Characteristics of Langmuir electric field waveforms and power spectra exhibiting nonlinear behavior in Earth’s foreshock - Sigsbee,K; Kletzing,CA; Pickett,JS; Gurnett,DA; Schwartz,SJ; Lefebvre,B; Lucek,E; Fazakerley,AN; Kucharek,H (Journal of Geophysical Research (Space Physics), 2010)