by Rodney Viereck Friday, July 10, 2015
If you live in hurricane-prone regions, you’re probably familiar with the Saffir-Simpson hurricane scale; if you’re in Tornado Alley, you probably know the Fujita scale. If a meteorologist tells you a Category-5 hurricane or an F-5 tornado is headed your way, you probably know to evacuate or take cover. But what happens if a solar storm is headed toward Earth? We’ve all likely heard from the media about the potential impacts of severe space weather events: no cellphone service, no GPS, no satellite TV, no way for airplanes to communicate, no electricity as the power grid goes down. But to whom do you turn for reliable information, and how do you know if you should worry? Scientists have now created a scaling system for solar storms like those used for hurricanes and tornadoes with the hope that such a system will help government agencies and the public prepare for and respond to space weather events.
“Space weather” describes conditions resulting from solar activity that impact humans and technologies in space and on the ground. Three important categories of space weather exist, each with different impacts on different technologies. NOAA has thus created three Space Weather Scales with ranges from 1 to 5, similar to the hurricane scale.
1. Radio Blackout Scale for Solar Flares: Solar flares are large solar eruptions that release vast amounts of energy, mostly in the form of X-ray and extreme ultraviolet radiation (photons). When X-rays reach Earth’s upper atmosphere, they ionize atoms and molecules in the air, creating an enhanced layer of electrons in the lower ionosphere. When this happens, the ionosphere absorbs or blocks much of the high-frequency radio communication that pilots and amateur radio operators use.
2. Solar Radiation Storm Scale for Solar Energetic Particles: Often accompanying larger solar flares are shocks that accelerate protons to speeds approaching one-third the speed of light. These particles ionize the upper atmosphere and create an enhanced lower ionosphere. Guided by both the sun’s and Earth’s magnetic fields, which tends to concentrate them over Earth’s polar regions, these energized protons penetrate satellite electronic circuitry, affect astronauts in space and block high-latitude high-frequency radio communication. The very largest radiation storms can increase radiation levels at aircraft altitudes.
3. Geomagnetic Storm Scale for Coronal Mass Ejections: The sun often ejects large clouds of magnetized plasma called Coronal Mass Ejections, or CMEs. These clouds expand until they are many times larger than the sun, can reach billion of tons in mass, and travel at speeds of 6 million kilometers per hour or more. (Although, even at these high velocities, it takes a day or more to cross from the sun to Earth.) When CMEs reach Earth, they energize the planet’s magnetosphere, thus creating geomagnetic storms. While other types of solar events can also cause geomagnetic storms, CMEs are responsible for the largest storms. Geomagnetic storms alter local geomagnetic fields, affecting compass needles, and they create currents in the ionosphere that induce currents in the ground and in electric power lines. These storms also produce waves in the ionosphere that degrade GPS positioning information; they heat the atmosphere, which increases satellite drag; and, in addition to affecting electric power grids, GPS navigation systems, satellite orbits, and radio communications, geomagnetic storms create aurorae, which are the only way most people directly experience space weather.
When any one of these types of events occurs, the NOAA Space Weather Prediction Center (SWPC) in Boulder, Colo., which is part of the National Weather Service, issues an alert, watch or warning based on the type and severity of an event. For most people, solar storms are merely a curiosity, not a cause for concern. But for some groups — astronauts and electricity providers, for example — the alerts are quite important and can help avoid deadly situations. SWPC operates the Space Weather Forecast Office, which is staffed 24 hours a day, seven days a week to support users in a number of commercial sectors, from energy to transportation. Most users, like aurora watchers, receive space weather information from the SWPC website. Others, such as satellite operators or GPS users, sign up for alerts and warnings to be sent directly to them through a subscription service. Those users for whom the effects of such storms could directly impact people’s safety, such as airlines and the electric power industry, receive direct phone calls alerting them to upcoming space weather storms. By providing reliable space weather forecasts, SWPC helps a number of industries prepare their systems and technologies to cope with space weather.
Most major impacts of space weather are well understood. Since the earliest days of radio, radio operators have known that their signals are affected by activity on the sun. Similarly, satellite operators know what to expect in space, so they design their systems to withstand radiation levels that are typically observed. Commercial airlines use HF radio for communication but have alternative communication systems that they can switch to during radio blackouts. Airlines avoid polar routes when there are large radiation storms (from energetic solar protons) because there are few alternatives to HF radio for communication at high latitudes.
We don’t have a great handle yet on how GPS is affected because there are so many new and evolving uses of the GPS navigation system. But GPS system designers and operators have either engineered around some of the problems or they modify their operating procedures or postpone activities when space weather creates large errors in the GPS positioning information. The electric power industry meanwhile has procedures and safeguards to protect the power grid from major space weather storms. For all of these technologies, preparing for the possibility of a very severe storm is important to minimize potential disruptions to their systems and services.
But uncertainties about space weather still exist. Could there be an extreme space weather storm that is 10 times or even 100 times larger than anything we have ever seen? And how would vulnerable technologies such as our electric power grid respond to such a storm? Could the grid sustain severe enough damage that it would take months or years to repair? Could radiation at high latitudes reach levels that could impact aircraft electronics or the health of airline passengers and crew? Even experts in the field can only speculate with regard to these questions.
Preparation for the possible (some might say inevitable) massive space weather storm must include three activities. First, we must continue to monitor space weather conditions and provide forecasts of major events, always seeking to improve the accuracy and lead time of notifications. Second, we must continue to work with industries that may be affected by space weather so they have procedures in place to mitigate potential impacts. And third, we must coordinate the activities of the relevant government agencies so they too are prepared for potentially severe events. In addition, it is important to continue researching space weather to better understand the underlying physics and transfer knowledge gained into improving operational forecasts.
Government agencies at the state and federal levels are establishing plans and procedures to prepare for extreme space weather and storms. Such efforts are similar to those undertaken on local and national levels to prepare for other low-probability, high-impact events such as earthquakes, floods, and hurricanes. The federal government’s Office of Science and Technology Policy recently began preparing a national strategy and an implementation plan for space weather, which is intended to define the roles and responsibilities of various agencies with regard to responding to extreme space weather.
Space weather poses a threat to technologies and systems that we rely on every day; in the worst case scenario, a powerful solar storm could disrupt our lives by causing significant damage to satellites or the electric power infrastructure. It’s important to put the risk into context with other events — meteorological, technical and otherwise — that can affect the same systems and which compete for limited resources. But paying attention to and preparing for space weather events, from national governments down to industry and local communities, is vital in ensuring the well-being of the country should a major solar outburst come our way.
© 2008-2021. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the expressed written permission of the American Geosciences Institute is expressly prohibited. Click here for all copyright requests.