Abstract. We present a general concept of mechanisms of preseismic phenomena in the atmosphere and ionosphere. After short review of observational results we conclude: 1. Upward migration of fluid substrate matter (bubble) can lead to ousting of the hot water/gas near the ground surface and cause an earthquake (EQ) itself in the strength-weakened area; 2. Thus, time and place of the bubble appearance could be random values, but EQ, geochemistry anomaly and foreshocks (seismic, SA and ULF electromagnetic ones) are casually connected; 3. Atmospheric perturbation of temperature and density could follow preseismic hot water/gas release resulting in generation of atmospheric gravity waves (AGW) with periods in a range of 6-60 min; 4. Seismoinduced AGW could lead to modification of the ionospheric turbulence and to the change of over-horizon radio-wave propagation in the atmosphere, perturbation of LF waves in the lower ionosphere and ULF emission depression at the ground.

[1] Local variations of the magnetic field in the ULF-ELF frequency range associated with seismicity are studied with the data of more than 3 a observations at Karimshimo complex observatory (latitude 52.83°N, longitude 158.13°E, Kamchatka, Russia). A wideband emission is found to start about 5 d before an earthquake and last until 5 d after it. Seismic ULF/ELF emission in the frequency range of 4-6 Hz as compared with the seismically quiet background has enhanced P hh /P dd spectral ratio and reduced standard deviation of ellipse orientation angle and the ellipticity, and it has a more linear polarization. Parameters of this emission are studied for more than 30 individual earthquakes and statistically with the superposed epoch method. The reliability of the earthquake predicting hypothesis is verified, and the favorable parameters for the earthquakes together with those for ELF magnetic field are selected. The following earthquake parameters are favorable for this emission: depths H < 50 km, magnitudes M S > 5.5, and epicenter distances R < 300 km. The changes of natural ULF/ELF emissions during the periods of enhanced seismic activity are interpreted as the result of the excitation of additional ULF/ELF emissions in the seismic zone to the east of the observatory or the redistribution of lightning discharges with their possible concentration near the active crust fault. The earthquake prediction hypothesis is verified for the complex field parameter DS and proved to be successful.

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The criticality of ULF (Ultra-low-frequency) magnetic variations is investigated for the 2011 March 11 Tohoku earthquake (EQ) by natural time analysis. For this attempt, some ULF parameters were considered: (1) Fh (horizontal magnetic field), (2) Fz (vertical magnetic field), and (3) Dh (inverse of horizontal magnetic field). The first two parameters refer to the ULF radiation, while the last parameter refers to another ULF effect of ionospheric signature. Nighttime (L.T. = 3 am ± 2 hours) data at Kakioka (KAK) were used, and the power of each quantity at a particular frequency band of 0.03–0.05 Hz was averaged for nighttime hours. The analysis results indicate that Fh fulfilled all criticality conditions on March 3–5, 2011, and that the additional parameter, Dh reached also a criticality on March 6 or 7. In conclusion, criticality has reached in the pre-EQ fracture region a few days to one week before the main shock of the Tohoku EQ.

The ULF/ELF short‐term electromagnetic precursor is discovered for the disastrous Japan earthquake (EQ) occurred on 11 March 2011. This analysis is based on the records measured by search coil magnetometers located at Nakatsugawa (geographic coordinates; 35.42°N, 137.55°E), Shinojima (34.67°N, 137.01°E), and Izu (34.64°N, 137.01°E) of the Chubu University network. The data of these magnetometers are extensively used to analyze the ULF/ELF seismo‐atmospheric radiation. It is then found that the ULF/ELF atmospheric radio emission is reliably detected on 6 March before the main shock on 11 March, probably as a precursory signature of the EQ. Further confirmation on its seismic origin was provided by the observational fact that the azimuths of the radiation source from all observation sites coincide approximately with the region of the forthcoming EQ.

[1] A theory of midlatitude Ionospheric Alfvén Resonator (IAR) excitation due to random cloud-to-ground lightning discharges is developed. Electromagnetic wave radiated from the lightning discharges penetrates into the ionosphere, thereby exciting the shear Alfvén and magnetosonic waves in the F region of ionosphere. The IAR arises due to wave reflection from the Alfvén velocity gradients in the topside ionosphere. Typically, the ionospheric resonance cavity accumulates the shear Alfvén wave energy with periods from 1 s to a few tenths of seconds. To proceed analytically, a suitably idealized plane-stratified model of the medium was used that ignores the magnetic field line curvature and dip angle but includes plasma conductivity variations with altitude. The thunderstorm centers distributed around a ground-recording station is assumed to be statistically independent sources of the lightning activity, which is a stochastic Poisson process. The lightning onset time and the current moment is supposed to be a random value, while the shape and duration of return strokes are deterministic. Model calculations of the IAR spectrum due to nearby thunderstorm activity were applied to interpret ULF observation made at Karimshino station (52.94°N, 158.25°E) in Kamchatka peninsula. It is shown that the sharp impulses which are in one-to-one correspondence with the appearance of the spectral resonance structure (SRS) in dynamic spectrograms can be the result from nearby lightning discharges followed by impulse IAR excitation. The correlation functions and power spectra of the IAR due to random lightning discharge process is studied both analytically and numerically. We found that the nearby thunderstorms in the range of 1000-2000 km make a main contribution to the SRS signature of the midlatitude IAR, whereas the remote/tropic thunderstorm activity is of minor importance. It is not inconceivable that there may exist other permanent mechanisms of the midlatitude IAR excitation, for example, the high-altitude neutral wind in the E region might also be operative.Citation: Surkov, V. V., M. Hayakawa, A. Y. Schekotov, E. N. Federov, and O. A. Molchanov (2006), Ionospheric Alfvén resonator excitation due to nearby thunderstorms,

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Abstract. Some results of ULF magnetic field observation at Karimshino site (Kamchatka, Russia) since June 2000 to September 2001 are presented here. Using case study we have found an effect of suppression of ULF intensity about 2-6 days before rather strong and nearby seismic shocks (magnitude M = 4.0 − 6.2). It is revealed for nighttime and horizontal component of ULF field (G) in the frequency range 0.01 − 0.1 Hz. Then we prove the reliability of the effect by computed correlation between G (or 1/G) and specially calculated seismic indexes K s for the whole period of observation. Basing on the simple criteria we conclude that reliability of seismo-associated ULF suppression effect is comparable with well-known effect of connection between ULF variation and K p index of global magnetic activity. It seems the reason of suppression is located at the atmosphere or ionosphere but not in the ground medium.