Study of VLF/LF wave propagations above seismic areas

Abstract: We report on radio transmitter signals recorded in Europe by INFREP network which is mainly devoted to search for earthquakes electromagnetic precursors (Biagi et al., 2011). We consider in this analysis the detection of transmitter signals recorded by INFREP receivers located in different regions of Europe, i.e. Romania, Italy, Greece and Austria. The aim is the investigation of the electromagnetic environment above earthquakes regions. We selected seismic events which occurred in the year 2016 and characterized by a moment magnitude (Mw) above 5.0 and a depth of less than 50 km. A common method is applied to all events and which involves the analysis of the VLF/LF signal detection taking into consideration the following parameters: (a) the distance transmitters-receivers, (b) the signal to noise ratio during the diurnal and night observations, (c) the daily and night averaged amplitude and (d) the sunset and sunrise termination times. This leads us to specify the key factors which can be considered as criteria to distinguish and to identify earthquakes precursors. We discuss in this contribution the radio wave propagation in the D- and E-layers and their impacts on the VLF/LF amplitude signal. We show that the 'seismic anomaly' requests a more precise analysis of the 'quiet' and 'disturbed' ionospheric conditions and their corresponding spectral traces on the VLF/LF transmitter signals

The Graz seismo-electromagnetic VLF facility

Abstract. In this paper we describe the Graz seismo-electromagnetic very low frequency (VLF) facility, as part of the European VLF receiver network, together with the scientific objectives and results from two years operation. After a brief technical summary of the present system – with heritage from a predecessor facility – i.e. hardware, software, operational modes and environmental influences, we discuss results from statistical data and scientific events related to terrestrial VLF propagation over Europe

Ray paths of VLF/LF transmitter radio signals in the seismic Adriatic regions

We analyze the radio wave propagations of VLF/LF transmitter signals along subionospheric paths using two different reception systems localized in the Graz seismo-electromagnetic facility (15.43E,47.06N). Those systems allow the simultaneous detection of more than fifteen transmitter signals emitting in the northern (i.e. France, Germany and United Kingdom) and southern (i.e. Italy and Turkey) parts of Europe. In this work, we investigate the transmitter radio wave propagations associated with two earthquakes (EQs) which occurred, at two occasions, in nearly the same Croatian regions (Geo. Long.=16°E; Geo. Lat.=45°N). The first and second EQs happened, respectively, on March 22 and December 29, 2020, with magnitudes Mw equal to 5.4 and 6.4. The use of two complementary reception systems, i.e. INFREP (Biagi et al., Open Journal of Earthquake Research, 8, 2019) and UltraMSK (Schwingenschuh et al., Nat. Hazards Earth Syst. Sci., 11, 2011), and the proximity to the epicenters lead us to characterize the behavior of the transmitter signal amplitudes particularly above the Croatian seismic regions. We analyze the amplitude variation for a given transmitter frequency starting few weeks before the earthquakes occurrences. We discuss the observed anomalies in the transmitter signals which may be considered as precursors due to the ionospheric disturbances of the transmitter ray paths above the earthquakes preparation zones

Effect of Breast Milk Calcium and Fluidity on Breast Cancer Cells: An In Vitro Cell Culture Study

Aim: The aims of this study were to investigate the effects of calcium at the same concentration as that found in human milk on the viability, proliferation, and adhesion of MCF-7 human breast ductal carcinoma cells by exposing them to calcium at the same frequency as in breastfeeding

Similar behaviors of natural ELF/VLF ionospheric emissions and transmitter signals over seismic Adriatic regions

