On detecting chromospheric limb by SDO/AIA observations

Our information from different layers of the solar atmosphere has mostly been modified in the last decades. The height of solar chromosphere has always been a favorite subject in many years. In the standard model, Chromosphere is defined as a layer with approximately 2000 km wideness. But it is now clear that, this layer does not have hydrostatic equilibrium including fine structures such as spic-ules, mottles, fibrils and so on. Therefore, studying this layer is important in terms of thermal evolu-tion created in corona. In this research, we aimed to extract the width of this region for two series of sequential images in wavelength of 304 with a spatial resolution of 0.6 arc second and temporal reso-lution of 12 s by the Atmospheric Imaging Assembly (AIA) of Solar Dynamics Observatory (SDO) mission By measuring the limb profiles in all angles from zero to 2pi radians over limb, we detect the limb of chromosphere. Furthermore, it is proved that thickness of this layer in active region is more than the status that sun is in its minimum activity.