First Solar energetic particles measured on the Lunar far-side
Zigong Xu, Jingnan Guo, Robert. F. Wimmer-Schweingruber, Johan L., Freiherr von Forstner, Henning Lohf, Yuming Wang, Nina Dresing, Shenyi Zhang,, Mei Yang

TL;DR
This study reports the first detection of solar energetic particles on the Moon's far side by Chang'E-4, revealing insights into particle release times, propagation mechanisms, and the Moon's role in space environment observations.
Contribution
It demonstrates the utility of lunar-based measurements for SEP observation and provides new data on particle release timing and propagation that challenge existing models.
Findings
Electrons released 22 minutes after flare onset.
Protons released over an hour after electrons.
SEPs propagation likely deviates from Parker spiral model.
Abstract
On 2019 May 6, the Lunar Lander Neutron & Dosimetry (LND) Experiment on board the Chang'E-4 on the far-side of the Moon detected its first small solar energetic particle (SEP) event with proton energies up to 21MeV. Combined proton energy spectra are studied based on the LND, SOHO/EPHIN and ACE/EPAM measurements which show that LND could provide a complementary dataset from a special location on the Moon, contributing to our existing observations and understanding of space environment. Velocity dispersion analysis (VDA) has been applied to the impulsive electron event and weak proton enhancement and the results demonstrate that electrons are released only 22 minutes after the flare onset and 15 minutes after type II radio burst, while protons are released more than one hour after the electron release. The impulsive enhancement of the in-situ electrons and the derived early release…
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Taxonomy
TopicsPlanetary Science and Exploration · Space Science and Extraterrestrial Life · Astro and Planetary Science
