vector in the field-of-view. Value $f$ lies between 0 and 1, where 1 means that the given point of the flare kernel is exactly at the maximum gradient of the magnetic field in a given active region.

![Histograms of quantity $f$ for a set of situations in the full range of $f$ values (upper panel) and their magnification in the high-tail part (bottom panel).[]{data-label="fig:histograms"}](hist.pdf "fig:"){width="50.00000%"}\
![Histograms of quantity $f$ for a set of situations in the full range of $f$ values (upper panel) and their magnification in the high-tail part (bottom panel).[]{data-label="fig:histograms"}](hist_detail.pdf "fig:"){width="50.00000%"}

We investigated namely four following situations: 1. $f$ values in the regions without VL emission, 2. $f$ values in the regions with VL emission, and 3. and 4. $f$ values in the flare-kernel points for flare classes C1 and CP, respectively. The histograms (normalised so that their integral be unity) for these four situations are displayed in Fig. \[fig:histograms\]. Occurrence frequencies of $f$ in the case of C1 and CP flare kernels are larger than in the whole regions in the high-tail range, essentially meaning that the flare kernels do systematically appear in the regions of a large gradient of the magnetic field, where also the appearance 