The radiation from the Sun travels in the space as electromagnetic wave. Above the earth
Links:
[1] http://admin.indiaenvironmentportal.org.in/books/solar-radiation-hand-book
[2] http://admin.indiaenvironmentportal.org.in/category/publisher/indian-metrological-department
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/atmosphere
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/solar-energy
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/radiation
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/energy
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/indian-meteorological-department-imd