## 3 Experimental Results  
Figure 4a presents the waveforms of an EMP having passed through GCL with isotropic plasma (without the magnetic field) at different values of the electron density \(N_{\rm e}\). For illustrative purposes, marks corresponding to the period of plasma oscillations \(f_{p}{}^{-1}\) are made next to the waveforms. Similarly to [20], a transformation of the EMP forms due to the dispersion and cutoff effects are observed. The spectral components having frequencies lower than \(f_{p}\) do not pass through the plasma, while for the components with the frequencies exceeding \(f_{p}\), the plasma is transparent. At high \(N_{\rm e}\), the transformation of an EMP into a train of oscillations with an increasing period is observed positively. The minimum (initial) period is determined by the EMP voltage rising time, while the maximum (final) period tends to reach the period of plasma oscillations \(f_{p}{}^{-1}\), but always remains somewhat shorter. The higher \(N_{\rm e}\) is, the greater is the group delay of the signal in the plasma. In a rarefied plasma (lower panels), the EMP propagation path is insufficient to let the dispersion effects manifest themselves. The distortion of the waveform is determined by the cutoff effect, and in this specific case, by filtration of the dc component of the voltage pulse in the plasma. The pattern is different in the presence of the magnetic field (see Figure 4b). In this case, the character of the transformation of the EMP waveform depends on the ratio between the electron cyclotron frequency and the plasma frequency. In the regime of \"dense\" plasma, under the condition of \(f_{p}>f_{c}\) (or \(f_{p}{}^{-1}<f_{c}{}^{-1}\), upper panels), division of the EMP breaks into two wave packets, specifically, into a high-frequency (HF) train propagating at a higher velocity and a low-frequency train propagating  
Figure 3: Scheme of generation and reception of EMP signals using the resistive splitter (attenuators are not shown). at a lower velocity and formed by oscillations with a significantly greater period. In terms of their form and delay times, the HF trains resemble the signals in isotropic plasma at the same density \(N_{e}\). The LF trains are formed by the oscillations whose frequencies are lower than or near to \(f_{p}\) and \(f_{c}\). The duration of the LF trains reaches 40 ns, which is four times as long as the time of passing of the pulse through the working GCL segment in vacuum (without plasma). In the regime of \"rarified\" plasma, under the condition of \(f_{p}<\)\(f_{c}\) (or \(f_{p}\)\({}^{-1}>\)\(f_{c}\)\({}^{-1}\), lower panels), the leading edge of the EMP passes through the magnetized plasma almost with no changes. Afterwards, the waveform distorts, and a tail of quasimonochromatic damped oscillations with a frequency close to \(f_{c}\) trails behind the pulse. Fourier analysis helps understanding the nature of EMP transformation in magnetized plasma. The results of processing of the EMP waveforms from Figure 4b by the Fourier transform method in a window with 54 ns duration are shown in Figure 5. The spectrum  
Figure 4: Waveforms of the EMPs transmitted through the plasma-filled GCL at different \(N_{e}\) values: (**a**) nonmagnetized plasma, (**b**) magnetized plasma. The grey color represents EMP waveform transmitted through GCL without plasma. For the sake of convenience, some waveforms are amplified (2\(\times\) or 5\(\times\)). The colored intervals represent the time scales of the periods of electron plasma oscillations and electron cyclotron rotation. of the initial EMP excited in the GCL is broad and continuous, and its upper limit is at about 2 GHz. In dense magnetized plasma (see the upper panel), the EMP spectrum consists of two bands, specifically, the low-frequency band at \(f<\)\(f_{c}\) (in the whistler frequency range) and the high-frequency band at \(f>\)\(f_{p}\), which are separated by the plasma evanescence region. As the plasma density \(N_{\rm e}\) decreases, the width of the evanescence region decreases as well.