A galactic cosmic ray cavity in Earth-Moon space.

Area of Science:

• Space Physics
• Cosmic Ray Physics
• Planetary Science

Background:

• Galactic cosmic rays (GCRs) are high-energy particles originating from outside the solar system.
• Previous assumptions suggested uniform GCR distribution across the Earth-Moon distance.
• Understanding GCR flux is critical for space exploration safety.

Purpose of the Study:

• To investigate the spatial distribution of GCRs in the vicinity of the Moon.
• To determine if Earth's magnetic field influences GCR flux at lunar distances.
• To identify potential radiation shielding regions for future space missions.

Main Methods:

• Analysis of data from the Lunar Lander Neutron and Dosimetry (LND) experiment on the Chang'E-4 lander.
• Investigating GCR flux variations in different sectors of the lunar orbit.
• Modeling the interaction of Earth's magnetic field with GCR propagation.

Main Results:

• A significant reduction in GCR flux was observed in the prenoon sector of the lunar orbit.
• Evidence suggests the formation of an energetic particle cavity caused by Earth's magnetic field.
• The Earth's magnetic field extends its influence on particle propagation beyond the Moon's orbit.

Conclusions:

• GCR distribution is not uniform and is influenced by Earth's magnetosphere.
• An energetic particle cavity exists, shielding the near-Moon environment from GCRs.
• This discovery has implications for radiation safety in lunar and deep-space exploration.