Whistler-mode wave-injection experiments in the plasmasphere with a radio sounder
Whistler-mode wave-injection experiments in the plasmasphere with a radio sounder
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使用无线电发声器在等离子体层中进行惠斯勒模式波注入实验
DOI：
10.1016/s1364-6826(00)00223-6
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发表时间：
2001
影响因子：
1.9
通讯作者：
T. Bell
中科院分区：
文献类型：
--
作者：
V. Sonwalkar;X. Chen;J. Harikumar;D. L. Carpenter;T. Bell
利用高空无线电测深仪进行的哨声模式波注入实验提供了一个机会，可以在卫星位于等离子体层内或附近或位于极地上空低空时，大大扩展磁顶-极光全球探测成像仪等卫星的观测能力。作为一个例子，我们使用的无线电等离子体成像仪（RPI）的IMAGE仪器，其中包括交叉的500米的电天线在自旋平面和一个20米的天线沿着自旋轴（仅用于接收）。500-m天线在3-30 kHz范围内的哨声模式频率处接近半波长，并且应该具有1- 10%的辐射效率。发射机周围100公里范围内的波能应大于南极洲西普尔地面甚低频发射机注入的波能，从而有可能进行波粒能量和动量交换实验。我们使用射线跟踪沿着一个样本IMAGE轨道（极地，远地点），以显示条件下，发送的信号可能会返回到卫星的回波，反射后，或被观察到的机会，如EXOS-D卫星。我们发现，地面接收的发射信号应该是可能的，作为一个线性模式转换过程中的电离层不规则区域的结果。我们讨论了返回信号的波法线角的确定，这将有助于识别信号路径和获得等离子体边界和不规则性的信息。可能涉及的科学问题包括：（1）弱相干波激发VLF辐射的非线性过程的研究;（2）探测等离子体层密度结构，包括等离子体层密度空腔、场对准波导、等离子体层顶区域中的密度不规则性，以及哨声波能量转换为准静电低杂波的电离层密度结构（反之亦然）可以发生。
Whistler-mode wave-injection experiments with a high-altitude radio sounder offer an opportunity to greatly extend the observing power of satellites such as imager for magnetopause-to-aurora global exploration (IMAGE) when the satellite is within or near the plasmasphere or at low altitudes over the polar regions. We use as an example the radio plasma imager (RPI) instrument on IMAGE, which includes crossed 500-m electric antennas in the spin plane and a 20-m antenna along the spin axis (for reception only). The 500-m antennas approach a half-wavelength at whistler-mode frequencies in the 3–30 kHz range and should have a radiation efficiency of 1–10%. The wave power within ∼100 km of the transmitter should be greater than that produced by wave injection from the ground-based very low-frequency (VLF) transmitter at Siple, Antarctica, thus making possible experiments on wave–particle energy and momentum exchange. We use ray tracings along a sample IMAGE orbit (polar, apogee ∼8RE) to show the conditions under which transmitted signals may return to the satellite as echoes, following reflection, or be observed by satellites of opportunity, such as EXOS-D. We find that ground reception of transmitted signals should be possible as a result of a linear mode conversion process in regions of ionospheric irregularities. We discuss the determination of wave-normal angles of returning signals, which will aid in identifying the signal path and obtaining information on plasma boundaries and irregularities. The science topics that may be addressed include: (1) investigation of the nonlinear process by which weak coherent waves excite VLF emissions; (2) probing plasmaspheric density structure, including plasmaspheric density cavities, field aligned waveducts, density irregularities in the plasmapause region, and the ionospheric density structure where conversion of whistler-mode wave energy to quasi-electrostatic lower hybrid (LHR) waves (and vice versa) can take place.