  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 $\sim$15 minutes after type II radio burst, while protons are
released more than one hour after the electron release. The impulsive
enhancement of the in-situ electrons and the derived early release time
indicate a good magnetic connection between the source and Earth. However,
stereoscopic remote-sensing observations from Earth and STA suggest that the
SEPs are associated with an active region nearly 100$^\circ$ away from the
magnetic footpoint of Earth. This suggests that the propagation of these SEPs
could not follow a nominal Parker spiral under the ballistic mapping model and
the release and propagation mechanism of electrons and protons are likely to
differ significantly during this event.
