The solar storms of August 1972 were a historically powerful series of solar storms with intense to extreme
solar flare
A solar flare is an intense localized eruption 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 solar phe ...
,
solar particle event
In solar physics, a solar particle event (SPE), also known as a solar energetic particle (SEP) event or solar radiation storm, is a solar phenomenon which occurs when particles emitted by the Sun, mostly protons, become accelerated either in the ...
, and
geomagnetic storm
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 and/or cloud of magnetic field that interacts with the Earth's magnetic field.
The disturbance that d ...
components in early August 1972, during
solar cycle 20
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 observ ...
. 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 mine
A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any ...
s near
Haiphong
Haiphong ( vi, Hải Phòng, ), or Hải Phòng, is a major industrial city and the third-largest in Vietnam. Hai Phong is also the center of technology, economy, culture, medicine, education, science and trade in the Red River delta.
Haiphong wa ...
,
North Vietnam
North Vietnam, officially the Democratic Republic of Vietnam (DRV; vi, Việt Nam Dân chủ Cộng hòa), was a socialist state supported by the Soviet Union (USSR) and the People's Republic of China (PRC) in Southeast Asia that existed f ...
.
The
coronal mass ejection
A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field 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 ...
(CME)'s transit time from the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
to the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
is the fastest ever recorded.
Solar-terrestrial characteristics
Sunspot region
The most significant detected solar flare activity occurred from 2 to 11 August. Most of the significant solar activity emanated from
active sunspot region McMath 11976 (MR 11976; active regions being clusters of
sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sun ...
pairs).
McMath 11976 was extraordinarily magnetically complex. Its size was large although not exceptionally so.
McMath 11976 produced 67 solar flares (4 of these
X-class) during the time it was facing Earth, from 29 July to 11 August.
It also produced multiple relatively rare white light flares over multiple days.
The same active area was long-lived. It persisted through five
solar rotation
Solar rotation varies with latitude. The Sun is not a solid body, but is composed of a gaseous plasma. Different latitudes rotate at different periods. The source of this differential rotation is an area of current research in solar astronomy. ...
cycles, first receiving the designation as Region 11947 as it faced Earth, going unseen as it rotated the far side of the Sun, then returning Earthside as Region 11976, before cycling as Regions 12007, 12045, and 12088, respectively.
Flare of 4 August
Electromagnetic effects
The 4 August flare was among the largest since records began.
It saturated the
Solrad 9
Solrad 9, also known Explorer 37 and Explorer SE-B, was one of the SOLRAD (Solar Radiation) program that began in 1960 to provide continuous coverage of solar radiation with a set of standard photometers.
Launch and operations
Was launched on Mar ...
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
sensor at approximately X5.3 but was estimated to be in the vicinity of X20,
the threshold of the very rarely reached R5 on the NOAA radio blackout space weather scale.
A radio burst of 76,000
sfu
Simon Fraser University (SFU) is a public research university in British Columbia, Canada, with three campuses, all in Greater Vancouver: Burnaby (main campus), Surrey, and Vancouver. The main Burnaby campus on Burnaby Mountain, located from ...
was measured at 1
GHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
.
This was an exceptionally long duration flare, generating
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
emissions above background level for more than 16 hours. Rare emissions in the
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
(
-ray) spectrum were detected for the first time, on both 4 and 7 August, by the Orbiting Solar Observatory (
OSO 7
OSO 7 or Orbiting Solar Observatory 7 (NSSDC ID: 1971-083A), before launch known as OSO H is the seventh in the series of American Orbiting Solar Observatory satellites launched by NASA between 1962 and 1975. OSO 7 was launched from Cape Kennedy ...
).
The broad spectrum electromagnetic emissions of the largest flare are estimated to total 1-5 x 10
32 erg
The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...
s in energy released.
