Abstract
We present observations of energetic particle flux increases up to 1 MeV at 1 AU,which cannot be associated with ordinary mechanisms of particle acceleration, such asacceleration at shocks or at the Sun. Such unusual energetic particle events very likely have alocal origin. Multi-spacecraft observations show that numerous cases of energetic particle fluxenhancements and spikes correspond to passages of spacecraft through areas filled withmagnetic islands with a typical width ∼0.01–0.001AU that experience dynamical mergingor/and contraction. The presence of magnetic islands inside magnetically confined cavities in the solar wind may lead to local particle energization, especially in the case when the particles have already been pre-accelerated to keV energies, for example, at shocks or due to magnetic reconnection at the heliospheric current sheet. We consider different magnetic configurations that provide favourable conditions for both the appearance of small-scale magnetic islands and their confinement.
Highlights
Small-scale magnetic islands with a typical size of l ~0.01 AU or less are commonly observed in the solar wind plasma at 1 AU
Sometimes an interplanetary coronal mass ejections (ICMEs) can move slower than plasma inside a coronal hole flow, but since the latter has a permanent source at the Sun, the entire picture looks like the ICME moves against the background of a stable slowly rotating stream
In this case-study paper, we have shown examples of energetic particle enhancements observed near the Earth orbit that cannot be explained in terms of the dominant paradigm for the acceleration of particles to keV-MeV energies in the solar wind
Summary
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