Influence of Sun variability on cosmic rays traversing heliosphere2017.10.11 13:49 - Anna Rędaszek
Our solar system central star is by no means a static body, it fluctuates at time scales covering a wide range. Even if history of observations is old (sunspots, obvious demonstration of Sun’s variability, were observed with unaided eyes already in antiquity), still numerous mysteries remain unsolved. The nature of the solar dynamo and the Sun’s corona heating mechanism are perhaps the most crucial among these yet unsolved mysteries. Periods of Sun’s variability cycles range from several thousand years (2,400-year long Hallstatt cycle, 1,000-year long Eddy cycle), through several hundred yeas (210-year de Vries cycle), down to several minutes (3- and 5-minute oscillations). However, the basic Sun’s variability is the Schwebe cycle: every 11 years Sun exhibits a period of an increased activity. Consequences of Sun rotation along its own axis are also clearly visible every 27 days.
Heliosphere i.e. a zone under Sun‘s direct influence is constantly penetrated by radiation originating both in our Galaxy and beyond it. Cosmic rays are subatomic charged particles, mainly protons and α particles with a small fraction of heavier ions. By default, cosmic rays are detected by a global network of terrestrial neutron monitors operated incessantly since 1951 (International Geophysics Year). The monitors log secondary cosmic rays i.e. showers of nucleons produced within Earth atmosphere by primary rays. These measurements have indicated that Sun’s variability is reflected in intensity of cosmic rays. Outcomes of studies on variability of cosmic rays at various time scales may help to study cosmic weather.
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