received by astronauts remains below established safety limits. Connectivity of the solar magnetic field plays a crucial role in determining where the particles propagate. CORHEL-E will provide a tool for assessing this connectivity. It complements tools presently used in operations such as MAG4, and can be used in conjunction with the SPE Threat Assessment Tool (STAT) already delivered to the CCMC at NASA GSFC.
SPEs are of concern to many government and commercial entities dependent on satellites and aircraft. For example, NOAA SWPC provides space weather information to customers requiring forecasting of SPEs. The Air Force is also interested in mitigation strategies for SPEs. CORHEL-E can improve longer range forecasting of SPE events/all clear forecasts for these agencies as well.