Understanding SEP properties at 1 AU through neutron monitor data modeling

Authors: Plainaki[a][b], M. Laurenza[a], H. Mavromichalaki[b], M. Storini[a]

Affiliation:

[a]INAF-IAPS, Via del Fosso del Cavaliere, 00133, Rome, Italy

[b]Nuclear and Particle Physics Section, Physics Dpt., National and Kapodistrian University of Athens, Greece

Abstract:

Ground-level enhancements (GLEs) are short-term increases of the cosmic ray intensity registered at the ground by particle detectors, such as ionization chambers, muon, and neutron monitors, related to the arrival in the terrestrial environment of solar relativistic particles. GLE events are related to the most energetic class of solar energetic particle (SEP) events, associated with both solar flares and coronal mass ejections (e.g. [1]), and requiring acceleration processes that produce particles with energies ≥500 MeV upon entry in the Earth’s atmosphere.

GLE data recorded by the worldwide neutron monitor network are a useful resource for space weather modeling during solar extreme events. Among the numerous space weather models available to the community, the NMBANGLE PPOLA [2] is a modified version of the original NMBANGLE model [3], based on Dorman’s coupling coefficient method [4], aiming at the calculation of the SEP properties during GLEs through the exclusive use of ground-based neutron monitor data from the worldwide network. Technically, the model treats this network as an integrated omnidirectional spectrometer and solves the inverse problem of the SEP-GLE coupling. In particular, the NMBANGLE PPOLA model dynamically calculates the SEP spectrum and flux spatial distribution at some altitude in the atmosphere, assuming a power-law in rigidity primary spectrum with two free parameters (spectral index and amplitude) and a narrow-beam angular distribution for the SEP flux direction [2]. In this paper, we present a short overview of the application of the NMBANGLE PPOLA model to different GLEs, discussing the derived characteristics of the relativistic SEP fluxes. We also discuss some improvements of the current model in the context of Space Weather efficient monitoring.

 

[1]       Laurenza M. et al. 2009 Space Weather 7 S04008 doi:10.1029/2007SW000379

[2]       Plainaki C, et al. 2010 Solar Phys. 264 239

[3]       Plainaki C, et al.  2007 J. Geophys. Res. A 112 4102

[4]       Dorman LI 2004 Astrophys. Space Sci. Libr. 303