The sun is the source of the most energetic outer space impact on our planet. Even rough estimates demonstrate that the thermonuclear fuel reserves inside the sun are enough to keep its physical condition unchanged for 1011 years. The sun annually radiates energy equal to 3х1033 cal and is a source of total electromagnetic radiation, an interplanetary plasma cloud, fast electrons, solar cosmic rays, etc. It loses most of its energy in the form of wave radiation (Y. I. Vitinsky, 1972, 1973, 1983; O. G. Shamina, 1981). The total amount of energy emitted into space by the sun can be determined experimentally based on the energy flow per unit area of Earth’s surface; it is called the solar constant and averages 1.95 cal/cm2 ∙ min, or about 1360 W/m2 (E. A. Makarova, 1972); the total flux of radiant energy is 3.8х1026J/sec.

The appearance of sunspots on the sun’s surface is an indicator of increasing solar activity. In 1908, Hale discovered that sunspots have a magnetic field whose intensity reaches 2000 – 4000 gauss, whereas the strength of the sun’s overall magnetic field is one gauss or less. At the beginning of a solar cycle, the spots appear at latitudes of 30– 400, then shift towards the equator from the south and north and reaching their maximum at about 10– 200 latitude, following which the number of spots decreases (V. M. Kiselev, 1980). Research findings indicate that the duration of sunspot drift towards the equator is about 11 years. At the end of each 11-year cycle, the magnetic field near the poles changes its polarity. Thus, the magnetic cycle of the sun is 22 years.

In the middle of the nineteenth century, S. H. Schwabe and R. Wolf established the fact that the number of sunspots changes with a mean periodicity of 11 years.

H. Babcock and R. Leighton (1961) (1969) proposed a model explaining the existence of the 22-year magnetic solar cycle. According to them, the rise of a magnetic flux tube to the photosphere’s surface is accompanied by the appearance of an initial leading sunspot followed by a second one. In adjacent 11-year cycles, the leading sunspots have different polarity.

The relative sunspot number is one of the most common indices of solar activity. R. Wolf suggested that the solar activity index be determined according to the following formula:

W = k (10g + f )   (1)

where W is the Wolf number, g is the number of sunspot groups on the visible solar disk, and is the number of sunspots (including nuclei and pores) in all groups. The value of the coefficient k depends on many factors: the particular methods of observations, visibility conditions at the time of observation, and the observer’s personal characteristics, to name a few.

Another index of solar activity is the total sunspot area corrected for foreshortening, according to the formula:


where S is the area of the first sunspot, θ is arc sin (ri/R), R is the radius of the visible solar disk, and ris the distance between its center and the sunspot being observed.

There is a statistical relationship between S and W with a correlation coefficient of +0.85 (V. M. Kiselev, 1980). The regression equation of S and W is as follows in equation (3) (Y. I. Vitinskii, 1976):

S = 16.7 W   (3)

There are several more solar activity indices examined by Y. I. Vitinskii in his work (1973).

Fig. 46. Graph for 
Wolf numbers variations (W)

According to Data Analysis Center (SIDC),
Royal Observatory of Belgium

Fig. 46 contains a graph for Wolf number variations from 1700 to 2010.

The generally accepted numbering pattern for 11-year solar activity cycles is that the number zero is assigned to the 11-year cycle whose maximum value occurred in 1750. The average length of a 11-year cycle is considered to be 11.1 years. However, the actual duration of an 11-year cycle varies considerably; if determined by the epochs of minimum, the cycle period ranges from 9.0 to 13.6 years, and it is between 7.3 to 17.1 years when determined by the epochs of maximum (Y. I. Vitinskii, 1976).

While many researchers acknowledge the existence of 11-year and 22-year cycles of solar activity, cycles with longer periods are a matter of much debate. This is due to the unreliability of solar activity observation data earlier than 200 years ago.

Based on analysis of the historical records of observations of sunspots and polar auroras, D. Schove provides some data that makes it possible to estimate the changes of solar activity qualitatively over the last 2000 years (Y. I. Vitinskii, 1973). The data by D. Schove prove the reality of the existence of a cycle with a period of 80-90 years in the Wolf numbers variations and allows us to single out a cycle with an average duration of 554 years (Y. I. Vitinskii, 1976).

Fig. 47. Graph for 
Wolf numbers variations (W) from 2000 to May 2010
According to Data Analysis Center (SIDC),
Royal Observatory of Belgium

An attempt to characterize solar activity in a way not predominated by the 11-year cyclicity was made by A. Stojko and N. Stojko (1969). For that, they used the values of short-lived sunspots’ areas W1, variations between 1900 and 1963 of which were compared with Earth’s diurnal rotation variations. These two phenomena correlate with

К = (+08); (+09).

