ELF receiver

ELF receiver has been developed in the Institute of Radio Astronomy NASU for monitoring of the Earth's electromagnetic fields within the extra low frequency range of 0.5 to 40 Hz. The major natural source of the radiation in this range is global lighting activity. Lightning discharges excite electromagnetic oscillations in the cavity formed by the Earth surface and the ionosphere. This global electromagnetic phenomenon is called Schumann resonances [1, 2]. The analysis of the received ELF data allows reconstructing space and time distribution of the global lightning activity around the globe [3, 4]. The instrument receives, quantizes and records two horizontal magnetic and one vertical electric field components simultaneously.

The data acquisition system consists of two parts. The first one is autonomous and located on the far bank of the Pechenegskoe lake. The place has been chosen in order to reduce anthropogenic noise. This part is responsible for receiving, amplification and quantizing of two horizontal magnetic field components as well as generating serial digital code and transmitting it to the base station over the VHF channel. It includes two magnetic antennas (solenoids with permalloy cores), one oriented South-North and the other East-West, antenna amplifiers, low-pass filters with the range of 0.5 to 40 Hz, 50 Hz rejection filters, analog digital converter, serial controller, 430 MHz transmitter, VHF antenna, power supply and batteries.

The second part is located on the observatory. It is responsible for receiving and decoding of the data transmitted by the autonomous part of the system, measuring and quantizing of the vertical electric field component. It also archives all the data on the computer hard drive and link it with UTC time by means of GPS. This part includes VHF antenna, 433 MHz receiver, capacitor antenna for measuring the vertical electrical component of the field, antenna amplifier, low-pass and high-pass filters, 50 Hz rejection filter, analog digital converter, serial controller, computer and GPS receiver.

ELF receiver functional diagram

Receiver characteristics