Magnetic storm

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A magnetic storm is a disturbance of the magnetosphere of a planet or especially the earth ( geomagnetic storm ).

Definition and origin

A geomagnetic storm is defined by the changes in the geomagnetic field it causes . Among other things, the Disturbance storm time index (Dst-Index) is used for classification, which indicates the globally averaged weakening of the horizontal earth's magnetic field based on measurements from some measuring stations distributed around the world. This value is determined every hour and is available in almost real time . There are many influences on the magnetic field, so fluctuations in magnetic flux density of ± 20 nT are normal. For comparison: In Central Europe the horizontal component of the normal earth's magnetic field is around 20 µT.

The disturbance is triggered by shock wave fronts from the solar wind , which are caused by solar flares or coronal mass ejections (KMA) and take around 24 to 36 hours to reach Earth. It lasts about 24 to 48 hours, in individual cases several days - depending on the cause of the malfunction in the sun . The impact of the shock front, consisting of electrically charged particles, on the magnetosphere leads to a weakening of the earth's magnetic field, which reaches its minimum after about twelve hours.

A geomagnetic storm is typically divided into three phases:

Initial phase

The initial phase is characterized by a weakening of the magnetic field by around 20–50 nT within a few dozen minutes. Not every storm event is preceded by such an initial phase, and conversely, not every such disturbance of the magnetic field is followed by a magnetic storm.

Storm phase

The storm phase begins when the disturbance is greater than 50 nT, which is an arbitrarily drawn limit. In the course of a typical magnetic storm, the disturbance continues to grow. The strength of a geomagnetic storm is described as “moderate” if the maximum disturbance is less than 100 nT, as “intense” if the disturbance does not exceed 250 nT and otherwise as a “superstorm”. A maximum attenuation of about 650 nT is rarely exceeded, which corresponds to about three percent of the normal value. The phase lasts a few hours and ends as soon as the strength of the disturbance decreases, i.e. the earth's magnetic field begins to grow again to its typical strength.

Recovery phase

The recovery phase ends when normal value is reached and can last between 8 hours and a week.


Magnetic storms can have a variety of effects, the best known being the occurrence of polar lights ( aurora borealis or aurora australis ) in temperate zones such as central Europe. In electrical power networks , the geomagnetically induced currents triggered can lead to direct damage to power transformers.

Temporal fluctuations in the earth's magnetic field due to a magnetic storm on March 31, 2001, measured in Ile-Ife , Nigeria. The time in minutes ( GMT ) is plotted on the abscissa, the magnetic field strength in nanotesla [nT] (minute mean) on the ordinate. The green curve shows the sq-gait (without magnetic storm) in Ile-Ife.

First of all, magnetic storms influence the earth's magnetic field, which in turn affects the formation of the Van Allen Belt . In the event of particularly strong magnetic storms, all living beings are exposed to increased cosmic radiation , especially in the polar regions , because the earth's magnetic field generally provides less protection there. As trees grow faster in increased solar activity, they have an 11-year period in their annual rings . The reasons for this have not yet been clarified.

Among other things, temporary changes in the ionosphere can interfere with radio transmissions (e.g. radio or mobile communications ). In elongated electrical conductors such as overhead power lines , compensating currents of sometimes considerable strength can flow, which can lead to the failure of the connected transformer stations. Pipelines are subject to increased corrosion during magnetic storms.

Before the shock wave front hits Earth, it can cause damage to satellites . In addition to the direct damage caused by current induction, as on the earth's surface, this is also possible in another, more indirect way: The shock wave can lead to local heating and thus to a deformation of the upper atmosphere , which leads to increased air resistance for satellites in low orbits ( Low Earth Orbit , LEO). Changes in path or increased fuel consumption would then be the result. Overall, the European Space Agency ( ESA) has estimated that in recent years, satellite failures alone have caused damage of more than $ 500 million. This and the distortion of the transit times that occur when the signals pass through ion clouds make GPS satellites particularly vulnerable.

The effects of a geomagnetic storm like the Carrington event in 1859 would be devastating today. Because at that time there was neither internet nor was the world as globally networked and dependent on the power supply as it is today. In 2014, researchers proposed a space weather early warning system consisting of 16 satellites . The US military classifies the effects of a severe magnetic storm as a military attack. The British Royal Academy of Engineering also sees clear dangers, but is more cautious.


