From solar sneezing to killer electrons: outer radiation belt response to solar eruptions.

Electrons in the outer Van Allen (radiation) belt occasionally reach relativistic energies, turning them into a potential hazard for spacecraft operating in geospace. Such electrons have secured the reputation of satellite killers and play a prominent role in space weather. The flux of these electrons can vary over time scales of years (related to the solar cycle) to minutes (related to sudden storm commencements). Electric fields and plasma waves are the main factors regulating the electron transport, acceleration and loss. Both the fields and the plasma waves are driven directly or indirectly by disturbances originating in the Sun, propagating through interplanetary space and impacting the Earth. This paper reviews our current understanding of the response of outer Van Allen belt electrons to solar eruptions and their interplanetary extensions, i.e. interplanetary coronal mass ejections and high-speed solar wind streams and the associated stream interaction regions. This article is part of the theme issue 'Solar eruptions and their space weather impact'.

The possible effects of the solar and geomagnetic activity on multiple sclerosis.

OBJECTIVES: Increasing observational evidence on the biological effects of Space Weather suggests that geomagnetic disturbances may be an environmental risk factor for multiple sclerosis (MS) relapses. In the present study, we aim to investigate the possible effect of geomagnetic disturbances on MS activity. PATIENTS AND METHODS: MS patient admittance rates were correlated with the solar and geophysical data covering an eleven-year period (1996-2006, 23rd solar cycle). We also examined the relationship of patterns of the solar flares, the coronal mass ejections (CMEs) and the solar wind with the recorded MS admission numbers. RESULTS: The rate of MS patient admittance due to acute relapses was found to be associated with the solar and geomagnetic events. There was a "primary" peak in MS admittance rates shortly after intense geomagnetic storms followed by a "secondary" peak 7-8 months later. CONCLUSION: We conclude that the geomagnetic and solar activity may represent an environmental health risk factor for multiple sclerosis and we discuss the possible mechanisms underlying this association. More data from larger case series are needed to confirm these preliminary results and to explore the possible influence of Space Weather on the biological and radiological markers of the disease.