Solar Activity is Declining—what to expect?

Is Earth slowly heading for a new ice age? Looking at the decreasing number of sunspots, it may seem that we are entering a nearly spotless solar cycle which could result in lower temperatures for decades. “The solar cycle is starting to decline. Now we have less active regions visible on the sun’s disk,” Yaireska M. Collado-Vega, a space weather forecaster at NASA’s Goddard Space Flight Center

Maunder Minimum is also known as the “prolonged sunspot minimum”, which was a period starting in about 1645 and continuing to about 1715 when sunspots became exceedingly rare, as noted by solar observers of the time.

But does it really mean a colder climate for our planet in the near future? In 1645, the so-called Maunder Minimum period started, when there were almost no sunspots. It lasted for 70 years and coincided with the well-known “Little Ice Age”, when Europe and North America experienced lower-than-average temperatures. However, the theory that decreased solar activity caused the climate change is still controversial as no convincing evidence to prove this correlation.

If the existing theories about the impact of solar activity on the climate are true, this minimum will lead to a significant cooling, similar to the one during the Maunder Minimum period based on math models. “Given that our future minimum will last for at least 3 solar cycles, which is about 30 years, it is possible that the lowering of the temperature will not be as deep as during the Maunder Minimum,” Popova said earlier in July. The solar cycle is the periodic change in the Sun’s activity and appearance like changes in the number of sunspots. It has an average duration of 11 years. The current solar cycle began on in Jan 2008, with minimal activity until early 2010. The sun is now on track to have the lowest recorded sunspot activity since accurate records began in 1750. The long-term decline in solar activity set in after the last grand solar maximum peaked in 1956.

The Sun by the Atmospheric Imaging Assembly of NASA’s Solar Dynamics Observatory. Credit: NASA

But the current minimum in the number of sunspots doesn’t mean that the sun won’t show us its violent nature in the coming years. “There is a development for coronal holes, due to the reconfiguration of the sun’s magnetic field, that bear the well-known high-speed streams. These high-speed streams have the ability to cause strong geomagnetic storms at Earth, and changes to the radiation environment in the inner magnetosphere,” Collado-Vega noted. Coronal holes have lower density and temperatures in the sun’s outer atmosphere, corona. The sun contains magnetic fields that arch away from areas in the corona that are very thin due to the lower levels of energy and gas, which cause coronal holes to appear when they do not fall back. Thus, solar particles or solar wind escape and create a lower density and lower temperature in that area.
http://phys.org/news/2015-08-solar-decliningwhat.htmljCp

Two coronal holes observed by the AIA instrument aboard SDO. The image was taken in the 193 Angstrom wavelength of extreme ultraviolet light.