As the Earth’s magnetic field begins to calm after several days of intense geomagnetic activity, the NOAA has announced that we experienced the largest solar radiation storm since 2003.

“Earlier, it was stated that the current Solar Radiation Storm was the largest since May 2005,” said Tuesday’s announcement on the NOAA Space Weather Prediction Center‘s Facebook page. “After the arrival of the CME earlier today … this is now the largest Solar Radiation Storm since October 2003 (The Halloween Storms).”

Although this solar storm is subsiding, there’s little doubt that more will come.

BIG PIC: Spectacular Aurorae Erupt Over Norway

As the sun increases in activity toward “solar maximum” (predicted to occur in 2013), we can expect more intense solar storms over the coming months. Magnetic activity is bursting through the solar “surface” (the photosphere), producing a rash of sunspots. This in turn has resulted in explosive events — solar flares and coronal mass ejections (CMEs) — boosting the intensity of radiation environment surrounding our planet.

The appearance of sunspots is a visible sign of the inner turmoil our nearest star experiencing, and over the weekend we felt the wrath of its magnetic stress.

Late on Sunday, a cluster of sunspots in an active region (called AR 1402) blasted a bubble of energized plasma — composed mainly of high-energy protons — in the general direction of Earth. But this wasn’t an isolated event; a CME that was launched on Friday had only just made contact earlier on Sunday, so solar physicists knew we could be in for a record-breaking space weather ride.

Although the weekend had its fair share of aurorae at high latitudes, impacting CMEs don’t always generate impressive light shows.

“Being hit by a CME does not automatically mean aurora,” NASA solar physicist C. Alex Young told Discovery News. “A CME has to be what we call ‘geo-effective.’ It must have enough mass, speed and magnetic field (including the orientation of the field) in order to disturb the magnetosphere sufficiently (to generate aurorae).”

Young administers The Sun Today website that focuses on solar science and space weather events. He also oversees a thriving solar Facebook community.

ANALYSIS: INCOMING! Sun Blasts Another CME at Earth and Mars

Over the weekend, to generate some of the bright aurorae observed within the “auroral oval” — an oval crowning the north and south poles where auroral activity will be most prevalent (pictured left) — it would appear Friday’s CME magnetic field was geo-effective as it made contact with the magnetosphere on Sunday.

The CME interacted with the Earth’s magnetosphere, sparking a global geomagnetic storm. The magnetic field of the CME aligned with the magnetic field of the Earth in such a way that they snapped and “reconnected.” When this happens, solar plasma will be injected into the layers of our magnetosphere, causing the high-energy particles to funnel into high-latitude regions, raining down around the polar regions’ auroral oval.

The particles collide with our atmosphere’s dense gases, generating auroral light. During geomagnetic storms, when our magnetic field is in its most tumultuous state, intense aurorae may occur.

“If the CME is big and fast enough it can compress the magnetosphere allowing access by more particles,” Young added. “If the CME’s magnetic field is southward directed then that allows for reconfiguration of the field when it meets the Earth’s northward directed field.

“This greatly increases the impact of the event and increases the release of energy from the magnetotail.”

The magnetotail is the component of the Earth’s magnetosphere that is swept back by the pressure of the solar wind. During periods of strong geomagnetic activity, regions of the magnetotail may be forced together, causing the solar plasma that is trapped inside the onion skin-like layers of the magnetosphere to be blasted into the polar atmosphere on the night-side of Earth (illustrated below). Once again, bright aurorae result.

ANALYSIS: Airline Diverts Aircraft During Solar Storm

According to Young, Tuesday’s CME impact was northward and not all of its mass was directed at Earth — so its impact was moderate when compared with the weekend’s fireworks (pictured top).

Although seeing an aurora snake across the sky is a very visible result of the magnetic storm erupting overhead, there are invisible, yet very powerful, impacts on our atmosphere.

As Young describes:

“If fluctuations in Earth’s magnetic field are strong enough we get the aurora and often ground induced currents. So the changing magnetic field induces currents on long conductors such as long transmission lines and pipe lines. If the currents are large enough they can overload power substations. Companies prepare for these but it could produce brown outs and black outs. But only the largest (and rarest) events would probably do that kind of damage. When currents are induced in pipelines they can corrode. High latitude (radio) communications can be impacted. I have heard from colleagues that airlines have already had to reroute polar flights for up to 2 days because of communication blackouts at the poles.”

Indeed, Delta Airlines have announced the re-routing of some of their aircraft that fly between Detroit and Asia, citing communication blackout concerns.

As this recent geomagnetic storm has proven, the sun is capable of having a global impact on our planet. Although auroral light shows are a beautiful (yet benign) side effect, the risk to satellites and entire national power grids are vulnerable to geomagnetic storms. According to Young, this increases the need for accurate space weather prediction methods.

What is needed, he says, are accurate predictions of the time and strength of a CME impact. Also, information on the CME’s geo-effectiveness is needed so we can understand the impacts a CME may have to modern society.

As it turned out, Tuesday’s CME impact was predicted to slam into the Earth at 9:18 a.m. EST “and in reality, it arrived at 9:31 a.m., so (our prediction had) a 13-minute error,” Yihua Zheng, a lead researcher at the Space Weather Center at NASA’s Goddard Space Flight Center in Greenbelt, Md., told SPACE.com.

“Usually for this kind of model, the average error is seven hours, so this is the best case.”

With the help of space-based solar observatories — like the Solar and Heliospheric Observatory (SOHO), Solar Dynamics Observatory (SDO), Advanced Composite Explorer (ACE) and the Geostationary Operational Environmental Satellite (GOES) — and ground-based observatories, the passage of Earth-bound CMEs can be tracked and predictions can be improved to an even higher degree of precision.

Image credits: Bjørn Jørgensen (top), NOAA, NASA