The large longitudinal spread of solar energetic particles during the January 17, 2010 solar event

We investigate multi-spacecraft observations of the January 17, 2010 solar energetic particle event. Energetic electrons and protons have been observed over a remarkable large longitudinal range at the two STEREO spacecraft and SOHO suggesting a longitudinal spread of nearly 360 degrees at 1AU. The flaring active region, which was on the backside of the Sun as seen from Earth, was separated by more than 100 degrees in longitude from the magnetic footpoints of each of the three spacecraft. The event is characterized by strongly delayed energetic particle onsets with respect to the flare and only small or no anisotropies in the intensity measurements at all three locations. The presence of a coronal shock is evidenced by the observation of a type II radio burst from the Earth and STEREO B. In order to describe the observations in terms of particle transport in the interplanetary medium, including perpendicular diffusion, a 1D model describing the propagation along a magnetic field line (model 1) (Dr\"oge, 2003) and the 3D propagation model (model 2) by (Dr\"oge et al., 2010) including perpendicular diffusion in the interplanetary medium have been applied, respectively. While both models are capable of reproducing the observations, model 1 requires injection functions at the Sun of several hours. Model 2, which includes lateral transport in the solar wind, reveals high values for the ratio of perpendicular to parallel diffusion. Because we do not find evidence for unusual long injection functions at the Sun we favor a scenario with strong perpendicular transport in the interplanetary medium as explanation for the observations.Comment: The final publication is available at http://www.springerlink.co

Applications of a phoswich-based detector for fast (similar to 1-10 MeV) solar neutrons for missions to the inner heliosphere

We describe a phoswich-based detector concept for studies of low energy (∼1–10 MeV) solar neutrons in the innermost heliosphere (R \u3c∼ 0.5 AU). The detector has applications both as a very low mass (\u3c∼1 kg), low power (∼1–2 W) stand-alone instrument, and as a component to enhance the capabilities of more sophisticated instruments, for example, the fast neutron imaging telescope instrument described by Moser et al. [Moser, M.R., Flückiger, E.O., Ryan, J.M., et al. A fast neutron imaging telescope for inner heliosphere missions. Adv. Space Res., in press, this issue, doi:10.1016/j.asr.2005.03.037]. In its most basic form, the detector consists of a small volume (∼1 cm3) of fast organic scintillator completely surrounded by a slow inorganic scintillator. The dimensions of the organic scintillator are chosen to minimize multiple n–p scatterings while retaining adequate sensitivity. The inorganic scintillator provides anti-coincidence protection against energetic charged particles. A single PM tube views light from both scintillators. Pulse shape analysis identifies as potential neutrons those events where only the organic scintillator contributes to the signal. The signal size corresponds to the energy of the recoil proton from an n–p elastic scatter, on average half the energy of the incident neutron. An instrument based on this concept would provide measurements of the neutron flux and, through statistical analysis of recoil proton energies, basic information about the neutron spectrum