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During a long lasting period of northward interplanetary magnetic field and high solar wind speed (above 700 km/s), the Cluster spacecraft go across a number of very large rolled-up Kelvin-Helmholtz (KH) vortices at the dusk magnetopause, close to the terminator. The peculiarity of the present event is a particular sequence of ions and electrons distribution functions observed repeatedly inside each vortex. In particular, whenever Cluster crosses the current layer inside the vortices, multiple field-aligned ion populations appear, suggesting the occurrence of reconnection. In addition, the ion data display a clear velocity filter effect both at the leading and at the trailing edge of each vortex. This effect is not present in the simultaneous electron data. Unlike other KH studies reported in the literature in which reconnection occurs within the vortices, in the present event the observations are not compatible with local reconnection, but are accounted for by lobe reconnection occurring along an extended X-line at the terminator in the Southern Hemisphere. The reconnected field lines "sink" across the magnetopause and then convect tailward-duskward where they become embedded in the vortices. Another observational evidence is the detected presence of solar wind plasma on the magnetospheric side of the vortices, which confirms unambiguously the occurrence of mass transport across the magnetopause already reported in the literature. The proposed reconnection scenario accounts for all the observational aspects, regarding both the transport process and the kinetic signatures. [ABSTRACT FROM AUTHOR]

To characterize the particle radiation environment at the Lagrangian point L1 and in the near-Earth space we performed a systematic analysis of the particle flux data recorded by different instruments on board different spacecraft (ACE EPAM/LEMS120, IMP-8 CPME, and Geotail EPIC-ICS). We focused on protons in the poorly explored energy range ∼0.05–5 MeV, including energies of the so-called soft protons, which are critical for the Advanced Telescope for High Energy Astrophysics (ATHENA) mission, as well as the 145–440 MeV one, because high-energy particles affect all interplanetary missions. We estimated the energetic proton environment by computing the cumulative distribution functions for the different energy channels of each instrument and studied its variations with respect to solar activity. We obtained energetic proton spectra at cumulative probabilities (CPs) of 50% and 90% and worst-case scenarios, which can be used by the ATHENA mission for operational purposes and more generally for space weather hazards. We found an increase in the ∼0.05–5 MeV proton spectrum at 90% CP during the maximum phase of solar cycle (SC) No. 23 of about a factor from 3 to 5, depending on the energy, with respect to the overall period (1997–2014). Moreover, the 300–500 keV proton flux at 90% CP is higher during SC No. 21 by about a factor 1.5 and 3 compared to SC No. 22 and SC No. 23, respectively. Finally, variations with solar activity of the 145–440 MeV proton flux are within a factor of 2 at both 90% and 50% CPs, thus representing the low-energy galactic cosmic rays. [ABSTRACT FROM AUTHOR]

Reconnection events in space plasmas are accompanied by the occurrence of large-amplitude turbulent fluctuations of the magnetic and electric field, covering a wide range of temporal and spatial scales. Here, we study the scaling and statistical features of magnetic and electric field fluctuations below the ion-gyroperiod (i.e., in the dissipation domain) by carefully investigating the occurrence of local or global scaling features during a reconnection event studied by Eastwood et al . Our results point toward the presence of a global scale invariance, i.e., a mono-fractal nature, of fluctuations above the ion-cyclotron frequency and at spatial scales near the ion-inertial length. [ABSTRACT FROM AUTHOR]