Whistler-Mode Radiation From a Dipole Antenna in Cold Magnetized Plasma
Whistler-Mode Radiation From a Dipole Antenna in Cold Magnetized Plasma
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DOI：
10.1109/tap.2021.3121144
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发表时间：
2022-04-01
影响因子：
5.7
通讯作者：
Johnston, William R.
中科院分区：
文献类型：
--
作者：
Song, Paul;Tu, Jiannan;Johnston, William R.
我们基于菲涅尔区构造理论研究冷磁化等离子体中偶极天线的哨声模辐射。天线沿不同传播方向辐射的波在空间中相互干涉。当在观测点处干涉主要为相长干涉时，就会形成波增强区域。相干增强波以群速度传播。如果天线垂直于背景磁场，强波区域会形成两个背对背的菲涅尔区，它们是沿天线方向的背景磁场的抛物面锥形。每个锥体内的功率随距离以1/r的速率下降，这比真空中球面波的1/r²衰减要慢得多。总辐射可近似通过对菲涅尔区积分的总能量通量得出。导出的辐射电阻比真空中的大得多。它与频率成1/f²比例关系，与天线长度成d²比例关系。为了辐射更多功率，更长的天线更可取，这一结果与之前一些理论研究相反。
We treat whistler-mode radiation from a dipole antenna in a cold magnetized plasma based on the Fresnel zone construction theory. Radiated waves from the antenna with different propagation directions interfere in space. Regions of enhanced waves are formed when the interference is predominantly constructive at the observing point. The coherently enhanced wave propagates at the group velocity. If the antenna is perpendicular to the background magnetic field, the regions of strong waves form two back-to-back Fresnel zones that are parabolic-shaped cones along the background magnetic field from the antenna. The power within each cone drops with distance at a rate of 1/r much more slowly than the 1/r(2) thinning of a spherical wave as in vacuum. The total radiation can be approximately derived by the total energy flux integrated over the Fresnel zone. The derived radiation resistance is much greater than that in vacuum. It is proportional to frequency as 1/f(2) and proportional to the antenna length as d(2). To radiate more power, a longer antenna is preferred, a result that is opposite to some previous theoretical studies.