## 3 Wide Tearing Modes
### Tearing Mode in H-Mode Discharge  
In previous sections, the tearing modes observed in Ohmic heating regimes were discussed; however, TMs also developed in discharges with auxiliary heating. They were found in experiments with a transition to high confinement or the H-mode which was initiated using NBI. This scenario in discharge #42142 is presented in Figure 8. The main parameters of the deuterium plasma were toroidal magnetic field \(\mathrm{B_{T}}\) up to 0.8 T and a plasma current \(\mathrm{I_{p}}\) up to 0.35 MA. Transition to the H-mode takes place at 161 ms and is characterized by an increase in electron density \(\mathrm{n_{e}}\), a drop in \(\mathrm{D_{\alpha}}\) signal and edge-localized mode (ELM) development [20; 25]. The TM was detected using the magnetic probe at a later stage of the discharge at 204 ms. The fluctuations lasted for 7 ms and ultimately ended in a disruption. Starting from 208 ms, the oscillation amplitude on the magnetic probe signal decreases (Figure 8f) with a simultaneous decrease in the TM frequency which is a characteristic sign of mode locking. The rotation of the mode slows down to a complete stop with a simultaneous increase in the locked mode amplitude, which leads to a disruption. The increase in the amplitude of the locked mode from 208 ms was recorded by a special magnetic sensor (Figure 8e). The sensor is a combination of two magnetic coils located outside the vacuum chamber in the equatorial plane. The integrated difference signal of the two coils describes the inhomogeneity of the radial magnetic flux caused by the appearance of the locked mode. During the existence of the TM in discharge #42142 a  
Figure 7: Poloidal cross-section of the Globus-M2 tokamak with magnetic field lines using EFIT and performed ray tracing for DBS probing waves for discharge #40515.  
degradation of plasma confinement leading to a transition back to the L-mode is observed. This is indicated by a decrease in the average electron density n\({}_{\rm e}\) from 7.4 \(\times\) 10\({}^{19}\) m\({}^{-3}\) to 6.2 \(\times\) 10\({}^{19}\) m\({}^{-3}\) and growth of the D\({}_{\alpha}\) signal. The soft X-ray (SXR) signal (Figure 8d) decreases steadily during this time which means that the temperature is reduced after the development of the tearing mode takes place. The poloidal rotation velocity of the plasma is affected by MHD activity [26], as during the TM there was an observable decrease in rotation velocity. This is demonstrated in Figure 8g in the form of the measured Doppler frequency shift of the 39 GHz channel. In discharge #42142 a disruption occurs at 211 ms. The scenario of a disruption after MHD activity is a studied phenomenon [27; 28]. The mode numbers of the TM in this case also appear to be \(m/n=2/1\).  
Figure 8: The Globus-M2 plasma parameters for discharge #42142: (**a**) plasma current I\({}_{\rm P}\), (**b**) electron density n\({}_{\rm e}\), (**c**) D\({}_{\alpha}\) signal, (**d**) soft X-ray (SXR) signal, (**e**) locked mode sensor signal \(\Phi_{\rm B}\), (**f**) magnetic probe signal U\({}_{\rm MP}\), (**g**) Doppler frequency shift f\({}_{\rm D}\).  
The tearing mode was detected using DBS. It was observed on several channels at the same time as it was seen on the magnetic probe signals in Figure 8e. The TM was found on channels with probing frequencies 29, 39, 48, 50, 55 and 60 GHz; however, it was not found on the 65 or 20 GHz channels. The calculated spectrograms of the DBS phase derivative for two of the channels are presented in Figure 9. The frequency of the TM decreases from 20 to 9 kHz over time. The fact that the area of detection spans a large range of radii indicates that this another example of a tearing mode with a large width of the magnetic island.