International audienceWe report on the analysis of ELF/VLF emissions observed by the Instrument Champ Electrique (ICE) experiment onboard the DEMETER micro-satellite. We consider principally selected seismic events reported by Molchanov et al. (2006). These authors studied the VLF signals radiated by ground transmitters and received on board the DEMETER micro-satellite. They revealed a drop of the signals (scattering spot) connected with the occurrence of large earthquakes. In our investigations, we proceed to a spectral analysis of ICE observations with the aim to find if the natural ionospheric VLF/ELF emissions show, or not, a similar ''drop'' in the intensity as it is the case of the VLF transmitter signal. We combine our results with those of Molchanov et al. (2006), and we discuss the origin of such interesting ionospheric features in the frame of the investigation of the pre-seismic electromagnetic emissions. We show that the geomagnetic activity is a key parameter which could disturb the natural VLF ionospheric emissions, and also the transmitter signal. We find that it is not possible to conclude the presence, or not, of a preseismic effect when the Kp-index is higher than one

Similar behaviors of natural ELF/VLF ionospheric emissions and transmitter signals over seismic Adriatic regions

We report on the analysis of ELF/VLF emissions observed by the Instrument Champ Electrique (ICE) experiment onboard the DEMETER micro-satellite. We consider principally selected seismic events reported by Molchanov et al. (2006). These authors studied the VLF signals radiated by ground transmitters and received on board the DEMETER micro-satellite. They revealed a drop of the signals (scattering spot) connected with the occurrence of large earthquakes. In our investigations, we proceed to a spectral analysis of ICE observations with the aim to find if the natural ionospheric VLF/ELF emissions show, or not, a similar ''drop'' in the intensity as it is the case of the VLF transmitter signal. We combine our results with those of Molchanov et al. (2006), and we discuss the origin of such interesting ionospheric features in the frame of the investigation of the pre-seismic electromagnetic emissions. We show that the geomagnetic activity is a key parameter which could disturb the natural VLF ionospheric emissions, and also the transmitter signal. We find that it is not possible to conclude the presence, or not, of a preseismic effect when the Kp-index is higher than one

Remote sensing of natural and artificial variations in the Earth-ionosphere cavity via very low frequency

In this article we present results from very low frequency (VLF) observations of transient and intermittent phenomena in the Earth-ionosphere waveguide. The scientific objectives are remote localisation and characterisation of short time disturbances. The VLF amplitude and phase variations aid to physically investigate the atmospheric media from the Earth's surface up to the lower ionosphere ( 70-90 km, D- and E-region) which is part of propagation channels for satellite communications and navigational applications. We consider two common types of anomalies in the waveguide, these events are associated with (i) solar flares and (ii) geomagnetic storms. We conclude that with a continuous operating VLF receiver network a service for lower atmospheric channel monitoring / characterisation can be established

EFD experiment onboard CSES satellite: Characterization of hiss and chorus whistler emissions during geomagnetic activity

International audienceWe study the geomagnetic activity effects on whistler emissions recorded by the Electric Field Detector (EFD) experiment onboard the China Seismo-Electromagnetic Satellite (CSES). This mission is devoted to investigate the ionospheric disturbances linked to the seismic activity. The satellite has a circular sun-synchronous orbit with a descending node at 14 LT and an altitude of 507 km [1]. Four probes are used to measure the electric field recorded by EDF instrument covering a frequency range from DC up to 3.5 MHz [2]. We consider in this analysis geomagnetic events which occurred in the year 2018 after the launch of the CSES satellite, i.e. on 02nd February 2018. The Kp-index leads us to estimate the variation of the geomagnetic activity which is found to have sudden enhancements on the following days: 21st April, 05th May, 26th Aug. and 10th Sept. We show in this analysis that the whistler emissions, i.e. hiss and chorus occurring in the frequency bandwidth 1 kHz to 20 kHz, are influenced by the Earth's magnetic activity. Hence whistler spectral shapes are globally found to develop towards higher frequencies. Two aspects are discussed: (a) the way to characterize an ionospheric disturbance index taking into consideration the CSES geographical configuration orbit and (b) the comparison of the electric field power levels as derived from EFD/CSES instrument and from ICE/DEMETER experiment [3]