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.
› View largerThe sun is a magnetic variable star that fluctuates on times scales ranging from a fraction of a second to billions of years. Credit: NASA
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.
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.
› View largerThe Sun unleashed a powerful flare on 4 November 2003. The Extreme ultraviolet Imager in the 195A emission line aboard the SOHO spacecraft captured the event. Credit: SOHO, ESA & NASA
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.
› View largerA solar eruptive prominence as seen in extreme UV light on March 30, 2010 with Earth superimposed for a sense of scale. Credit: NASA/SDO
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
What is a Coronal Mass Ejection 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.
› View largerA coronal mass ejection on Feb. 27, 2000 taken by SOHO LASCO C2 and C3. A CME blasts into space a billion tons of particles traveling millions of miles an hour. Credit: SOHO ESA & NASA 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.
Does all Solar Activity Affect the 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.
› View largerA closeup of an erupting prominence with Earth inset at the approximate scale of the image. Taken on July 1, 2002. Credit: SOHO, ESA & NASA
- 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.
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
› View largerThe dark shape sprawling across the face of the active Sun is a coronal hole, a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space. Credit: SOHO EIT, ESA/NASA
What is Solar Maximum and Minimum?
› View largerEleven years in the life of the Sun, spanning most of solar cycle 23, as it progressed from solar minimum to maximum conditions and back to minimum (upper right) again, seen as a collage of ten full-disk images of the lower corona. Of note is the prevalence of activity and the relatively few years when our Sun might be described as “quiet.” Credit: SOHO EIT, ESA/NASA
What are some of the Real World Examples of Space Weather Impacts?
Aurora are a well-known example of the impacts of space weather events. Credit: University of Alaska
› View larger- 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.
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.
› View largerThe Heliophysics System Observatory (HSO) showing current operating missions, missions in development, and missions under study. Credit: NASA
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.
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.
› View largerThe image gives a basic overview of the Sun’s parts. The cut-out shows the three major interior zones: the core (where energy is generated by nuclear reactions), the radiative zone (where energy travels outward by radiation through about 70% of the Sun), and the convection zone (where convection currents circulate the Sun’s energy to the surface). The surface features (flare, sunspots and photosphere, chromosphere, and the prominence) are all clipped from actual SOHO images of the Sun. Credit: NASA/SOHO
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.
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