## 2 Description of the Experiment  
The experiments were performed using the gigantic coaxial line (GCL) [19; 20] installed inside the chamber of the large-scale Krot plasma device (Figure 1). This device is used for simulating space plasma and is described in detail in [18]. It is a vacuum chamber with a volume of about 170 cubic meters, in which a large quasiuniform plasma column can be produced using several pulsed radio-frequency (rf) generators. In experiments, various working gases can be used in continuous injection mode; the most commonly used are argon, helium, and air. The plasma is magnetized using a solenoid 3.5 m long and 1.5 m in diameter installed inside the chamber. The GCL is installed within a solenoid. It consists of three sections, specifically, the 3 m long working segment and two tapering transitions that are 3.5 m long each, which act as wave transformers (see Figure 1). The diameters of the external and internal conductors of the working segment are 140 cm and 8 cm, respectively. The wave impedance of the working segment in vacuum is 170 Ohm, and the input and output impedances are 50 Ohm. The external conductor of the coaxial line is assembled from metal strips about 10 cm wide each. The internal conductor is a solid metal pipe, which is supported in place relative to the external conductor with polyamide spokes and rings. The line was filled with plasma by means of pulsed rf inductive discharge in argon under the pressure \(p\) = 4 \(\times\) 10\({}^{-4}\) Torr. Argon is used as an accessible and relatively inexpensive noble gas, which makes it possible to obtain slowly decaying plasma with well-reproducible parameters. Four induction coils (or inductors) 90 cm in diameter were installed inside the working segment of the line at a distance about 75 cm from each other, which ensured sufficiently uniform filling of the line with the plasma. The inductors were excited in pairs in parallel by two rf generators. The rf power applied to each couple of inductors was about 100 kW, the frequency was 5 MHz, the duration of the ionizing pulse was 1 ms, and the repetition rate of the ionizing pulses was one every 20 s.  
The parallel (axial) magnetic field with strength from zero to several hundreds of Gauss (G) was generated by a pulsed current in solenoid as shown in Figure 1. The ionizing rf pulse was applied to inductors as the current in the solenoid reached its maximum value. The characteristic time of the current (and magnetic field) variation was about 100 ms and significantly exceeded the characteristic times of plasma production and decay. All the results presented in this paper were obtained at the magnetic field strength with the maximum of the solenoid current being \(B_{0\,max}\) = 90 G (\(f_{c\,max}\) = 252 MHz). Figure 1: Schematic diagram of the experimental setup. All the measurements were performed after the end of the ionizing pulse in quiescent afterglow plasma. The plasma parameters were measured by means of microwave resonator probes based on sections of the double lines with resonance frequencies of 930 MHz and 2650 MHz [25; 26] and a Langmuir probe. The probes were mounted on rods which can be moved in the radial direction freely to obtain the profiles of plasma parameters. Microwave resonator probes were used to measure the plasma density; the Langmuir probe data were mainly used to obtain the electron temperature. The maximum plasma density (\(N_{e}\)-\(10^{11}\) cm\({}^{-3}\), \(f_{p}\)-2.85 GHz) was reached by the end of the ionizing pulse. Then, the electron density decreases due to the diffusion decay of the plasma with a characteristic time of about 2 ms. The electron temperature at the end of ionizing pulse was several eV and relaxed to \(T_{e}\)-0.2-0.3 eV during several hundreds of microseconds. The measurements showed that the decaying plasma density distribution across the GCL was quasiuniform (bell-shaped).