Acceleration and transport in the magnetotail

In this dissertation we studied the propagation of charged particles throughout the magnetosphere from a few sources and examined some of the various particle acceleration mechanisms at work in the Earth's magnetotail.; We performed accessibility studies in different magnetic field models and assessed the sensitivity of the results to the choice of magnetic field model. We launched ions (H+) from the plasma mantle, and also launched H+ ions from the auroral ionosphere. We investigated the importance of non-adiabatic heating of the plasma mantle and ionospheric ions in the magnetotail. Our results show that the plasma mantle and the ionosphere are viable sources of protons to populate the plasma sheet and the quasi-trapping region. Although the differences between the two magnetic field models were substantial, the particle behavior, including the non-adiabatic heating, was similar.; We also examined the effect of the electromagnetic proton cyclotron instability on the shape of the proton velocity distribution function in the outer magnetosphere. The response of bi-Maxwellian hot and cool proton distributions to the instability were studied using one-dimensional hybrid simulations in a homogeneous plasma. We found that the enhanced fluctuations from the instability preserve the initially bi-Maxwellian character of the hot proton distribution and that it can also drive an initially nongyrotropic distribution into a gyrotropic one rapidly.; Another mechanism for particle acceleration we studied was that due to magnetic field reconnection in a tail-like magnetic field configuration. We modeled a magnetotail magnetic field undergoing rapid reconnection by adding an explosively growing tearing mode perturbation to a standard Harris neutral sheet. We found that protons can be accelerated by the electric field that is induced by the growing magnetic field to energies above 1 MeV, and that a proton's final energy depends strongly on its initial position relative to the reconnection site. We observed both regular and inverse temporal velocity dispersion of the particles in this model as a result of the time dependent acceleration process. We also examined the spectra of the protons accelerated and compared them to observations. Using data from the Interball spacecraft that displayed velocity dispersion we estimated the location of the reconnection site responsible for those observations. Electrons were also examined in similar circumstances. Electrons thanks to their small mass were thought to behave adiabatically in the vicinity of the reconnection. This has been seen not to be the case. Their acceleration takes them also beyond 1MeV in energy. Temporal velocity dispersion is dominated by inverse velocity dispersion. Because of the magnetic field topology that includes magnetic islands, electrons were able to access a multiple number of acceleration regions before saturation thus allowing them to be accelerated at more than one reconnection region.