BOOK OF EXTENDED ABSTRACTS. “Electromagnetic ULF/ELF Fields on Earth and in Space” Conference, Warsaw, Poland, 3-5 July 2019

Abstract:

This year’s meeting is a new conference in the series “ULF/ELF Fields on Earth and in Space”, which used to take place in the Bieszczady mountains in Poland under the name “Bieszczady Meetings”. The “Meetings” organised for years on the initiative of the Krakow ELF Group took place 15 times in Dwerniczek and Zatwarnica in Bieszczady (1996-2012), once in Skawica in Beskid Żywiecki (1997), in Niepołomice (2011), Solec-Zdrój (2014), Jaroszowiec (2015) and again in Solec-Zdrój (2015). This year, after a few years break, we have the pleasure to participate in the XXI “Meeting”, this time taking place at the Institute of Geophysics PAS in Warsaw.

With great pleasure, at the initiative of the Department of the Earth’s Interior and Near-Space Physics at Polish Geophysical Society, we host the next conference “Electromagnetic Fields ULF/ELF on Earth and in Space” in the new location at the Institute of Geophysics, Polish Academy of Sciences in Warsaw.

Abstract:

In 1952, W.O. Schumann unexpectedly published a series of works on the Earth-ionosphere cavity (Schumann 1952a, b, c). He opened a new field of geophysical research, focusing on the issues of ELF wave propagation in the Earth-ionosphere waveguide. The cavity consid-ered by Schumann was idealised; it consisted of two concentric perfectly conductive spherical surfaces, spaced by the “height of the ionosphere” h. Schumann’s solutions showed that the resonance frequencies of the cavity are practically independent of h and are given by the equation fn = 7.49 (n (n + 1))1/2, which gives the first modes: 10.6, 18.4, 26.0, 33.5, 41.1,... Hz. The first attempt to observe resonances of atmospheric noise carried out in Munich failed (Schumann and König 1954).

Abstract:

The measurement and assessment of global thunderstorm activity is an important and frequent aspect of both meteorological and climatic as well as geophysical research. The assessment of this activity can be considered on the basis of indicators based on the intensity and frequency of the occurrence of various phenomena and processes, such as storm clouds (Kohl 1980), their altitude, wind speed, precipitation intensity (Twardosz 2010), the frequency of atmospheric lightning discharges (Christian et al. 2003). Such indicators are developed on the basis of ob-servations and results of measurements carried out on the ground surface (Nieckarz and Zięba 2013) and by instruments placed on satellites (Turman 1978, Dai 2001).

Abstract:

Many studies have been conducted on thunderstorm activity in recent decades, one of them was started by W.O. Schumann (1952). He discovered a resonance phenomenon associated with ELF (Extremely Low Frequencies) electromagnetic waves propagating around the Earth. The Schumann resonance (SR) can be observed at frequencies close to 8, 14, 20, 26 Hz (Balser and Wagner 1960). These frequencies are associated with the existence of the Earth-ionosphere cavity, in which the ELF waves are excited mainly by atmospheric discharges. In 1992, E. Williams from Massachusetts Institute of Technology (Williams 1992) noticed a strong corre-lation between the amplitude of the first Schumann resonance mode, and a mean subtropical temperature. In the following years many scientist tried to map storm centres located in South America, Africa and Asia (e.g. Heckman et al. 1998, Nickolaenko et al. 1998, Shvets 2001, Ando et al. 2005).

Abstract:

W.O. Schumann’s (1888–1974) scientific biography is full of surprising episodes and ambigu-ities. Over the course of his life he changed his interests several times. Unexpectedly in 1952 he opened a new field of geophysical research: the studies of the propagation of Extremely Low Frequency (ELF) waves in the Earth-ionosphere cavity.

Abstract:

Schumann resonances are resonances of electromagnetic waves in the Earth-ionosphere cavity, and were first predicted and discussed by W.O. Schumann (1952). They are excited by world-wide thunderstorm activity. Maximal amplitudes (modes) can be observed at around 8 Hz, 14 Hz, 21 Hz, and so on. Monitoring of Schumann resonances provides information about proper-ties of the lower ionosphere, world thunderstorm activity, and global climatic change.

Abstract:

We have built a new broadband ELF (extremely low frequency) measurement system (Mlynar-czyk et al. 2018). It enables us to study atmospheric discharges, in particular those associated with Transient Luminous Events (Pasko 2010, Bór 2013 and references therein), with high temporal resolution. It also allows us to study other natural phenomena in the ELF range and to conduct research on radio wave propagation.

Abstract:

Since about the last 30 years one can notice an increasing interest in the so called “calculus of fractional order” (also known under different names, as e.g. “fractional calculus” or “fractional differ-integrals”). Using the opportunity of an open formula of this meeting, I would like to bring this topic a bit closer and to present some ideas potentially applicable in the domain of our interest. Because the topic is extensive, this presentation is a brief introduction, accompa-nied with a few examples and bibliography.

