Magnetic activity from LAMOST DR9, Gaia & TESS

Based on the equivalent width of the H{alpha} line, we ascertain the activity properties of the stars, identifying a total of 107,134 active stars, with 31175 exhibiting H{alpha} variations. Furthermore, we establish a positive correlation between starspot activity from Transiting Exoplanet Survey Satellite light curves, and chromospheric activity observed through LAMOST spectra on M dwarf stars.

Utilizing LAMOST and Gaia data, we map the two-dimensional distribution of active fractions across all M dwarfs in the Milky Way based on H{alpha} and H{beta} lines, confirming a decrease in the active fraction as the distance above the Galactic disk increases. Additionally, we investigate the relationship between chromospheric activity and absolute height above the Galactic disk in various M subtypes. Our findings reveal distinct trends: for M0 to M5 dwarf stars, the active fraction of H{alpha} and H{beta} lines rapidly decreases within the 0-300pc range.