1. Electromagnetic Study on Earthquakes and Volcanoes (EMSEV 2012) 7th General Assembly, September 30 - October 4, 2012 , Shizuoka, Japan. Perturbation of the atmosphere – ionosphere electric current and the formation of accompanying earthquake precursors V.M. Sorokin and M. Hayakawa Puskov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Russian Academy of Sciences, Troitsk, Moscow Region, , RUSSIA. The University of Electro-Communications, Advanced Wireless Communications research Center, Chofu Tokyo, JAPAN.
This report presents a summary of models for LAI coupling by quasi-static electric field and a brief description of the formation mechanisms of electromagnetic and plasma disturbances in near-Earth space at the preparatory phase of earthquakes(EQs). Spatial distribution of this field has a horizontal scale of 100 – 1000 km and the temporal scale of field is (1 – 10) days.

2. Basic experimental results
Enhancements of seismic activity and typhoons produce DC electric field disturbances in the ionosphere with magnitudes up to 10 mV/m.
These disturbances occupy an area of the order of several hundred km in diameter over an EQ region.
DC electric field enhancements arise in the ionosphere from hours to 10 days before EQs.
Chmyrev et al., Phys. Earth Planet. Inter. 1989;
Sorokin et al., J. Atmos. Solar-Terr. Phys. 2005;
Gousheva et al., Nat. Haz. Earth Syst. Sci. 2008, 2009.
Computer simulation shows that pre-seismic TEC variations occur by a quasi-static electric field disturbance in the ionosphere with amplitude (3 – 9) mV/m .
Zolotov et al., 7th International Conference "Problems of Geocosmos" 2008
Namgaladze et al., Geomagn. Aeron. 2009
Klimenko et al., Adv. Space Res. 2011; 2012
Pre-earthquake VHF electromagnetic radiation is generated by electric discharges in the troposphere at altitudes (1 – 10) km over the EQ zone.
Vallianatos and Nomicos, Phys. Chem. Earth 1998;
Ruzhin et al., Proc. 15th Wroclaw EMC Symposium 2000;
Ruzhin and Nomicos, Nat. Hazards 2007.

3. Basic experimental results (continuation)
Quasi-static electric fields on the Earth surface in an EQ epicenter area do not exceed the background value ~100 V/m. The spike of electric field reaching (1 – 10) kV/m in the local area has a duration over 10 min.
Jianguo, Acta Seismol. Sin., 1989
Vershinin et al., Atmos. Ionosph. Elect.-Magn. Phenom., 1999
Nikiforova and Michnovski, IUGG XXI General Assem. 1995
Hao et al., J. Earthquake Pred. Res., 2000
Rulenko, Vulcanology and Seismology, 2000
Lithosphere activity stimulates the processes of active substances injection in the atmosphere during days and weeks before EQs. Number density of charged aerosols enhancement of one – two order. Atmosphere radioactivity level is increased by radon and other radioactive elements in several times.
King, J. Geophys. Res., 1986
Alekseev and Alekseeva, Nucl. Geophys., 1992
Virk and Singh, Geophys. Res. Lett., 1994
Heinke et al., Geophys. Res. Lett., 1994
Voitov and Dobrovolsky, Izvestiya AN SSSR, Fizika Zemli, 1994
Igarashi et al., Science, 1995
Pulinets et al., Adv. Space Res. 1997
Boyarchuk, Proceed. of RAS, Afmos. Ocean. Phys. 1997
Yasuoka et al., Appl. Geochem 2006;
Omori et al., Nat. Hzards Earth Syst. Sci. 2007

4. Above-mentioned works show that the amplitude of quasi-static electric fields can reach 10 mV/m in the ionosphere, a breakdown value in the lower atmosphere and, in the same time, it does not exceed the background value on the Earth`s surface.
Any model of the quasi-static electric field formation related to EQ preparing has to satisfy these basic properties.
Variation of DC electric field in the ionosphere over a seismic region can be realized in the two ways.
First of all is to change the load resistance of low atmosphere
Second is to include an additional EMF in the global circuit. 4

5. First way of DC field generation
Change the load resistance
Mechanisms for quasi – static electric field generation by a variation of atmosphere conductivity. Equivalent electric circuit of DC electric field formation in the ionosphere over a region of conductivity disturbance in the lower atmosphere. Black colour denotes the global circuit. Red colour denotes the part of circuit over a region of disturbed conductivity.