Fig. 47 shows the solar activity change from 2000 to May 2010.


It has become evident in recent decades that the significance of the solar activity’s impact on terrestrial processes is much broader and deeper than previously thought. In our view, B. M. Vladimirsky in his work (2002) is quite right in his attempt to attribute many highly sensitive physical and chemical processes taking place on Earth to the influence of various components of solar activity. There are given some interesting examples of heliospheric parameters affecting anthropogenic processes.

Volcanic activity

Efforts to identify the statistical relationship between solar activity and volcanic manifestations have been made by a number of scientists: A. I. Abdurakhmanov (1976); N. K. Bulin (1982); Y. A. Hajiyev (1985); Sh. F. Mehdiyev, E. N. Khalilov (1984, 1985); S. V. Tsirel (2002); and V. E. Khain, E. N. Khalilov (2008, 2009), among others.

For instance, A. I. Abdurakhmanov, P. P. Firstov and V. A. Shirokov suggested a link between volcanic eruptions and the 11-year cyclicity of solar activity. According to the authors, years in the vicinity of maximum solar activity are unfavorable for volcanic eruptions, whereas the years most favorable for eruptions lie near the minimum of solar activity, mostly in the middle and end of solar cycle decline (A. I. Abdurakhmanov, 1976).

A number of researchers (Sh. F. Mehdiyev, E. N. Khalilov, 1987; V. E. Khain, E. N. Khalilov, 2008, 2009) indicate in their works that the effect of solar activity on earthquakes and volcano eruptions occurring in different geodynamic zones (in Earth’s compression and extension zones) is not equal. They have divided all earthquakes and volcanoes according to their association with Earth’s zones of compression (lithospheric plates’ subduction and collision zones) and extension (rift zones). The research findings show that during increased solar activity periods there is generally a rise in the activity of Earth’s compression zone earthquakes and a drop in the activity of Earth’s extension zones. The authors conclude that due to non-simultaneity of the extension and compression processes, Earth experiences periodic deformations and changes in radius, which are reflected in Earth’s angular velocity variations and global sea level fluctuations (V. E. Khain, E. N. Khalilov, 2008, 2009).

Of interest is the initial analysis of a possible correlation between solar activity and Earth’s volcanic activity. We took the solar constant graph as a basic parameter of solar activity. It is this parameter that, in our view, most perfectly reflects the actual influx of solar energy into outer space, including towards Earth.

Fig. 48 provides a comparison of graphs for the solar constant and volcanic eruption numbers, smoothed out over 5-year running averages. Both images are identical, differing only in the graphical style for better perception. One can see a certain correlation between the 11-year solar activity cycles and volcanic activity cycles. The greatest overlap is observed in solar activity cycles #14, 16, 17, 18, 20, 22, and 23

However, the most interesting correlation is, in our opinion, full coincidence in the general type of the straight-line solar and volcanic activity trends. Around 1950, the angle of the straight-line trends in both processes decreased sharply, meaning volcanic activity growth became less intense. This fact may be yet another indication of a possible solar activity impact on Earth’s geodynamic activity.

Fig. 48. Comparison of solar activity (solar constant) graph and volcanic
eruption numbers smoothed out over 5-year running averages (by E. N. Khalilov, 2010)

Solar activity (solar constant) graph is marked in red;

Volcanic eruption numbers graph smoothed with 5-year averages is marked in dark blue and azure;
Lines reflecting general nature of parameter variations in all graphs are marked in green, yellow and white

Determination of a statistical relationship between the timelines of volcanic activity and solar activity suggests the existence of a similar link between solar activity and Earth’s seismicity as well. The precondition for this supposition is the commonly known existence of geodynamic and correlated relations between volcanism and seismicity.

Seismic activity

A number of works have been dedicated to studying the statistical relations between the solar and seismic activity parameters: A. D. Sytinskii (1963-1998); P. M. Sychev (1964); John F. Simpson (1968); O. V. Lusmanashvili (1972, 1973); F. A. Makadov (1973); Y. D. Kalinin (1973, 1974); Gribin (1974); G. Y. Vasilyeva (1975); P. Velinov (1975); H. Kanamori (1977); V. D. Talalayev (1980); N. V. Kulanin (1984); Y. D. Boulanger (1984); Sh. F. Mehdiyev, E. N. Khalilov (1984, 1985); Jakubcova and M. Pick (1987); A. D. Sytinskii (1989); R. M. C. Lopes, S. R. C. Malin, A. Mazzarella (1990); O. A. Khachay (1994); L. N. Makarova, Gui-Qing Zhang (1998); A. V. Shirochkov (1999); X. Wu, W. Mao, Y. Huang (2001); I. V. Ananyin, A. O. Fadeev (2002); K. Schulenberg (2006); S. D. Odintsov, G. S. Ivanov-Kholodnyi and K. Georgieva (2007); and V. E. Khain, E. N. Khalilov (2008, 2009), among others.

