Why does the intensity of the flux of cosmic rays increase when approaching the Earth? Why does the flow rate decrease

Why does the intensity of the flux of cosmic rays increase when approaching the Earth? Why does the flow rate decrease at an altitude of less than 20 km?

The increase in the flux of cosmic rays as it approaches the Earth is explained by the appearance of secondary cosmic rays, which are formed during the interaction of primary cosmic rays with the nuclei of atoms in the atmosphere. In the dense layers of the atmosphere (below 20 km), secondary cosmic rays are absorbed.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.