Energetic Particle Observations and Propagation in the Three-Dimensional Heliosphere During the 2006 December Events

Abstract

We report observations of solar energetic particles obtained by the HI-SCALE and COSPIN/LET instruments onboard Ulysses during the period of isolated but intense solar activity in 2006 December, in the declining phase of the solar activity cycle. We present measurements of particle intensities and also discuss observations of particle anisotropies and composition in selected energy ranges. Active Region 10930 produced a series of major solar flares with the strongest one (X9.0) recorded on December 5 after it rotated into view on the solar east limb. Located over the South Pole of the Sun, at >72 • S heliographic latitude and 2.8 AU radial distance, Ulysses provided unique measurements for assessing the nature of particle propagation to high latitudes under near-minimum solar activity conditions, in a relatively undisturbed heliosphere. The observations seem to exclude the possibility that magnetic field lines originating at low latitudes reached Ulysses, suggesting either that the energetic particles observed as large solar energetic particle (SEP) events over the South Pole of the Sun in 2006 December were released when propagating coronal waves reached high-latitude field lines connected to Ulysses, or underwent perpendicular diffusion. We also discuss comparisons with energetic particle data acquired by the STEREO and Advanced Composition Explorer in the ecliptic plane near 1 AU during this period.

ASSOCIATION OF 3He-RICH SOLAR ENERGETIC PARTICLES WITH LARGE-SCALE CORONAL WAVES

“…It has been noted that the connection to a distant source can not be sufficiently explained by a divergence of the coronal field lines below the source surface (Wiedenbeck et al 2013). The magnetic connection controlled by large scale EUV waves in the corona has been discussed in several LSEP events (e.g., Torsti et al 1999;Krucker et al 1999;Malandraki et al 2009;Rouillard et al 2012;Nitta 2012;Park et al 2013;Richardson et al 2014) and recently suggested as a possible mechanism also for 3 Herich SEPs (Nitta et al 2015). We examined magnetic connection combining the PFSS extrapolations of coronal field with Parker spiral model of IMF.…”

Solar Energetic Particles and Associated EIT Disturbances in Solar Cycle 23

“…In a recent, very detailed, multi-spacecraft analysis Rouillard et al (2012) show that the arrival time of the CME flank and the associated EIT wave at the respective footpoints of the spacecraft-connected Parker spirals could explain the arrival timing of the first energetic electrons and protons at different spacecraft. Malandraki et al (2009) argued that both electrons and protons observed in December 2006 by Ulysses and Advanced Composition Explorer (ACE), in association with an active region near the eastern limb, could be attributed to EIT disturbances reaching magnetic field lines connected to the spacecraft.…”

Solar Energetic Particles and Space Weather: Science and Applications

“…Comparison of simultaneous SEP observations near the ecliptic plane with the Ulysses observations at high latitudes showed that most events that produce large high-energy (>20 MeV) proton and near-relativistic electron flux increases near Earth also produce flux increases at high latitudes, regardless of the longitudinal, latitudinal and radial separation between the s/c, although with somewhat lower maximum intensities and slower rise at Ulysses (McKibben et al 2003;Lario and Pick 2008;Malandraki et al 2009). Particle anisotropies during SEP events at high latitudes are typically directed outward from the Sun and aligned with the local magnetic field (McKibben et al 2003;Malandraki et al 2009). …”