A new study published in the Nature Scientific Reports on July 13 suggests that powerful eruptions on the Sun can trigger large earthquakes on Earth. In the paper, the authors analyzed 20 years of proton density and velocity data, as recorded by the SOHO satellite, and the worldwide seismicity in the corresponding period, as reported by the ISC-GEM catalogue. They found a clear correlation between proton density and the occurrence of large earthquakes (M > 5.6), with a time shift of one day.
The Sun may seem relatively docile, but it is constantly bombarding the solar system with energy and particles in the form of the solar wind.
Sometimes, eruptions on the Sun’s surface cause coronal mass ejections that hurtle through the solar system at extremely fast rates.
The new study suggests that particles from eruptions like this may be responsible for triggering groups of powerful earthquakes.
“Large earthquakes all around the world are not evenly distributed– there is some correlation among them,” said co-author Giuseppe De Natale, research director at the National Institute of Geophysics and Volcanology in Rome, Italy.
“We have tested the hypothesis that solar activity can influence the worldwide [occurrence of earthquakes].”
Scientists noted a pattern in some massive earthquakes around the planet– they tend to occur in groups, not randomly. This indicates that there may be some global phenomenon triggering these worldwide tremors.
To address this, researchers searched through 20 years of data on both earthquakes and solar activity– specifically from NASA-ESA’s Solar and Heliospheric Observatory (SOHO) satellite– seeking any probable correlations.
Image credit: NASA/SDO
SOHO, located about 1.45 million km (900 000 miles) from our planet, monitors the Sun, which helps scientists track how much solar material strikes the Earth.
By comparing the ISC-GEM Global Instrumental Earthquake Catalogue– a historical record of powerful tremors– to SOHO data, the researchers noticed more strong earthquakes happened when the number and velocities of incoming solar protons increased.
When protons from the Sun peaked, there was also a spike in earthquakes above M5.6 for the next 24 hours.
“This statistical test of the hypothesis is very significant,” said De Natale. “The probability that it’s just by chance that we observe this, is very, very low– less than 1 in 100 000.”
After noticing there was a correlation between solar proton flux and strong earthquakes, the researchers went on to propose a mechanism called the reverse piezoelectric effect.
Compressing quartz rock, something common in the Earth’s crust, can produce electrical pulse through a process called the piezoelectric effect. The researchers think that such small pulses could destabilize faults that are nearing rupture, triggering earthquakes. Signals from electromagnetic evens, such as earthquake lightning and radio waves, have been recorded occurring alongside quakes in the past.
Some scientists think these events are caused by the quakes themselves, but other studies have spotted strong electromagnetic anomalies before huge earthquakes and not after, so the exact nature of the correlation of earthquakes and electromagnetic fields is still debated.
Meanwhile, this new explanation suggests that electromagnetic anomalies are not the result of earthquakes, but cause them instead. As positively charged protons from the Sun hit the Earth’s magnetic bubble, they generate electromagnetic currents that propagate across the world. Pulses created by these currents go on to deform quartz in the crust, ultimately triggering earthquakes.
Large earthquakes occurring worldwide have long been recognized to be non Poisson distributed, so involving some large scale correlation mechanism, which could be internal or external to the Earth. Till now, no statistically significant correlation of the global seismicity with one of the possible mechanisms has been demonstrated yet. In this paper, we analyze 20 years of proton density and velocity data, as recorded by the SOHO satellite, and the worldwide seismicity in the corresponding period, as reported by the ISC-GEM catalogue. We found clear correlation between proton density and the occurrence of large earthquakes (M > 5.6), with a time shift of one day. The significance of such correlation is very high, with probability to be wrong lower than 10–5. The correlation increases with the magnitude threshold of the seismic catalogue. A tentative model explaining such a correlation is also proposed, in terms of the reverse piezoelectric effect induced by the applied electric field related to the proton density. This result opens new perspectives in seismological interpretations, as well as in earthquake forecast.
Based on the observations of ocean heat content in the North Atlantic Ocean, the climate in the northern hemisphere is on the verge of a change that could last for several decades. This change is associated with the Atlantic Multidecadal Oscillation (AMO)1 – a mode of natural variability occurring, with a period of 60 – 80 years, in the North Atlantic Ocean sea surface temperature (SST) field.
