Solar Storm Cycle Every 11 years

It will have the peak in late 2011 and mid-2012
Every 11 years, the Sun experiences a period of massive solar storms, when violent solar flares and vast explosions known as Coronal Mass Ejections (CME) have the strongest manifestations of the entire cycle.
When the ejections reach the Earth as an ICME (Interplanetary CME), they may disrupt the Earth's magnetosphere, compressing it on the dayside and extending the nightside tail. When the magnetosphere reconnects on the nightside, it creates trillions of watts of power which is directed back towards the Earth's upper atmosphere.

This process can cause particularly strong aurora also known as the Northern Lights (in the Northern Hemisphere) and the Southern Lights (in the Southern Hemisphere). CME events, along with solar flares, can disrupt radio transmissions, cause power outages (blackouts), and cause damage to satellites, GPSs and electrical transmission lines.

The fact that the solar storms cycle is one year late has troubled some astronomers, and they are wondering if this means that a weak or strong period of solar storms lays ahead, but neither predicts a record-breaker.

They measure the intensity of the solar cycle in maximum number of sunspots (dark blotches on the sun that mark areas of heightened magnetic activity) and the more sunspots there are, the more likely it is that major solar storms will occur.

The effects on human society have to do mostly with the technological advance than to biological threats, although health hazards are not inexistent.

A solar eruption in December disrupted the Global Positioning System, creating radio bursts that traveled to Earth, covering a broad frequency range. In addition to the GPS system, the December solar flare affected satellites and induced unexpected currents in the electrical grid.

Many government and private institutions have demanded a forecast of the Sun's activity during the storm cycle to help them prevent damage to their infrastructures and business activities, for more than a year, so the NOAA Space Environment Center led the prediction panel and issued the forecast at its annual Space Weather Workshop in Boulder, Colorado.

source : here

Phenomena, measurement, and causes
Spots from multiple cycles can co-exist for some time and since it was discovered the sun reverses magnetic polarity one solar half cycle to the next, spots from different cycles can be told apart. However it takes some months before a definite decision to be made on the true date of solar minimum, which is announced by the relevant expert authorities.

One of the main authorities is SIDAC (the Solar Influences Data Analysis Center) which is located in Belgium, and works with agencies such as NASA and ESA.

The most important information today comes from SOHO (a project of international cooperation between ESA and NASA), such as the MDI magnetogram, where the solar "surface" magnetic field can be seen.

It has been noticed that sunspots from a dying solar cycle tend to appear near the solar equator whereas spots from a new cycle tend to appear at mid-latitudes. The basic causes of the solar variability and solar cycles are still under debate, with some researchers suggesting a link with the tidal forces due to the gas giants Jupiter and Saturn or due to the solar inertial motion. Another cause of sun spots can be solar jet stream "torsional oscillation".

Solar Storm Effects on Earth
The impact of Solar cycle on living organisms has been investigated (see chronobiology). Some researchers claim to have found connections with human health.
The amount of UVB light at 300 nm reaching the Earth varies by as much as 400% over the solar cycle due to variations in the protective ozone layer. In the stratosphere, ozone is continuously regenerated by the splitting of O2 molecules by ultraviolet light. During a solar minimum, the decrease in ultraviolet light received from the Sun leads to a decrease in the concentration of ozone, allowing increased UVB to penetrate to the Earth's surface.
The sunspot cycle has been implicated in having effects on climate, and may play a part in determining global temperature.
(wikipedia.org)