On reflection of Alfven waves in the solar wind
The authors have revisited the problem of propagation of toroidal and linear Alfven waves formulated by Heinemann and Olbert to compare WKB and non-WKB waves and their effects on the solar wind. They considered two solar wind models and showed that reflection is important for Alfven waves with periods of the order of one day and longer, and that non-WKB Alfven waves are no more effective in accelerating the solar wind than WKB waves. There are several recently published papers which seem to indicate that Alfven waves with periods of the order of several minutes should be treated as non-WKB waves and that these non-WKB waves exert a stronger acceleration force than WKB waves. The purpose of this paper is to study the origin of these discrepancies by performing parametric studies of the behavior of the waves under a variety of different conditions. In addition, the authors want to investigate two problems that have not been addressed by Heinemann and Olbert, namely, calculate the efficiency of Alfven wave reflection by using the reflection coefficient and identify the region of strongest wave reflection in different wind models. To achieve these goals, they investigated the influence of temperature, electron density distribution, wind velocity and magnetic field strength on the waves. The obtained results clearly demonstrate that Alfven wave reflection is strongly model dependent and that the strongest reflection can be expected in models with the base temperatures higher than 10(exp 6) K and with the base densities lower than 7 x 10(exp 7) cm(exp -3). In these models as well as in the models with lower temperatures and higher densities, Alfven waves with periods as short as several minutes have negligible reflection so that they can be treated as WKB waves; however, for Alfven waves with periods of the order of one hour or longer reflection is significant, requiring a non-WKB treatment.
- Research Organization:
- National Aeronautics and Space Administration, Huntsville, AL (United States). George C. Marshall Space Flight Center
- OSTI ID:
- 102025
- Report Number(s):
- N--95-30582; NASA-TM--110642; NAS--1.15:110642; CNN: NAGW-2933; NAG8-839; NSF INT-90-16514; NSF ATM-91-19580
- Country of Publication:
- United States
- Language:
- English
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