Over the three decades, lots of coronal EUV waves were detected by space missions, but their counterparts in the chromosphere were rarely detected. Why the chromosphere rarely bears the imprints of solar moreton waves remained a mystery. Recently, the phenomenon has come back into focus prompted by the higher spatial resolution observations with the Chinese H$\alpha$ Solar Explorer (CHASE). Here, to shed light on this problem, we investigated the photospheric vector magnetograms of the events associated with solar flares larger than GOES M-class in 2010–2023. The H$\alpha$ data are taken with the Global Oscillation Network Group (GONG) and CHASE. Ninety percent of the events are that the main magnetic polarity contains the parasitic polarity. Based on the potential field extrapolation, all the magnetic configurations above the eruptive regions are inclined. Combined with the atmospheric model, We found that the eruption direction of the moreton wave not only tends towards weaker magnetic field region, but also coincides with the direction of the rapid descent of the fast magnetoacoustic wave. Two key factors, the over expansion and inclination, play a crucial role in generating morton waves. We also discussed why those large flares accompanied with CME did not generate moreton waves. In addition, high spatial resolution off-band of H$\alpha$ observations can significantly improve the recognition rate of morton waves.

Solar coronal waves,Solar Magnetic fields,Solar activity