July 2012 solar storm

Short description: Notable coronal mass ejection

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Solar storm of 2012

The coronal mass ejection, as photographed by STEREO

Date| July 23, 2012 (2012-07-23)
Type| Coronal mass ejection
Outcome| Missed striking the Earth by nine days
Part of Solar cycle 24

The solar storm of 2012 was a solar storm involving an unusually large and strong coronal mass ejection that occurred on July 23, 2012. It missed Earth with a margin of approximately nine days, as the equator of the Sun rotates around its own axis with a period of about 25 days.[1]

The region that produced the outburst was thus not pointed directly towards Earth at that time. The strength of the eruption has been predicted to be comparable to the 1859 Carrington Event that caused damage to electrical equipment worldwide, which at that time consisted mostly of telegraph systems.[2]

## Contents

* 1 Overview
* 1.1 Predicted effects
* 2 Historical comparisons
* 3 See also
* 4 References
* 5 External links

## Overview

The event occurred in 2012, near the local maximum of sunspots that can be seen in this graph.

At 02:08 UT on 23 July 2012, a large coronal mass ejection (CME) was launched from the Sun.[3] The eruption emanated from solar active region 11520 and coincided with what was at most an X2.5-class solar flare.[4] The CME expelled a pair of adjacent magnetic clouds that drove a fast-moving shock wave outward from the Sun.[3] The eruption tore through Earth's orbit, hitting the STEREO-A spacecraft.[2] The spacecraft is a solar observatory equipped to measure such activity, and because it was far away from the Earth and thus not exposed to the strong electrical currents that can be induced when a CME hits the Earth's magnetosphere,[2] it survived the encounter and provided researchers with valuable data. Spacecraft observations recorded the shockwave at 20:55 UTC on 23 July while the magnetic clouds arrived two hours later. The leading shock wave associated with the CME was travelling radially at a speed of around 3,300 km/s (2,100 mi/s) relative to STEREO-A by the time it reached the spacecraft. The CME travelled from the Sun to Earth's orbit in about 20.78 hours, indicating an average speed of 2,000 km/s (1,200 mi/s).[3]

Based on the collected data, the eruption consisted of two separate ejections which were able to reach exceptionally high strength as the interplanetary medium around the Sun had been cleared by a smaller CME four days earlier.[2] Interaction between the primary CME and the preceding CMEs as they traversed the interplanetary medium also led to amplification of the magnetic field of the ejecta that continued by the time the primary CME reached Earth's orbit.[5]

The event occurred at a time of high sunspot activity during solar cycle 24.

### Predicted effects

Had the CME hit the Earth, it is likely that it would have inflicted serious damage to electronic systems on a global scale.[2] The resulting geomagnetic storm may have had a strength of −1,150 to −600 nT, comparable to the impact of the Carrington Event.[5] A 2013 study estimated that the economic cost to the United States would have been between US$600 billion and $2.6 trillion.[6] Ying D. Liu, professor at China's State Key Laboratory of Space Weather, estimated that the recovery time from such a disaster would have been about four to ten years.[7]

## Historical comparisons

The record fastest CME associated with the August 1972 solar storm is thought to have occurred in a similar process of earlier CMEs clearing particles in the path to Earth. This storm arrived in 14.6 hours, an even shorter duration after the parent flare erupted than for the great solar storm of 1859.

## See also

* List of solar storms

## References

1. ↑ Williams, David R. (1 July 2013). "Sun Fact Sheet". NASA. http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html. Retrieved 13 January 2015.
2. ↑ 2.0 2.1 2.2 2.3 2.4 Phillips, Tony (23 July 2014). "Near Miss: The Solar Superstorm of July 2012". NASA. https://science.nasa.gov/science-news/science-at-nasa/2014/23jul_superstorm/. Retrieved 10 January 2015.
3. ↑ 3.0 3.1 3.2 Riley, Pete; Caplan, Ronald M.; Giacalone, Joe; Lario, David; Liu, Ying (26 February 2016). "Properties of the fast forward shock driven by the 2012 July 23 extreme coronal mass ejection". The Astrophysical Journal 819 (1): 57. doi:10.3847/0004-637X/819/1/57.
4. ↑ Riley, Pete; Baker, Dan; Liu, Ying D.; Verronen, Pekka; Singer, Howard; Güdel, Manuel (February 2018). "Extreme Space Weather Events: From Cradle to Grave". Space Science Reviews 214 (1): 21. doi:10.1007/s11214-017-0456-3. Bibcode: 2018SSRv..214...21R.
5. ↑ 5.0 5.1 Liu, Ying D.; Luhmann, Janet G.; Kajdič, Primož; Kilpua, Emilia K.J.; Lugaz, Noé; Nitta, Nariaki V.; Möstl, Christian; Lavraud, Benoit et al. (18 March 2014). "Observations of an extreme storm in interplanetary space caused by successive coronal mass ejections". Nature Communications 5 (1): 3481. doi:10.1038/ncomms4481. PMID 24642508. Bibcode: 2014NatCo...5.3481L.
6. ↑ Lloyd's (2013). ﻿Solar Storm Risk to the North American Electric Grid﻿ (Report). https://assets.lloyds.com/assets/pdf-solar-storm-risk-to-the-north-american-electric-grid/1/pdf-Solar-Storm-Risk-to-the-North-American-Electric-Grid.pdf. Retrieved 2023-09-16.
7. ↑ Sanders, Robert (18 March 2014). "Fierce solar magnetic storm barely missed Earth in 2012". UC Berkeley News Center. http://newscenter.berkeley.edu/2014/03/18/fierce-solar-magnetic-storm-barely-missed-earth-in-2012/. Retrieved 10 January 2015.

* Gopalswamy, N.; S. Yashiro; N. Thakur; P. Mäkelä; H. Xie; S. Akiyama (2016). "The 2012 July 23 Backside Eruption: An Extreme Energetic Particle Event?". Astrophysical Journal 833 (2): 216. doi:10.3847/1538-4357/833/2/216. Bibcode: 2016ApJ...833..216G.

## External links

* v
* t
* e

Solar storms

* List of solar storms

Early|

* 774–775 solar event (hypothesized)
* 993–994 solar event (hypothesized)

1800s|

* Solar storm of 1859
* Aurora of November 17, 1882

1900s|

* May 1921 geomagnetic storm
* January 1938 geomagnetic storm
* Solar storm of August 1972
* March 1989 geomagnetic storm

2000s|

* Bastille Day Event, 2000
* Halloween solar storms, 2003
* Solar storm of 2012

See also|

* Solar flare
* Coronal mass ejection
* Coronal cloud
* Geomagnetic storm
* Solar particle event
* Space weather
* Heliophysics

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