Speaker
Description
Solar eruptions (solar flares and coronal mass ejections) are known to cause various space–weather phenomena in the Sun–Earth system that can have severe impacts on modern society. As the magnitude of a solar eruption increases, its frequency of occurrence decreases, but the severity of its impact increases. Therefore, it is important to understand the long-term characteristics of extreme solar eruptions. To investigate such extreme solar eruptions on a timescale that exceeds that of modern observations, we have used cosmogenic nuclides such as 14C, 10Be, and 36Cl. Because solar energetic particles (SEPs) that originate from solar eruptions have sufficient energy to produce cosmogenic nuclides, as also do galactic cosmic rays, extreme SEP events cause rapid increases (spikes) in cosmogenic nuclide concentrations.
To date, several cosmogenic nuclide spikes have been found e.g., in 774 CE, 993 CE, around 660 BCE, and 7176 BCE, via analyses of 14C in tree rings and of 10Be and 36Cl in ice cores. The magnitudes of these events have been estimated to be several dozen times larger than that of the largest SEP event observed using modern instruments. We are currently conducting a long-term exploration of extreme SEP events by analyzing the 14C concentrations in tree rings. In this presentation, we report the latest updates regarding our SEP event exploration and event candidates reported recently.
| Student Submission | No |
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