- What is solar activity?
- What is a solar flare?
- What is a solar prominence?
- What is a coronal mass ejection or CME?
- Does ALL solar activity impact Earth? Why or why not?
- What are coronal holes?
- What is a geomagnetic storm?
- What is a sunspot?
- What is the solar cycle?
- What is solar maximum and solar minimum?
- What is space weather?
- Does the Sun cause space weather?
- Do space weather effects/solar storms affect Earth?
- What are some real-world examples of space weather impacts?
- Do scientists expect a huge solar storm in 2013?
- How long do space weather events usually last?
- How are space weather events observed?
- What are our current capabilities to predict space weather?
- How long have we known about space weather?
- Have scientists seen changes in the intensity of space weather?
- How strong is solar wind (compared to wind on Earth)?
- What are the northern and southern lights and are they related to space weather?
- Who is responsible for predicting space weather and sending alerts when there is solar activity?
- How do you forecast space weather?
- Why is forecasting space weather important?
- When do the effects of space weather show up?
- Where can I get more information?
- Sun facts
- Why didn’t the world end in 2012?
1. What is solar activity?
Solar flares, coronal mass ejections, high-speed solar wind, and solar energetic particles are all forms of solar activity. All solar activity is driven by the solar magnetic field.
2. What is a solar flare?
A solar flare is an intense burst of radiation coming from the release of magnetic energy associated with sunspots. Flares are our solar system’s largest explosive events. They are seen as bright areas on the sun and they can last from minutes to hours. We typically see a solar flare by the photons (or light) it releases, at most every wavelength of the spectrum. The primary ways we monitor flares are in x-rays and optical light. Flares are also sites where particles (electrons, protons, and heavier particles) are accelerated.
NASA Goddard heliophysics scientists answer some common questions about the sun, space weather, and how they affect the Earth. This is part one of a two-part series. It addresses: 1. What is space weather? 2. What are coronal mass ejections? 3. What are solar flares? 4. What are solar energetic particles? 5. What causes flares and CMEs?
3. What is a solar prominence?
A solar prominence (also known as a filament when viewed against the solar disk) is a large, bright feature extending outward from the Sun’s surface. Prominences are anchored to the Sun’s surface in the photosphere, and extend outwards into the Sun’s hot outer atmosphere, called the corona. A prominence forms over timescales of about a day, and stable prominences may persist in the corona for several months, looping hundreds of thousands of miles into space. Scientists are still researching how and why prominences are formed.
The red-glowing looped material is plasma, a hot gas comprised of electrically charged hydrogen and helium. The prominence plasma flows along a tangled and twisted structure of magnetic fields generated by the sun’s internal dynamo. An erupting prominence occurs when such a structure becomes unstable and bursts outward, releasing the plasma.
4. What is a coronal mass ejection or CME?
The outer solar atmosphere, the corona, is structured by strong magnetic fields. Where these fields are closed, often above sunspot groups, the confined solar atmosphere can suddenly and violently release bubbles of gas and magnetic fields called coronal mass ejections. A large CME can contain a billion tons of matter that can be accelerated to several million miles per hour in a spectacular explosion. Solar material streams out through the interplanetary medium, impacting any planet or spacecraft in its path. CMEs are sometimes associated with flares but can occur independently.
5. Does ALL solar activity impact Earth? Why or why not?
Solar activity associated with Space Weather can be divided into four main components: solar flares, coronal mass ejections, high-speed solar wind, and solar energetic particles.Solar flares impact Earth only when they occur on the side of the sun facing Earth. Because flares are made of photons, they travel out directly from the flare site, so if we can see the flare, we can be impacted by it.
- Coronal mass ejections, also called CMEs, are large clouds of plasma and magnetic field that erupt from the sun. These clouds can erupt in any direction, and then continue on in that direction, plowing right through the solar wind. Only when the cloud is aimed at Earth will the CME hit Earth and therefore cause impacts.
- High-speed solar wind streams come from areas on the sun known as coronal holes. These holes can form anywhere on the sun and usually, only when they are closer to the solar equator, do the winds they produce impact Earth.
