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Effect of solar activities to the Earth's atmosphere

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Effect of solar activities to the Earth's atmosphere

Q: If solar activities become active, what are the effects to the Earth's atmosphere?  

A: When the sun becomes active, the occurrences of phenomena such as solar flares, coronal mass ejection become frequent.  The amount of high-energy particles and extreme shortwave radiation released, such as X-rays and UV, will also increase.  These phenomena affect the ionosphere of the Earth's atmosphere the most.  It can disturb Earth's magnetic field, affect communications and create auroras.

Q: When the sun is active, would the Earth be heated up and lead to temperature rise? 

A: The atmosphere of the Earth can absorb and scatter the solar radiation.  In simple words, the atmosphere can absorb radiation of different wavelengths of the solar spectrum.  However, it absorbs the radiation mainly in the long wave and extreme short wave regimes.  The energy released from solar activities is mainly extreme short wave radiation; and will be absorbed by the gases in the upper atmosphere.  The extra amount of radiation reaching the ground level will be minimal.  Thus the effect to the temperature at ground level is negligible.

Q: In the long run, is there any effect to the Earth's climate? 

A: A research suggested that the particles from cosmic rays in outer space can reach the Earth easily during a weak solar activity period.  The particles can act as condensation nuclei and cloud forms easier.  Hence, the effect is the decrease in temperature and increase in rainfall.  However, take Hong Kong as an example, years with above-average rainfall seem to be unrelated to the strength of the solar activity.  In addition, the issue of anthropogenic climate change in the past years complicated the problem.  As such, there is not enough evidence to prove that solar activities can affect the long term climate of the Earth.

Q: Is there any effect to the weather of a small city like Hong Kong? 

A: The short-term weather of a city should not be related to the activities of the Sun.  Weather only relates to the weather system in different scales, such as ridges of high pressure, troughs of low pressure, typhoons, etc.