feat(core): add ReferenceAbundances for Asplund 2009 photospheric data

[blalterman]

Summary

• Add ReferenceAbundances class for elemental abundance ratios from Asplund et al. (2009) "The Chemical Composition of the Sun"
• Load photospheric and meteoritic abundances from bundled CSV (Table 1)
• Access elements by symbol ('Fe') or atomic number (26)
• Calculate abundance ratios with uncertainty propagation
• Comprehensive test suite (22 tests) following SolarWindPy patterns

Files Added

File	Purpose
solarwindpy/core/abundances.py	ReferenceAbundances class
solarwindpy/core/data/asplund2009.csv	Table 1 data (83 elements)
tests/core/test_abundances.py	Test suite

Test Plan

• All 22 tests pass (pytest tests/core/test_abundances.py -v)
• Test audit completed (no anti-patterns, 6 isinstance assertions, pytest.raises with match)
• Scientific values verified against published Asplund 2009 Table 1
• CI pipeline

Reference

Asplund, M., Grevesse, N., Sauval, A. J., & Scott, P. (2009). The Chemical Composition of the Sun. Annual Review of Astronomy and Astrophysics, 47(1), 481–522. https://doi.org/10.1146/annurev.astro.46.060407.145222

🤖 Generated with Claude Code

[claude]

Claude finished @blalterman's task —— View job

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Code Review Complete ✅

Summary

The ReferenceAbundances implementation is well-designed and ready to merge. The code follows SolarWindPy conventions with excellent scientific attribution, comprehensive testing, and solid error handling.

✅ Strengths

Code Quality

• Excellent docstrings: Proper NumPy format with mathematical notation and scientific citation (solarwindpy/core/abundances.py:12-22)
• Clean API design: Intuitive get_element() method supporting both symbols and atomic numbers (solarwindpy/core/abundances.py:45-64)
• Proper scientific attribution: Full DOI citation in docstring following CLAUDE.md requirements
• Good use of pandas: Efficient MultiIndex structure for element lookup

Test Coverage (22 comprehensive tests)

• Structure validation: Verifies CSV loads correctly with 83 elements and proper MultiIndex (tests/core/test_abundances.py:33-46)
• Scientific accuracy: Tests actual Asplund 2009 values (Fe: 7.50, O: 8.69) (tests/core/test_abundances.py:70-85)
• Edge case coverage: NaN handling, invalid inputs, H denominator special case (tests/core/test_abundances.py:198-214)
• Mathematical verification: Uncertainty propagation formulas tested against manual calculations (tests/core/test_abundances.py:148-156)

Performance & Security

• Efficient data access: Uses pandas .xs() for fast MultiIndex lookups
• Memory efficient: Single CSV load on initialization, data cached as property
• No security concerns: Pure scientific data processing, no user input vulnerabilities

🔍 Minor Observations (Not Blocking)

1. Assertion in Production Code

Location: solarwindpy/core/abundances.py:63

assert out.shape[0] == 1

Issue: Using assert in production code that could be removed with -O flag.
Recommendation: Consider replacing with explicit ValueError:

if out.shape[0] != 1:
    raise ValueError(f"Expected 1 element, found {out.shape[0]} for key {key}")

2. Data Validation on Load

Observation: CSV structure is assumed correct without validation.
Enhancement: Could add basic validation in load_data():

• Verify 83 rows for expected element count
• Check column structure matches expected format

3. Type Hints

Current: No type annotations
Enhancement: Adding type hints would improve IDE support:

def get_element(self, key: Union[str, int], kind: str = "Photosphere") -> pd.Series:

📊 Test Quality Analysis

Excellent test patterns observed:

• ✅ Specific assertions instead of trivial ones (isinstance checks with meaningful messages)
• ✅ Scientific validation using published values
• ✅ Proper pytest.raises usage with match= parameter
• ✅ Mathematical formula verification with manual calculations
• ✅ Edge case coverage (NaN, invalid types, missing elements)

🔄 Integration Review

Clean integration:

• ✅ Properly added to solarwindpy/core/__init__.py
• ✅ CSV data bundled in solarwindpy/core/data/ directory
• ✅ No breaking changes to existing APIs

🚀 Recommendation

APPROVE - This is high-quality scientific code that:

1. Follows SolarWindPy conventions and coding standards
2. Includes comprehensive test coverage with scientific validation
3. Provides clean, well-documented API
4. Has no security or performance concerns
5. Integrates cleanly without breaking changes

The minor observations above are enhancements for future consideration, not blockers for this PR.

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[github-actions]

SolarWindPy Documentation Validation - Python 3.11

✅ Status: PASSED

Essential Metrics:

• Files: 41
• Tests: 20
• Failed: 0
• Success Rate: 100.0%
• Approach: Targeted validation (core physics modules)

🎉 All essential documentation examples working!