Читать книгу Introduction to Nanoscience and Nanotechnology - Chris Binns - Страница 37

It is known that the constant stream of fast charged particles, mostly protons that emanate from the sun affects our climate. The details of the interaction are complex and there may be several different mechanisms but a prominent one involving nanoparticles is that the cosmic rays entering the atmosphere leave a trail of ionized gas molecules that can act as nucleation centers for CCNs. Put simply the cosmic rays encourage cloud formation. As described above this can, in turn, affect the atmospheric aerosol load via, for example, the feedback mechanism involving DMS and phytoplankton. The relatively small flux of cosmic rays incident on the Earth can thus have a disproportionately large effect on atmospheric conditions. The amplifying effect arises from cosmic rays influencing the amount of atmospheric aerosol, mostly in the form of nanoparticles. The solar cosmic‐ray flux shows large variations with conditions in the sun, for example, the 11‐year sunspot cycle. A possible illustration of how influential solar activity can be is the correlation of the period of the Maunder minimum, when very few sunspots were observed, indicating low activity and cosmic ray flux, and the coldest part of the so‐called Mini Ice Age in the seventeenth and eighteenth centuries (Figure 2.13).

Strong evidence for a direct link between atmospheric aerosol and solar activity comes from the Greenland Ice Sheet Project 2 (GISP2), which examines the depth profile of impurities in Greenland ice. This is a convenient way to determine atmospheric conditions in the past as any particular concentrations of chemicals or particles are frozen into the ice at a depth that depends on how long ago they were present in the atmosphere. Analysis of the variations in particle concentration of the top 120 m, corresponding to the last 400 years, shows a correlation of the aerosol load with the sunspot number, that is, with the solar cosmic ray flux [20]. Not all cosmic rays come from the sun and there is a significant flux, especially of higher energy particles, from sources outside our own galaxy. It is sobering to realize that events in the far reaches of the Universe influence our climate.

Figure 2.13 Maunder minimum and the little ice age. The Plot, using historical records, of the observed sunspot number over the last 400 years. The Maunder minimum between 1645 and 1715 coincides with the coldest part of the so‐called Mini Ice Age in the seventeenth and eighteenth centuries in which unusually cold winters occurred.

Source: NCdave. https://commons.wikimedia.org/wiki/File:Sunspot_Numbers.png, Licensed under CC BY‐SA 3.0 (https://creativecommons.org/licenses/by‐sa/3.0/deed.en).