Solar and Galactic Cosmic Rays observed by SOHO
Werner Curdt, Bernhard Fleck

TL;DR
This study analyzes SOHO data to distinguish the impacts of galactic cosmic rays and solar energetic particles on spacecraft systems and solar array degradation over solar cycle 23.
Contribution
It provides a comparative analysis of cosmic ray and SEP effects on SOHO's systems, quantifying their relative contributions to system anomalies and solar array degradation.
Findings
94% of SSR SEUs caused by galactic cosmic rays
SEP events contributed up to 30% of SEUs during peak periods
Proton events account for about 40% of solar array degradation
Abstract
Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs) have left an imprint on SOHO technical systems. While the solar array efficiency degraded irreversibly down to ~77% of its original level over roughly 1 1/2 solar cycles, Single Event Upsets (SEUs) in the solid state recorder (SSR) have been reversed by the memory protection mechanism. We compare the daily CRF observed by the Oulu station with the daily SOHO SEU rate and with the Degradation curve of the solar arrays. The Oulu CRF and the SOHO SSR SEU rate are both modulated by the solar cycle and are highly correlated, except for sharp spikes in the SEU rate, caused by isolated SEP events, which also show up as discontinuities in the otherwise slowly decreasing solar ray efficiency. This allows to discriminate between effects with solar and non-solar origin and to compare the relative strength of both. We find that…
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Taxonomy
TopicsSolar Radiation and Photovoltaics · Solar and Space Plasma Dynamics · Radiation Therapy and Dosimetry