6. Calculations show that the electric field can be changed in (1
Calculations show that the electric field can be changed in (1.5 – 2) times in the ionosphere by a growth of conductivity in the surface atmosphere. Field variation is invisible in the ionosphere.
Sorokin and Yaschenko, Adv. Space Res., 2000
Sorokin et al., JASTP, 2001
Quasi-static electric field is reduced to 1.5 times due to a growth of radioactivity by radon injection.
Omori et al., Nat. Haz. Earth Syst. Sci., 2007
Increase of ionization rate in two times by radon leads to variation of the current in 10%.
Harrison et al., JASTP, 2010
Models using the ionization of lower atmosphere by radon is in contradiction with the experimental data and they do not explain the mechanism of LAI coupling.

7. Second way of DC field generation
Second way of DC field generation. Inclusion of an additional EMF in the global circuit.
The schema of altitude dependence of total electric current in three cases: EMF can be located in the lithosphere, in the atmosphere and in the vicinity of boundary between the lithosphere and atmosphere.

8. First case: EMF is located in the lithosphere
First case: EMF is located in the lithosphere. Model of DC electric field penetration from the lithosphere into the ionosphere This model assumes that the field source is situated in the lithosphere and the field is transferred through the atmospheric layer with altitude dependent electric conductivity. The layer is a part of the closed global atmosphere-ionosphere electric circuit at given electric field on the ground.
1. Earth surface
2. Conductive layer of the ionosphere
3. Lithosphere source of electric field.
4. Electric field on the ground.
5. DC electric field in the ionosphere
6. Atmosphere – ionosphere electric circuit.

9. The same results for the second case: EMF is located in the atmosphere
This model gives a maximum magnitude of the electric field in the ionosphere not exceeding mV/m when the ground field value is ~100 V/m and therefore seems to be impracticable. Kim and Hegai, Atm. Ion. EM Phen. Ass. Eqs., Pulinets et al., Adv. Space Res., Grimalsky et al., JASTP, Pulinets et al., JASTP, Rapoport et al., Phys. Chem. of the Earth, Denisenko et al., Nat. Haz. Earth Syst. Sci., Ampferer et al., Ann. Geoph., 2010
The same results for the second case: EMF is located in the atmosphere
Considered models contradict with the well known experimental data. They cannot explain the occurrence of the seismic related quasi-static electric fields in the ionosphere and absence of the visible field variation on the surface of EQ preparing area. Thus, these models cannot be used for the explanation of LAI coupling.

10. Third case: EMF is located in the near ground layer
Third case: EMF is located in the near ground layer. Principally different model is based on the assumption that the current source is situated in the near ground atmospheric layer including the surface.
The key role in seismo-ionospheric interaction belongs to the electromotive force (EMF) in the lower atmosphere. The external current of EMF is excited in a process of vertical atmospheric convection and gravitational sedimentation of charged aerosols. Aerosols are injected into the atmosphere due to intensified soil gas elevation in the lithosphere during the enhancement of seismic activity.
1. Atmospheric convection and turbulent diffusion.
2. Gravitational sedimentation.
3. Atmospheric radioactivity.
4. Soil gases.
5. Conduction electric current.
6. Electromotive force.

11. Equivalent circuit of DC electric field formation in the ionosphere over a region of EMF occurring in the surface atmosphere. Black color illustrates the global circuit. Red color denotes the part of circuit over a region of EMF generation.

