SEPs from Heliosphere to Magnetosphere

Candidate SHINE co-convener: Janet Luhmann <jgluhman [at] ssl.berkeley.edu>

Candidate GEM co-convener: Mary Hudson <mary.hudson [at] dartmouth.edu>

A brief but productive discussion of the problem of SEPs (Solar Energetic Particles) from their production in the heliosphere to their geospace effects, was held on Thursday, June 26. This is a particularly rich and appropriate GEM/SHINE topical area because it involves connecting a chain of processes occurring in the solar corona and interplanetary medium to responses in the middle atmosphere, via the magnetosphere. The large solar proton events that are of most interest were the main focus of the discussion, which was kicked off with an overview of the heliospheric end by David Lario (JHUAPL). David described the still outstanding problems of a lack of understanding of the details of the particle production, energization and transport. This was followed by a more specific discussion by David Ruffolo (Mahidol Univ.) of the most energetic of SEP events, GLEs or Ground Level Events, which are detected on the ground by Neutron Monitors. The major events which represent the deepest penetrations of SEP event effects typically occur only once or twice per solar cycle, and the reason for their particularly great fluxes of protons at high energies reaching into the GeV range is still a subject of investigation. These events have certain properties such as prompt arrival and high antisunward, field-aligned anisotropies that affect the way they are perceived on the ground. Brian Kress (Dartmouth) spoke on the magnetospheric access of the SEPs, and coincidentally, on the effect of the particle flux anisotropy on access to high latitudes along open field lines. Simulations of the proton access in MHD magnetosphere models show geomagnetic cutoffs will appear different in measurements when significant anisotropies exist. Thus ground (and LEO and atmosphere) exposure to SEP effects for the most energetic events is somewhat less predictable using cutoffs computed for isotropic incident fluxes. Tamitha Mulligan (Aerospace) spoke on several recent large SEP events observed in both the heliosphere and magnetosphere. She showed that there were features in the magnetospheric time profiles not present in the interplanetary time profiles, suggesting magnetospheric modulation of the intrinsic time profiles, perhaps. Finally, Stan Solomon (HAO) spoke on the recent modeling of SEP event effects in the atmosphere using the WACCM (Whole Atmosphere Community Climate Model). This model can trace the 3D dynamical and chemical effects of SEP events from the top of the thermosphere to the ground. Stan showed some results from Jackman and coworkers for some previous large proton events. The NO and ozone chemistry effects can be seen to last for months after the event, and to make their way well into the middle atmosphere- and occasionally into the stratosphere. The potential for tracing this full chain of SEP physics from end to end has never been greater.