M dwarf stars (red dwarfs), the most common stars in the Milky Way (70 percent of all stars), have low temperatures and masses but exhibit strong magnetic activity, such as flares, starspots, and coronal mass ejection (CME). Studying their magnetic activity helps understand the internal structure and evolutionary processes of stars, as well as their impact on the environments of surrounding planets. This study uses medium-resolution spectral (MRS) data of M dwarf stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 10 (DR) to conduct a comprehensive and in-depth investigation of stellar magnetic activity, flare, and starspot variations. By cross-matching the low-resolution spectral (LRS) M dwarf star catalog from LAMOST DR10 MRS data, we have successfully identified 20279 M dwarfs and obtained a total of 708969 medium-resolution spectral datasets. These data provide a rich foundation for studying stellar magnetic fields and activity characteristics. Additionally, we cross-matched the data with light curves from the Transiting Exoplanet Survey Satellite (TESS), acquiring light curve data for 2868 stars, among which 891 flare stars were identified, providing important samples for the statistical characteristics and physical mechanisms of flare events. By combining with Gaia data, we clarified the spatial distribution characteristics of M dwarfs in the Milky Way. In statistical studies of M dwarf stars magnetic activity using LAMOST medium- resolution spectra, it has been found that as the effective temperature of M dwarf stars increases, their stellar activity diminishes, though this trend becomes less evident for Teff>3600K, and the amplitude of Halpha line variations becomes more dramatic for later spectral types. In a sample of 11868 M dwarfs with a signal-to-noise ratio exceeding 10, we found that 1676 exhibited Halpha emission features, i.e., were active stars. Also, among the 891 flare stars identified from TESS light curve data, 7496 flare events were detected. Among the 119 stars with EW Halpha flare-like variations, 25 were flare stars in TESS light curve data. Research has also clarified that the activity of M dwarf stars in the Milky Way decreases with increasing vertical distance from the galactic disk. Furthermore, by combining LAMOST spectral surveys with TESS light curve data, a positive correlation between chromospheric activity, as indicated by Halpha lines, and star spot area has been established.Additionally, studies show a positive correlation between flare energy and duration in M dwarf stars, with the slope of this correlation decreasing for later spectral types. Finally, through analyzing the asymmetry of Halpha lines, two potential CME candidates have been identified.

Cone search capability for table J/A+A/704/A274/table1 (Stellar parameters of M dwarf stars from LAMOST DR10)