Electron Holes and Heating in the Reconnection Dissipation Region

Using particle-in-cell simulations and kinetic theory, we explore the current-driven turbulence and associated electron heating in the dissipation region during 3D magnetic reconnection with a guide field. At late time the turbulence is dominated by the Buneman and lower hybrid instabilities. Both produce electron holes that co-exist but have very different propagation speeds. The associated scattering of electrons by the holes enhances electron heating in the dissipation region.Comment: 14 pages, 5 figures, submitted to GR

Nonlinear Development of Streaming Instabilities In Strongly Magnetized Plasmas

The nonlinear development of streaming instabilities in the current layers formed during magnetic reconnection with a guide field is explored. Theory and 3-D particle-in-cell simulations reveal two distinct phases. First, the parallel Buneman instability grows and traps low velocity electrons. The remaining electrons then drive two forms of turbulence: the parallel electron-electron two-stream instability and the nearly-perpendicular lower hybrid instability. The high velocity electrons resonate with the turbulence and transfer momentum to the ions and low velocity electrons.Comment: Accepted by PR

Economic Deposits at Blue Hill

Guidebook for field trips in east-central and north-central Maine: 66th annual meeting October 12 and 13, 1974: Trip B-

A Search for Stellar Obscuration Events due to Dark Clouds

The recent detections of a large population of faint submillimetre sources, an excess halo gamma-ray background, and the extreme scattering events observed for extragalactic radio sources have been explained as being due to baryonic dark matter in the form of small, dark, gas clouds. In this paper we present the results of a search for the transient stellar obscurations such clouds are expected to cause. We examine the Macho project light curves of 48 x 10^6 stars toward the Galactic bulge, LMC and SMC for the presence of dark cloud extinction events. We find no evidence for the existence of a population of dark gas clouds with Av > 0.2 and masses between ~ 10^-4 and 10^-2 M_solar in the Galactic disk or halo. However, it is possible that such dark cloud populations could exist if they are clustered in regions away from the observed lines of sight.Comment: 13 pages, 9 figures, submitted to Ap