Observation of an impulsive solar electron event extending down to ∼0.5 keV energy

Abstract

We present the first observation of a solar impulsive electron event spanning the entire solar wind‐suprathermal particle energy range (few eV to hundreds of keV), obtained with the 3‐D Plasma and Energetic Particle experiment on the WIND spacecraft. The electron energy spectrum fits to a power‐law ∼ E −3 from ∼40 keV down to a peak at ≲ 1 keV, with significant flux detected down to ∼0.5 keV. Since the range of such low energy electrons in ionized hydrogen is much less than the column density of the corona, they must be accelerated high, ∼1 R ⊙ (solar radius) above the photosphere, for typical active coronal density models.