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Shock Geometry, Seed Populations, and the Origin of Variable Elemental Composition at High Energies in Large Gradual Solar Particle Events
Cohen, C. M. S.; Mewaldt, R. A.; Maclennan, C. G. +5 more
Above a few tens of MeV per nucleon, large, gradual solar energetic particle (SEP) events are highly variable in their spectral characteristics and elemental composition. The origin of this variability has been a matter of intense and ongoing debate. In this paper, we propose that this variability arises from the interplay of two factors-shock geo…
The Model Dependence of Solar Energetic Particle Mean Free Paths under Weak Scattering
Mason, G. M.; Zhang, M.; Qin, G. +2 more
The mean free path is widely used to measure the level of solar energetic particles' diffusive transport. We model a solar energetic particle event observed by Wind STEP at 0.31-0.62 MeV nucleon-1, by solving the focused transport equation using the Markov stochastic process theory. With different functions of the pitch angle diffusion …
The Heliospheric He II 30.4 nm Solar Flux During Cycle 23
Auchère, F.; von Steiger, R.; Witte, M. +3 more
Because of the orbit characteristics of the vast majority of spacecraft, the solar flux has predominantly been measured at Earth or at least in the plane of the ecliptic. Therefore, the existing data do not directly demonstrate the fact that the latitudinal distribution of the extreme-ultraviolet (EUV) solar flux is largely anisotropic. Indeed, in…
Study of Hα Macrospicules in Coronal Holes: Magnetic Structure and Evolution in Relation to Photospheric Magnetic Setting
Wang, H.; Moore, R. L.; Jiang, Y. +2 more
Small-scale solar dynamic events such as spicules, macrospicules, and microflares may play an important role in the coronal heating and solar wind acceleration in coronal holes. In these regions, the network fields concentrated along edges of supergranules are probably the source of the fine-scale activity that may drive the heating and accelerati…
Stagnation Flow in Thin Streamer Boundaries
Nerney, Steven; Suess, Steven T.
Slow solar wind is believed to arise in the legs or near the cusp of streamers, inside the brightness boundary. In an earlier study, we used an analytic model of flow in this layer to analyze the effect of the magnetic field on the geometry of the flow. That study successfully described those conditions that can lead to a decrease of the flow spee…