12. Model of DC electric field generation in the ionosphere by seismic-related Electro Motive Force (EMF) in the lower atmosphere
1. Earth surface
2. Conductive layer of the ionosphere
3. External electric current in the lower atmosphere
4. Conductivity electric current in the atmosphere – ionosphere circuit
5. DC electric field in the ionosphere
6. Field - aligned electric current
7. Charged aerosols injected into the atmosphere by soil gases

13. Simple estimation of electric field in the ionosphere
Inclusion of EMF into the atmosphere – ionosphere electric circuit leads to DC electric field growth up to 10 mV/m in the lower ionosphere. Limitation of the field on the surface is explained by the mechanism of feedback between the electric field and the causal external currents. Such a feedback is caused by the formation of a potential barrier on the ground-atmosphere boundary. Sorokin et al., JASTP, Sorokin et al., JASTP, Sorokin et al., Nat. Haz. and Earth Sys. Sci., Sorokin et al., Adv. Space Res., 2006 Sorokin et al., Nat. Haz. and Earth Sys. Sci., Sorokin and Chmyrev, The Atmosphere and Ionosphere, 2010
Simple estimation of electric field in the ionosphere
We have found the mechanism for enhancement of conducting electric current with altitude and the mechanism for limitation of electric field on the ground surface. This model can be used to explain the LAI coupling because it satisfies the experimental data.

14. The ionization-recombination processes
Equilibrium value of ions number density is determined by the recombination process and the adhesion of one to aerosols in the atmosphere.
The light single-charged ions and the heavy ions are produced as a result of light ions adhesion to aerosols in the atmosphere near the Earth’s surface.
Sorokin et al., Nat. Haz. and Earth Sys. Sci., 2007
EMF electric current and charge densities:

15. The self-consistent system of nonlinear equations for the calculation of spatial distribution of external current, atmosphere conductivity and DC electric field in the Earth – ionosphere circuit (the feedback effect is taken into account):

16. The theory of electric field limitation by the feedback between the electric field and the causal external currents on the Earth’s surface. Calculation result of the dependence of vertical electric field value on the Earth surface on the magnitude of EMF external current Sorokin et al., JASTP 2005;

17. Calculation results based on the theory of quasi-static electric field generation by EMF formation in the global circuit.
The altitude dependences of source of ionization, atmosphere conductivity and external electric current over the center of disturbed region. Sorokin et al., Nat. Haz. and Earth Sys. Sci., 2007

18. Calculation results of the spatial distribution of horizontal electric field in the ionosphere and vertical electric field near the Earth surface over the ellipsoidal fault Sorokin et al., Nat. Haz. Earth Sys. Sci., 2005

19. An example of calculation of the quasi-static electric field spatial distribution in the atmosphere normalized to the breakdown electric field
Sorokin et al., JASTP, 2011
Sorokin et al., The frontier of earthquake prediction studies, 2012
At definite conditions the seismic-related DC electric field can reach the breakdown value in some region of the atmosphere (marked out by red in the figures).

20. Acoustic Gravity Wave (AGW) instability related to DC electric field enhancement in the lower ionosphere The formation of large enough DC electric field in the ionosphere exceeding a definite threshold value leads to an instability of acoustic-gravity waves and the generation of periodic or localized ionospheric structures in a form of solitary dipole vortices or vortex chains and associated plasma density and electric conductivity disturbances in the ionosphere Sorokin et al., JASTP, 1998; Chmyrev and Sorokin, JASTP, 2010
The frequency dependence of the refraction index and the absorption coefficient of acoustic-gravity wave in the ionosphere in the presence of an external electric field.
Vortex formation.

