B. R. T. Cotts

Observation of local and conjugate ionospheric perturbations from individual oceanic lightning flashes

Very low frequency (VLF) remote sensing observations of multifaceted local and conjugate ionospheric perturbations from geographically identified and well-characterized oceanic lightning discharges are presented for the first time. Lightning-induced electron precipitation (LEP) events are shown to produce disturbances first in the conjugate hemisphere and subsequently in the hemisphere of the causative lightning discharge in agreement with theoretical predictions. A rough threshold peak current of ∼100 kA is identified for lightning discharges to generate LEP events for the geomagnetic conditions present during observations. The occurrence of early VLF events and the subsequent duration of their recovery do not seem to fit any simple metric of lightning discharge peak current or proximity to great circle path. Knowledge of the full spectral density of the lightning electromagnetic pulse, not just its peak current, and the subionospheric mode structure are likely necessary to determine if a specific lightning discharge will generate an early VLF perturbation.

Electromagnetic Interference Considerations for Electrical Power Systems

Electromagnetic interference (EMI) is an important consideration for electrical systems and can come from many forms. This chapter discusses some of the common sources of potential EMI from electrical power systems including corona, scattering, and reflections as well as field effects and induction. These sources are discussed as to how they can potentially affect other electrical devices as well as worker and public safety.

HVDC Transmission for Renewable Energy Integration

Abstract Renewable energy such as wind and solar are increasing their penetration in the worldwide market with many countries taking proactive approaches and requiring that an increased percentage of total power consumption and/or generation come from renewable energy sources. However, in many cases, the optimal locations for these renewable energy sources are found in rural or offshore locations that are long distances away from urban areas. Therefore, the generated power from these remote renewable energy sources must be transmitted to the urban areas for consumption. This chapter examines the present and future High Voltage Direct Current (HVDC) technologies used to transmit the generated power from remote renewable energy sources as well as provide a cost comparison with Alternative Current transmission systems. Multiple HVDC transmission link designs are presented and their unique advantages and applications are explained.

The VLF fingerprint of elves: Step-like and long-recovery early VLF perturbations caused by powerful ±CG lightning EM pulses

Summary form only given. Subionospheric VLF recordings are investigated in relation with intense cloud-to-ground (CG) lightning data. Lightning impacts the lower ionosphere via heating and ionization changes which produce VLF signal perturbations known as early VLF events. Typically, early events recover in about 100 s, but a small subclass does not recover for many minutes, known as long-recovery early events (LORE). In this study, we identify LORE as a distinct category of early VLF events, whose signature may occur either on its own or alongside the short-lived typical early VLF event. Since LORE onsets coincide with powerful lightning strokes of either polarity (±), we infer that they are due to long-lasting ionization changes in the uppermost D region ionosphere caused by electromagnetic pulses emitted by strong ±CG lightning peak currents of typically>250 kA, which are also known to generate elves. The LORE perturbations are detected when the discharge is located within ~250 km from the great circle path (GCP) of a VLF transmitter-receiver link. The probability of occurrence increases with stroke intensity and approaches unity for discharges with peak currents greater than ~300 kA. LOREs are nighttime phenomena that occur preferentially, at least in the present regional data set, during winter when strong ±CG discharges are more frequent and intense. The evidence suggests LORE as a distinct signature representing the VLF fingerprint of elves, a fact which, although was predicted by theory, it escaped identification in the long-going VLF research of lightning effects in the lower ionosphere.