Analysis of the Rhode Island schumann resonance daily-average data

© International Conference on Atmospheric Electricity, ICAE 2014 A variety of putative influences upon Schumann resonance (SR) signals have been evaluated for the case of a 20 year record of measurements of two magnetic-field detectors and one electric-field detector located at West Greenwich Rhode Island, U.S.A. (71.6?W, 41.6?N). The detector-specific SR signals considered are the values of the parameters of the first six modes of an eight-mode, three-parameter, Lorentzian-line-shape model. The three parameters of the model are peak-center frequency, peak-quality factor, and peak intensity. This model was used to fit the daily-average Fourier-transform intensity spectra spanning the frequency range 3 Hz - 56 Hz. This results in 54 SR signals: 3 channels × 6 modes / channel × 3 parameters / mode. We also computed an expected climatological-daily-average intensity spectra for each day and detector and fit these spectra to the above mentioned Lorentzian model. A linear regression of the observed parameters to the expected parameters finds that on average the climatological-daily-average data account for 35% of the variance (R2 = 0.35) of the original SR series, with the best fits obtained for the Lorentzian-fit parameter peak-intensity where 70% of the variance of the original series was explained. Averaging across channels and parameters, the second and third modes were best modeled by the climatological-average data, explaining 50% of the total variance; all above results are significant at the p = 0.001 level. We then subtracted the observed SR signals from the expected SR signals to generate residual SR signals. The residual SR time series display a systematic variation following the 11-year sunspot cycle. A linear regression of a nominal sunspot cycle with the residual time series averaged across all modes and channels, finds R2 values for peak-center frequency = 0.59, peak-quality factor = 0.31, and peak intensity = 0.0. Averaging the residual time series across all modes and fit parameters, the sunspot cycle is found in each channel; the R2 value for the E/W channel = 0.30, the R2 for the N/S channel = 0.37, and the R2 value for the Ez channel = 0.24 The sunspot-cycle pattern is strongest the mode 1 data (R2 = 0.48) and decreases with increasing mode number; the R2 for mode 6 = 0.15; all significant at the p = 0.001 level. We then examined various putative influences upon these residual SR signals using a variety of techniques. The results indicate that direct measures of solar activity (e.g. sunspot number and area) most strongly influence peak-center frequency and peak-quality factor (median R2 = 0.50) and less so the peak-intensity (median R2 = 0.02). Terrestrial temperature signals (e.g. Ocean temperature anomalies) influence peak-intensity (median R2 = 0.15) but not peak-center frequency nor peak-quality factor (median R2 = 0.01). We also examined the spectral characteristics of the residual SR signals. Both the peak-center frequency and peak-quality factor parameters, averaged over all of the modes and channels, display strong peaks at 11 years, 365 days, 180 days; in contrast, the peak-intensity parameter displays no similar features. This indicates that the values of the peak intensity parameter are well predicted by the global total lightning and the uniform-cavity model, while the peak-center frequency and peak-quality factor parameters are not. The values of these two parameters have a significant variation over the sunspot cycle unaccounted for by the global total lightning and the uniform-cavity model

Determination of the Global-Average Charge Moment of a Lightning Flash Using Schumann Resonances and the LIS/OTD Lightning Data

©2017. American Geophysical Union. All Rights Reserved. In this paper, we use (1) the 20 year record of Schumann resonance (SR) signals measured at West Greenwich Rhode Island, USA, (2) the 19 year Lightning Imaging Sensor (LIS)/Optical Transient Detector (OTD) lightning data, and (3) the normal mode equations for a uniform cavity model to quantify the relationship between the observed Schumann resonance modal intensity and the global-average vertical charge moment change M (C km) per lightning flash. This work, by integrating SR measurements with satellite-based optical measurements of global flash rate, accomplishes this quantification for the first time. To do this, we first fit the intensity spectra of the observed SR signals to an eight-mode, three parameter per mode, (symmetric) Lorentzian line shape model. Next, using the LIS/OTD lightning data and the normal mode equations for a uniform cavity model, we computed the expected climatological-daily-average intensity spectra. We then regressed the observed modal intensity values against the expected modal intensity values to find the best fit value of the global-average vertical charge moment change of a lightning flash (M) to be 41 C km per flash with a 99% confidence interval of ±3.9 C km per flash, independent of mode. Mode independence argues that the model adequately captured the modal intensity, the most important fit parameter herein considered. We also tested this relationship for the presence of residual modal intensity at zero lightning flashes per second and found no evidence that modal intensity is significantly different than zero at zero lightning flashes per second, setting an upper limit to the amount of nonlightning contributions to the observed modal intensity

