Theoretical Model of Possible Disturbances in the Nighttime Mid-Latitude Ionospheric D Region over an Area of Strong-Earthquake Preparation

We present a theoretical model of possible electron-density disturbances in the nighttime mid-latitude ionospheric D region, preceding strong earthquakes. It is found that the electron density in the nighttime D region over an earthquake epicentral zone can considerably increase before severe earthquakes. The horizontal size of the area of disturbed electron density is about 300 km. The disturbance effect is expected to be more pronounced if a powerful VLF transmitter operates in the vicinity of an imminent earthquake epicentral zone. In this case, a very dense ionization layer of daytime D-layer type can be formed at the altitudes of the upper nighttime mesosphere and can give rise to the effect of strong absorption of HF radio waves propagating over the earthquake preparation area.     

Magnetospheric substorms and discrete arcs of the polar aurora

A brief review of the results of the research in physics of the Earth’s magnetosphere leading to a substantial modification of the previously developed approaches is presented. The main emphasis is placed on physics of magnetospheric substorms and the nature of auroral arcs. It is shown that the formation of powerful electron beams that produce multiple arcs can be associated with the penetration of cold electrons of an ionospheric origin into the region of field-aligned acceleration of hot magnetospheric electrons.