A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other eruptive solar phenomena. The occurrence of solar flares varies with the 11-year solar cycle.
Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the varying conditions within the Solar System and its heliosphere. This includes the effects of the solar wind, especially on the Earth's magnetosphere, ionosphere, thermosphere, and exosphere. Though physically distinct, space weather is analogous to the terrestrial weather of Earth's atmosphere. The term "space weather" was first used in the 1950s and popularized in the 1990s. Later, it prompted research into "space climate", the large-scale and long-term patterns of space weather.
A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth's magnetosphere caused by a solar wind shock wave.
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation from a period of minimum activity to a period of a maximum activity back to a period of minimum activity.
A coronal mass ejection (CME) is a significant ejection of magnetic field and accompanying plasma mass from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted theoretical understanding of these relationships has not been established.
A solar storm is a disturbance on the Sun, which can emanate outward across the heliosphere, affecting the entire Solar System, including Earth and its magnetosphere, and is the cause of space weather in the short-term with long-term patterns comprising space climate.
A coronal hole is a temporary region of relatively cool, less dense plasma in the solar corona where the Sun's magnetic field extends into interplanetary space as an open field. Compared to the corona's usual closed magnetic field that arches between regions of opposite magnetic polarity, the open magnetic field of a coronal hole allows solar wind to escape into space at a much quicker rate. This results in decreased temperature and density of the plasma at the site of a coronal hole, as well as an increased speed in the average solar wind measured in interplanetary space. If streams of high-speed solar wind from coronal holes encounter the Earth, they can cause major displays of aurorae. Near solar minimum, when activity such as coronal mass ejections is less frequent, such streams are the main cause of geomagnetic storms and associated aurorae.
Solar cycle 24 is the most recently completed solar cycle, the 24th since 1755, when extensive recording of solar sunspot activity began. It began in December 2008 with a minimum smoothed sunspot number of 2.2, and ended in December 2019. Activity was minimal until early 2010. It reached its maximum in April 2014 with a 23 months smoothed sunspot number of 81.8. This maximum value was substantially lower than other recent solar cycles, down to a level which had not been seen since cycles 12 to 15 (1878-1923).
The March 1989 geomagnetic storm occurred as part of severe to extreme solar storms during early to mid March 1989, the most notable being a geomagnetic storm that struck Earth on March 13. This geomagnetic storm caused a nine-hour outage of Hydro-Québec's electricity transmission system. The onset time was exceptionally rapid. Other historically significant solar storms occurred later in 1989, during a very active period of solar cycle 22.
Solar cycle 20 was the twentieth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 11.4 years, beginning in October 1964 and ending in March 1976. The maximum smoothed sunspot number observed during the solar cycle was 156.6, and the starting minimum was 14.3. During the minimum transit from solar cycle 20 to 21, there were a total of 272 days with no sunspots.
Solar cycle 22 was the 22nd solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 9.9 years, beginning in September 1986 and ending in August 1996. The maximum smoothed sunspot number observed during the solar cycle was 212.5, and the starting minimum was 13.5. During the minimum transit from solar cycle 22 to 23, there were a total of 309 days with no sunspots.
Solar cycle 23 was the 23rd solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 12.3 years, beginning in August 1996 and ending in December 2008. The maximum smoothed sunspot number observed during the solar cycle was 180.3, and the starting minimum was 11.2. During the minimum transit from solar cycle 23 to 24, there were a total of 817 days with no sunspots. Compared to the last several solar cycles, it was fairly average in terms of activity.
The Bastille Day solar storm was a powerful solar storm on 14-16 July 2000 during the solar maximum of solar cycle 23. The storm began on the national day of France, Bastille Day. It involved a solar flare, a solar particle event, and a coronal mass ejection which caused a severe geomagnetic storm.
The Halloween solar storms were a series of solar storms involving solar flares and coronal mass ejections that occurred from mid-October to early November 2003, peaking around October 28–29. This series of storms generated the largest solar flare ever recorded by the GOES system, modeled as strong as X45.
Solar observation is the scientific endeavor of studying the Sun and its behavior and relation to the Earth and the remainder of the Solar System. Deliberate solar observation began thousands of years ago. That initial era of direct observation gave way to telescopes in the 1600s followed by satellites in the twentieth century.
Solar phenomena are natural phenomena which occur within the atmosphere of the Sun. They take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots.
The solar storms of August 1972 were a historically powerful series of solar storms with intense to extreme solar flare, solar particle event, and geomagnetic storm components in early August 1972, during solar cycle 20. The storm caused widespread electric‐ and communication‐grid disturbances through large portions of North America as well as satellite disruptions. On 4 August 1972 the storm caused the accidental detonation of numerous U.S. naval mines near Haiphong, North Vietnam. The coronal mass ejection (CME)'s transit time from the Sun to the Earth is the fastest ever recorded.