Observations made by Argo buoys2 have shown that the North Atlantic Ocean (60-0W, 30-65N) is rapidly cooling since 20073. This is associated with the natural variability in the North Atlantic Ocean sea surface temperatures – the Atlantic Multidecadal Oscillation (AMO). However, the observed cooling does not only apply to the sea surface, but to the uppermost 700 m (2 296 feet) of the ocean.
The AMO index appears to be correlated to air temperatures and rainfall over much of the northern hemisphere4. The association appears to be high for North Eastern Brazil, African Sahel rainfall and North American and European summer climate. The AMO index also appears to be associated with changes in the frequency of North American droughts and is reflected in the frequency of severe Atlantic hurricanes.
“As one example, the AMO index may be related to the past occurrence of major droughts in the US Midwest and the Southwest. When the AMO is high, these droughts tend to be more frequent or prolonged, and vice-versa for low values of AMO. Two of the most severe droughts of the 20th century in the US occurred during the peak AMO values between 1925 and 1965: The Dust Bowl of the 1930s and the 1950s drought. On the other hand, Florida and the Pacific Northwest tend to be the opposite; high AMO is associated with relatively high precipitation.”
Cooling of the Atlantic is likely to bring drier summers in Britain and Ireland, accelerated sea-level rise along the northeast coast of the United States, and drought in the developing countries of the African Sahel region, a press release for a study by scientists from the University of Southampton and National Oceanography Centre (NOC) published last year said5. “Since this new climatic phase could be half a degree cooler, it may well offer a brief reprise from the rise of global temperatures, as well as result in fewer hurricanes hitting the United States. The study proves that ocean circulation is the link between weather and decadal scale climatic change. It is based on observational evidence of the link between ocean circulation and the decadal variability of sea surface temperatures in the Atlantic Ocean.”
Lead author of this study, Dr. Gerard McCarthy from the NOC, said: “Sea-surface temperatures in the Atlantic vary between warm and cold over time-scales of many decades. These variations have been shown to influence temperature, rainfall, drought and even the frequency of hurricanes in many regions of the world. This decadal variability is a notable feature of the Atlantic Ocean and the climate of the regions it influences.”
These climatic phases, referred to as positive or negative AMO’s, are the result of the movement of heat northwards by a system of ocean currents. This movement of heat changes the temperature of the sea surface, which has a profound impact on climate on timescales of 20 – 30 years. The strength of these currents is determined by the same atmospheric conditions that control the position of the jet stream. Negative AMO’s occur when the currents are weaker and so less heat is carried northwards towards Europe from the tropics. The strength of ocean currents has been measured by a network of sensors, called the RAPID array, which have been collecting data on the flow rate of the Atlantic Meridional Overturning Circulation (AMOC) for a decade.
The AMOC, part of which is known as the Gulf Stream, has been seen to weaken over the past 10 years, a study by Laura Jackson of the UK’s Met Office said6. Her study also suggests that this weakening trend is likely due to variability over decades. “The AMOC plays a vital role in our climate as it transports heat northwards in the Atlantic and keeps Europe relatively warm,” Jackson said. Any substantial weakening of a major North Atlantic ocean current system would have a profound impact on the climate of northwest Europe, including the UK. The research also showed a link between the weakening in the AMOC and decreases in density in the Labrador Sea (between Greenland and Canada) several years earlier.
In the diagrams below, courtesy of Ole Humlum4, only original (raw) AMO values are shown.
Humlum writes: “As is seen from the annual diagram, the AMO index has been increasing since the beginning of the record in 1856, although with a clear, about 60 yr long, variation superimposed. Often, AMO values are shown linearly detrended to remove the overall increase since 1856, to emphasize the apparent rhythmic 60 yr variation. This detrending is usually intended to remove the alleged influence of greenhouse gas-induced global warming from the analysis, believed to cause the overall increase. However, as is seen in the diagram below, the overall increase has taken place since at least 1856, long before the alleged strong influence of increasing atmospheric CO2 began around 1975 (IPCC 2007). Therefore, the overall increase is likely to have another explanation; it may simply represent a natural recovery since the end of the previous cold period (the Little Ice Age). If so, the general AMO increase since 1856 may well represent part of a longer natural variation, too long to be fully represented by the AMO data series since 1856. For the above reasons, only the original (not detrended) AMO values are shown in the two diagrams below:”
Annual Atlantic Multidecadal Oscillation (AMO) index values since 1856. The thin line indicates 3-month average values, and the thick line is the simple running 11-year average. Data source: Earth System Research Laboratory at NOAA. Last year shown: 2015. Last diagram update January 20, 2016.
