Observation of ionospheric Alfven resonance at a middle latitude station

This paper intends to report on the statistical results on the spectral resonance structures of the ionospheric Alfven resonances (IAR) in the ULF frequency range 0.1-5.0 Hz on the basis of the analysis of long-term data obtained from July 2000 to December 2002 (2.5 years) at the Karimshino station (Kamchatka, Russia) (L=2.1) by the conventional 3-component search-coil magnetometer. We analyze both the dynamic spectra of three components and polarization spectra in order to distinguish IAR from other possible noises. The average frequency difference _F between the adjacent maxima, intensity and occurrence rate of the IAR spectra have been estimated from the averaged spectra. Early papers at middle latitudes have been based on a small data base. Based on our first long-term observation at middle latitude, new findings, especially related to the seasonal variation, have emerged from this analysis. (1) There is an evident seasonal variation in the occurrence rate with a maximum in the September-January period and an almost complete absence of IAR structures in the spring-early summer time. (2) Occurrence maximum in the diurnal variation is found at 21-23 LT in the autumn and winter. Almost all the IAR structures are observed at local nighttime. (3) The averaged _F is found to be about 0.2-0.5 Hz in the autumn period but it seems to increase up to 0.5-0.7 Hz in winter. (4) The IAR occurrence rate is inversely correlated with the Kp index of global magnetic activity. (5) The intensity of D component exceeds essentially that of H component of the IAR structures in a majority of cases. Diurnal variations of resonance frequencies in the H and D components are not always identical. Finally the mechanisms to explain the observed characteristics of the IAR have been discussed

Preseismic ULF electromagnetic effect from observation at Kamchatka

International audienceSome 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 Ks 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 Kp index of global magnetic activity. It seems the reason of suppression is located at the atmosphere or ionosphere but not in the ground medium

Depression of the ULF geomagnetic pulsation related to ionospheric irregularities

We consider a depression in intensity of ULF magnetic pulsations, which is observed on the ground surface due to appearance of the irregularities in the ionosphere. It is supposed that oblique Alfven waves in the ULF frequency range are downgoing from the magnetosphere and the horizontal irregularities of ionospheric conductivity are created by upgoing atmospheric gravity waves from seismic source. Unlike the companion paper by Molchanov et al. (2003), we used a simple model of the ionospheric layer but took into consideration the lateral inhomogeneity of the perturbation region in the ionosphere. It is shown that ULF intensity could be essentially decreased for frequencies f = 0.001-0.1 Hz at nighttime but the change is negligible at daytime in coincidence with observational results

ULF magnetic field depression as a possible precursor to the 2011/3.11 Japan earthquake

The depression (reduction in amplitude) of ULF magnetic field variations of magnetospheric origin is studied at various distances from the epicenter of the strongest earthquake (EQ), which occurred in Japan on March 11, 2011. For this purpose, we have used the ULF data in Japan recorded by fluxgate magnetometers at three places located at distances of ~300 km to ~1300 km from the epicenter of the main shock. The period of data analysis is from December 1, 2010 to May 31, 2011. We have found a sharp depression of the horizontal ULF magnetic field component at the frequency of 0.03…0.05 Hz (30…50 mHz) at all of three Japanese observatories (Kakioka, Memambetsu and Kanoya) three days before the first strong foreshock (Mw 7.5) and five days before the main shock (Mw 9). This maximum depression is found to be several times greater than all previous deviations, but the depression seems to be most enhanced at Kakioka, the station nearest to the EQ epicenter. So that it is likely that this phenomenon could be a possible precursor to the huge 3.11 EQ.Розглядаються електромагнітні провісники землетрусів; на різних відстанях від епіцентру сильного землетрусу в Японії 11 березня 2011 досліджується депресія (зменшення амплітуди) УНЧ-варіацій геомагнітного поля, що спричинена магнітосферними джерелами. Використовуються записи флюксгейт-магнетометрів, розташованих від епіцентру на відстанях ~300 і ~1300 км. Інтервал спостережень відноситься до періоду з 1 грудня 2010 р. по 31 травня 2011 р. Виявлено різке зниження УНЧ-коливань геомагнітного поля в діапазоні частот 0,03…0,05 Гц (30…50 мГц) у всіх японських обсерваторіях (Какіока, Мамабетсу і Канойя). Ефект спостерігали за 3 дні до форшоку магнітудою М 7,5 і за 5 днів до головного поштовху магнітудою М 9. Максимальна депресія в кілька разів перевищила ті, що спостерігалися раніше, причому в найближчій до епіцентру обсерваторії (Какіока) ефект був найбільшим. Таким чином, депресію можна розглядати як провісника гігантського землетрусу в Японії 11 березня 2011 р.Рассматриваются электромагнитные предвестники землетрясений; на различных расстояниях от эпицентра сильнейшего землетрясения в Японии 11 марта 2011 г. исследуется депрессия (уменьшение амплитуды) УНЧ-вариаций геомагнитного поля, вызванная магнитосферными источниками. Используются записи флюксгейт-магнетометров, расположенных от эпицентра на расстояниях ~300 и ~1300 км. Интервал наблюдений относится к периоду с 1 декабря 2010 г. по 31 мая 2011 г. Обнаружено резкое снижение УНЧ-колебаний геомагнитного поля в диапазоне частот 0,03…0,05 Гц (30…50 мГц) во всех японских обсерваториях (Какиока, Мамабетсу и Канойя). Эффект наблюдался за 3 дня до форшока магнитудой М 7,5 и за 5 дней до главного толчка магнитудой М 9. Максимальная депрессия в несколько раз превысила те, которые наблюдались ранее, причем в ближайшей к эпицентру обсерватории (Какиока) эффект был наибольшим. Таким образом, депрессию можно рассматривать как предвестника гигантского землетрясения в Японии 11 марта 2011 г

