Geomagnetic Storms When Power Grids Collapse Contents 1 Geomagnetic storm 1 1.1 History ................................................. 1 1.2 Definition of a geomagnetic storm ................................... 1 1.3 Historical occurrences ........................................ 2 1.4 Interactions with planetary processes ................................. 3 1.5 Instruments for researching geomagnetic storms ........................... 3 1.6 Geomagnetic storm effects ...................................... 3 1.6.1 Radiation hazards to humans ................................. 3 1.6.2 Fauna and flora ........................................ 4 1.6.3 Disruption of electrical systems ............................... 4 1.7 Preparations against solar storms ................................... 6 1.8 See also ................................................ 6 1.9 References .............................................. 6 1.10 Further reading ............................................ 7 1.11 External links ............................................. 8 2 Solar storm of 1859 9 2.1 Carrington super flare ......................................... 9 2.2 Similar events ............................................. 10 2.3 See also ................................................ 10 2.4 References .............................................. 10 2.5 Further reading ............................................ 11 2.6 External links ............................................. 12 3 March 1989 geomagnetic storm 13 3.1 Geomagnetic storm and auroras .................................... 13 3.2 Quebec blackout ........................................... 13 3.3 Aftermath ............................................... 14 3.4 See also ................................................ 14 3.5 References ............................................... 14 4 Solar and Heliospheric Observatory 15 4.1 Orbit .................................................. 15 i ii CONTENTS 4.2 Communication with Earth ...................................... 15 4.3 Near loss of SOHO .......................................... 15 4.3.1 Additional references ..................................... 16 4.4 Scientific objectives .......................................... 16 4.5 Instruments .............................................. 16 4.5.1 Public availability of images ................................. 17 4.5.2 Comet discovery ....................................... 17 4.5.3 Instrument contributors .................................... 17 4.6 See also ................................................ 18 4.7 References ............................................... 18 4.8 External links ............................................. 18 4.9 Text and image sources, contributors, and licenses .......................... 19 4.9.1 Text .............................................. 19 4.9.2 Images ............................................ 19 4.9.3 Content license ........................................ 20 Chapter 1 Geomagnetic storm This article is about disturbances within Earth’s magneto- be associated with or are caused by a geomagnetic storm. sphere. For other uses of “magnetic storm”, see Magnetic These include: Solar Energetic Particle (SEP) events, storm (disambiguation). geomagnetically induced currents (GIC), ionospheric dis- A geomagnetic storm is a temporary disturbance of turbances which cause radio and radar scintillation, dis- ruption of navigation by magnetic compass and auroral displays at much lower latitudes than normal. In 1989, a geomagnetic storm energized ground induced currents which disrupted electric power distribution throughout most of the province of Quebec[2] and caused aurorae as far south as Texas.[3] 1.1 History In 1931, Sydney Chapman and Vincenzo C. A. Fer- Artist’s depiction of solar wind particles interacting with Earth’s raro wrote an article, A New Theory of Magnetic Storms, magnetosphere. Sizes are not to scale. that sought to explain the phenomenon of geomagnetic storms.[4] They argued that whenever the Sun emits a the Earth's magnetosphere caused by a solar wind shock solar flare it will also emit a plasma cloud, now known as wave and/or cloud of magnetic field which interacts with a coronal mass ejection. This plasma will travel at a ve- the Earth’s magnetic field. The increase in the solar wind locity such that it reaches Earth within 113 days, though pressure initially compresses the magnetosphere and the we now know this journey takes 1 to 5 days. The cloud solar wind’s magnetic field interacts with the Earth’s mag- will then compress the Earth’s magnetic field and thus in- netic field and transfers an increased energy into the mag- crease this magnetic field at the Earth’s surface.