中文摘要：

建立了离子回旋共振机制驱动的一维三元（电子、质子、alpha粒子）低速太阳风流管模型,重点分析流管参数对alpha粒子丰度（定义为alpha粒子与质子数密度之比）的影响.流管几何形式与有关观测数据分析及二维太阳风模型的计算结果相一致.与以往研究相符,在太阳附近alpha粒子的丰度先增加（可超过冕底丰度的1～5倍）,尔后迅速降至行星际空间中的平均观测数值.alpha粒子丰度极大值αmax在大约1.5～1.7 Rs范围内获得,具体数值主要取决于流管的几何参数包括冕流尖点的高度与相应膨胀因子的极大值：尖点越靠近太阳、极大膨胀因子越大,则αmax越大.但是这两个参数对于行星际空间中alpha粒子的特征影响不大;而合理地改变流管在远处的膨胀因子,可定性解释低年低速太阳风中alpha粒子的平均丰度与太阳风速度正相关的观测现象.

英文摘要：

A one-dimensional ion-cyclotron-resonance driven three-fluid model for the slow solar wind consisting of electrons, protons and alpha particles was constructed with emphasis on the effect of flow tube parameters on the alpha particle abundance. The flow tube geometry used in the model is in general consistent with the observational results and the calculation of the recent two-dimensional solar wind model. Consistently with previous results, the abundance of alpha particles increases dramatically near the sun exceeding that at the coronal base by a factor of 1 - 5, and then decreases rapidly to the observed average value in the interplanetary space. The maximum value of the abundance （αmax）, which is located around 1.5-1.7 solar radii, mainly depends on the flow tube geometric parameters, including the cusp point location and the maximum expansion factor near the cusp point. It is found that the closer the cusp point to the sun or the larger the maximum expansion factor, the larger αmax will be. However, these two parameters have little impact on the alpha abundance far away from the sun. By adjusting the expansion factor far away from the sun in a reasonable range, the authors are able to reproduce qualitatively the observed phenomenon that the average abundance in the slow solar wind correlates positively to the wind speed around solar minimum.