21. Examples of satellite observations of ULF magnetic field oscillations, electron number density fluctuations and ELF electromagnetic emissions caused by the formation of the ionosphere conductivity irregularities Chmyrev et al., Phys. Earth Planet. Inter., 1989; Chmyrev et al., JASTP, 1997
1. Earthquake.
2. Irregularities of the ionosphere conductivity.
3. Field-aligned currents and irregularities of electron number density.
4. Satellite trajectory crossing the disturbed region.
ULF magnetic field.
Electron number density fluctuations.
ELF electromagnetic emissions

22. The generation mechanism of electromagnetic ELF wave precursors to EQs.
Excitation of horizontal small-scale irregularities of electric conductivity in the lower ionosphere is a key factor for ELF wave radiation to the ionosphere.
Borisov et al., JASTP, 2001
These waves are generated by an interaction of thunderstorm related EM radiation with small-scale plasma irregularities excited in the lower ionosphere before EQs. These EM pulses radiated by lightning discharges and propagated in sub-ionospheric waveguide with small attenuation are scattered by the irregularities and re-emitted into the upper ionosphere.

23. Other applications of the model for periodic disturbances of electric conductivity in the lower ionosphere.
Generation of the narrow-band gyrotropic waves and associated magnetic field oscillations on the Earth surface through the interaction of background electromagnetic noise with periodic inhomogeneities of electric conductivity in the ionosphere over seismic region.
Sorokin and Hayakawa, JGR, 2008
Interpretation in terms of gyrotropic waves of Schumann-resonance-like anomalous line emissions observed before earthquakes.
Hayakawa et al., IEEJ, 2011

24. Model for electron number density distribution in the ionosphic E - region disturbed by the electric current flowing into the ionosphere from the atmosphere. Sorokin et al., JASTP, 2006
Self-consistent system of non-linear equations for ion number density and electric field in the lower ionosphere:

25. Model for electron number density distribution in the D layer of the ionosphere disturbed by the electric current flowing from the atmosphere to the ionosphere Laptukhov et al., Geomagn. Aeronom., 2009
Self-consistent system of non-linear equations for electron and ion number density, temperature and the electric field:

26. Pre-EQ DC electric field reaching the breakdown value initiates numerous chaotic electrical discharges and related phenomena in the lower atmosphere Sorokin et al., The Frontier of Earthquake Prediction Studies, 2012
Chaotic electric discharges.
Heating of the atmosphere in the discharge region and the generation of outgoing long wave (8-12 μm) radiation.
Broadband electromagnetic VHF emission.
Airglow in visible range of wavelengths.
Refraction and scattering of VHF radio waves in the troposphere providing the over-horizon reception of ground-based VHF transmitter signals.

27. Calculated spectrum of VHF electromagnetic radiation at distance 300 km from the epicenter of disturbed area
The radiation source is modeled by the disk-like random discharges region with radius 40 km and thickness 1 km located at 6 km altitude in the atmosphere. Two vertical lines on the curve in figure show the spectral densities observed in experiment (Ruzhin and Nomicos, 2007).
Sorokin et al., JASTP, 2011

28. The scheme of processes form the atmosphere – ionosphere coupling

29. Conclusion.
Experimental data and modeling show that the quasi-static electric field in the ionosphere can reach a value up to 10 mV/m during several days before EQs and, at the same time, it does not exceed the background value on the Earth’s surface.
Variation of the low atmosphere conductivity by radon injection leads to an occurrence of electric field in the ionosphere with magnitude over mV/m is much smaller than the background value 1 mV/m. Thus, radon injection does not have an effect to the ionosphere and it does not explain LAI coupling.
Model for penetration of electric field through the conducting atmosphere at given field on surface leads to the occurrence of electric field in the ionosphere with magnitude over mV/m much less than the background value. Thus, this model does not explain LAI coupling.
Model for electric field generation by including an additional EMF in the global circuit allow us to explain above-mentioned experimental data. Thus, this model can only be used for the explanation of LAI coupling.
Electrodynamic model allows us to make calculations of measured parameters of plasma and electromagnetic precursors.