- Solar energetic particles are high-energy charged particles, primarily thought to be released by shocks formed at the front of coronal mass ejections and solar flares. When a CME cloud plows through the solar wind, high velocity solar energetic particles can be produced and because they are charged, they must follow the magnetic field lines that pervade the space between the Sun and the Earth. Therefore, only the charged particles that follow magnetic field lines that intersect the Earth will result in impacts.
6. What are coronal holes?
Coronal holes are variable solar features that can last for weeks to months. They are large, dark areas (representing regions of lower coronal density) when the sun is viewed in EUV or x-ray wavelengths, sometimes as large as a quarter of the sun’s surface. These holes are rooted in large cells of unipolar magnetic fields on the sun’s surface; their field lines extend far out into the solar system. These open field lines allow a continuous outflow of high-speed solar wind. Coronal holes tend to be most numerous in the years following solar maximum.
7. What is a geomagnetic storm?
The Earth’s magnetosphere is created by our magnetic field and protects us from most of the particles the sun emits. When a CME or high-speed stream arrives at Earth it buffets the magnetosphere. If the arriving solar magnetic field is directed southward it interacts strongly with the oppositely oriented magnetic field of the Earth. The Earth’s magnetic field is then peeled open like an onion allowing energetic solar wind particles to stream down the field lines to hit the atmosphere over the poles. At the Earth’s surface a magnetic storm is seen as a rapid drop in the Earth’s magnetic field strength. This decrease lasts about 6 to 12 hours, after which the magnetic field gradually recovers over a period of several days.
8. What is a sunspot?
Sunspots, dark areas on the solar surface, contain strong magnetic fields that are constantly shifting. A moderate-sized sunspot is about as large as the Earth. Sunspots form and dissipate over periods of days or weeks. They occur when strong magnetic fields emerge through the solar surface and allow the area to cool slightly, from a background value of 6000 ° C down to about 4200 ° C; this area appears as a dark spot in contrast with the very bright photosphere of the sun. The rotation of these sunspots can be seen on the solar surface; they take about 27 days to make a complete rotation as seen from Earth.
Sunspots remain more or less in place on the sun. Near the solar equator the surface rotates at a faster rate than near the solar poles. Groups of sunspots, especially those with complex magnetic field configurations, are often the sites of solar flares. Over the last 300 years, the average number of sunspots has regularly waxed and waned in an 11-year (on average) solar or sunspot cycle.
9. What is the solar cycle?
The sun goes through periodic variations or cycles of high and low activity that repeat approximately every 11 years. Although cycles as short as 9 years and as long as 14 years have been observed. The solar or sunspot cycle is a useful way to mark the changes in the sun.
10. What is solar maximum and solar minimum?
Solar minimum refers to a period of several Earth years when the number of sunspots is lowest; solar maximum occurs in the years when sunspots are most numerous. During solar maximum, activity on the Sun and the effects of space weather on our terrestrial environment are high. At solar minimum, the sun may go many days with no sunspots visible. At maximum, there may be several hundred sunspots on any day.
11. What is space weather?
The term “space weather” was coined not long ago to describe the dynamic conditions in the Earth’s outer space environment, in the same way that “weather” and “climate” refer to conditions in Earth’s lower atmosphere. Space weather includes any and all conditions and events on the sun, in the solar wind, in near-Earth space and in our upper atmosphere that can affect space-borne and ground-based technological systems and through these, human life and endeavor. Heliophysics is the science of space weather.
12. Does the Sun cause space weather?
Looking at the sky with the naked eye, the sun seems static, placid, and constant. But our sun gives us more than just a steady stream of warmth and light. The sun regularly bathes Earth and the rest of our solar system in energy in the forms of light and electrically charged particles and magnetic fields. The resulting impacts are what we call space weather. The sun is a huge thermo-nuclear reactor, fusing hydrogen atoms into helium and producing million degree temperatures and intense magnetic fields. The outer layer of the sun near its surface is like a pot of boiling water, with bubbles of hot, electrified gas—electrons and protons in a fourth state of matter known as plasma—circulating up from the interior and bursting out into space. The steady stream of particles blowing away from the sun is known as the solar wind. Blustering at 800,000 to 5 million miles per hour, the solar wind carries a million tons of matter into space every second (that’s the mass of Utah’s Great Salt Lake) and reaches well beyond the solar system’s planets. Its speed, density and the magnetic fields associated with that plasma affect Earth’s protective magnetic shield in space (the magnetosphere).
