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Description
The energy spectrum of solar energetic electron (SEE) events carries crucial information on the origin/acceleration at the Sun. We present ten solar energetic electron (SEE) events measured by Wind/3DP at ~1 to 200 keV with a bump break in the electron peak flux vs. energy spectrum. We assume that these bump SEE events consist of two electron populations: primary population (described by the pan-spectrum (PS) function) and bump population (described by the Gaussian function) that dominate at low and high energies, respectively. We construct two formulae to fit the SEE energy spectrum by multiplying a PS function with a natural exponential form of Gaussian function (i.e., the MUL formula) and by adding a PS function with a Gaussian function (i.e., the ADD formula). The fitting results suggest that the MUL fitting reflect the physics nature in the formation process. For the primary electron population, the MUL fitting obtains an upward-bending double-power-law spectrum for the #10 event with a spectral index of 3.85 (1.74) at energies below (above) ~4.6 keV, and a single-power-law spectrum for the other nine events with a median spectral index of 2.52. For the bump electron population, the fitted center energy has a median value of 59 keV. For the events associated with SXR flares (west-limb CMEs), the flare class (CME angular width) shows a positive correlation with the estimated electron number of power-law population Npl and of number ratio Nbp/Npl at 10-400 keV. These results indicate that for these bump SEE events, the power-law electron population can be produced by some flare-related processes that occur high in the corona, while the bump population can be accelerated by some CME-related processes acting on the power-law population. The bump-like spectrum might also be the intermediate spectrum during the evolution from single-power-law to downward-bending double-power-law.
