Magnetic Energy Available in a Tail Disconnection Event

This paper examines the magnetic energy stored in a comet plasma tail before a disconnection event. Using only published input values and transparent formulae, the calculation obtains the following headline results: tail_field_nT = 50; magnetic_energy_density_J_m3 = 9.947e-10; tail_volume_m3 = 7.854e+24. The energy density is about 10^-9 joules per cubic metre, small in terrestrial terms, but the volume is enormous, giving a total stored energy near 8 x 10^15 joules. For the magnetic energy stored in a comet plasma tail before a disconnection event, every input is named and every formula is stated, and the deposited script regenerates each quoted value, so the calculation can be audited or rescaled by any reader. 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 tail flux rope of radius fifty thousand kilometres and length a million kilometres supports.