Observation of fine structures in a small-medium mass ejection — evidence for magnetic reconnection in the lower solar atmosphere

On June 18, 2000, a small ejection phenomenon at the western limb of the sun was observed by Ganyu Station of Purple Mountain Observatory. Its lifetime was merely 15 minutes, and it did not belong to the ejection phenomena in late stages of solar flares. A very fine helical structure was visible. Assuming a velocity of 100 km/s produced by magnetic reconnection in the lower atmosphere and ignoring the Lorentz force, the height attainable by a column of ejecta of quasi-uniform density is derived, and the result is consistent with the observations.