Spatial scale of geomagnetic Pc5/Pi3 pulsations as a factor of their efficiency in generation of geomagnetically induced currents

Geomagnetically induced currents (GICs) in a quasi-meridional power transmission line on the Kola Peninsula are analyzed during the intervals of Pc5/Pi3 (frequency range from 1.5 to 5 mHz) pulsations recorded at the IMAGE magnetometer network. We have analyzed GIC in a transformer at the terminal station Vykhodnoy ($$68^{\circ }$$ 68 ∘ N, $$33^{\circ }$$ 33 ∘ E) during the entire year of 2015, near the maximum of the 24th Solar cycle. To quantify the efficiency of GIC generation by geomagnetic pulsations, a ratio between power spectral densities of GIC and magnetic field variations is introduced. Upon examination of the geomagnetic pulsation efficiency in GIC generation, the emphasis is given to its dependence on frequency and spatial scale. To estimate pulsation spatial scales in latitudinal and longitudinal directions, the triangle of stations KEV-SOD-KIL has been used. Large-scale pulsations (with a high spectral coherence, low phase difference, and similar amplitudes at latitudinally separated stations) are found to be more effective in GIC generation than small-scale pulsations. The GIC response also depends on the pulsation scale across the electric power line.

A multi-scale ground and drone-borne magnetic survey approach for the detection and investigation of archaeological structures

<p><span>Ground magnetic surveys are commonly used for imaging near-surface structures in archaeological studies. Usually, surveys are conducted using vertical component gradiometers or scalar gradiometers to produce a vertical pseudo-gradient map. Scalar magnetometers can also be used, albeit less frequently, to produce maps of the total magnetic anomaly. In all these cases, the equipment is pushed or pulled by an operator or carried behind a vehicle. Here we present a third approach made available by the use of three-component fluxgate magnetometers: fast surveys over large areas using a compact lightweight drone flying automatically 1 to 2 m above the ground and high precision surveys acquired by an operator 0,2 to 1 m above the ground. A case study on the gallo-roman site of Oedenburg, </span><span>located</span><span> along the Rhine River in its upper valley, illustrates the results that can be obtained with the approach. A comparison with previously acquired pseudo-gradient surveys show</span><span>s</span><span> that the presented method allows a faster coverage, a greater resolution for the imaging of short wavelength structures (such as walls) and a better capacity of imaging large wavelength structures (such as pathways, palaeochannels or soil composition variations). As the site is crossed by a high voltage electric power line, a method to suppress the high-amplitude 50 Hz frequency magnetic field is presented.</span></p>

Lightning, the Science. Part 1: Modern View

Lightning can be defined as a transient, high-current (typically tens of kA) electric discharge in air whose length is measured in km. As for any discharge in air, lightning channel is composed of ionized gas, that is, of plasma, whose peak temperature is typically 30,000 K, about five times higher than the temperature of the surface of the Sun. Lightning was present on Earth long before human life evolved and it may even have played a crucial role in the evolution of life on our planet. The global lightning flash rate is some tens to a hundred km per second. Each year, some 25 million cloud-to-ground lightning discharges occur in the United States, and this number is expected to increase by about 50% due to global warming over the 21st century. Lightning initiates many forest fires, and over 30% of all electric power line failures are lightning related. Each commercial aircraft is struck by lightning on average once a year. A lightning strike to an unprotected object or system can be catastrophic. In the first part of the article, an overview of thunderclouds and their charge structure is given, basic lightning terminology is introduced, and different types of lightning (including the so-called rocket-triggered lightning) are described. For the most common negative cloud-to-ground lightning, main lightning processes are identified and the existing hypotheses of lightning initiation in thunderclouds are reviewed.

Spatial scale of geomagnetic Pc5/Pi3 pulsations as a factor of their efficiency in generation of geomagnetically induced currents

Geomagnetically induced currents (GICs) in a meridional power transmission line on the Kola Peninsula are analyzed during the intervals of Pc5/Pi3 (frequency range from 1.5 to 5 mHz) pulsations recorded at the IMAGE magnetometer network. We have analyzed GIC in a transformer at the terminal station Vykhodnoj (68 N, 33 E) during the entire year of 2015, near the maximum of 24-th Solar cycle. To quantify the efficiency of GIC generation by geomagnetic pulsations, a ratio between power spectral densities of GIC and magnetic field variations is introduced. Upon examination of the geomagnetic pulsation efficiency in GIC generation, the emphasis is given to its dependence on frequency and spatial scale. To estimate pulsation spatial scales in latitudinal and longitudinal directions, the triangle of stations KEV-SOD-KIL has been used. Large-scale pulsations (with a high spectral coherence, low phase difference, and similar amplitudes at latitudinally separated stations) are found to be more effective in GIC generation than small-scale pulsations. The GIC response also depends on the pulsation scale across the electric power line.

Spatial Scale of Geomagnetic Pc5/pi3 Pulsations as a Factor of Their Efficiency in Generation of Geomagnetically Induced Currents

Geomagnetically induced currents (GICs) in a meridional power transmission line at the Kola Peninsula are analyzed during the intervals of Pc5/Pi3 (frequency range from 1.5 to 5 mHz) pulsation activity observed at the IMAGE magnetometer network. We have analyzed GIC in a transformer at the terminal station Vykhodnoj (68◦N, 33◦E) during the entire year of 2015, near the maximum of 24-th Solar cycle. To quantify the efficiency of GIC generation by a geomagnetic pulsation, a ratio between power spectral densities of GIC and magnetic field variations is introduced. Upon examination of the efficiency of geomagnetic pulsations in GIC generation, the emphasis is given to its dependence on frequency and spatial scale. To estimate pulsation spatial scales in latitudinal and longitudinal directions, the triangle of stations KEV-SOD-KIL has been used. Large-scale pulsations along the electric power line (with a high spectral coherence, low phase difference, and similar amplitudes) are found to be more effective in GIC generation than small-scale pulsations. The accuracy of GIC prediction also depends on the pulsation scale transversal to the electric power line.