CMEs
The arrival time of the associated coronal mass ejection (CME) and its coronal cloud, 14.6 hours, remains the record shortest duration as of February 2022, indicating an exceptionally fast and typically an exceptionally geoeffective event (normal transit time is two to three days). A preceding series of solar flares and CMEs cleared the
interplanetary medium
The interplanetary medium (IPM) or interplanetary space consists of the mass and energy which fills the Solar System, and through which all the larger Solar System bodies, such as planets, dwarf planets, asteroids, and comets, move. The IPM sto ...
of particles, enabling the rapid arrival in a process similar to the
July 2012 solar storm
The solar storm of 2012 was an unusually large and strong coronal mass ejection (CME) event that occurred on July 23 that year. It missed Earth with a margin of approximately nine days, as the equator of the Sun rotates around its own axis with ...
.
Normalizing the transit times of other known extreme events to a standard 1
AU to account for the varying distance of the Earth from the Sun throughout the year, one study found the ultrafast 4 August flare to be an
outlier
In statistics, an outlier is a data point that differs significantly from other observations. An outlier may be due to a variability in the measurement, an indication of novel data, or it may be the result of experimental error; the latter are ...
to all other events, even compared to the great solar storm of 1859, the overall most extreme known solar storm, which is known as the "
Carrington Event
The Carrington Event was the most intense geomagnetic storm in recorded history, peaking from 1 to 2 September 1859 during solar cycle 10. It created strong auroral displays that were reported globally and caused sparking and even fires in mult ...
".
This corresponds to an
ejecta
Ejecta (from the Latin: "things thrown out", singular ejectum) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic materials (tephra) that came out of a volcanic explosion and magma ...
speed of an estimated .
The near Earth vicinity
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...
velocity may also be record-breaking and is calculated to have exceeded . The velocity was not directly measurable as instrumentation was off-scale high.
Analysis of a Guam
magnetogram
Magnetogram may refer to:
* Solar magnetogram
In solar observation, a magnetogram is a pictorial representation of the spatial variations in strength of the solar magnetic field.
Solar magnetograms are produced by solar magnetographs. Some magne ...
indicated a shockwave traversing the
magnetosphere
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynam ...
at and astonishing sudden storm commencement (SSC) time of 62 s.
Estimated
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
strength of 73-103
nT and
electric field
An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...
strength of >200
mV/m was calculated at 1 AU.
Solar particle event
Reanalysis based on IMP-5 (a.k.a.
Explorer 41
Explorer 41, also called as IMP-G and IMP-5, was a NASA satellite launched as part of Explorer program. Explorer 41 as launched on 21 June 1969 on Vandenberg AFB, California, with a Thor-Delta E1 launch vehicle. Explorer 41 was the seventh sat ...
) space solar observatory data suggests that >10‐
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an Voltage, electric potential difference of one volt i ...
ion
flux
Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...
reached 70,000 cm−2 s−1 sr−1 bringing it near the exceedingly rarely reached NOAA S5 level on the solar radiation scale.
Fluxes at other energy levels, from soft to hard, at >1 MeV, >30 MeV, and >60 MeV, also reached extreme levels, as well as inferred for >100 MeV.
The particle storm led to northern hemisphere polar stratospheric
ozone depletion
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...
of about 46% at altitude for several days before the atmosphere recovered and which persisted for 53 days at the lower altitude of .
The intense solar wind and particle storm associated with the CMEs led to one of the largest decreases in
cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
radiation from outside the Solar System, known as a
Forbush decrease
A Forbush decrease is a rapid decrease in the observed galactic cosmic ray intensity following a coronal mass ejection (CME). It occurs due to the magnetic field of the plasma solar wind sweeping some of the galactic cosmic rays away from Earth. ...
, ever observed.
Solar energetic particle
Solar energetic particles (SEP), formerly known as solar cosmic rays, are Particle physics, high-energy, charged particles originating in the solar atmosphere and solar wind. They consist of protons, electrons and heavy ions with energies rangin ...
(SEP) onslaught was so strong that the Forbush decrease in fact partially abated.
SEPs reached the Earth's surface, causing a
ground level event (GLE).
Geomagnetic storm
The 4 August flare and ejecta caused significant to extreme effects on the Earth's magnetosphere, which responded in an unusually complex manner.
