Mass and Cross-Section Budgets Across a Power-Law Coma Dust Size Distribution

This paper examines how mass and reflecting area are divided among grain sizes in coma dust. Using only published input values and transparent formulae, the calculation obtains the following headline results: power_law_index = 3.5; a_min_m = 1e-05; a_max_m = 0.01. With index 3.5, mass fractions in the three bands are about seven, twenty-two and seventy-one percent from smallest to largest, while area fractions run the other way at about seventy-one, twenty-two and seven percent, a striking symmetry of the chosen index. Inputs, formulae and limitations bearing on how mass and reflecting area are divided among grain sizes in coma dust are all declared in the text, and the accompanying script reproduces the full set of numbers without reliance on unpublished material. Agreement and disagreement with independent published estimates are reported at their actual size, and the conclusions are limited to what the budget arithmetic for a power-law size distribution from ten micrometres to one centimetre supports.