Magnetic Anomaly Catalog

spn.moon.magnetic_anomalies() returns a list of lunar magnetic anomalies built from published location tables, as a pandas.DataFrame. The tables are bundled with the package, so no network access or SVM file is needed.

import sopran as spn

sites = spn.moon.magnetic_anomalies()       # corrected Blewett (2011) table, 15 entries
sites[["name", "lon_deg", "lat_deg", "peak_field_30km_nt", "swirl"]]

# substring match on name and feature_id; handles Gamma/γ, hyphens, and underscores
reiner = spn.moon.magnetic_anomalies("all", name="Reiner Gamma")

# search near (east longitude, latitude); 57.5°W can be -57.5 or 302.5
nearby = spn.moon.magnetic_anomalies("all", near=(-57.5, 7.5), radius_deg=5)

# analysis centers of isolated anomalies and the observation radii used in the paper
isolated = spn.moon.magnetic_anomalies("oliveira2017")

Included tables

catalog	Contents	Source
blewett2011 (default)	15 entries: approximate location, peak field at 30 km altitude, terrain setting, swirl classification at the time	Blewett et al. (2011), corrected Table 1
oliveira2017	15 entries: analysis centers of isolated anomalies, observation radius \(r_o\), dipole placement radius \(r_d\)	Oliveira & Wieczorek (2017), Table 1
all	30 rows from both tables, 23 feature_id values; different published values for the same region stay in separate rows	Both tables

This is the list of regions chosen in the literature, not a complete inventory of lunar magnetic anomalies. name keeps the published spelling, and feature_id links Reiner-γ with Reiner Gamma and Sirsalis with Rima Sirsalis. Rows with different coordinates are never averaged or merged. Blewett's original paper has coordinate errors, so the corrected table is used.

Columns

Column	Meaning
lon_deg, lat_deg	Published Moon-fixed coordinates, east longitude 0–360°, north latitude positive. No precise MOON_ME/MOON_PA conversion is applied
position_kind	approximate_anomaly_location for approximate locations, analysis_center for the center of an analysis region
peak_field_30km_nt	Estimated regional peak \(\lvert B\rvert\) at 30 km altitude (nT); not a surface value or a point value at the listed coordinates
setting, swirl	Terrain and swirl classification from Blewett's table; not_recognized means not recognized as of 2011
observation_radius_deg, dipole_radius_deg	Angular radii of the analysis regions in Oliveira's paper; not physical boundaries or sizes of the anomalies
reference_doi, note	Per-row source and notes; Marginis has sparse Lunar Prospector magnetometer coverage
distance_deg, distance_km	Only with near: great-circle distance to the listed coordinates; km uses a lunar radius of 1737.4 km

Values absent from the literature are missing. With near, rows are sorted by distance, and radius_deg keeps rows whose listed point is within that angular distance. It cannot test intersections with regions. Give radius_deg together with near, between 0 and 180°. Empty results keep their columns and the DataFrame.attrs metadata.

Combining with the SVM

To combine the location table with the SVM, pass the coordinates to the SVM's sample(). The added column is the SVM point value, a different quantity from the published regional peak.

svm = spn.moon.svm.load(path="/path/to/LunarSVM_000_02_v02.dat")
sites["svm_surface_point_nt"] = svm.sample(lat=sites.lat_deg, lon=sites.lon_deg)