13. Do space weather effects / solar storms affect Earth?
Modern society depends on a variety of technologies susceptible to the extremes of space weather. Strong electrical currents driven along the Earth’s surface during auroral events disrupt electric power grids and contribute to the corrosion of oil and gas pipelines. Changes in the ionosphere during geomagnetic storms interfere with high-frequency radio communications and Global Positioning System (GPS) navigation. During polar cap absorption events caused by solar protons, radio communications can be compromised for commercial airliners on transpolar crossing routes. Exposure of spacecraft to energetic particles during solar energetic particle events and radiation belt enhancements cause temporary operational anomalies, damage critical electronics, degrade solar arrays, and blind optical systems such as imagers and star trackers.
Human and robotic explorers across the solar system are also affected by solar activity. Research has shown, in a worst-case scenario, astronauts exposed to solar particle radiation can reach their permissible exposure limits within hours of the onset of an event. Surface-to-orbit and surface-to-surface communications are sensitive to space weather storms.
14. What are some real-world examples of space weather impacts?
- September 2, 1859, disruption of telegraph service.
- One of the best-known examples of space weather events is the collapse of the Hydro-Québec power network on March 13, 1989 due to geomagnetically induced currents (GICs). Caused by a transformer failure, this event led to a general blackout that lasted more than 9 hours and affected over 6 million people. The geomagnetic storm causing this event was itself the result of a CME ejected from the sun on March 9, 1989.
- Today, airlines fly over 7,500 polar routes per year. These routes take aircraft to latitudes where satellite communication cannot be used, and flight crews must rely instead on high-frequency (HF) radio to maintain communication with air traffic control, as required by federal regulation. During certain space weather events, solar energetic particles spiral down geomagnetic field lines in the polar regions, where they increase the density of ionized gas, which in turn affects the propagation of radio waves and can result in radio blackouts. These events can last for several days, during which time aircraft must be diverted to latitudes where satellite communications can be used. No large Solar Energetic Particles events have happened during a manned space mission. However, such a large event happened on August 7, 1972, between the Apollo 16 and Apollo 17 lunar missions. The dose of particles would have hit an astronaut outside of Earth’s protective magnetic field, had this event happened during one of these missions, the effects could have been life threatening.
15. Do scientists expect a huge solar storm in 2013?
The sun goes through cycles of high and low activity that repeat approximately every 11 years. Solar minimum refers to the several Earth years when the number of sunspots is lowest; solar maximum occurs in the years when sunspots are most numerous. During solar maximum, activity on the sun and the possibility of space weather effects on our terrestrial environment is higher. The next solar maximum is expected in the 2013-2014 time frame. No current observations or data show any impending catastrophic solar event. In fact, scientists believe the intensity of the upcoming coming solar maximum will be similar to the previous maximum in 2002.
We have never been so well prepared for the onset of the next solar cycle. NASA maintains a fleet of Heliophysics spacecraft to monitor the sun, geospace, and the space environment between the sun and the Earth.
NASA cooperates with other U.S. agencies to enable new knowledge in studying the sun and its processes. To facilitate and enable this cooperation, NASA’s Heliophysics Division makes its vast research data sets and models publicly available online to industry, academia, and other civil and military space weather interests. Also provided are publicly available sites for citizen science and space situational awareness through various cell phone and e-tablet applications.
16. How long do space weather events usually last?
Solar storms can last only a few minutes to several hours but the affects of geomagnetic storms can linger in the Earth’s magnetosphere and atmosphere for days to weeks.
17. How are space weather events observed?
Scientists utilize a variety of ground- and space-based sensors and imaging systems to view activity at various depths in the solar atmosphere. Telescopes are used to detect visible light, ultraviolet light, gamma rays, and X rays. They use receivers and transmitters that detect the radio shock waves created when a CME crashes into the solar wind and produces a shock wave. Particle detectors to count ions and electrons, magnetometers record changes in magnetic fields, and UV and visible cameras observe auroral patterns above the Earth.
NASA Goddard heliophysics scientists answer some common questions about the sun, space weather, and how they affect the Earth. This is part two of a two-part series. It addresses: 1. Do all flares and CMEs affect the Earth? 2. What happens when a flare or CME hits the Earth? 3. How quickly can we feel the effects of space weather? 4. Why are there more flares and CMEs happening now?
