The conditions of production of the solar X rays are briefly discussed. The comparison of the results of recent calculations and experimental measurements supports the assumption of a thermal origin of the X ray radiation. In the “tail” of the solar spectrum below 15 Å, the main contribution comes from the free-bound radiation of electrons and ions of carbon, nitrogen, oxygen and other elements.
The solar X ray radiation consist of a “quasi-stable” component, produced in undisturbed coronal regions and a “slowly varying” component generated in the active regions of the corona.