The
disturbance storm time index
The disturbance storm time (Dst, Kyoto Dst) index is a measure in the context of space weather. It gives information about the strength of the ring current around Earth caused by solar protons and electrons.
The ring current around Earth produces ...
(Dst) was only -125 nT, falling merely within the relatively common "intense" storm category. Initially an exceptional geomagnetic response occurred and some extreme storming occurred locally later (some of these possibly within
substorm
A substorm, sometimes referred to as a magnetospheric substorm or an auroral substorm, is a brief disturbance in the Earth's magnetosphere that causes energy to be released from the "tail" of the magnetosphere and injected into the high latitude ...
s), but arrival of subsequent CMEs with northward oriented magnetic fields is thought to have shifted the
interplanetary magnetic field
The interplanetary magnetic field (IMF), now more commonly referred to as the heliospheric magnetic field (HMF), is the component of the solar magnetic field that is dragged out from the solar corona by the solar wind flow to fill the Solar Syst ...
(IMF) from an initial southward to northward orientation, thus substantially suppressing geomagnetic activity as the solar blast was largely deflected away from rather than toward Earth. An early study found an extraordinary asymmetry range of ≈450 nT.
A 2006 study found that if a favorable IMF southward orientation were present that the Dst may have surpassed 1,600 nT, comparable to the 1859 Carrington Event.
Magnetometer
A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, o ...
s in
Boulder, Colorado
Boulder is a home rule city that is the county seat and most populous municipality of Boulder County, Colorado, United States. The city population was 108,250 at the 2020 United States census, making it the 12th most populous city in Color ...
,
Honolulu, Hawaii
Honolulu (; ) is the capital and largest city of the U.S. state of Hawaii, which is in the Pacific Ocean. It is an unincorporated county seat of the consolidated City and County of Honolulu, situated along the southeast coast of the island o ...
,
and elsewhere went off-scale high. Stations in India recorded geomagnetic sudden impulses (GSIs) of 301-486 nT. Estimated
AE index peaked at over 3,000 nT and
Kp reached 9 at several hourly intervals
(corresponding to NOAA G5 level).
The magnetosphere compressed rapidly and substantially with the
magnetopause
The magnetopause is the abrupt boundary between a magnetosphere and the surrounding plasma. For planetary science, the magnetopause is the boundary between the planet's magnetic field and the solar wind. The location of the magnetopause is d ...
reduced to 4-5
RE and the
plasmapause
The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined by ...
(boundary of the
plasmasphere
The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined by ...
, or lower magnetosphere) reduced to 2 R
E or less. This is a contraction of at least one half and up to two-thirds the size of the magnetosphere under normal conditions, to a distance of less than .
Solar wind dynamic pressure increased to about 100 times normal, based upon data from
Prognoz 1.
Impacts
Spacecraft
Astronomers first reported unusual flares on 2 August, later corroborated by orbiting spacecraft. On 3 August,
Pioneer 9
Pioneer commonly refers to a settler who migrates to previously uninhabited or sparsely inhabited land.
In the United States pioneer commonly refers to an American pioneer, a person in American history who migrated west to join in settling and dev ...
detected a shock wave and sudden increase in solar wind speed from approximately .
A shockwave passed
Pioneer 10
''Pioneer 10'' (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing , that completed the first mission to the planet Jupiter. Thereafter, ''Pioneer 10'' became the first of five artificial objects to ach ...
, which was 2.2 AU from the Sun at the time.
The greatly constricted magnetosphere caused many satellites to cross outside Earth's protective
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
, such boundary crossings into the
magnetosheath
The magnetosheath is the region of space between the magnetopause and the bow shock of a planet's magnetosphere. The regularly organized magnetic field generated by the planet becomes weak and irregular in the magnetosheath due to interaction with ...
led to erratic space weather conditions and potentially destructive solar particle bombardment.
