What is the interaction of nitrogen oxygen and ozone molecules with high energy solar radiation in the mesosphere?

Answer 1

High energy radiation from the sun (gamma, x-ray, and short wavelength ultraviolet) is intercepted by gas molecules in the thermosphere and upper mesosphere. Oxygen molecules (O2) can be broken apart into atomic oxygen (O).

O2 + hi energy radiation --> O + O

Atoms can also have electrons stripped thereby becoming positively charged atoms, or ions. These charged ions of the ionosphere can reflect radio waves allowing very long transmission, for example of AM radio broadcasts at night.

Very energetic charged particles from the sun (solar wind), when they interact with the ions of the ionosphere can release light in the form of the auroras.

These interactions in the upper atmosphere shield the Earth's surface from the damaging effects of high energy, short wavelength radiation. It is also responsible for the heating of the thermosphere.

Ozonosphere At altitudes between around 20 to 30 km in the stratosphere the remaining ultraviolet radiation is absorbed by oxygen molecules, breaking them apart.

O2 + UV --> O + O

But unlike in the ionosphere where the gas molecules and atoms are widely spread apart, the density of the gas in the stratosphere is sufficient to allow the freed oxygen atoms (O) to bond with oxygen molecules (O2) forming ozone (O3).

O + O2 --> O3

The ozone molecules will also absorb ultraviolet radiation and break apart into oxygen molecules and single oxygen atoms again.

O3 + UV --> O2 + O

The forming, breaking, forming, breakingä of ozone is part of the atmosphere's barrier against harmful ultraviolet radiation. The absorption of UV is also the reason that the stratosphere warms with altitude, rather than cooling with altitude like the troposphere.

Ozone loss Ground-based and satellite-based monitoring of ozone levels in the stratosphere has shown a steady decline, especially in the Antarctic. During the Antarctic spring every year, an "ozone hole" or area of greatly depleted ozone larger than the United States forms. A similar depletion is now recognized in the Arctic, though it is not yet as bad as in the Antarctic. Even in midlatitudes stratospheric ozone is declining by around 7% every 10 years.

Beginning in the 1970s researchers suspected and then confirmed that ozone was being destroyed by chlorine (Cl) atoms liberated from CFCs (chlorinated fluorocarbons) used as a refrigerant, as solvent for cleaning electronic circuit boards, and for making foam rubber. Each chlorine atom can decompose around 100,000 ozone molecules which would otherwise decompose via absorbing ultraviolet radiation. Therefore thee destruction of ozone by chlorine atoms leads to an increase in harmful ultraviolet radiation reaching the Earth's surface.

The chlorine atoms can stay in the atmosphere fro 40 to 100 years, so even if we were to completely stop manufacturing all CFCs today the ozone losses would persist for some time. Happily, the international community has acted together to create laws to phase out CFCs. Much less CFCs are being used now. The "ozone hole" should gradually heal.