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Astrophysics and Astronomy

Dartmouth College

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Geophysics

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Articles 1 - 2 of 2

Full-Text Articles in Physics

Discontinuities And Alfvenic Fluctuations In The Solar Wind, G. Paschmann, S. Haaland, B. Sonnerup, T. Knetter May 2013

Discontinuities And Alfvenic Fluctuations In The Solar Wind, G. Paschmann, S. Haaland, B. Sonnerup, T. Knetter

Dartmouth Scholarship

We examine the Alfvenicity of a set of 188 solar wind directional discontinuities (DDs) identified in the Cluster data from 2003 by Knetter (2005), with the objective of separating rotational discontinuities (RDs) from tangential ones (TDs). The DDs occurred over the full range of solar wind velocities and magnetic shear angles. By performing the Walen test in the de Hoffmann–Teller (HT) frame, we show that 77 of the 127 crossings for which a good HT frame was found had plasma flow speeds exceeding 80 % of the Alfven speed at an average angular deviation of 7.7◦; 33 cases had speeds …


First Results From Ideal 2-D Mhd Reconstruction: Magnetopause Reconnection Event Seen By Cluster, W. L. Teh, B. U. O. Sonnerup Jan 2008

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 …