Global lightning activity and the hiatus in global warming

© 2019 Elsevier Ltd Multiple records of global temperature contain periods of decadal length with flat or declining temperature trend, often termed a ‘hiatus’. Towards assessing the physical reality of two such periods (1940–1972 and 1998–2014), lightning data are examined. Lightning activity is of particular interest because on many different time scales it has been shown to be non-linearly dependent on temperature. During the earlier hiatus, declining trends in regional thunder days have been documented. During the more recent hiatus, lightning observations from the Lightning Imaging Sensor in space show no trend in flash rate. Surface-based, radiosonde-based and satellite-based estimates of global temperature have all been examined to support the veracity of the hiatus in global warming over the time interval of the satellite-based lightning record. Future measurements are needed to capture the total global lightning activity on a continuous basis

Cyclone Shaheen: the exceptional tropical cyclone of October 2021 in the Gulf of Oman

Early October 2021 saw Cyclone Shaheen track westward across the far northern Arabian Sea, penetrate the Gulf of Oman and strike the northeast Oman coastline – the first storm to make such a unique landfall in more than 130 years. This paper describes how the unusual cyclogenesis location, favourable initial trajectory and steering, conducive environmental conditions and anomalously warm sea‐surface temperatures were the main influences responsible for Shaheen\u27s extraordinary genesis, intensification and remarkable geographical landfall

Global circuit response to the 11-year solar cycle: Changes in source or in medium?

© International Conference on Atmospheric Electricity, ICAE 2014 Modifications to both the DC and AC global circuits are considered on both short time scales and on the 11-year solar cycle time scale. New long-term records of Schumann resonances are considered as documentation of the AC global circuit. In most cases, changes in the medium of the global circuit provide a better qualitative explanation than intrinsic source changes (i.e., lightning and electrified clouds) for the variations in the global circuit. Further work is needed with the quantitative details

Schumann Resonance spectral characteristics: A useful tool to study Transient Luminous Events (TLEs) on a global scale

© International Conference on Atmospheric Electricity, ICAE 2014 The background Schumann Resonance (SR) spectra require a natural stabilization period of ~10-12 minutes for the three modal parameters, namely, the frequency, intensity and Q-factor to be derived from Lorentzian fitting. Before the spectra are computed and the fitting process is initiated, the raw time series data need to be properly filtered for local cultural noise, narrow band interference as well as large transients in the form of global Q-bursts. Mushtak and Williams [2009] describe an effective technique named as Isolated Lorentzian (I-LOR), in which, the contribution from local cultural and various other noises are minimized to a great extent, and enabling the problem of inter-modal interference to be more effectively addressed in the SR background spectra. An automated technique based on median filtering of time series data and the rejection of events exceeding 16 core standard deviations (CSD) (where \u27core\u27 pertains to the central portion of the spectral power content ) from the average of the period of interest has also been developed by Mushtak et al. [2012]. This cleaning of data before obtaining the modal parameters is essential for work related to the background SR, for example, finding the source strength of tropical \u27chimney\u27 regions by inversion of multi-station data. The methodology used for removing the effect of Q-bursts from background SR spectra could also be used to search for big sprite-producing positive lightning flashes in mesoscale convective systems worldwide. These special lightning flashes are known to have greater contribution in the ELF range (below 1 kHz) compared to negative CG strikes [Cummer 2006]. The global distributions of these Q-bursts have been studied by Huang et al., [1999] and Hobara et al. [2006] by wave impedance methods from single station ELF measurements at Rhode Island, USA. The present work aims to demonstrate the effect of Q-bursts on SR spectra using GPS time-stamped observation of TLEs and average energy data from the VLF World Wide Lightning Location Network (WWLLN). It is observed that the Q-bursts selected for the present work do alias with the background spectra over a five second period, through the amplitudes of these Q-bursts are far below the 16 CSD limit so that they do not strongly alias the background spectra of 10-12 minute duration. The extent of this aliasing is yet to be investigated thoroughly. It is expected that the spectral ELF methodology could be used effectively to detect TLEs globally with a small number of networked stations, especially during daylight conditions, when optical measurements of sprites are not possible

Aliasing of the Schumann resonance background signal by sprite-associated Q-bursts

