Dataset DOI: 10.5061/dryad.rjdfn2zqb

Description of the data and file structure

This dataset contains galactic cosmic ray (GCR) proton measurements on the lunar surface obtained by the Chang’E 4/LND experiment, together with interplanetary magnetic field (IMF) and solar wind parameters measured by the ARTEMIS mission. The ARTEMIS data have been resampled to a one-minute cadence to match the temporal resolution of the LND observations. The uploaded LND data files (01.txt–38.txt) cover 31 lunar cycles from January 2019 to January 2022 and are used for the analyses presented in Figures 3–4 of the associated manuscript.

Figures 1 and 2 rely on the uploaded Chang’E 4/LND dataset and publicly available ARTEMIS measurements and thus do not require additional figure-specific data files.

In addition, lists of the start and end times of stream/corotating interaction region (S/CIR) and interplanetary coronal mass ejection (ICME) events are provided and are used to exclude periods affected by transient solar wind disturbances.

The dataset also includes simulation outputs and derived products used to generate Figure 5 (A–D). These data are obtained from test-particle simulations of energetic protons propagating in the near-lunar environment at energies of 20 MeV and 100 MeV. For each energy, multiple independent realizations are performed on a fixed two-dimensional spatial grid extending from −100 to +100 R_E in both x and y directions. Ensemble-averaged, normalized particle density maps are provided for Figures 5A and 5C, and orbital phase–dependent mean particle densities with corresponding standard errors are provided for Figures 5B and 5D.

Files and variables

Files: 01.txt - 38.txt

Description: This file contains proton flux, proton count rate, interplanetary magnetic field (IMF), solar wind parameters, and lunar geometry information for the lunar day after the Chang’E-4 landing (as indicated in the file name, i.e. 01 is first day, 02 is second day, etc.), measured by Chang’E 4/LND and the ARTEMIS mission. The data are provided at a 1-minute time resolution and are used for the statistical analyses in Figures 3–4 of the associated manuscript.

Each row corresponds to one time step. The file contains 28 columns, ordered as follows:

1. Time (UT)
2. Proton flux (9.18–34.14 MeV)
3. Proton flux (9.18–21.20 MeV)
4. Proton flux (21.20–34.14 MeV)
5. Proton flux (34.94–41.76 MeV)
6. Proton flux (42.3–139.2 MeV)
7. Proton flux (139.2–368.4 MeV)
8. Proton count rate (9.18–34.14 MeV)
9. Proton count rate (9.18–21.20 MeV)
10. Proton count rate (21.20–34.14 MeV)
11. Proton count rate (34.94–41.76 MeV)
12. Proton count rate (42.3–139.2 MeV)
13. Proton count rate (139.2–368.4 MeV)
14. IMF Bx (nT)
15. IMF By (nT)
16. IMF Bz (nT)
17. IMF total magnetic field strength |B| (nT)
18. Solar wind proton density (cm⁻³)
19. Solar wind velocity (km s⁻¹)
20. Bx / |B|
21. (Bx + By) / |B|
22. Lunar phase
23. Moon position X component in GSE coordinates (R_E)
24. Moon position Y component in GSE coordinates (R_E)
25. Moon position Z component in GSE coordinates (R_E)
26. Angle between IMF and the Earth–Moon direction (degrees)
27. Angle between IMF and the LND field of view (degrees)
28. Lunar phase

File: SA_FIG3.m

Description: This file contains the MATLAB code used to process the data and generate Figure 3 of the associated manuscript.

File: SIR.txt

Description: This file lists the start and end times of stream/corotating interaction region (S/CIR) events used to identify and exclude time intervals affected by recurrent solar wind disturbances in the statistical analysis.

File: ICME.txt

Description: This file lists the start and end times of interplanetary coronal mass ejection (ICME) events.

File: errorbar_xc.m

Description: This MATLAB function is used by SA_FIG3.m and SA_FIG4.m to calculate binned mean values and their statistical uncertainties.

File: SA_FIG4.m

Description: This file contains the MATLAB code used to process the data and generate Figure 4 of the associated manuscript.

File: process_fig5CD_data.py

Description: This Python code processes test-particle simulation outputs at 100 MeV to generate ensemble-averaged, normalized spatial particle density distributions used for Figures 5C and 5D of the associated manuscript.

File: process_fig5AB_data.py

Description: This Python code processes test-particle simulation outputs at 20 MeV to generate ensemble-averaged, normalized spatial particle density distributions used for Figures 5A and 5B of the associated manuscript.

File: SA_FIG5CD.py

Description: This Python code reads the processed simulation data and produces the visualization for Figures 5C and 5D, including the two-dimensional particle density map and the corresponding orbital-phase-dependent statistics at 100 MeV.

File: SA_FIG5AB.py

Description: This Python code reads the processed simulation data and produces the visualization for Figures 5A and 5B, including the two-dimensional particle density map and the corresponding orbital-phase-dependent statistics at 20 MeV.

File: orbit_statistics_20MeV.txt

Description: This file contains orbital-phase-dependent mean particle densities and their standard errors derived from the 20 MeV test particle simulations. These data are used to generate Figure 5B of the associated manuscript.

File: orbit_statistics_100MeV.txt

Description: This file contains orbital-phase-dependent mean particle densities and their standard errors derived from the 100 MeV test particle simulations. These data are used to generate Figure 5B of the associated manuscript.

File: overview_dis_density_100MeV.txt

Description: This file contains the ensemble-averaged and globally normalized spatial distribution of energetic protons at 100 MeV obtained from test particle simulations. The data are used to generate Figure 5C of the associated manuscript.

File: overview_dis_density_20MeV.txt

Description: This file contains the ensemble-averaged and globally normalized spatial distribution of energetic protons at 20 MeV obtained from test-particle simulations. The data are used to generate Figure 5C of the associated manuscript.

Code/software

All data processing and figure generation were performed using **Python 3.10 **and MATLAB R2017a. The Python codes rely on standard scientific libraries, including NumPy, Matplotlib, and os.

The included scripts are organized as follows:

• process_fig5AB_data.py / process_fig5CD_data.py – Python codes to process test particle simulation outputs for Figures 5 (A–D). These scripts calculate ensemble-averaged particle density maps and orbital-phase-dependent statistics.
• SA_FIG5AB.py / SA_FIG5CD.py – Python codes to generate Figures 5 (A–D) from the processed data.
• SA_FIG3.m / SA_FIG4.m – MATLAB codes used to generate Figures 3 and 4, including data selection and statistical analyses.
• errorbar_xc.m – MATLAB function called by SA_FIG3.m and SA_FIG4.m to compute local means and standard errors for plotting.

Workflow:

1. For Figures 3–4, the LND observational data files (01.txt–38.txt) are processed in MATLAB using SA_FIG3.m / SA_FIG4.m, with errorbar_xc.m used for statistical calculations.
2. For Figure 5 (A–D), the Python codes process simulation outputs to produce normalized particle density maps and orbital-phase statistics. The SA_FIG5AB.py / SA_FIG5CD.py scripts generate the final figures.

No additional proprietary software is required to view or use the processed data files, which are provided in plain text format.

Access information

Other publicly accessible locations of the data:

• The IMFand solar wind parameters used in this study are publicly available from the ARTEMIS mission archive at http://themis.ssl.berkeley.edu/data/themis/

Data was derived from the following sources:

• Chang’E 4/ LND experiment measurements of galactic cosmic ray (GCR) proton count rates on the lunar far-side surface (2019–2022).
• ARTEMIS mission measurements of IMF and solar wind parameters.