Physics Commons^™

Comparison Of Birkeland Current Observations During Two Magnetic Cloud Events With Mhd Simulations, H Korth, B J. Anderson, J G. Lyon, M Wiltberger

Dartmouth Scholarship

Low altitude field-aligned current densities ob-

tained from global magnetospheric simulations are compared

with two-dimensional distributions of Birkeland currents at

the topside ionosphere derived from magnetic field observa-

tions by the constellation of Iridium satellites. We present the

analysis of two magnetic cloud events, 17–19 August 2003

and 19–21 March 2001, where the interplanetary magnetic

field (IMF) rotates slowly (∼10◦/h) to avoid time-aliasing in

the magnetic perturbations used to calculate the Birkeland

currents. In the August 2003 event the IMF rotates from

southward to northward while maintaining a negative IMF

By during much of the interval. During the March 2001 …

Lower Limit To The Scale Of An Effective Quantum Theory Of Gravitation, R. R. Caldwell, Daniel Grin

Dartmouth Scholarship

An effective quantum theory of gravitation in which gravity weakens at energies higher than ∼10−3  eV is one way to accommodate the apparent smallness of the cosmological constant. Such a theory predicts departures from the Newtonian inverse-square force law on distances below ∼0.05  mm. However, it is shown that this modification also leads to changes in the long-range behavior of gravity and is inconsistent with observed gravitational lenses.

First Results From Ideal 2-D Mhd Reconstruction: Magnetopause Reconnection Event Seen By Cluster, W. L. Teh, B. U. O. Sonnerup

Dartmouth Scholarship

We have applied a new reconstruction method (Sonnerup and Teh, 2008), based on the ideal single-fluid MHD equations in a steady-state, two-dimensional geometry, to a reconnection event observed by the Cluster-3 (C3) space- craft on 5 July 2001, 06:23 UT, at the dawn-side Northern- Hemisphere magnetopause. The event has been previously studied by use of Grad-Shafranov (GS) reconstruction, per- formed in the deHoffmann-Teller frame, and using the as- sumption that the flow effects were either negligible or the flow was aligned with the magnetic field. Our new method allows the reconstruction to be performed in the frame of reference moving …