2004 Fiscal Year Final Research Report Summary
Phase coherence in the solar wind MHD waves : Geotail data analysis and numerical simulation studies
| Project/Area Number |
15540428
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Space and upper atmospheric physics
|
|---|
| Research Institution | KYUSHU UNIVERSITY |
|---|
Principal Investigator |
HADA Tohru KYUSHU UNIVERSITY, Interdisciplinary Graduate School of Engineering Sciences, Associate Professor, 大学院・総合理工学研究院, 助教授 (30218490)
|
|---|
| Project Period (FY) |
2003 – 2004
|
| Keywords | MHD waves / MHD turbulence / Phase coherence / Nonlinear waves / Particle diffusion |
|---|
| Research Abstract |
By analyzing magnetic field data obtained by Geotail spacecraft, and also by performing numerical simulations of various systems modeling nonlinear coupling of MHD waves, we have made research on several issues related to the wave phases.
1.We have developed a method to quantitatively evaluate the phase coherence among waves, by comparing structure functions of the original and its phase shuffled and phase correlated surrogates. Application of the method to Geotail magnetic field data revealed that the MHD waves in the foreshock is in fact phase correlated, and the correlation is stronger as the turbulence amplitude is increased. We have further identified the origin of the phase coherence by a method using the wavelet filtering technique.
2.By numerical time integration of various systems which model the nonlinear coupling of MHD waves, such as the triplet model, multiply-coupled triplet model, the DNLS equation, and the Hall-MHD set of equations, we discussed the relationship between the phase coherence, nonlinear dispersion relations, and transfer of energy among the different waves (or eigenmodes). We showed that the phase coherence is self-generated as the energy is transferred between the waves, and the phenomena can be modeled by avalanches.
3.By performing test particle simulations, we discussed diffusion and acceleration of energetic particles in the MHD turbulence with phase coherent structures. We argued the relationship between statistics of the particle transport and that of the field fluctuations.
|
