摘要
In the early 20th century,thanks to improved precision of ionization measurement,atmospheric ionization was widely observed and attributed to high-energy radiations generated by the decay of radioactive elements on the Earth.From 1911 to 1913,by carrying out a series of high-altitude balloon experiments,Austrian physicist Victor Franz Hess discovered high-energy radiations originated from the outer space that could also ionize the air–the cosmic rays(Hess,1912),and this discovery earned him the Nobel Prize in Physics in 1936(shown in Figure 1 left).In the 1930s,by analyzing the asymmetry of cosmic ray fluxes arriving from the east and the west.