Monthly Atlantic Multidecadal Oscillation (AMO) index values since January 1979. The thin line indicates 3-month average values, and the thick line is the simple running 11-year average. By choosing January 1979 as starting point, the diagram is easy to compare with other types of temperature diagrams covering the satellite period since 1979. Data source: Earth System Research Laboratory at NOAA. Last month shown: May 2016. Last diagram update: June 13, 2016.
The map below shows the North Atlantic area within 60-0W and 30-65N, for which the heat content within the uppermost 700 m is shown in the diagrams below it3.
North Atlantic area within 60-0W and 30-65N. Credit: Climate4you
Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the North Atlantic (60-0W, 30-65N) ocean since January 1979. The thin line indicates monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. The starting month (January 1979) is chosen to enable easy comparison with global air temperature estimates within the satellite period. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2016. Last diagram update June 7, 2016.
Global monthly heat content anomaly (GJ/m2) in the uppermost 700 m of the North Atlantic (60-0W, 30-65N) ocean since January 1955. The thin line indicates monthly values, and the thick line represents the simple running 37 month (c. 3 year) average. Data source: National Oceanographic Data Center (NODC). Last period shown: January-March 2016. Last diagram update June 7, 2016.
Interestingly, in a study by Zhou et al.7, a significant correlation was found between the solar wind speed (SWS) and sea surface temperature (SST) in the region of the North Atlantic Ocean for the northern hemisphere winter from 1963 to 2010, based on 3-month seasonal averages. “The correlation is dependent on Bz (the interplanetary magnetic field component parallel to the Earth’s magnetic dipole) as well as the SWS, and somewhat stronger in the stratospheric quasi-biennial oscillation (QBO) west phase than in the east phase. The correlations with the SWS are stronger than those with the F10.7 parameter representing solar UV inputs to the stratosphere. SST responds to changes in tropospheric dynamics via wind stress, and to changes in cloud cover affecting the radiative balance. Suggested mechanisms for the solar influence on SST include changes in atmospheric ionization and cloud microphysics affecting cloud cover, storm invigoration, and tropospheric dynamics. Such changes modify upward wave propagation to the stratosphere, affecting the dynamics of the polar vortex. Also, direct solar inputs, including energetic particles and solar UV, produce stratospheric dynamical changes. Downward propagation of stratospheric dynamical changes eventually further perturbs tropospheric dynamics and SST.”
The solar-wind speeds peak about 3 or 4 years after the Total Solar Irradiance (TSI) and sunspots peak in each cycle8.
Sunspot number progression observed from 2000 – May 2016. Credit NOAA/SWPC
Based on the current sunspot observations, their number for this solar cycle has peaked in January 2015, and our star is now on a steady path toward its next Solar Minimum, expected to hit the base just after 2020.
Global sea surface temperature anomaly for June 13, 2016 – current deviation of the surface temperature of Earth’s oceans from normal. Credit: NCEP (link leads to the latest map)
North Atlantic Ocean sea surface anomaly for June 13, 2016 – current deviation from normal. Credit: NCEP (link leads to the latest map)
Argo – UCSanDiego – Argo is a major contributor to the WCRP ‘s Climate Variability and Predictability Experiment (CLIVAR) project and to the Global Ocean Data Assimilation Experiment (GODAE). The Argo array is part of the Global Climate Observing System/Global Ocean Observing System GCOS /GOOS
March 8, 2013: Using data from an aging NASA spacecraft, researchers have found signs of an energy source in the solar wind that has caught the attention of fusion researchers. NASA will be able to test the theory later this decade when it sends a new probe into the sun for a closer look.
The discovery was made by a group of astronomers trying to solve a decades-old mystery: What heats and accelerates the solar wind?
Solar wind flows away from the sun at speeds up to and exceeding 500 km/s (a million mph). More
The solar wind is a hot and fast flow of magnetized gas that streams away from the sun’s upper atmosphere. It is made of hydrogen and helium ions with a sprinkling of heavier elements. Researchers liken it to the steam from a pot of water boiling on a stove; the sun is literally boiling itself away.
“But,” says Adam Szabo of the NASA Goddard Space Flight Center, “solar wind does something that steam in your kitchen never does. As steam rises from a pot, it slows and cools. As solar wind leaves the sun, it accelerates, tripling in speed as it passes through the corona. Furthermore, something inside the solar wind continues to add heat even as it blows into the cold of space.”
