## 3 Results and Discussion  
### Generation of the Discharge  
It was found that it was possible to generate various types of discharges between the pin electrode and the liquid depending on the input power. In the case of a low input power of 6 W supplied to the push-pull generator, it was possible to generate a stable positive corona. During the corona discharge, the current was negligible, resulting in a charge of the reservoir capacitor at the high-voltage side and stabilization of the voltage at about 11.25 kV, as shown in Figure 2a. A photo of the corona discharge is shown in Figure 2b. With an increase in input power to 6.5 W, the voltage during the corona discharge increased to about 12 kV, resulting in the generation of occasional spark discharges. The moment of breakdown and the number of consequent spark discharges were random. After breakdown, the voltage dropped to 1-2 kV and a short current pulse was observed during the spark discharge. After termination of the spark discharge, the current dropped to 0 following oscillation and the voltage increased to the initial value. Owing to a low input power, it took several tens of milliseconds to charge the reservoir capacitor and reach the initial voltage. A further increase of power resulted in an increase in the number of occasional spark discharges, and finally at an input power of 9.5 W, consequent spark discharges were observed, as shown in Figure 2c,d. In the case of the 9.5 W input power, the spark discharges were similar to those observed for the lower input powers. On the basis of the current and voltage (I and V) waveforms, the type of discharge was the same. Some variation of peak current and voltage and frequency observed in the I and V waveforms were related to the migration of the discharge spot on the surface of the liquid. In the case of repeating spark discharges, the sparks had a scanning area of about 5 mm in diameter on the surface of the liquid, as shown in Figure 2d. A further increase of power up to 23 W did not change the discharge type and the same type of repeating sparks was observed, however, the increase of the input power resulted in some changes of the current and voltage waveforms, as shown in Figure 2e. An increase of input power resulted in an increase of peak current during the spark discharge, which decreased the time required for charging the reservoir capacitor, causing an increase of frequency of the spark discharges. On the other hand, the increase of input power resulted in stabilization of the spot of the spark and the repeating spark discharges looked like steady glow plasma (Figure 2f). Increasing the input power to values above 23 W resulted in the occasional formation of low-current arc discharges, and a stable repulsing low-current arc discharge was generated at an input power of 25 W. Compared with the repeating spark discharges, the repulsing low-current arc discharge featured a lower peak voltage of about 2.5 kV, continuous current during the discharge, and high stability of the current and voltage waveforms, as shown in Figure 2g. A photo of AALCA at the input power of 25 W is presented in the Figure 2h. In the present setup, a low-pass filter was not employed, resulting in an AC ripple of voltage, which can be observed in Figure 2e,g. In the case of the direct application of an input power of 25 W, the discharges occurred in the same order as described above, that is, as a sequence of a corona discharge, repeating sparks with increasing frequency, and finally, a low-current arc discharge. At the moment of voltage application, a corona discharge was generated first and was followed by repeating spark discharges for several seconds. Corona and spark discharges delivered RONS and ions originating from the air, evaporated liquid, and electrodes to the liquid, resulting in an increase of the electric conductivity of the liquid in a similar way to what was reported elsewhere [18; 24; 42].