Table 1.

Inhomogeneity factor (S) for nonlinear wave growth at V_res (Event 1)

	$v_{\mathrm{e}\perp }$ (energy, pitch angle)
Bw	5000 km s−1 (373 eV, 154°)	8500 km s−1 (508 eV, 140°)	12,000 km s−1 (711 eV, 131°)
0.2 nT	−0.75	−0.49	−0.40
0.5 nT	−0.30	−0.20	−0.16
0.8 nT	−0.19	−0.12	−0.10

Parameters observed by MMS1 around 15:59:19.64 UT were used for this calculation of S. At V_res of −10,300 km s⁻¹, estimated S satisfied the condition that the trapping can occur ($-1<S<0$) in the range of $v_{\mathrm{e}\perp }$ where electrons became strongly nongyrotropic (Fig. 3).