How does the atmosphere protect us against radiation?

Thanks to the Probe-01 outcomes we can analyse gathered data and tell something more in terms of radiation in our atmosphere at various altitude levels. The probe was equipped with a dosimeter, i.e. a device with Geiger–Müller tube, which allowed measuring gamma radiation along the stratospheric mission time. The outcomes at ground were at the level of 0,09 µSv/h which is very close to the official data of radiation measurement stations for the region, from which the probe has been launched.

After the launch, the radiation level have been rising along the mission time to the level of 1 – 1.4 µSv/h at airliners flight altitude (10 – 11.5 km) and till approx. 3 µSv/h at level of 17 km altitude, at which the Concorde aircraft used to fly. This means that during a typical flight the human body is exposed to the radiation 11-15 times higher than on the ground (35 times higher during the Concorde flight), which is still relatively a safe dose, however significantly higher.

Surprisingly, above the 17 km altitude the radiation level is more or less constant till the approx. level of 22 km. Above this altitude the radiation level decreases. Why? To answer this question we need to know the origin of the radiation first. In fact, it is cosmic radiation, which comes to the Earth’s atmosphere as a high-energy particles, which collide with the atoms of atmosphere gasses and scatter into particles with less energy, creating the “air shower”.

Actually at higher altitudes there are less cosmic radiation particles, but with high energy (primary cosmic radiation), which may disrupt the operation of the electronics. At approx. 22 km and beneath there are much more particles, but with less energy (secondary cosmic radiation). Below 17 km the particles are more and more scattered , and their energy decreases, which in turn decreases overall radiation level. The lowest is at ground level (sea level).

This is another salutary function of our, Earth atmosphere.

The above outcomes from stratospheric flight refer to the day of flight (2020-08-08) at southern-west Poland. In other places of the globe the outcomes may differ.

The research conducted during the flight was in fact an expansion of the experiment from 1912, done by Victor Hess, who reached in his balloon 5300 m above the sea level, and during the flight he measured the radiation manually. Thanks to new technologies our unmanned probe flew much higher, to the level of 33 200 m (almost 109 000 ft) and did the analogous measurements 100% automatically.

References:

  1. Own research using the Probe-01 outcomes from stratospheric flight which took place in southern -west Poland, 2020-08-08.
  2. Cosmic Radiation: 2009, Maryla Moczulska, Warsaw University of Technology: http://www.if.pw.edu.pl/~pluta/pl/dyd/mtj/zal1/pz07/Maryla-Moczulska.pdf
  3. National Atomic Energy Agency: https://www.paa.gov.pl/strona-455-sytuacja_radiacyjna.html
  4. Wikipedia: https://en.wikipedia.org/wiki/Air_shower_(physics)