The mode conversion process responsible for radio wave generation has been studied for several decades; however, the properties of the condition required for an efficient conversion process are still unknown. The aim of this study is to determine the value of plasma frequency required for an efficient mode conversion process from slow Z -mode to left-hand ordinary (LO)-mode waves in the matching cases, where the two branches of the dispersion relation of the two modes are perfectly connected. We derive the dispersion relations for electromagnetic wave propagation in an inhomogeneous plasma considering Snell’s law and investigated them in detail. We quantify the minimum variation of plasma frequency required for the efficient mode conversion process, which we call “the plasma frequency demand.” We show that the condition required for the efficient mode conversion can be satisfied by waves propagating first toward the high-density region and then returning toward the low-density region before reaching the region where the wave frequency matches the cutoff frequency; therefore, a large inhomogeneity is not always required. We show that the angle between the background magnetic field and the density gradient has a significant effect on the plasma frequency demand.

中文翻译：

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非均匀等离子体中从慢 Z 模式波到 LO 模式波的模式转换过程的等离子体频率需求

负责无线电波生成的模式转换过程已经研究了几十年；然而，高效转化过程所需条件的特性仍然未知。本研究的目的是确定在匹配情况下从慢 Z 模式到左手普通 (LO) 模式波的有效模式转换过程所需的等离子体频率值，其中色散关系的两个分支为两种模式完美结合。我们根据斯涅尔定律推导出电磁波在非均匀等离子体中传播的色散关系，并对其进行了详细研究。我们量化了高效模式转换过程所需的等离子体频率的最小变化，我们称之为“等离子体频率需求”。” 我们表明，通过波首先向高密度区域传播，然后在到达波频率与截止频率匹配的区域之前返回低密度区域，可以满足高效模式转换所需的条件；因此，并不总是需要大的不均匀性。我们表明背景磁场和密度梯度之间的角度对等离子体频率需求有显着影响。