The
Intelsat IV F-2
Intelsat IV F-2 was a geostationary communication satellite built by Hughes and owned by Intelsat. The satellite was based on the HS-312 platform and its estimated useful life was 7 years.
History
The Intelsat IV F-2 was part of the Intelsa ...
communications satellite
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...
solar panel arrays power generation was degraded by 5%, about 2 years worth of wear. An on-orbit power failure ended the mission of a
Defense Satellite Communications System
The Defense Satellite Communications System (DSCS) is a United States Space Force satellite constellation that provides the United States with military communications to support globally distributed military users. Beginning in 2007, DSCS is be ...
(DSCS II)
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
. Disruptions of
Defense Meteorological Satellite Program
The Defense Meteorological Satellite Program (DMSP) monitors meteorological, oceanographic, and solar-terrestrial physics for the United States Department of Defense. The program is managed by the United States Space Force with on-orbit operati ...
(DMSP) scanner electronics caused anomalous dots of light in the southern polar cap imagery.
Terrestrial effects and aurora
On 4 August, an
aurora
An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...
shone so luminously that shadows were cast on the southern coast of the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
and shortly later as far south as
Bilbao
)
, motto =
, image_map =
, mapsize = 275 px
, map_caption = Interactive map outlining Bilbao
, pushpin_map = Spain Basque Country#Spain#Europe
, pushpin_map_caption ...
, Spain at
magnetic latitude 46°.
Extending to 5 August, intense geomagnetic storming continued with bright red (a relatively rare color associated with extreme events) and fast-moving aurora visible at midday from dark regions of the Southern Hemisphere.
Radio frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...
(RF) effects were rapid and intense.
Blackouts commenced nearly instantaneously on the sunlit side of Earth on
HF and other vulnerable bands. A nighttime
mid-latitude
The middle latitudes (also called the mid-latitudes, sometimes midlatitudes, or moderate latitudes) are a spatial region on Earth located between the Tropic of Cancer (latitudes 23°26'22") to the Arctic Circle (66°33'39"), and Tropic of Caprico ...
E layer
E, or e, is the fifth letter and the second vowel letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''e'' (pronounced ); plura ...
developed.
Geomagnetically induced current
Geomagnetically induced currents (GIC) are electrical currents induced at the Earth's surface by rapid changes in the geomagnetic field caused by space weather events. GICs can affect the normal operation of long electrical conductor systems such a ...
s (GICs) were generated and produced significant
electrical grid
An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
disturbances throughout Canada and across much of eastern and central United States, with strong anomalies reported as far south as
Maryland
Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...
and
Ohio
Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
, moderate anomalies in
Tennessee
Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...
, and weak anomalies in
Alabama
(We dare defend our rights)
, anthem = "Alabama (state song), Alabama"
, image_map = Alabama in United States.svg
, seat = Montgomery, Alabama, Montgomery
, LargestCity = Huntsville, Alabama, Huntsville
, LargestCounty = Baldwin County, Al ...
and north
Texas
Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
. The
voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
collapse of 64% on the
North Dakota
North Dakota () is a U.S. state in the Upper Midwest, named after the Native Americans in the United States, indigenous Dakota people, Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north a ...
to
Manitoba
Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
interconnection
In telecommunications, interconnection is the physical linking of a carrier's network with equipment or facilities not belonging to that network. The term may refer to a connection between a carrier's facilities and the equipment belonging to ...
would have been sufficient to cause a system breakup if occurring during high export conditions on the
line
Line most often refers to:
* Line (geometry), object with zero thickness and curvature that stretches to infinity
* Telephone line, a single-user circuit on a telephone communication system
Line, lines, The Line, or LINE may also refer to:
Arts ...
, which would have precipitated a large
power outage
A power outage (also called a powercut, a power out, a power failure, a power blackout, a power loss, or a blackout) is the loss of the electrical power network supply to an end user.
There are many causes of power failures in an electricit ...
. Many U.S. utilities in these regions reported no disturbances, with the presence of
igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock ...
geology a suspected factor, as well as geomagnetic latitude and differences in operational characteristics of respective electrical grids.
