Speaker
Description
Constraining the magnitude and occurrence of extreme solar energetic particle (SEP) events beyond the instrumental era remains central to space climate research and risk assessment. Cosmogenic radionuclides archived in polar ice cores, particularly beryllium-$^{10}$ ($^{10}$Be) and chlorine-$^{36}$ ($^{36}$Cl), provide one of the few direct observational windows into past solar activity. Here we present new high resolution $^{10}$Be and $^{36}$Cl measurements from Greenland and Antarctic ice cores spanning three intervals of particular interest: (i) the Carrington event (1859 CE), (ii) the recently identified radionuclide event at 7,208-year Before Present, and (iii) the post bomb period, which serves as a benchmark for atmospheric transport and depositional processes under well constrained conditions. Across the Carrington interval, we did not observe a significant enhancement in $^{36}$Cl concentrations. This result implies either that no exceptionally large SEP event occurred or that associated particles did not intersect Earth. In contrast, the 7,208-year BP interval is robustly confirmed in both nuclides, allowing us to assess its fluence spectrum and relative magnitude. Finally, the post bomb data reveal a clear 11-year cyclicity in $^{36}$Cl concentrations and good agreement with the $^{10}$Be records from both hemispheres. Together, these results place new observational constraints on the sensitivity and limits of ice core radionuclide proxies for reconstructing extreme solar activity.
Co-author list:
C. I. Paleari (1), R. Muscheler (2), M. Christl (3), A. Smith (4), C. Vockenhuber (3)
(1) Department of Physical Geography and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
(2) Department of Earth and Environmental Sciences, Lund University, Lund, Sweden
(3) ETH Zürich, Laboratory of Ion Beam Physics, Zürich, Switzerland
(4) Centre for Accelerator Science, ANSTO, Lucas Heights, NSW, Australia