What is/are the effect(s) produced by atmospheric refraction?

The effects produced by atmospheric refraction are the twinkling of stars, advanced sunrise and delayed sunset.
Atmospheric refraction is the refraction caused by the earth's atmosphere. Earth's atmosphere consists of various layers with different optical densities. When light passes over these layers, it undergoes refraction. The effects of atmospheric refraction are the twinkling of stars, advanced sunrise and delayed sunset.
●       The intensity of starlight varies due to the optical diffraction of light, which is different at different layers of the atmosphere. Thus, there is a change in the intensities of the star's light which results in the twinkling. 
●       The actual sunrise takes place when the sun is just above the horizon. But due to the atmospheric refraction of sunlight, we can see the sun before 2 minutes of the actual sunrise.
●       Due to the atmospheric refraction of sunlight, we can see the sun for about 2 minutes even after sunset.