magnetopause-lmn-analysis

Magnetopause / bow-shock crossing — full LMN study

The canonical SPEDAS boundary-crossing analysis, end to end. Where boundary-minimum-variance does the pure MVA step, this skill is the complete study: it pairs the field rotation with the plasma signature (density/velocity jump) and the spacecraft position that together identify the boundary and confirm the crossing.

When to use

• "Screen for a magnetopause / bow-shock crossing near ."
• "Characterize this boundary: normal, LMN field, plasma jump, where was the spacecraft?"
• Any single-spacecraft current-sheet / discontinuity study needing field + plasma + geometry.

Tool chain (all existing)

search_spedas_data_sources → plan_spedas_observation → create_spedas_analysis_bundle → load_data_source → browse_data_parameters → fetch_data_product (B and ion moments) → analyze_minvar_coordinates → transform_timeseries_coordinates (optional, Earth frames) → get_ephemeris / calculate_lshell (position) → render_tplot.

Procedure

1. Plan & bundle. plan_spedas_observation(science_goal) to confirm source + a tight window around the crossing; create_spedas_analysis_bundle(...) for data/+plots/+provenance/. Keep the window short — one boundary, minutes not hours (the MMS example uses a 2-minute window).

2. Pick datasets — field AND plasma. A boundary is identified by both the magnetic rotation and the plasma jump:

   • Magnetic field: the mission's FGM/MAG vector (confirm the variable with browse_data_parameters).
   • Ion moments: density, bulk velocity, temperature (e.g. FPI-DIS for MMS, SWE/3DP for Wind, SWEAP for PSP). Fetch each with fetch_data_product(source_type=..., dataset_id=..., parameters=[...], start, stop, output_dir=<bundle>/data). Check the returned stats/quality_checks before trusting the data.

3. MVA on the field → boundary normal. analyze_minvar_coordinates(input_file=<B csv>, vector_cols=[Bx,By,Bz], output_dir=<bundle>/data). Gate on reliability: require λ_int/λ_min ≳ 5–10 before trusting the normal; report the ratio. (If the ratio is low, the window likely spans more than one structure — re-scope.)