Abstract:

The lowest region of the upper atmosphere plasma environment is the ionospheric D-region, which exists in the altitude range of 65-95 km. D-region electron densities are maximum during the daytime and significantly reduced at night, but the plasma state persists at these altitudes at all hours and dominates the propagation and reflection of electromagnetic waves with frequencies below 100 kHz and the absorption of MF (Medium Frequency: 300 kHz - 3 MHz) and HF (High Frequency: 3 MHz - 30 MHz) waves. The D-region is affected by magnetosphere-iono-sphere coupling since energetic electron precipitation from the Earth's radiation belts and solar flare X-ray fluxes increase D-region ionization levels. Therefore monitoring the D-region electron is an important part of space weather monitoring.

Abstract:

Recently, due to a start of extensive space exploration, studies on propagation of electromagnetic waves in other bodies in the Solar System have become an important issue. In Martian exploration especially useful can be waves in extremely low frequency (ELF, 3 Hz – 3 kHz) range. Attenuation of these waves in the Martian environment is very low, and they can propagate around the globe in a cavity, made of two high-conductivity spherical layers: the ionosphere and the ground. On Mars, as there is no liquid water at the planetary surface, the high-conductivity layers of the ground are located in the subsurface. Therefore, ELF waves can prop-agate to the depth of many kilometers. In the Martian atmosphere, ELF waves can be generated by dust events, such as dust storms and dust devils, which are important factors influencing global atmospheric circulation. If ELF sources occur on Mars, an ELF station can be used as a tool to investigate not only the properties of the ionosphere, but also atmosphere, and the subsurface of Mars.

Abstract:

Usually, scientific, continuous records of electromagnetic variations in the ELF frequency range are collected with the aim to investigate phenomena (e.g., signal generation and propagation mechanisms, signal detection, quantification, and monitoring) that occur above the surface of the solid Earth. In this contribution we want to demonstrate that such data also have the potential to act as an important auxiliary for investigation of subsurface structures.

Abstract:

The radio waves in ranges from LF (Low Frequency) to HF (High Frequency) which propagate in the Earth's atmosphere are affected by the ionosphere. Observation of phase, amplitude and direction of incoming radio signals can provide information about the current state of the ionised medium. In our studies for HF observations we use PL610 LOFAR (Low-Frequency Array for Radio astronomy) station, which is located in Astrogeodynamical Observatory in Borowiec. For LF and MF (Medium Frequency) band measurements dedicated receiver based on Universal Software Radio Peripheral (USRP) is used. We observe phase and amplitude signals from radio broadcast station. The time measurement is based on GPS.

Abstract:

SuperDARN radars are coherent scatter radars which use the Bragg scattering phenomenon on structures characterised by a certain spatial periodicity whose distances are comparable to the sounding wavelength. For a certain range of the probe’s wavelength, in the case of objects with a periodic structure and constant distances between the elements of the structure, a coherent echo superposition occurs, which results in the amplification or weakening of the signal by interference. In this way, an echo signal gain towards the radar receiver can be obtained.

Abstract:

Strong convective events in Europe are relatively regular, especially in the summer season, when there is an advection of warm tropical airmass from the southern regions. High water vapour content in the warm air, convection, atmosphere instability and strong vertical thermal gradients, are favouring development of strong storm complexes, such as MCS (Mesoscale Convective System) (Bonner 1968, Banta et al. 2002, Houze 2014). They are created by strongly developed Cumulonimbus and Nimbostratus clouds and they can cover an area up to 100 000 km². They are characterized by significant hail and naval precipitation (Chomicz 1951), strong winds, which can reach the level of 150 km/h, many atmospheric discharges and relatively long time of the occurrence, from 6 up to 12 hours (Chappell 1986).

Abstract:

The occurrence of multiple Cloud-to-Ground (CG) flash incident is a manifestation of the complex electric charge space configuration existing in the bottom layer of a thundercloud. Thus, if we are able to evaluate the 3D location and the amount of the electric charge Q, involved in the particular component of this lightning discharge, i.e., the return stroke or the continuing current stage, from our multi-station E-field recordings on the ground (at least in four distant locations), then it is possible to have an insight into how such electric structure of the particular thunder-cloud region favorable for lightning initiation is built. Sometimes these multiple CG flashes are grouped in repeated episodes in short time intervals, e. g., from a few to several minutes, what can inform us about the time changes of the electric charge space redistribution in this thundercloud region.

Abstract:

The ionospheric Alfvén resonance (IAR) results from the resonant interference of the shear mode of the magnetohydrodynamic Alfvén waves in a cavity created by the bottom conductive ionosphere in the E-layer and by the gradient of the mass density in the Earth’s ionospheric upper F-layer (Polyakov and Rapoport 1981), where the waves are partly reflected. The eigen-frequencies of the resonance depend on the parameters of the Alfvén speed profile in the F layer, proportionally dependent to the ambient geomagnetic field, and inversely proportional to the square root of mass density.