insolation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or an instance of exposing to sunlight.
• noun Therapeutic exposure to sunlight.
• noun The solar radiation striking Earth or another planet.
• noun The rate of delivery of solar radiation per unit of horizontal surface.

from The Century Dictionary.

• noun Exposure to the sun's rays; subjection to the influence of solar heat and light, as for drying, maturing, or the production of chemical action; in medicine, treatment by exposure to the sun, in order to stimulate the vital forces.
• noun A local injury of plants caused by exposure to too strong light, or to the rays of the sun concentrated as by inequalities in the glass of a greenhouse, producing excessively rapid evaporation which kills the part affected.
• noun The state of being heated by the sun; the effect of exposure to the sun's rays; specifically, as applied to persons, sunstroke.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act or process to exposing to the rays of the sun for the purpose of drying or maturing, as fruits, drugs, etc., or of rendering acid, as vinegar.
• noun A sunstroke.
• noun Exposure of a patient to the sun's rays; a sun bath.
• noun (Meteorology) The amount of sunlight impinging on the Earth's surface.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The incident radiant energy emitted by the sun which reaches a unit area over a period of time, typically measured over a horizontal area at the Earth's surface or at the top of Earth's atmosphere.
• noun The rate of delivery of such radiation.
• noun The act or process of exposing to the rays of the sun, such as for the purpose of medical treatment, drying or maturing, as fruits, drugs, etc., or of rendering acid, as vinegar.
• noun medicine, dated sunstroke.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun sudden prostration due to exposure to the sun or excessive heat
• noun therapeutic exposure to sunlight
• noun incident solar radiation