1. Model of the D-layer disturbances related to natural disasters. Alexey I. Laptukhov, Valery M. Sorokin, and Alexey K. Yaschenko PUSHKOV INSTITUTE OF TERRESTRIAL MAGNETISM, IONOSPHERE AND RADIO WAVE PROPAGATION (IZMIRAN) RUSSIAN ACADEMY OF SCIENCES The formationmechanism of ionosphere D-layer disturbance by electric current flowing from the atmosphere to the ionosphere was considered. Latest observations revealed such disturbance due to variations of amplitude and a phase of the very low-frequency (20 - 50 KHz) radio waves. These waves were propagated in the Earth - ionosphere wave guide near to an epicenter of preparing earthquakes. Transmitters and receivers of these waves were located on a surface of the Earth. Similar anomalies of radio wave characteristics were observed during few days prior to earthquake. The formation mechanism of ionosphere D-layer disturbance by electric current flowing from the atmosphere to the ionosphere was considered. Latest observations revealed such disturbance due to variations of amplitude and a phase of the very low-frequency (20 - 50 KHz) radio waves. These waves were propagated in the Earth - ionosphere wave guide near to an epicenter of preparing earthquakes. Transmitters and receivers of these waves were located on a surface of the Earth. Similar anomalies of radio wave characteristics were observed during few days prior to earthquake..

2. Observations of the VLF-LF signal anomalies associated with earthquakes Enlargement of the trend of the radio-signal in the period March–May 2002. The arrow indicates the occurrence of the gulf of Taranto main earthquakes. P.F.Biagi, R. Piccolo,L. Castellana, et.al., Natural Hazards and Earth System Sciences (2004) 4: 685–689

3. Model description  Intensive natural and artificial disasters generate external electric current in the lower atmosphere due to convective transport of charged aerosols.  External electric current generates conductivity electric current in the Earth-ionosphere layer.  Conductivity electric current flowing through D-layer of the ionosphere leads to transport of electrons and negative charged ions.  The electric field leads to transfer of electrons, positive and negative charged ions in D - layer of the ionosphere. In the top part of layer there are free electrons, and in its bottom part there are negative charged ions which occur at quickly absorption of electrons to neutral molecules. The electron number density perturbation appears in the D layer of the ionosphere caused by changed of type of carriers at current flowing through this layer.

4. The model of electric current formation in the Earth- ionosphere layer. 1. Earth surface. 2. Conducting layer of the ionosphere. 3. External electric current in natural disaster region. 4. Conducting electric current in the atmosphere - ionosphere circuit. 5. Field – aligned electric current. Sorokin, V.M., Chmyrev, V.M., Yaschenko, A.K., Journal of Atmospheric and Solar-Terrestrial Physics 63, pp. 1681-1691.

5. Basic equation set in the quasi stationary approximation  Continuity equations  Quasi neutrality condition

6.  Electric current conservation j 0 is the electric current density flowing to the ionosphere from the zone of natural disaster  Heating equation

7. Simplified equation set

8. Calculation result of the altitude dependence of electron number density at different value of electric current.

9. Calculation result of the altitude dependence of positive ion number density at different value of electric current.

10. Calculation result of the altitude dependence of electric field at different value of electric current.

11. Calculation result of the altitude dependence of electron number density performed with taking into account electron heating by electric field.

12. Two-dimensional spatial distributions of electron number density

13. Conclusion  Calculation of the disturbances of electron number density in the D- layer of ionosphere has been carried out. These disturbances caused by changing type of charge carriers at their transport in the atmosphere electric current flowing upward to the ionosphere. Eeffect of Joule heating of electrons by electric field to the disturbances formation has been analyzed. Result of calculations shows that growth of external electric current density by 3-4 orders of magnitude leads to occurrence of the disturbance of electron density up to one order, reaching its maximum at heights of 40-60 km. This model can be applied to the interpretation of observation data of the lower ionosphere perturbations over seismic regions and other natural and technogenic catastrophes related to formation of electric current in the atmosphere.