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Full-Text Articles in Physics
More About Arc-Polarized Structures In The Solar Wind, S A. Haaland, B Sonnerup, G Paschmann
More About Arc-Polarized Structures In The Solar Wind, S A. Haaland, B Sonnerup, G Paschmann
Dartmouth Scholarship
We report results from a Cluster-based study of the properties of 28 arc-polarized magnetic structures (also called rotational discontinuities) in the solar wind. These Alfve ́nic events were selected from the database created and analyzed by Knetter (2005) by use of criteria chosen to elim- inate ambiguous cases. His studies showed that standard, four-spacecraft timing analysis in most cases lacks sufficient accuracy to identify the small normal magnetic field compo- nents expected to accompany such structures, leaving unan- swered the question of their existence. Our study aims to break this impasse. By careful application of minimum vari- ance analysis of …
Magnetic Field Amplification In Electron Phase-Space Holes And Related Effects, R. A. Treumann, W. Baumjohann
Magnetic Field Amplification In Electron Phase-Space Holes And Related Effects, R. A. Treumann, W. Baumjohann
Dartmouth Scholarship
No abstract provided.
Resistive Mhd Reconstruction Of Two-Dimensional Coherent Structures In Space, W L. Teh, B U. Sonnerup, J Birn, R E. Denton
Resistive Mhd Reconstruction Of Two-Dimensional Coherent Structures In Space, W L. Teh, B U. Sonnerup, J Birn, R E. Denton
Dartmouth Scholarship
We present a reconstruction technique to solve the steady resistive MHD equations in two dimensions with initial inputs of field and plasma data from a single space- craft as it passes through a coherent structure in space. At least two components of directly measured electric fields (the spacecraft spin-plane components) are required for the reconstruction, to produce two-dimensional (2-D) field and plasma maps of the cross section of the structure. For con- venience, the resistivity tensor η is assumed diagonal in the reconstruction coordinates, which allows its values to be es- timated from Ohm’s law, E+v×B=η·j. In the present paper, …
On Arc-Polarized Structures In The Solar Wind, B U. Sonnerup, S E. Haaland, G Paschmann
On Arc-Polarized Structures In The Solar Wind, B U. Sonnerup, S E. Haaland, G Paschmann
Dartmouth Scholarship
A theoretical model is proposed to account for some of the behavior of arc-polarized magnetic structures seen in the solar wind. To this end, an exact analytical solu- tion is developed that describes infinite plane wave trains of arbitrary amplitude in a plasma governed by ideal Hall MHD. The main focus is on intermediate-mode wave trains, which display double-branched magnetic hodogram signatures sim- ilar to those seen in the solar wind. The theoretically derived hodograms have field rotation in the ion-polarized sense at a slightly depressed field magnitude on one branch and an electron-polarized rotation at a slightly enhanced field …
Field Line Distribution Of Density At L=4.8 Inferred From Observations By Cluster, R E. Denton, P Décréau, M J. Engebretson, F Darrouzet
Field Line Distribution Of Density At L=4.8 Inferred From Observations By Cluster, R E. Denton, P Décréau, M J. Engebretson, F Darrouzet
Dartmouth Scholarship
For two events observed by the CLUSTER space- craft, the field line distribution of mass density ρ was inferred from Alfve ́n wave harmonic frequencies and compared to the electron density ne from plasma wave data and the oxy- gen density nO+ from the ion composition experiment. In one case, the average ion mass M≡ρ/ne was about 5amu (28 October 2002), while in the other it was about 3 amu (10 September 2002). Both events occurred when the CLUSTER 1 (C1) spacecraft was in the plasmatrough. Nevertheless, the electron density ne was significantly lower for the first event (ne =8 …
The Structure Of Flux Transfer Events Recovered From Cluster Data, H Hasegawa, B U. Ö Sonnerup, C J. Owen, B Klecker, G Paschmann, A Balogh, H Re`Me
The Structure Of Flux Transfer Events Recovered From Cluster Data, H Hasegawa, B U. Ö Sonnerup, C J. Owen, B Klecker, G Paschmann, A Balogh, H Re`Me
Dartmouth Scholarship
The structure and formation mechanism of a to- tal of five Flux Transfer Events (FTEs), encountered on the equatorward side of the northern cusp by the Cluster space- craft, with separation of ∼5000 km, are studied by apply- ing the Grad-Shafranov (GS) reconstruction technique to the events. The technique generates a magnetic field/plasma map of the FTE cross section, using combined magnetic field and plasma data from all four spacecraft, under the assump- tion that the structure is two-dimensional (2-D) and time- independent. The reconstructed FTEs consist of one or more magnetic flux ropes embedded in the magnetopause, suggest- ing …
Optimal Reconstruction Of Magnetopause Structures From Cluster Data, H Hasegawa, B U. Ö Sonnerup, B Klecker, G Paschmann
Optimal Reconstruction Of Magnetopause Structures From Cluster Data, H Hasegawa, B U. Ö Sonnerup, B Klecker, G Paschmann
Dartmouth Scholarship
The Grad-Shafranov (GS) reconstruction tech- nique, a single-spacecraft based data analysis method for recovering approximately two-dimensional (2-D) magneto- hydrostatic plasma/field structures in space, is improved to become a multi-spacecraft technique that produces a single field map by ingesting data from all four Cluster spacecraft into the calculation. The plasma pressure, required for the technique, is measured in high time resolution by only two of the spacecraft, C1 and C3, but, with the help of spacecraft po- tential measurements available from all four spacecraft, the pressure can be estimated at the other spacecraft as well via a relationship, established from C1 …
High-Latitude Propagation Studies Using A Meridional Chain Of Lf/Mf/Hf Receivers, J Labelle
High-Latitude Propagation Studies Using A Meridional Chain Of Lf/Mf/Hf Receivers, J Labelle
Dartmouth Scholarship
For over a decade, Dartmouth College has oper- ated programmable radio receivers at multiple high-latitude sites covering the frequency range 100–5000 kHz with about a 1-s resolution. Besides detecting radio emissions of auro- ral origin, these receivers record characteristics of the iono- spheric propagation of natural and man-made signals, docu- menting well-known effects, such as the diurnal variation in the propagation characteristics of short and long waves, and also revealing more subtle effects. For example, at auroral zone sites in equinoctial conditions, the amplitudes of dis- tant transmissions on MF/HF frequencies are often enhanced by a few dB just before …
A Study Of Pc-5 Ulf Oscillations, M K. Hudson, R E. Denton, M R. Lessard, E G. Miftakhova, R R. Anderson
A Study Of Pc-5 Ulf Oscillations, M K. Hudson, R E. Denton, M R. Lessard, E G. Miftakhova, R R. Anderson
Dartmouth Scholarship
A study of Pc-5 magnetic pulsations using data from the Combined Release and Radiation Effects Satellite (CRRES) was carried out. Three-component dynamic mag- netic field spectrograms have been used to survey ULF pul- sation activity for the approximate fourteen month lifetime of CRRES. Two-hour panels of dynamic spectra were exam- ined to find events which fall into two basic categories: 1) toroidal modes (fundamental and harmonic resonances) and 2) poloidal modes, which include compressional oscillations. The occurence rates were determined as a function of L value and local time. The main result is a comparable probabil- ity of occurence of …