The north and south poles of the earth allow more cosmic radiation through because the earth’s magnetic field, at these points, is weaker. The majority of electrified particles arriving at the earth, via the solar wind, are deflected around it by the magnetic field of the earth. An electrified particle is called an ion and ions, obviously, have positive or negative charges. Many of these ions are radioactive. Some radioactive particles, such as free neutrons (technically called secondary neutrons), don’t have a charge. These particles aren’t stopped by the earth’s magnetosphere, but are stopped by the earth’s atmosphere. So we really have two things protecting us from cosmic radiation. The magnetosphere and the atmosphere. The poles are less protected by the magnetosphere and the upper altitudes are less protected from the atmosphere. So then it follows that the closer you get to the equator, the less cosmic radiation there will be. And we proved it with this flight. As we flew south, the radiation dose rate looked like this:
At 41,000′ and 46 degrees north latitude, the dose rate was 3.2 uSv/hr
At 41,000′ and 22 degrees north latitude, the dose rate was 2.0 uSv/hr
It was nice to get to some warm air. Eighty degree weather and a beachfront hotel awaited me in Jeddah, on the Red Sea.