Before the 19th century

Various findings, for example an increased 14 C content in wooden parts that can be precisely dated using the annual rings , point to events, for example in the years 660 BC. AD, 774/775 AD and 993/994, which are mainly interpreted as magnetic storms or "solar storms" (for the event of 774/775, however, a gamma ray burst from a celestial body about 3000 light years away is also considered as the cause ). These events could have exceeded the Carrington event of 1859 (see below) in its intensity on the earth's surface several times over.

19th century

  • Magnetic storms were observed as early as the early 19th century. From May 1806 to June 1807, Alexander von Humboldt examined the variation in the direction in which a magnetic compass pointed in Berlin . He registered strong disturbances on December 21, 1806 and could see northern lights the following night; the next morning the disturbances were over.
  • On the night of September 1st to 2nd, 1859, the most powerful geomagnetic storm to date was recorded, which is now known as the Carrington Event . It led to the northern lights, which could even be observed in Rome, Havana and Hawaii - i.e. close to the equator. In the higher latitudes of Northern Europe and North America, high currents shot through telegraph lines, these struck sparks, telegraph papers caught fire and the telegraph network that had just been installed worldwide was severely impaired. As early as August 28, 1859, the development of sunspots could be observed, which were associated with extremely strong magnetic fields and solar flares. Ice core studies show that an event of this magnitude occurs on a statistical average every 500 years.

20th century

  • In 1921, a large geomagnetic storm in overhead power lines generated currents ten times greater than the following in March 1989.
  • On May 25, 1967, a magnetic storm disrupted the radar systems of the American missile early warning system and almost triggered a nuclear war. All early warning radar stations of the Ballistic Missile Early Warning System (BMEWS) in Canada, Greenland and England failed. They had been blinded by one of the most violent geomagnetic storms of the 20th century. The high-energy radiation had reached Earth shortly before and ionized the molecules in the upper layers of the atmosphere. The astrophysicists who observed the space weather and were able to convince the commanders that it was a geomagnetic storm had only recently been hired.
  • In Québec , a violent geomagnetic storm caused by geomagnetically induced currents in 1989 led to the thermal failure of several transformers, which resulted in a 9-hour power outage in the Montreal region . This caused chaos because traffic control systems, airports and district heating failed. Six million people were affected. The Dst index determined was −589 nT.
  • On July 14, 2000, a class X5 flare was observed on the Sun with a coronal mass ejection directed directly at Earth. After the shock front hit Earth, a superstorm was measured between July 15 and 17, 2000 with a maximum disturbance of −301 nT. No technical failures were known.

21st century

  • Between October 19 and November 5, 2003, 17 larger flares were observed, which were combined to form the geomagnetic storms of Halloween 2003 . Among them was the strongest flare detected up to then: a class X28 flare, which on November 4, 2003 led to very strong interference in radio traffic. Subsequently, several coronal mass ejections (KMA) hit the earth, which led to temporally overlapping magnetic storms with maximum Dst values ​​of −383 nT, −353 nT and −151 nT. On October 30, 2003, due to the high level of geomagnetic activity in Malmö, Sweden, part of the power grid failed for 20 to 50 minutes. 50,000 electricity customers were affected. Because the technical systems for air surveillance had failed for 30 hours, air corridors in northern Canada were closed to passenger aircraft. Signals from the satellite and navigation systems are intermittently interrupted. According to Japanese data, the particle cloud was thirteen times the size of the earth and traveling at 1.6 million km / h (0.15% of the speed of light ). Northern lights could be seen as far as tropical regions.
  • In June 2011, a magnetic storm caused the Venus Express probe to malfunction briefly ; A warning was given about a possible failure of the GPS navigation satellite system . The eruption on June 7, 2011 was observed by the Solar Dynamics Observatory (SDO), a satellite designed for solar observation.
  • After analyzing observation data from the STEREO probes, NASA researchers announced in 2014 that two years earlier, on July 23, 2012, the earth had narrowly escaped a “solar super storm”. The event was the strongest solar storm in over 150 years and at least as strong as the Carrington event of 1859.

