The chromospheric line-of-sight velocity variations in a solar microflare

Abstract The variations of the chromospheric line-of-sight velocity in the active region NOAA 11024 are studied before, during, and after a solar microflare on 2009 July 4. At the day of the observations the main emergence phase was in this active region. The new emerging flux has interacted with the pre-existing magnetic field. The spectropolarimetric observations were carried out with the French–Italian THEMIS telescope (Spain, Tenerife). We used Hα spectra of the high resolution obtained over 21 min. The spatial resolution was ∼1 arcsec. The time interval between the spectra was 2.84 s. Doppler velocities were measured in the microflare location and its surroundings. We have revealed strong temporal variations of the line-of-sight velocity in the chromosphere. The velocities changed in the range −33–10 km/s. We revealed the velocity oscillations with the amplitude of 4–5 km/s. 12–14 min before the microflare both upward and downward motions with velocity values reaching about 20 km/s are found on the outer edge of the region studied. The amplitude of the oscillations increased. It may be the signature of the magnetic reconnection.