Finding that “something” has been a goal of researchers for decades. In the 1970s and 80s, observations by two German/US Helios spacecraft set the stage for early theories, which usually included some mixture of plasma instabilities, magnetohydrodynamic waves, and turbulent heating. Narrowing down the possibilities was a challenge. The answer, it turns out, has been hiding in a dataset from one of NASA’s oldest active spacecraft, a solar probe named Wind.
Launched in 1994, Wind is so old that it uses magnetic tapes similar to old-fashioned 8-track tapes to record and play back its data. Equipped with heavy shielding and double-redundant systems to safeguard against failure, the spacecraft was built to last; at least one researcher at NASA calls it the “Battlestar Gallactica” of the heliophysics fleet. Wind has survived almost two complete solar cycles and innumerable solar flares.
“After all these years, Wind is still sending us excellent data,” says Szabo, the mission’s project scientist, “and it still has 60 years’ worth of fuel left in its tanks.”
An artist’s concept of the Wind spacecraft sampling the solar wind. Justin Kasper’s science result is inset.
Using Wind to unravel the mystery was, to Justin Kasper of the Harvard-Smithsonian Center for Astrophysics, a “no brainer.” He and his team processed the spacecraft’s entire 19-year record of solar wind temperatures, magnetic field and energy readings and …
“I think we found it,” he says. “The source of the heating in the solar wind is ion cyclotron waves.”
Ion cyclotron waves are made of protons that circle in wavelike-rhythms around the sun’s magnetic field. According to a theory developed by Phil Isenberg (University of New Hampshire) and expanded by Vitaly Galinsky and Valentin Shevchenko (UC San Diego), ion cyclotron waves emanate from the sun; coursing through the solar wind, they heat the gas to millions of degrees and accelerate its flow to millions of miles per hour. Kasper’s findings confirm that ion cyclotron waves are indeed active, at least in the vicinity of Earth where the Wind probe operates.
Ion cyclotron waves can do much more than heat and accelerate the solar wind, notes Kasper. “They also account for some of the wind’s very strange properties.”
The solar wind is not like wind on Earth. Here on Earth, atmospheric winds carry nitrogen, oxygen, water vapor along together; all species move with the same speed and they have the same temperature. The solar wind, however, is much stranger. Chemical elements of the solar wind such as hydrogen, helium, and heavier ions, blow at different speeds; they have different temperatures; and, strangest of all, the temperatures change with direction.
“We have long wondered why heavier elements in the solar wind move faster and have higher temperatures than the lighter elements,” says Kasper. “This is completely counterintuitive.”
The ion cyclotron theory explains it: Heavy ions resonate well with ion cyclotron waves. Compared to their lighter counterparts, they gain more energy and heat as they surf.
An artist’s concept of Solar Probe Plus approaching the sun where it can test the ion cyclotron theory. More
The behavior of heavy ions in the solar wind is what intrigues fusion researchers. Kasper explains: “When you look at fusion reactors on Earth, one of the big challenges is contamination. Heavy ions that sputter off the metal walls of the fusion chamber get into the plasma where the fusion takes place. Heavy ions radiate heat. This can cool the plasma so much that it shuts down the fusion reaction.”
Ion cyclotron waves of the type Kasper has found in the solar wind might provide a way to reverse this process. Theoretically, they could be used to heat and/or remove the heavy ions, restoring thermal balance to the fusing plasma.
“I have been invited to several fusion conferences to talk about our work with the solar wind,” he says.
The next step, agree Kasper and Szabo, is to find out if ion cyclotron waves work the same way deep inside the sun’s atmosphere where the solar wind begins its journey. To find out, NASA is planning to send a spacecraft into the sun itself.
Solar Probe Plus, scheduled for launch in 2018, will plunge so far into the sun’s atmosphere that the sun will appear as much as 23 times wider than it does in the skies of Earth. At closest approach, about 7 million km from the sun’s surface, Solar Probe Plus must withstand temperatures greater than 1400 deg. C and survive blasts of radiation at levels not experienced by any previous spacecraft. The mission’s goal is to sample the sun’s plasma and magnetic field at the very source of the solar wind.
“With Solar Probe Plus we’ll be able to conduct specific tests of the ion cyclotron theory using sensors far more advanced than the ones on the Wind spacecraft,” says Kasper. “This should give us a much deeper understanding of the solar wind’s energy source.”