See also


Web links

Individual evidence

  1. ^ Hourly Equatorial Dst Values ​​(Real-time). Dst index at the World Data Center for Geomagnetism, Kyoto, Japan. Online at, accessed December 25, 2016.
  2. ^ Udo Backhaus, Klaus Lindner: Astronomy Plus. 1st edition, Cornelsen Verlag, Berlin 2011, 5th print, ISBN 978-3-06-081012-3 , p. 83.
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  5. Humanity 'risks catastrophe from a solar superstorm'. In: The Telegraph. July 31, 2014, online at, accessed December 25, 2016.
  6. ^ Ashley Dale: Scientist underlines threat of inevitable "solar super-storms". ( Memento of August 5, 2014 in the Internet Archive ) In: PhysicsWorld magazine, August 1, 2014, online at, accessed on December 25, 2016.
  7. ^ Brian W. Kabat: The Sun as a Non-state Actor: The Implications on Military Operations and Theater Security of a Catastrophic Space Weather Event. Naval War College, Newport, RI, May 3, 2010, online at (English, PDF; 573 kB), accessed December 25, 2016.
  8. ^ Paul Cannon et al .: Extreme space weather: impacts on engineered systems and infrastructure. Royal Academy of Engineering, London February 2013, ISBN 1-903496-95-0 , online at (English, PDF; 2.8 MB), accessed December 25, 2016.
  9. Paschal O'Hare et al .: Multiradionuclide evidence for an extreme solar proton event around 2.610 BP (∼660 BC). Proceedings of the National Academy of Sciences of the United States of America , March 26, 2019, accessed February 11, 2020 . doi : 10.1073 / pnas.1815725116
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  12. Mysterious radiation storm hit earth in the year 775 - supernova or plasma eruption of the sun cannot explain the event. scinexx , June 4, 2012, accessed on February 11, 2020 .
  13. Cosmic ray pulse hit earth - A gamma ray burst could have hit earth in 775 AD. scinexx , January 21, 2013, accessed February 13, 2020 .
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  16. ↑ In 1967 solar storm almost triggered a nuclear war. In: SciNexx online magazine. Retrieved January 16, 2017.
  17. Jan Hattenbach: Dangerous space weather: When the sun almost triggered the 3rd World War. In: Frankfurter Allgemeine , August 17, 2016, online at, accessed on January 16, 2017.
  18. Thomas Häusler: Just past the nuclear war - how physicists saved the world in 1967. In: SRF , August 19, 2016, online at, accessed on January 16, 2017.
  19. ^ Neil R. Thomson, Craig J. Rodger, Richard L. Dowden: Ionosphere gives size of greatest solar flare. In: Geophysical Research Letter. Ed. 31, L06803, University of Otago, Dunedin New Zealand March 17, 2004, doi: 10.1029 / 2003GL019345 , online at, accessed January 17, 2017.
  20. Michael Weaver, William Murtagh et al .: Halloween Space Weather Storms of 2003. NOAA Technical Memorandum OAR SEC-88, Space Environment Center, Boulder, Colorado, June 2004 (PDF; 7.7 MB), accessed January 17 2017.
  21. Spiegel Online : Particle cloud in space: solar storm could interfere with GPS reception. In: Spiegel Online. June 8, 2011, online at, accessed on January 17, 2017.
  22. ^ Karen C. Fox, Tony Phillips, Holly Zell: Having a Solar Blast - Update. NASA press release on June 7, 2011 (images and video), online at, accessed January 17, 2017.
  23. New satellite data: Extreme solar storm missed the earth. In: Spiegel Online. July 24, 2014, online at, accessed on January 17, 2017.
  24. Tony Phillips: Near Miss: The Solar Superstorm of July 2012. In: Science News. July 23, 2014, online at, accessed January 17, 2017.
  25. DN Baker et al .: A major solar eruptive event in July 2012: Defining extreme space weather scenarios. In: Space Weather. Issue 11, October 9, 2013, pp. 585–591, doi: 10.1002 / swe.20097 , online at, accessed on January 17, 2017.