Low-latitude ionospheric turbulence observed by Aureol-3 satellite

Using PSD (Power Spectral Density) data on electron density and electric field variations observed on board Aureol-3 satellite at low-to-mid-latitude ionosphere we analyze a scale distribution of the ionospheric turbulence in a form <i>k<sup>-α</sup></i>, where <i>k</i> is the wave number and α is the spectral index. At first, high-resolution data in the near-equator region for several orbits have been processed. In this case the frequency range is from 6Hz to 100Hz (corresponding spatial scales from 80m to 1.3km), each power spectrum obeys a single power law fairly well, and the mean spectral indices are rather stable with α<sub><i>N</i></sub>=2.2±0.3 and α<sub><i>E</i></sub>=1.8±0.2, for the density and electric field, respectively. Then we produce a statistical study of 96 electric field bursts in the frequency range 10-100Hz from low-time resolution data (filter bank envelope). These bursts concentrate on the side of the Equatorial Anomaly crest (geomagnetic latitude 30-40°). Spectral indices of the bursts vary in the interval α<sub><i>E</i></sub>=2.0-2.5 but are fairly stable in seasons and local times. The electric field power of the burst has rather a large variability but has a relative increase in mean values for the summer and winter, as well as the daytime. The effect of major seismic activities toward the ionospheric turbulence is not conclusive either for the refractive index or for the electric field power. However, the mean value for the electric field power of bursts during seismic periods is larger than that for non seismic periods, and the statistical difference of the mean values is rather significant

The effect of a gamma ray flare on Schumann resonances

We describe the ionospheric modification by the <I>SGR</I> 1806-20 gamma flare (27 December 2004) seen in the global electromagnetic (Schumann) resonance. The gamma rays lowered the ionosphere over the dayside of the globe and modified the Schumann resonance spectra. We present the extremely low frequency (ELF) data monitored at the Moshiri observatory, Japan (44.365° N, 142.24° E). Records are compared with the expected modifications, which facilitate detection of the simultaneous abrupt change in the dynamic resonance pattern of the experimental record. The gamma flare modified the current of the global electric circuit and thus caused the "parametric" ELF transient. Model results are compared with observations enabling evaluation of changes in the global electric circuit

FRONTAL PLANE TAKE-OFF STEP MECHANICS OF LONG JUMPERS WITH AND WITHOUT A BELOW THE KNEE AMPUTATION

Frontal plane mechanics during the long jump take-off step are unknown for athletes with and without a transtibial amputation. This is an issue due to the importance of the knowledge for training and rehabilitation protocols or prosthetic design. In this study the take-off step of three long jumpers with and seven without a below the knee amputation (BKA) were analysed with regard to frontal plane mechanics. Three-dimensional motion capture (Vicon) and a force plate (Kistler) were used to capture kinematic and kinetic data. Inverse dynamic calculations (Dynamicus, Alaska) revealed differences in frontal plane center of mass kinematics and joint kinetics between groups. Specifically, athletes with BKA had lower medio-lateral ground reaction forces, lower frontal plane joint loads and an altered foot position pattern compared to non-amputee athletes

Ionospheric perturbations in possible association with the 2010 Haiti earthquake, as based on medium-distance subionospheric VLF propagation data

Ionospheric perturbations in possible association with the 2010 Haiti earthquake occurred on 12 January 2010 (with a magnitude of 7.0 and depth of 10 km) are investigated on the basis of subionospheric propagation data from the NAA transmitter on the east coast of the USA to a VLF receiving station in Peru. The local nighttime VLF amplitude data are extensively investigated during the period from the beginning of October 2009 to the end of March 2010, in which the trend (nighttime average amplitude), dispersion and nighttime fluctuation are analysed. It is found that a clear precursory ionosphere perturbation is detected just around New Years day of 2010, about 12 days before the main shock, which is characterised by the simultaneous decrease in the trend and the increases in dispersion and nighttime fluctuation. An additional finding might be the presence of the effect of the Earth's tide one and two months before the main shock, which can only be seen for a huge EQ

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

LONG JUMP MECHANICS – OLYMPIC VERSUS PARALYMPIC CHAMPION

In the last 20 years the long jump world record of athletes with an amputation of the lower extremities has improved by over two meters. However, there is no recent research on amputee long jumping and no information about amputee long jump kinetics. In this study the take-off step of an Olympic and a Paralympic champion were analyzed with regard to jumping mechanics. A 3D motion capturing system (Vicon) and a force plate (Kistler) were used to capture kinematic and kinetic data. Inverse dynamic calculations (Dynamicus, Alaska) revealed remarkable differences with respect to mechanical loading and motor solutions between the transtibial amputee and non-amputee long jumper. Mechanical constraints and material properties of the prosthesis might influence the kinematic chain of the amputee athlete and impose the need for an alternative motor solution

First Very Low Frequency detection of short repeated bursts from magnetar SGR J1550-5418

We report on the first detection of ionospheric disturbances caused by short repeated gamma-ray bursts from the magnetar SGR J1550-5418. Very low frequency (VLF) radio wave data obtained in South America clearly show sudden amplitude and phase changes at the corresponding times of eight SGR bursts. Maximum amplitude and phase changes of the VLF signals appear to be correlated with the gamma-ray fluence. On the other hand, VLF recovery timescales do not show any significant correlation with the fluence, possibly suggesting that the bursts' spectra are not similar to each other. In summary, the Earth's ionosphere can be used as a very large gamma-ray detector and the VLF observations provide us with a new method to monitor high energy astrophysical phenomena without interruption such as Earth Occultation.Comment: 14 pages, 4 figures, accepted by ApJ

Detection of tsunami-driven phase and amplitude perturbations of subionospheric VLF signals following the 2010 Chile earthquake

We report on specific fluctuations in phase and amplitude of VLF signals that correlate both spatially and temporally with the passage of the tsunamis recorded by the Deep‐ocean Assessments and Reporting of Tsunamis bottom pressure stations. Measurements from the VLF/LF receiver sited in Petropavlovsk‐Kamchatsky and sensor buoys placed throughout the Pacific Ocean at great distances (Hawaii and Japan) from the epicenter are consistent with the hypothesis that the ocean tsunami following the Chile earthquake on 27 February 2010 radiated internal gravity waves which propagated through the lower ionosphere