© 2017 The Authors The Earth\u27s naturally occurring Schumann resonances (SR) are composed of a quasi-continuous background component and a larger-amplitude, short-duration transient component, otherwise called ‘Q-burst’ (Ogawa et al., 1967). Sprites in the mesosphere are also known to accompany the energetic positive ground flashes that launch the Q-bursts (Boccippio et al., 1995). Spectra of the background Schumann Resonances (SR) require a natural stabilization period of ∼10–12 min for the three conspicuous modal parameters to be derived from Lorentzian fitting. Before the spectra are computed and the fitting process is initiated, the raw time series data need to be properly filtered for local cultural noise, narrow band interference as well as for large transients in the form of global Q-bursts. Mushtak and Williams (2009) describe an effective technique called Isolated Lorentzian (I-LOR), in which, the contributions from local cultural and various other noises are minimized to a great extent. An automated technique based on median filtering of time series data has been developed. These special lightning flashes are known to have greater contribution in the ELF range (below 1 kHz) compared to general negative CG strikes (Huang et al., 1999; Cummer et al., 2006). The global distributions of these Q-bursts have been studied by Huang et al. (1999) Rhode Island, USA by wave impedance methods from single station ELF measurements at Rhode Island, USA and from Japan Hobara et al. (2006). The present work aims to demonstrate the effect of Q-bursts on SR background spectra using GPS time-stamped observation of TLEs. It is observed that the Q-bursts selected for the present work do alias the background spectra over a 5-s period, though the amplitudes of these Q-bursts are far below the background threshold of 16 Core Standard Deviation (CSD) so that they do not strongly alias the background spectra of 10–12 min duration. The examination of one exceptional Q-burst shows that appreciable spectral aliasing can occur even when 12-min spectral integrations are considered. The statistical result shows that for a 12-min spectrum, events above 16 CSD are capable of producing significant frequency aliasing of the modal frequencies, although the intensity aliasing might have a negligible effect unless the events are exceptionally large (∼200 CSD). The spectral CSD methodology may be used to extract the time of arrival of the Q-burst transients. This methodology may be combined with a hyperbolic ranging, thus becoming an effective tool to detect TLEs globally with a modest number of networked observational stations

Effects of Energetic Solar Emissions on the Earth–Ionosphere Cavity of Schumann Resonances

© 2016, Springer Science+Business Media Dordrecht. Schumann resonances (SR) are the electromagnetic oscillations of the spherical cavity bounded by the electrically conductive Earth and the conductive but dissipative lower ionosphere (Schumann in Z Naturforsch A 7:6627–6628, 1952). Energetic emissions from the Sun can exert a varied influence on the various parameters of the Earth’s SR: modal frequencies, amplitudes and dissipation parameters. The SR response at multiple receiving stations is considered for two extraordinary solar events from Solar Cycle 23: the Bastille Day event (July 14, 2000) and the Halloween event (October/November 2003). Distinct differences are noted in the ionospheric depths of penetration for X-radiation and solar protons with correspondingly distinct signs of the frequency response. The preferential impact of the protons in the magnetically unshielded polar regions leads to a marked anisotropic frequency response in the two magnetic field components. The general immunity of SR amplitudes to these extreme external perturbations serves to remind us that the amplitude parameter is largely controlled by lightning activity within the Earth–ionosphere cavity

Inversion of Multi-Station Schumann Resonance Background Records for Global Lightning Activity in Absolute Units

Every lightning flash contributes energy to the TEM mode of the natural global waveguide that contains the Earth’s Schumann resonances. The modest attenuation at ELF (0.1 dB/Mm) allows for the continuous monitoring of the global lightning with a small number of receiving stations worldwide. In this study, nine ELF receiving sites (in Antarctica (3 sites), Hungary, India, Japan, Poland, Spitsbergen and USA) are used to provide power spectra at 12-minute intervals in two absolutely calibrated magnetic fields and occasionally, one electric field, with up to five resonance modes each. The observables are the extracted modal parameters (peak intensity, peak frequency and Q-factor) for each spectrum. The unknown quantities are the geographical locations of three continental lightning ‘chimneys’ and their lightning source strengths in absolute units (C2 km2/sec). The unknowns are calculated from the observables by the iterative inversion of an evolving ‘sensitivity matrix’ whose elements are the partial derivatives of each observable for all receiving sites with respect to each unknown quantity. The propagation model includes the important day-night asymmetry of the natural waveguide. To overcome the problem of multiple minima (common in inversion problems of this kind), location information from the World Wide Lightning Location Network has been used to make initial guess solutions based on centroids of stroke locations in each chimney. Results for five consecutive days in 2009 (Jan 7-11) show UT variations with the African chimney dominating on four of five days, and America dominating on the fifth day. The amplitude variations in absolute source strength exceed that of the ‘Carnegie curve’ of the DC global circuit by roughly twofold. Day-to-day variations in chimney source strength are of the order of tens of percent. Examination of forward calculations performed with the global inversion solution often show good agreement with the observed diurnal variations at individual receiving sites, lending confidence to the 3-chimney model for global lightning