Manitoba Hydro
The Manitoba Hydro-Electric Board, operating as Manitoba Hydro, is the electric power and natural gas utility in the province of Manitoba, Canada. Founded in 1961, it is a provincial Crown Corporation, governed by the Manitoba Hydro-Electric Boa ...
reported that power going the other way, from Manitoba to the U.S., plummeted 120
MW within a few minutes. Protective relays were repeatedly activated in
Newfoundland
Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...
.
An outage was reported along American Telephone and Telegraph (now
AT&T
AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile tel ...
)'s L4 coaxial cable between
Illinois
Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolita ...
and
Iowa
Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the ...
. Magnetic field variations (dB/dt) of ≈800 nT/min were estimated locally at the time
and the peak rate of change of magnetic field intensity reached >2,200 nT/min in central and western Canada, although the outage was most likely caused by swift intensification of the eastward
electrojet
An electrojet is an electric current which travels around the E region of the Earth's ionosphere. There are three electrojets: one above the magnetic equator (the equatorial electrojet), and one each near the Northern and Southern Polar Circles (th ...
of the
ionosphere
The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...
.
AT&T also experienced a surge of 60
volt
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defi ...
s on their telephone cable between
Chicago
(''City in a Garden''); I Will
, image_map =
, map_caption = Interactive Map of Chicago
, coordinates =
, coordinates_footnotes =
, subdivision_type = Country
, subdivision_name ...
and
Nebraska
Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...
.
Exceeding the high-current shutdown threshold, an induced electric field was measured at 7.0 V/km. The storm was detected in low-latitude areas such as the Philippines and Brazil, as well as Japan.
Military operations
![Mine explosion Operation End Sweep 9 March 1973](https://upload.wikimedia.org/wikipedia/commons/0/02/Mine_explosion_Operation_End_Sweep_9_March_1973.jpg)
The
U.S. Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
's
Vela nuclear detonation detection satellites mistook that an explosion occurred, but this was quickly dealt with by
personnel
Employment is a relationship between two parties regulating the provision of paid labour services. Usually based on a contract, one party, the employer, which might be a corporation, a not-for-profit organization, a co-operative, or any othe ...
monitoring the data in real-time.
The
U.S. Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...
concluded, as shown in declassified documents,
that the seemingly spontaneous detonation of dozens of Destructor
magnetic-influence sea mines (DSTs) within about 30 seconds in the Hon La area (magnetic latitude ≈9°) was highly likely the result of an intense solar storm. One account claims that 4,000 mines were detonated. It was known that solar storms caused terrestrial geomagnetic disturbances but it was as yet unknown to the military whether these effects could be sufficiently intense. It was confirmed as possible in a meeting of Navy investigators at the NOAA
Space Environment Center (SEC)
as well as by other facilities and experts.
Human spaceflight
Although it occurred between
Apollo missions
The Apollo program was a United States human spaceflight program carried out from 1961 to 1972 by the National Aeronautics and Space Administration (NASA), which landed the first astronauts on the Moon. The program used the Saturn IB and Saturn ...
, the storm has long been chronicled within
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
.
Apollo 16
Apollo 16 (April 1627, 1972) was the tenth crewed mission in the United States Apollo space program, administered by NASA, and the fifth and penultimate to land on the Moon. It was the second of Apollo's " J missions", with an extended sta ...
returned to Earth on April 27 1972, with the subsequent (and ultimately final) Apollo
Moon landing
A Moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both crewed and robotic missions. The first human-made object to touch the Moon was the Soviet Union's Luna 2, on 13 September 1959.
The United St ...
scheduled to depart on December 7 that same year. Had a mission been taking place during August, those inside the Apollo command module would have been shielded from 90% of the incoming radiation. However, this reduced dose could still have caused
acute radiation sickness if the astronauts were located outside the protective magnetic field of Earth, which was the case for much of a lunar mission. An astronaut engaged in
EVA
Eva or EVA may refer to:
* Eva (name), a feminine given name
Arts, entertainment, and media Fictional characters
* Eva (Dynamite Entertainment), a comic book character by Dynamite Entertainment
* Eva (''Devil May Cry''), Dante's mother in t ...
in orbit or on a moonwalk could have experienced severe radiation poisoning, or even absorbed a potentially lethal dose. Regardless of location, an astronaut would have suffered an enhanced risk of contracting cancer after being exposed to that amount of radiation.