18. What are our current capabilities to predict space weather?
NASA operates a system observatory of Heliophysics missions, utilizing the entire fleet of solar, heliospheric, and geospace spacecraft to discover the processes at work throughout the space environment. In addition to its science program, NASA’s Heliophysics Division routinely partners with other agencies to fulfill the space weather research or operational objectives of the nation.
Presently, this is accomplished with the existing fleet of NOAA satellites and some NASA scientific satellites. Space weather “beacons” on NASA spacecraft provide real-time science data to space weather forecasters. Examples include ACE measurements of interplanetary conditions from the Lagrangian point L1 where objects are never shadowed by the Earth or the Moon; CME alerts from SOHO; STEREO beacon images of the far side of the Sun; and super high-resolution images from SDO. NASA will continue to cooperate with other agencies to enable new knowledge in this area and to measure conditions in space critical to both operational and scientific research.
To facilitate and enable this cooperation, NASA’s makes its Heliophysics research data sets and models continuously available to industry, academia, and other civil and military space weather interests via existing Internet sites. These include the Combined Community Modeling Center (CCMC) and the Integrated Space Weather Analysis System (ISWA) associated with GSFC. Also provided are publicly available sites for citizen science and space situational awareness through various cell phone and e-tablet applications.
Beyond NASA, interagency coordination in space weather activities has been formalized through the Committee on Space Weather, which is hosted by the Office of the Federal Coordinator for Meteorology. This multiagency organization is co-chaired by representatives from NASA, NOAA, DoD, and NSF and functions as a steering group responsible for tracking the progress of the National Space Weather Program.
19. How long have we known about space weather?
Space weather is a relatively new term that combines several research fields. Disruptions of the telegraph system by solar storms were seen in the mid-1800’s. Radio operators knew that the sun interfered with radio transmissions soon after radio was invented in the early 1900’s. Problems (such as outages and loss of data) related to space weather were seen in weather satellites when they began operating in the 1960’s. All of these effects come from the same source (solar activity) and the term “space weather” was used to group the causes and effects into one subject.
20. Have scientists seen changes in the intensity of space weather?
On a short time scale, the intensity of space weather is always changing. Conditions can be mild one minute and stormy the next. On longer time scales, space weather varies with the solar cycle. Solar flares, coronal mass ejections and solar energetic particles all increase in frequency as we get closer to solar maximum. High-speed wind streams are more frequent at solar minimum, thus ensuring that space weather is something to watch for no matter where we are in the solar cycle.
21. How strong is solar wind (compared to wind on Earth)?
The solar wind is very weak compared to the wind on Earth, though it is much, much faster. When we measure solar wind speeds, we typically get speeds of 1-2 million miles per hour. They end up being weaker because there is very little of it. Solar wind density is usually about 100 particles per cubic inch. Thus, a typical pressure from the solar wind is measure in nanopascals whereas at the Earth’s surface, the atmospheric pressure is 100 kilopascals, and surface winds are about 100 pascals. Since solar wind is measured in nanopascals it is approximately 1000 million times weaker than winds here on Earth.
22. What are the northern and southern lights and are they related to space weather?
An aurora is a natural display of light in the sky that can be seen with the unaided eye at night. An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights. A similar phenomenon in the Southern Hemisphere is called the aurora australis. Auroras are the most visible effect of the sun’s activity on the Earth’s atmosphere.
Most auroras occur in far northern and southern regions. The most common color in an aurora is green. But displays that occur extremely high in the sky may be red or purple. Most auroras occur about 50 to 200 miles above the Earth. Some extend lengthwise across the sky for thousands of miles.
Auroral displays are associated with the solar wind, the continuous flow of electrically charged particles from the sun. When these particles reach the earth’s magnetic field, some get trapped. Many of these particles travel toward the Earth’s magnetic poles. When the charged particles strike atoms and molecules in the atmosphere, energy is released. Some of this energy appears in the form of auroras. Auroras occur most frequently during solar maximum, the most intense phase of the 11-year solar or sunspot cycle. Electrons and protons released by solar storms add to the number of solar particles that interact with the Earth’s atmosphere. This increased interaction produces extremely bright auroras.
