Publication Date:
2014-09-16
Description:
Recent spacecraft’s observations of kilometric continuum radiation showed that the linear mode conversion theory (LMCT) cannot explain the beaming angle of these observations; on the other hand satellite observations show some local fluctuation in the density gradient. In this research, we consider the mode conversion process from UHR-mode (slow Z- mode) to LO-mode (ordinary) waves, focusing on the effect of the angle between the density gradient and the external magnetic field on the efficiency of the LMCT and the resultant beaming angle of converted LO-mode waves; a comparison of the LMCT and simulation results are presented. We first consider a condition that the density gradient is perpendicular to the external magnetic field, corresponding to the condition assumed in the conventional LMCT. Next, we extend the discussion to the condition that the density gradient is oblique to the external magnetic field. Our aim here is to investigate a condition where the efficient mode conversion can occur and to study the deviation of the beaming angle from that estimated by LMCT. From the results of analyses, for both perpendicular and oblique cases, the highest conversion efficiency is obtained for a certain value of the wave normal angle (critical wave normal angle) of the incident slow Z-mode waves, corresponding to the case when two mode branches are matched. The simulation results show in the perpendicular case that the beaming angle is consistent with the conventional LMCT; but in the oblique case a critical wave normal angle becomes different from the perpendicular case and the beaming angle is different from the LMCT prediction.
Print ISSN:
0167-9295
Electronic ISSN:
1573-0794
Topics:
Geosciences
,
Physics