[5] netosphere. Both interactions cause an increase in move- ment of plasma through the magnetosphere (driven by increased electric fields inside the magnetosphere) and an increase in electric current in the magnetosphere and 1.2 Definition of a geomagnetic ionosphere. storm During the main phase of a geomagnetic storm, electric current in the magnetosphere creates a magnetic force A geomagnetic storm is defined[6] by changes in the which pushes out the boundary between the magneto- DST[7] (disturbance – storm time) index. The Dst index sphere and the solar wind. The disturbance in the inter- estimates the globally averaged change of the horizontal planetary medium which drives the geomagnetic storm component of the Earth’s magnetic field at the magnetic may be due to a solar coronal mass ejection (CME) or equator based on measurements from a few magnetome- a high speed stream (co-rotating interaction region or ter stations. Dst is computed once per hour and reported CIR)[1] of the solar wind originating from a region of in near-real-time.[8] During quiet times, Dst is between weak magnetic field on the Sun’s surface. The frequency +20 and −20 nano-Tesla (nT). of geomagnetic storms increases and decreases with the A geomagnetic storm has three phases:[6] an initial phase, sunspot cycle. CME driven storms are more common a main phase and a recovery phase. The initial phase is during the maximum of the solar cycle and CIR driven characterized by Dst (or its one-minute component SYM- storms are more common during the minimum of the so- H) increasing by 20 to 50 nT in tens of minutes. The lar cycle. initial phase is also referred to as a storm sudden com- There are several space weather phenomena which tend to mencement (SSC). However, not all geomagnetic storms 1 2 CHAPTER 1. GEOMAGNETIC STORM have an initial phase and not all sudden increases in Dst or SYM-H are followed by a geomagnetic storm. The main phase of a geomagnetic storm is defined by Dst de- creasing to less than −50 nT. The selection of −50 nT to define a storm is somewhat arbitrary. The minimum value during a storm will be between −50 and approxi- mately −600 nT. The duration of the main phase is typ- ically between 2 and 8 hours. The recovery phase is the period when Dst changes from its minimum value to its quiet time value. The period of the recovery phase may be as short as 8 hours or as long as 7 days. The size of a geomagnetic storm is classified as moderate (−50 nT > minimum of Dst < −100 nT), intense (−100 nT > minimum Dst < −250 nT) or super-storm (mini- mum of Dst > −250 nT). GOES-7 monitors the space weather conditions during the Great Geomagnetic storm of March 1989, the Moscow neutron monitor recorded the passage of a CME as a drop in levels known as a [12] 1.3 Historical occurrences Forbush decrease. The first observation of the effects of a geomagnetic storm occurred early in the 19th century: From May 1806 The geomagnetic storm causing this event was itself the until June 1807 the German Alexander von Humboldt result of a coronal mass ejection, ejected from the Sun on recorded the bearing of a magnetic compass in Berlin. March 9, 1989.[14] The minimum of Dst was −589 nT. On 21 December 1806 he noticed that his compass had become erratic during a bright auroral event.[9] On July 14, 2000, an X5 class flare erupted on the Sun (known as the Bastille Day event) and a coronal mass On September 1 – 2, 1859, the largest recorded geomag- ejection was launched directly at the Earth. A geomag- netic storm occurred. From August 28 until September netic super storm occurred on July 15–17; the minimum 2, 1859, numerous sunspots and solar flares were ob- of the Dst index was – 301 nT. Despite the strength of served on the Sun, the largest flare occurring on Septem- the geomagnetic storm, no electrical power distribution ber 1. This is referred to as the Solar storm of 1859 or failures were reported.[15] The Bastille Day event was ob- the Carrington Event. It can be assumed that a massive served by Voyager 1 and Voyager 2,[16] thus it is the far- coronal mass ejection (CME), associated with the flare, thest out in the Solar System that a solar storm has been was launched from the Sun and reached the Earth within observed. eighteen hours — a trip that normally takes three to four days. The horizontal intensity of geomagnetic field was Seventeen major flares erupted on the Sun between 19 reduced by 1600 nT as recorded by the Colaba Obser- October and 5 November 2003, including perhaps the vatory. It is estimated that Dst would have been ap- most intense flare ever measured on the GOES XRS sen- proximately −1760 nT.[10] Telegraph wires in both the sor – a huge X28 flare,[17] resulting in an extreme ra- United States and Europe experienced induced emf, in dio blackout, on 4 November. These flares were as- some cases even