Particle simulations and polar spacecraft observations of solitary waves in the magnetosphere

Both linear and nonlinear electromagnetic waves are ubiquitous in the magnetosphere. In this study, the problem of waves, which previously had been identified as electrostatic ion cyclotron waves, but now have been found to have magnetic as well as electric fluctuations, is examined. Cold and kinetic dispersion relations are used to study these waves, and the results support the idea that these ion cyclotron waves are actually a generalized EIC wave mode that has magnetic, as well as electric, field fluctuations.; Solitary waves are isolated, nonlinear waves which travel parallel to the background magnetic field and have been observed throughout the magnetosphere. Solitary waves are divided into two classes: slower waves which are associated with ion beams, and faster waves which are associated with electron beams. In this study, solitary waves are examined both observationally and through the use of computer simulations. The computer simulations of solitary waves use ES2, a 2.5D particle-in-cell simulation. The observations of solitary waves rely on data from EFI, the Polar spacecraft's electric field instrument. Solitary wave characteristics, including the speeds, electric potential, and spatial extent, are presented from and compared between the observations and simulations. These results show that the speeds of the ion solitary waves lie between the hydrogen and oxygen beam speeds, which supports the theory that ion solitary waves may form from two-stream interactions between ion beams. These observations and simulations also show that the scale size of solitary waves is roughly 22 Debye lengths in both the directions parallel and perpendicular to the background magnetic field. High altitude electron solitary waves in this study are found to have speeds of thousands of km/s and have potential amplitudes that are directly proportional to their scale size parallel to the magnetic field. The median parallel scale sizes for the electron solitary waves are approximately 15 Debye lengths. Though perpendicular scale sizes cannot be observed directly, the ratio of the parallel electric field to the perpendicular electric field, which should scale as the ratio of the perpendicular to parallel scale size, matches a theoretical predicted relation for electron solitary waves.