Energy Spectrum of Solar Energetic Electron Events Over 25 Years

We investigate 427 SEEs with good energy spectrum at energies from 4.2keV to 108keV observed by WIND/3DP from 1994 Dec through 2019 Dec. The SEE energy spectrum can be classified into three types: Power-Law (PL), Ellison-Ramaty (ER) and Log-parabola (LP), respectively. Among the 335 PL cases, 253 are downward DPL cases where 2 > 1 with low energy spectral index 1 = 2.1 0.4, high energy spectral index 2 = 4.1 1.0 and a double peak distribution of break energy EB: first peak at 6.3keV and the second peak at 69 keV ; 39 cases are upward DPL where 2 < 1 with 1 = 3.1 0.6, 2 = 2.2 0.3 and average break energy EB = 7.0keV ; 43 cases are SPL where 2 1 with 1 = 2.70.5, 2 = 3.20.8. 33 cases are ER with low energy spectral index ER = 2.00.4 and average cut-off energy Ec = 47 keV; 59 cases are LP with low energy spectral index 1 = 1.7 0.5 and high energy spectral index 2 = 3.8 0.8. By comparing HXR-related events with HXR-not-related events, we find that: no differences for spectral indexes of PL but PL break energy EB and energy flux of HXR-related events are larger than that of HXR-not-related events; No differences for spectral indexes and energy flux of LP. By comparing solar cycle 23 events with solar cycle 24 events, we find that: energy flux of events in solar cycle 23 is larger than that in cycle 24 for PL, ER and LP events; No significant solar cycle differences found in spectral indexes for PL, ER and LP events.