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[1] We study the dynamical behavior of potential structures in the auroral upward current region. The study is based on a large two-dimensional particle-in-cell simulation. A double layer (DL) forms in the auroral potential structure in the counterstreaming expansion of cold and hot plasmas from bottom (ionospheric side) and top (magnetospheric side), respectively. Transversely nonuniform converging perpendicular electric field drives the plasma from the top, generating V-shaped potential structure within the expanding plasmas. The dynamical features include (1) recurring formation of the DL, (2) downward motion of the DL over the distance of thousands of Debye lengths, (3) collapse of the existing double layer after the reformation of a new one near the top in the hot magnetospheric plasma, and (4) generation of electron holes (EHs) on the high-potential side of the DL and their downward propagation over a few thousand of Debye lengths, where they are dissipated. The EHs are associated with broadband plasma waves with spectrum peaked near the lower hybrid frequency. The EH turbulence is temporally modulated by low-frequency plasma waves near the ion cyclotron frequency W i . Electrostatic ion cyclotron waves above W i occur on the low-potential side of the DL. Transverse and parallel acceleration/heating of both electrons and ions are studied. The fast moving electron holes are found effective in transverse heating of the cold ionospheric electrons trapped below the DL. Relevance of our results to satellite observations in the auroral plasma is discussed.Citation: Singh, N., S. Araveti, and E. B. Wells (2011), Mesoscale PIC simulation of double layers and electron holes affecting parallel and transverse accelerations of electrons and ions,

Using two-dimensional particle-in-cell (PIC) simulations, we study the formation of density cavities in plasmas driven by transversely large-scale Alfvén waves (LSSAWs) when they reflect from a boundary, like in the topside auroral ionosphere. The ponderomotive force, associated with the resulting standing waves, causes strong modification in the density distribution, including density cavities. Based on our findings we suggest that the ubiquity of density cavities in the auroral plasma is possibly a direct consequence of the ubiquity of the LSSAWs. In the cavities the amplitudes of the transverse wave electric (|E ⊥ |) and magnetic (|B ⊥ |) fields are, respectively, diminished and enhanced so that E ⊥ VAB ⊥ , where VA is the Alfvén velocity, as recently reported from a statistical analysis of FAST data at an altitude of ∼4000 km (Chaston C. C. et al., Phys.