You are cordially invited to a Colloquium by Dr Stepan Poluianov.
Title: The Sun and Heliosphere studied with lunar cosmogenic nuclides.
Abstract:
The radiation environment inside the Heliosphere is largely defined by very energetic cosmic rays of solar and galactic origins. The varying intensities of those two populations of particles reflect many important properties of the Sun, Heliosphere, and the local interstellar medium, and are useful tools for revealing the history of our star. One of the methods to study them via cosmic rays are long-living cosmogenic nuclides like C-14, Cl-36, Al-26, Be-10, Mn-53 with half-life times ranging from 5.7 kyr to 3.7 Myr. Here I focus specifically on nuclides produced in the lunar rocks and soil. Those objects are not protected by a magnetic field, in contrast to the Earth's cosmogenic nuclides, therefore they contain valuable information about low-energy cosmic rays over long time scales. Unfortunately, in contrast to stratified natural nuclide archives at the Earth, e.g, tree trunks, ice sheets, marine and lake sediments, it is impossible to resolve lunar nuclide records in time, at least, easily. The only help here comes from the fact that different nuclides have different half-life times, and this provides a clue about the temporal evolution of the cosmic-ray environment.
"In this talk, I give an overview of the landscape of cosmic-ray studies with cosmogenic nuclides in lunar samples and also report results of our several works related to the topic, namely, an assessment of the average SEP spectra and solar activity level at the scale of about 1 million years, comparison of contributions of "regular" SEP and "extreme" SEP events to the total megayear-average spectra, and our recent attempt to find signatures of a cold interstellar cloud passage by the Heliosphere in Al-26 measured in lunar soil."
For more information, kindly contact Joseph Magwanya.