Expert: Philip Stahl - 1/22/2010

Question
Mr. Stahl

While reading an article on the sun I noted that it is composed of six "core" parts with various functions.  The article further discussed other solar activities i.e., sunspots, prominences, solar flares (violent eruptions that cause communication blackouts), and solar winds.  

How can the Earth and the humans who inhabit it can be affected by the solar activity?

It appears as though humans would be affected by the solar activities more than any other species.  Is this true or can you provide a clearer understanding?

Thank you for any further clarification.

Answer
Hello,

I think you already discovered (yourself) at least one way- since you identified communication blackouts. Generally, these occur mainly on short wave bands - but can also affect others if solar flares are large enough, with an intense x-ray component. In addition, such flares can also knock out satellites orbiting the Earth (including weather and military satellites, spy satellites) and affect navigation controls on aircraft.

In 1973, the Skylab orbiting platform, with solar observing equipment aboard, detected a solar flare that wiped out twenty percent of the (then) ozone layer over North America.  In March, 1989, a mammoth solar flare erupted in a region of very large spots, knocking out Ottawa's power grid 3 days after its high energy particle stream left the Sun. Nearly a half-million people were deprived of electricity, for nearly ten hours.

A massive magnetized cloud, from a solar eruption on January 6, 1997, is believed to have knocked out a Telstar 401 communications satellite on January 11.

Sunspots also figure into this milieu. Not only are solar flares primarily spawned in the vicinity of large and complex spots, but changes in the sunspot cycle itself can affect life on Earth. The late solar physicist John Eddy, made it his research specialty to study long-term solar variations (connected to sunspots) associated with climate change, and first noted the period of 12th century warming in his book, ‘The New Solar Physics’(Westview Press).

Eddy noted that long term sunspot changes coincided with periods of higher or lower total solar *irradiance* and affected conditions at Earth. (Total solar irradiance is defined as the amount of radiant energy emitted by the Sun over all wavelengths that fall each second on 11 sq ft (1 sq m) outside the Earth's atmosphere).

For example, many more spots in a cycle than normal would give rise to the 12th century warming uncovered by Eddy. Conversely, fewer or no spots in a given cycle (or multiple consecutive cycles) gave rise to the well-documented "Maunder Minimum" - or "little ice age" - that occurred from 1645 to 1715. During this period there were much more severe winters, and much cooler summers than normal - affecting agricultural output, for example.

In the above context of sunspot cycles and large solar flares, of course humans would be affected more than most other species because human activities range more widely and are thus more susceptible to disruption. For example, it is humans that fly aircraft which can have their navigation controls affected, and humans who launch satellites which can be knocked out, and humans that operate power grids - like in Ottawa in 1989, which can be felled by a large flare.

We also need to bear such things in mind if a new solar cycle- for example- should usher in a period with many more spots and higher total solar irradiance that would *reinforce* global warming and enhance its affects on Earth.

We ignore such influences, especially in terms of amplifying our own unwise actions (such as injecting millions of tons of carbon dioxide into the atmosphere each year) at our own risk.

Hope this helps to shed more light.