回旋同步辐射自吸收的特性

Characteristics of the Self Absorption of Gyrosynchrotron Radiation

详细研究了高能电子产生的回旋同步辐射自吸收的特性,并用磁偶极子场的 射电微波源模型计算了它的光学厚度.发现: (1)自吸率Kv随谐波数s的增加迅速地 下降,以致只有低次谐波(s<5)上的自吸收才会对微波爆发谱产生实质性的影响; (2) 自吸率κv随暗波数s下降的陡度还随高能电子的能谱指数δ的增加和其低能截止能量 E0的下降而迅速增加; (3)κv值还随传播角的增大而增加,并在70°至75°范围内达到 极值; (4)假设高能电子数密度为103cm-3,则在2≤s≤5范围内的自吸收的光学厚 度τvself在101-10-2之间变化,这些值约比回旋共振吸收的光学厚度τvgyro小3至4 个数量级.τvself在均匀磁场情况下可能被高估.只有当被加速的高能电子的数密度大于 104cm-3时,自吸收的光学厚度才开始能与回旋共振吸收的光学厚度相比较.

The characteristics of the self absorption of gyrosynchrotron emission arc-investigated detail and its optical depth is estimated from radio microwave source with a magnetic dipole field. It is shown that: (1) the self absorptivities κV(?) dicrease rapidly with increasing harmonic number s(= v/vB), so that only these absorptions of the lower harmonics (s ≤ 5) can affect substantially microwave burst sprectra; (2) this decrease becomes more quickly as increasing energy spectral index 5 and decreasing low-energy cutoff E0 of energetic electrons; (3) κv(?)increase also obviously as increasing propagation angle θ and reach maximum in the range of 70° - 75°; (4) for 2 ≤ s ≤ 5 the optical depths of the self absorption, τv(?)self,s, are in the range of 101 - 10-2. This value is 103 - 104 lower than that of the gyroresonance absorption, assuming the number density of energetic electrons. N - 103cm-3. τv(?)self would be overestimated in the uniform magnetic field case. Only when N is larger than 104 cm-3, the optical depth of the self absorption can compare with one of gyroresonance absorption.