Based on the study of about 2000 earthquakes in Earth’s different regions for one solar activity cycle period between 1962 and 1973, G. Y. Vasilieva and V. I. Kozhanchikov concluded that the number of near-surface earthquakes increases with intensification of solar activity whereas the number of deep-focus earthquakes drops during the epoch of maximum solar activity. For all earthquakes, seismic activity in the years of both maximum and minimum solar activity is 10-30% higher when the planet crosses the galactic magnetic field’s projection onto the ecliptic plane. It is claimed that earthquakes are electromagnetic in nature and related to the structure of the magnetosphere (G. Y. Vasilyeva, 1975). In a work by Y. D. Boulanger (1984), the number of earthquakes in USSR seismically active zones is compared with solar activity, based on which there is assumed to be a link between these phenomena as well. On comparing earthquake data for the periods between 1897-1958 and 1963-1968 with solar activity, Y. D. Kalinin points out that the high seismic activity areas appear consistently within the 11-year solar cycle at geographical latitudes more and more distant from the North Pole. Seismic activity is thought to be influenced by the solar wind (Y. D. Kalinin, 1973).

Elaborating the proposed hypothesis, Y. D. Kalinin in his subsequent work (1974) states that changes in solar activity bring about irregular fluctuations of Earth’s angular velocity, affecting thereby seismic activity.

O. V. Lusmanashvili in his study (1972) mentions the possibility of solar activity impact on the distribution of Caucasian earthquakes. Reviewing earthquakes of the Caucasus between 1900 and 1970, O. V. Lusmanashvili concludes that there is a close link between the seismic activity of the Caucasus and Caspian Sea level fluctuation on the one hand and between sea level changes and solar activity on the other. When compared, a solar activity spectrum and a large Caucasian earthquakes recurrence spectrum showed high similarity (O. V. Lusmanashvili, 1972, 1973).

Other attempts to find a relation between Earth’s seismicity and solar activity were made in a number of works by A. D. Sytinskii (1963 – 1998), as well as by P.M. Sychev (1964) and V. D. Talalayev (1980). They state in particular that Earth’s overall seismicity represented by the total energy of earthquakes and the annual number of catastrophic earthquakes depends on the phases of the 11-year solar cycle. The highest seismic activity coincides with the epochs of maximum and minimum of the 11-year solar cycle. It is also pointed out that most earthquakes occur 2-3 days after the active region crosses the central solar meridian.

A study by A. D. Sytinskii (1973) suggests that the relation between seismicity and solar activity is realized via planetary atmospheric processes. The mechanism of dependence is as follows: due to increased solar activity there is a perturbation of the atmosphere’s quasi-stationary state, leading to global redistribution of the atmospheric mass, i.e. to shifting of the Earth – atmosphere system’s center of gravity and consequently, to distortion of Earth’s figure.

As A. D. Sytinskii (1998) points out, seismicity’s dependence on the 11-year cycle, discovered by him earlier was verified and confirmed by experimental forecasting of Earth’s overall seismicity and that of its specific regions. Earth’s seismic activity maxima were predicted for the period from 1963 to 1995. I. V. Ananyin and A. O. Fadeev in their works (2002) come to the conclusion about the existence of correlation between seismic activity variations, average annual temperatures at Earth’s surface and solar activity. They see this correlation as a possible basis for the solar activity impact on both average annual temperatures and seismic activity.

I. K. Gribin in his work (1974) examines the causes of the devastating 1982 Californiaearthquake in the San Andreas Fault area. He considers opposition of the Solar system’s key planets and solar activity growth with an 11-year period as the main forces triggering the earthquake. The impact of the 11-year solar activity cycle on Earth’s seismicity is also mentioned in F. A. Makadov’s work (1973).  In a study by I. F. Simpson (1968), solar activity is seen as a trigger mechanism to defuse tensions in Earth’s interior.

