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Abstract. In this work, solar¯are energetic particlē uxes (E e ³ 42 keV) observed by the HI-SCALE instrument onboard Ulysses, a spacecraft that is probing the heliosphere in 3-D, are utilized as diagnostics of the large-scale structure and topology of the interplanetary magnetic ®eld (IMF) embedded within two well-identi®ed interplanetary coronal mass ejection (ICME) structures. On the basis of the energetic solar¯are particle observations ®rm conclusions are drawn on whether the detected ICMEs have been detached from the solar corona or are still magnetically anchored to it when they arrive at 2.5 AU. From the development of the angular distributions of the particle intensities, we have inferred that portions of the ICMEs studied consisted of both open and closed magnetic ®eld lines. Both ICMEs present a ®lamentary structure comprising magnetic ®laments with distinct electron anisotropy characteristics. Subsequently, we studied the evolution of the anisotropies of the energetic electrons along the magnetic ®eld loop-like structure of one ICME and computed the characteristic decay time of the anisotropy which is a measure of the amount of scattering that the trapped electron population underwent after injection at the Sun.

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Abstract. This study presents an interplanetary particle (electrons and ions) event which was detected at 4.7 AU by the instruments on the Ulysses spacecraft inside a corotating interaction region between a fast and slow solar wind stream. A particle propagation channel is identified where the particles can propagate from the Sun nearly scatter free within a region bounded by tangential discontinuities. This channel is found to be rooted in the vicinity of a solar active region where the flare associated with the interplanetary event was produced. The ions (energy over 600 keV) detected inside this channel are shown to be of solar origin: dispersion occurs in the proton arrival time versus proton energy, there is a strong anisotropy in the proton pitch angle distribution, and a hard energy-spectrum for the protons. The electrons were already present when the spacecraft crossed the structure. The chemical composition is also indicative of a solar origin, with a decrease in the 4He/H (4He in the energy range 389-1278 keV and H in the range 480-1204 keV) abundance ratio by a factor of 2 inside the channel. Mapped back to the solar surface, the size of the propagation channel is estimated to be of the order of 30,000 km. The channel is found to be magnetically quiet, without a preferred direction for the minimum of variance.

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Fine time resolution observations of the angular distributions of the intensities of energetic electrons (220 < E e < 500 keV) by the IMP-7 and 8 spacecraft during the onsets of solar electron events and the technique of mapping the solar wind to the solar corona have been incorporated in this work in order to obtain the large-angle scattering distance of these particles under different configurations of the large scale structure of the interplanetary medium. It is found that in the presence of stream-stream interaction regions with compressed magnetic fieids beyong 1 AU, the large-angle scattering is determined by the distance along the streamlines from the spacecraft to their intersection by a faster solar wind stream. In cases of diverging magnetic fields the estimated large-angle scattering distance exceeds 1 AU.

Abstract. In this work, solar¯are energetic particlē uxes (E e ³ 42 keV) observed by the HI-SCALE instrument onboard Ulysses, a spacecraft that is probing the heliosphere in 3-D, are utilized as diagnostics of the large-scale structure and topology of the interplanetary magnetic ®eld (IMF) embedded within two well-identi®ed interplanetary coronal mass ejection (ICME) structures. On the basis of the energetic solar¯are particle observations ®rm conclusions are drawn on whether the detected ICMEs have been detached from the solar corona or are still magnetically anchored to it when they arrive at 2.5 AU. From the development of the angular distributions of the particle intensities, we have inferred that portions of the ICMEs studied consisted of both open and closed magnetic ®eld lines. Both ICMEs present a ®lamentary structure comprising magnetic ®laments with distinct electron anisotropy characteristics. Subsequently, we studied the evolution of the anisotropies of the energetic electrons along the magnetic ®eld loop-like structure of one ICME and computed the characteristic decay time of the anisotropy which is a measure of the amount of scattering that the trapped electron population underwent after injection at the Sun.