23. Who is responsible for predicting space weather and sending alerts when there is solar activity?
NOAA’s Space Weather Prediction Center (SWPC) is the nation’s official source of space weather alerts, watches and warnings. It provides real-time monitoring and forecasting of solar and geophysical events. SWPC is part of the National Weather Service and is one of the nine National Centers for Environmental Prediction.
24. How do you forecast space weather?
A good space weather forecast begins with a thorough analysis. Forecasters analyze near-real-time ground- and space-based observations to assess the current state of the solar-geophysical environment (from the sun to the Earth and points in between). Space weather forecasters also analyze the 27-day recurrent pattern of solar activity. Based on a thorough analysis of current conditions, comparing these conditions to past situations, and using numerical models similar to weather models, forecasters are able to predict space weather on times scales of hours to weeks.
25. Why is forecasting space weather important?
As society’s reliance on technological systems grows, so does our vulnerability to space weather. The ultimate goal in studying space weather is an ability to foretell events and conditions on the Sun and in near-Earth space that will produce potentially harmful societal and economic effects, and to do this adequately far in advance and with sufficient accuracy to allow preventive or mitigating actions to be taken.
26. When do the effects of space weather show up?
Solar flares (sudden brightenings) affect the ionosphere immediately, with adverse effects upon communications and radio navigation.Solar energetic particles arrive in 20 minutes to several hours, threatening the electronics of spacecraft and unprotected astronauts, as they rise to 10,000 times the quiet background flux.Ejected bulk plasma and its pervading magnetic field arrive in 30 – 72 hours (depending upon initial speed and deceleration) setting off a geomagnetic storm, causing currents to flow in the magnetosphere and particles to be energized. The currents cause atmospheric heating and increased drag for satellite operators; they also induce voltages and currents in long conductors at ground level, adversely affecting pipelines and electric power grids. The energetic particles cause the northern lights, as well as surface and deep dielectric charging of spacecraft; subsequent electrostatic discharge of the excess charge build-up can damage spacecraft electronics. The ionosphere departs from its normal state, due to the currents and the energetic particles, thereby adversely affecting communications and radio navigation.
27. Where can I get more information?
- As the Sun Awakens, NASA Keeps a Wary Eye on Space Weather
- NASA-Funded Study Reveals Hazards of Severe Space Weather
- Space Weather Turns into an International Problem
- The Solar Dynamics Observatory (SDO)
- The Solar Terrestrial Relations Observatory (STEREO)
- The Solar and Heliospheric Observatory (SOHO)
28. Sun facts:
The Sun is a magnetic variable star at the center of our solar system that drives the space environment of the planets, including the Earth. The distance of the Sun from the Earth is approximately 93 million miles. At this distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The Sun has a diameter of about 865,000 miles, about 109 times that of Earth. Its mass, about 330,000 times that of Earth, accounts for about 99.86% of the total mass of the Solar System. About three quarters of the Sun’s mass consists of hydrogen, while the rest is mostly helium. Less than 2% consists of heavier elements, including oxygen, carbon, neon, iron, and others. The Sun is neither a solid nor a gas but is actually plasma. This plasma is tenuous and gaseous near the surface, but gets denser down towards the Sun’s fusion core.
The Sun, as shown by the illustration at right, can be divided into six layers. From the center out, the layers of the Sun are as follows: the solar interior composed of the core (which occupies the innermost quarter or so of the Sun’s radius), the radiative zone, and the convective zone, then there is the visible surface known as the photosphere, the chromosphere, and finally the outermost layer, the corona. The energy produced through fusion in the Sun’s core powers the Sun and produces all of the heat and light that we receive here on Earth.
The Sun, like most stars, is a main sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 430–600 million tons of hydrogen each second. The Sun’s hot corona continuously expands in space creating the solar wind, a stream of charged particles that extends to the heliopause at roughly 100 astronomical units. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.
Stars like our Sun shine for nine to ten billion years. The Sun is about 4.5 billion years old, judging by the age of moon rocks. Based on this information, current astrophysical theory predicts that the Sun will become a red giant in about five billion (5,000,000,000) years.
- Why didn’t the world end in 2012?For an answer to this and other 2012 questions, please visit the NASA 2012 FAQ page at
Should we be concerned about solar storms in 2012? Heliophysicist Alex Young from NASA Goddard Space Flight Center sorts out truth from fiction.