## 4 Discussion  
Two types of tearing modes were detected on the Globus-M2: the narrow TM and the wide TM. While both scenarios can take place, the wide TM is more typical for Globus-M2 discharges. This is due to the conditions of its formation being more favorable. As the narrow TM develops at the stage of the plasma current growth, it means that the magnetic field geometry of the plasma is changing rapidly at this point, meaning the conditions necessary for this type of TM to develop do not last long enough for the mode to always become unstable. This is not the case for the wide TM which occurs when the plasma current has reached the plateau phase.  
The different tearing modes found on the Globus-M2 raise a series of questions when it comes to explaining the differences in their behavior. One of those is the nature of the TMs observed. Additional analysis is necessary to understand whether it is the classical [29] or neoclassical tearing mode (NTM) [30]. On the Globus-M it was noted that the high value of the poloidal plasma pressure \(\beta_{\rm P}\) of around 0.3 seemed to determine the development of the NTM. This is why discharges with the MHD mode supposedly to be the NTM need to be modelled to determine the \(\beta_{\rm P}\).  
Additionally, the difference in island width is an important topic for investigation. For instance, the tearing modes in discharges #40420 and #40515 are both characterized by a magnetic field amplitude of around 2.5 mT meaning that this parameter cannot explain the difference in island width between them. However, the TM in discharge #42142 (which developed under different conditions compared to the other cases) has a magnetic field  
Figure 9: Spectrograms of the DBS phase derivative for discharge #42142.  
amplitude of 5 mT which might be enough to justify the large island width. This why modelling of the magnetic island width will be performed using magnetic probe signals and compared to the modified Rutherford theory. The results will also be compared with values from experiments.  
Apart from that, it is important to explain the employment of the DBS diagnostics for tearing mode study. A similar analysis has previously been performed for a different type of MHD activity, the Alfven eigenmode (AE) [10], and it led to the conclusion that the magnetic field amplitude could be calculated from the DBS measurements without having to deal with the spatial damping of the instability. Thus, depending on the explanation for why the TM is found in DBS phase derivative signals, DBS might be a useful tool for obtaining direct measurements of the magnetic field in the presence of TMs as well. Large-scale MHD instabilities of a 10 cm scale cannot lead to the backscattering of super-high-frequency (SHF) radiation due to the fact that [PERSON]'s law would not be satisfied. Based on DBS measurements the scale of plasma fluctuations \(\frac{2\pi}{k}\) is around 1 cm and is much smaller than the TM observed. However, they might have been observed due to possible significant magnetic field perturbations near the position of the cut-offs. This, for example, can lead to changes in the angle of incidence of the incident beam and can be potentially responsible for the detection of the TM in the DBS phase derivative signals. Additionally, full-wave modelling of the processes of backscattering in the case of the presence of NTMs will be undertaken.