Global Energetics of Solar Flares. V. Energy Closure in Flares and Coronal Mass Ejections

Abstract

In this study we synthesize the results of four previous studies on the global energetics of solar flares and associated coronal mass ejections (CMEs), which include magnetic, thermal, nonthermal, and CME energies in 399 solar M- and X-class flare events observed during the first 3.5 yr of the Solar Dynamics Observatory (SDO) mission. Our findings are as follows. (1) The sum of the mean nonthermal energy of flare-accelerated particles (E_(nt)), the energy of direct heating (E_(dir)), and the energy in CMEs (E_(CME)), which are the primary energy dissipation processes in a flare, is found to have a ratio of E_(nt) + E_(dir) + E_(CME)/E_(mag) = 0.87 ± 0.18, compared with the dissipated magnetic free energy E_(mag), which confirms energy closure within the measurement uncertainties and corroborates the magnetic origin of flares and CMEs. (2) The energy partition of the dissipated magnetic free energy is: 0.51 ± 0.17 in nonthermal energy of ⩾ 6 keV electrons, 0.17 ± 0.17 in nonthermal ⩾ 1 MeV ions, 0.07 ± 0.14 in CMEs, and 0.07 ± 0.17 in direct heating. (3) The thermal energy is almost always less than the nonthermal energy, which is consistent with the thick-target model. (4) The bolometric luminosity in white-light flares is comparable to the thermal energy in soft X-rays (SXR). (5) Solar energetic particle events carry a fraction ≈ 0.03 of the CME energy, which is consistent with CME-driven shock acceleration. (6) The warm-target model predicts a lower limit of the low-energy cutoff at e_c ≈ 6 keV, based on the mean peak temperature of the differential emission measure of T_e = 8.6 MK during flares. This work represents the first statistical study that establishes energy closure in solar flare/CME events.

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