This was one of only a handful of solar storms which have occurred in the
Space Age
The Space Age is a period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events, beginning with the Sputnik_1#Launch_and_mission, launch of Sputnik 1 ...
that could cause severe illness, and was potentially the most hazardous.
Had the most intense solar activity of early August occurred during a mission, it would have forced the crew to abort the flight and resort to contingency measures, including an emergency return and landing for medical treatment.
Implications for heliophysics and society
The storm was an important event in the field of
heliophysics
Heliophysics (from the prefix " helio", from Attic Greek ''hḗlios'', meaning Sun, and the noun "physics": the science of matter and energy and their interactions) is the physics of the Sun and its connection with the Solar System. NASA define ...
, the study of
space weather
Space weather is a branch of space physics and aeronomy, or heliophysics, concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the ma ...
, with numerous studies published in the next few years and throughout the 1970s and 1980s, as well as leading to several influential internal investigations and to significant policy changes. Almost fifty years after the fact, the storm was reexamined in an October 2018 article published in the
American Geophysical Union
The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's act ...
(AGU) journal ''Space Weather''. The initial and early studies as well as the later reanalysis studies were only possible due to initial monitoring facilities installed during the
International Geophysical Year
The International Geophysical Year (IGY; french: Année géophysique internationale) was an international scientific project that lasted from 1 July 1957 to 31 December 1958. It marked the end of a long period during the Cold War when scientific ...
(IGY) in 1957-1958 and subsequent global scientific cooperation to maintain the data sets. That initial terrestrial data from ground stations and balloons was later combined with spaceborne observatories to form far more complete information than had been previously possible, with this storm being one of the first widely documented of the then young Space Age. It convinced both the military and NASA to take space weather seriously and accordingly devote resources to its monitoring and study.
The authors of the 2018 paper compared the 1972 storm to the great storm of 1859 in some aspects of intensity. They posit that it was a Carrington‐class storm.
Other researchers conclude that the 1972 event could have been comparable to 1859 for geomagnetic storming if
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
orientation parameters were favorable,
or as a "failed Carrington-type storm" based on related considerations,
which is also the finding of a 2013
Royal Academy of Engineering
The Royal Academy of Engineering (RAEng) is the United Kingdom's national academy of engineering.
The Academy was founded in June 1976 as the Fellowship of Engineering with support from Prince Philip, Duke of Edinburgh, who became the first senior ...
report.
See also
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List of solar storms
Solar storms of different types are caused by disturbances on the Sun, most often from coronal mass ejections (CMEs) and solar flares from active regions, or, less often, from coronal holes. Minor to active solar storms (i.e. storming restricted t ...
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Military meteorology
Military meteorology is meteorology applied to military purposes, by armed forces or other agencies. It is one of the most common fields of employment for meteorologists.
World War II brought great advances in meteorology as large-scale military ...
*
Operation Pocket Money
Operation Pocket Money was the title of a U.S. Navy Task Force 77 aerial mining campaign conducted against the Democratic Republic of Vietnam (North Vietnam) from 9 May 1972 (Vietnamese time), during the Vietnam War. Its purpose was to halt or s ...
*
Operation End Sweep
Operation End Sweep was a United States Navy and United States Marine Corps operation to remove naval mines from Haiphong harbor and other coastal and inland waterways in North Vietnam between February and July 1973. The operation fulfilled an Am ...
References
Further reading
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External links
Video of the seahorse flare of 7 August 1972 recorded at Big Bear Solar Observatory(NASA)
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{{Portal bar, Astronomy, Physics, Science, Space
1972 natural disasters
1972 in science
Geomagnetic storms
August 1972 events