The cosmic ray increases at 35 and 60 kyr BP.

• Main Authors: Florinski, V, Axford, W I, Zank, G P
• Format: Article in Journal/Newspaper
• Language: English
• Published: Radiocarbon 2004
• Subjects: alkaline earth metals;Antarctica ;Arctic region;Be 10;beryllium ;California ;Cenozoic ;concentration ;cores ;correlation ;cosmic rays;global ;Greenland ;Holocene ;ice cores;isotopes ;marine sediments;Mediterranean Sea;metals ;models ;Mono County California;Mono Lake;paleoenvironment ;Quaternary ;radioactive isotopes;sediments ;solar activity;solar wind;Sun ;United States;variations; Arctic; Greenland; Antarc*; Antarctica
• Online Access: https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/4202

Concentrations of (super 10) Be in ice cores and marine sediments exhibit 2 peaks with significant enhancements at 35,000 and 60,000 BP. This radioisotope is produced in the upper atmosphere by spallation of cosmic-ray protons and secondary neutrons on atmospheric nitrogen and oxygen. Previously suggested explanations for the increases include geomagnetic field reversals, a decrease in solar activity, and a supernova explosion. We propose an alternative explanation which involves a change in the galactic environment of the solar system. The structure of the heliosphere is investigated for a period when the Sun enters a cold, dense, unmagnetized interstellar cloud. Under these conditions, the heliosphere contracts to 25% its present size, significantly affecting galactic cosmic ray modulation and increasing anomalous cosmic ray fluxes. A tenfold increase in anomalous cosmic ray flux and a twofold increase in galactic cosmic ray intensity at Earth are possible in this high-density case if heliosheath modulation is reduced. We show that this increase in galactic cosmic ray intensity could be responsible for the peaks in (super 10) Be records.