Electron cyclotron harmonic (ECH) waves can scatter electrons into the atmosphere causing diffuse aurora with diffusion coefficients depending on the wave frequency. Here we report the Van Allen Probe observations of chirping ECH elements, which are fine structures with a frequency-chirping rate of ∼kHz/s. 1,834 samples are identified in the 51-month database and over 93 percent of them exhibit a falling tone pattern. ECH elements cover a broad region from 18 Magnetic Local Time (MLT) through dawn to 14 MLT with L = 4 − 7, and mainly occur in...