Preseismic ULF effectand possible interpretation

We present the results of ULF magnetic field observation at Karimshino station (Kamchatka, Russia). Using a case study we discovered an effect of suppression of ULF intensity about 2-6 days before rather strong and isolated seismic shocks (magnitude M = 4.6-6.6). It is revealed for nighttime and the 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 especially calculated seismic indexes Ks for the rather long period of observation from June 2000 to November 2001. Our recent data confirm the validity of the effect. We show here a similar result during a period of frequent strong seismic activity in April-May 2002. It is highly probable that the effect observed is connected with the increase in plasma density perturbations inside the ionosphere, which are induced by preseismic water and gas release at the ground surface and following energy transportation into the ionosphere by atmospheric gravity waves. Two models are discussed and computed: the first is a decrease of penetration coefficient of Alfven waves from the magnetosphere due to a turbulent increase in effective Pedersen conductivity in the ionosphere, and the second is a change in wave number (k) distribution of source ionospheric turbulence. One of the mechanisms or both could be responsible for the observed 2-3 times suppression of ULF magnetic field noise at the ground

Near-seismic effects in ULF fields and seismo-acoustic emission: statistics and explanation

International audiencePreseismic intensification of fracturing has been investigated from occurrence analysis of seismo-acoustic pulses (SA foreshocks) and ULF magnetic pulses (ULF foreshocks) observed in Karimshino station in addition to seismic foreshocks. Such analysis is produced for about 40 rather strong and nearby isolated earthquakes during 2 years of recording. It is found that occurrence rate of SA foreshocks increases in the interval (-12, 0 h) before main shock with 3-times exceeding of background level in the interval (-6, -3 h), and occurrence probability of SA foreshocks (pA~75%) is higher than probability of seismic foreshocks (ps~30%) in the same time interval.ULF foreshocks are masked by regular ULF activity at local morning and daytime, nevertheless we have discovered an essential ULF intensity increase in the interval (-3, +1 h) at the frequency range 0.05-0.3 Hz. Estimated occurrence probability of ULF foreshocks is about 40%. After theoretical consideration we conclude: 1) Taking into account the number rate of SA foreshocks, their amplitude and frequency range, they emit due to opening of fractures with size of L=70-200 m (M=1-2); 2) The electro-kinetic effect is the most promising mechanism of ULF foreshocks, but it is efficient only if two special conditions are fulfilled: a) origin of fractures near fluid-saturated places or liquid reservoirs (aquifers); b) appearance of open porosity or initiation of percolation instability; 3) Both SA and ULF magnetic field pulses are related to near-distant fractures (r<20-30 km); 4) Taking into account number rate and activation period of seismic, SA and ULF foreshocks, it is rather probable that opening of fractures and rupture of fluid reservoirs occur in the large preparation area with horizontal size about 100-200km

About possibility to locate an EQ epicenter using parameters of ELF/ULF preseismic emission

A relation between parameters of preseismic ULF/ELF emissions and EQ is studied. The magnetic data measured at Karymshino station (Kamchatka, Russia) along with data on local seismic activity during eight years of observations (2001–2008) are taken for the analysis. Source azimuth is detected in different techniques, based on the analysis of the total field and its polarized pulsed component. The latter technique shows a better accuracy in the source azimuth detection. The errors of the method are associated with existence of non-seismic sources and with use of one-point observation. The second error can be eliminated by development of multi-point observations

Study of electromagnetic emissions associated with seismic activity in Kamchatka region

International audienceA review of data processing of electromagnetic emission observation collected at the Complex Geophysical Observatory Karimshino (Kamchatka peninsula) during the first 5 months (July?November, 2000) of its operation is given. The main goal of this study addresses the detection of the phenomena associated with Kamchatka seismic activity. The following observations have been conducted at CGO: variations of ULF/ELF magnetic field, geoelectric potentials (telluric currents), and VLF signals from navigation radio transmitters. The methods of data processing of these observations are discussed. The examples of the first experimental results are presented

Нейрореспираторный синдром у больных бронхиальной астмой

Personal features, cerebral bioelectrical activity, vegetative regulation, bronchial hyperreactivity and lung function regulation were analyzed in 219 bronchial asthma patients. The detected disorders allowed to characterize two-staged neuro-respiratory disadaptation syndrome. The mild disorders (the 1st stage) are described as adjusting overwork of neuro-regulatory systems. More severe disorders (the 2nd stage) are less adaptive and enhance the disease resulting in ventilation disorders and bronchial hyperreativity.У 219 больных бронхиальной астмой проанализированы особенности личности, биоэлектрической активности мозга, вегетативной регуляции, бронхиальной гиперреактивности и регуляции внешнего дыхания. Выявленные нарушения позволили выделить синдром нейрореспираторной дезадаптации, в течении которого выявлена этапность. При легком течении заболевания (первый этап) обнаружено напряжение нейрорегуляторных систем, носящее в основном адаптивный характер. При более тяжелом течении заболевания (второй этап) выявлены нарушения, которые носят не столько приспособительный характер, сколько усугубляют течение болезни и приводят к нарушению вентиляции легких и бронхиальной гиперреактивности