Logo of the Physikalisch-Technische Bundesanstalt

Notice of the "Ground Level Event" on January 20, 2005 Provisional dose estimation of EURADOS Working Group "Aircrew Dosimetry"

10.05.2006

As a result of a solar eruption on January 20, the earth was hit by so many high-energy particles that radiation exposure at flight altitudes temporarily increased. The additional radiation exposure at flight altitudes was estimated by PTB and other European partners to be less than 0.2 mSv. This corresponds to approx. 1 % of the annual limiting value permitted for persons occupationally exposed to radiation.


On January 20, 2005, a high-energy solar particle event ("Solar Particle Event") occurred whose beginning was observed on earth at 0650 UTC and which reached its maximum intensity at about 0700 UTC. The particle energies of this event were sufficiently high so that it could be detected by neutron monitors (Ground Level Neutron Monitor, GLNM) installed on the ground for the detection of cosmic radiation. The event will be registered as a so-called "Ground Level Event" (GLE68 or 69).

In the polar regions, where the earth’s shielding by its magnetic field is not so good, the counting rates of the GLNM locally increased - compared with the period between the 14th and 16th of January 2005 - in the northern hemisphere by 125 % (hourly mean value of the neutron monitor Oulu) and in the southern hemisphere locally by up to 380 % (hourly mean value of the neutron monitor South Pole). The increase in the counting rate noticeably decreased with decreasing magnetic latitude. This is why it can be expected that only very high latitudes (>60°) were really affected.

After the peak, the intensity of the event rapidly decreased, the total duration of approx. 6 hours was comparably short. Provisional determinations of probable radiation doses to which flight staff was exposed during this time, are at present performed by several working groups. From first estimations it can be expected that the additional dose will probably not exceed 200 µSv per flight - for example on routes from Europe to the American West Coast or to Japan.

Final dose estimations will be published after the satellite and neutron monitor data as well as possible measurement data in airplanes have been analysed in more detail.

Source:
www.euradnews.org: "EURADOS Aircraft Crew Dosimetry Group assessment of doses"