V. M. Lyatkher’s study indicates that the course of changes of the average interval between large earthquakes corresponds to solar cycle length variations. It is pointed out in particular that a quasi-periodic component with a period of about 60-100 years is observed in solar activity variations. The discovered correlation between solar activity and the frequency of large earthquakes suggests that local seismicity characteristics identified on the basis of time-limited statistical material can also vary in time with about the same periodicity as the smoothed solar cycle lengths.

John F. Simpson (1968) considers solar flares to be a trigger for large earthquakes in areas where the mechanical stresses have reached the critical values. However, he points out that solar flares should not be seen as an earthquake-causing factor.

It should be noted that there are also studies that have found no clear relationship between Earth’s seismicity and solar activity. For instance, Van Gils who has analyzed more than 20000 weak earthquakes between 1910 and 1945 declared the absence of any relation between solar activity and low seismicity.

Chinese scientist Gui-Qing Zhang (1998) concluded that earthquakes often occur around the minimum years of solar activity. In the peak years of solar activity, the number of earthquakes is relatively lower than around the peaks.

A study by a group of scientists (S. D. Odintsov, G. S. Ivanov-Kholodnyi and K. Georgieva, 2007) showed that the maximum seismic energy released by earthquakes within the 11-year solar activity cycle is observed during the cycle’s decline phase and before its solar maximum. They found that the maximum in the number of earthquakes directly correlates to the moment of sudden increase in the solar wind velocity.

Of certain interest is, in our view, a work by K. Schulenberg (2006, taking a non-standard approach to the sun’s possible effect on earthquakes. It reveals quite a convincing statistical relationship between the periods preceding sunrise and following sunset, and large earthquakes in China. According to the author, the physical mechanism of the sun’s influence on the ionosphere and lithosphere is different before sunrise and after sunset. It is sort of a trigger mechanism set off by the sun to discharge the crustal stress in the form of earthquakes.

Fig. 49. Comparison of large earthquake caused fatality numbers graph
(white) with solar activity graph (blue). By E. N. Khalilov, 2010

Fig. 49 shows a comparison of graphs for solar activity (Wolf numbers) and for the number of killed during strong earthquakes from 1900 to May 2010. Even a cursory glance at the graphs reveals a high correlation. The more detailed analysis allows us to notice that, except for solar activity cycles #21 and 23, the remaining cycles correspond to the higher numbers of dead. A very high maximum of 1977 fatality numbers occurred at the beginning of the 21st cycle whose maximum was in 1980 while the maximum number of 2004 deaths falls on the end of 23rd solar activity cycle.

Obviously, the correlation between numbers of dead during large earthquakes and solar activity implies the existence of a similar link between large earthquakes and solar activity.

Fig. 50 contains a comparison of graphs for numbers of large magnitude (М>8) earthquakes and solar activity for the period from 1900 to May 2010. The large earthquakes graph is drawn with 5-year running averages. The high correlation between the two graphs can be seen even at primary visual analysis. Of 10 reviewed 11-year solar activity cycles, only two (16th and 17thsolar activity cycles) do not coincide with the cycles of increased numbers of large earthquakes.

Fig. 50. Comparison of large (M>8) earthquake numbers graph (red)
with solar activity graph (blue). By E. N. Khalilov, 2010

In some cases, there is a slight misalignment between the solar and seismic activity cycles. For instance, the seismic activity cycle is shifted by 2 years towards the end of the 19th solar activity cycle. Nevertheless, in general, the picture of the high correlation between these two processes is quite impressive.


Fig. 51. Comparison of large tsunami numbers graph (yellow)
with solar activity graph (blue). By E. N. Khalilov, 2010

Large earthquakes are known to be closely associated with tsunamis, which usually result from strong earthquakes in the aquatic environment. Fig. 51 contains a comparison graph for solar activity and large tsunamis. As can be seen from the comparison, most powerful tsunamis have occurred during high solar activity times, that is, during solar activity cycles #16, 18, 19, 21, 22, and 23.


– From 1980 to present, the North Magnetic Pole’s drift velocity has increased by more than 500%. This might indicate the beginning of an increase in Earth’s geodynamic activity since Earth’s magnetic field is formed as a result of complex energy processes in its inner and outer core.

– It has been established that variations of the angular velocity of Earth’s rotation are correlated with the solar constant trend.

– A correlation between the solar and volcanic activity trends has been found.

– A direct correlation has been discovered between solar activity (11-year cycles) and the numbers of large earthquakes, of fatalities during large earthquakes, and of tsunami.

These conclusions are provisional and intended for better understanding of the research findings presented in the following sections. 

GEOCHANGE: Problems of Global Changes of the Geological Environment. Vol.1, London, 2010,  ISSN 2218-5798



About sooteris kyritsis

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