Sudden Impulse Research Articles

Superposed Epoch Analyses of Geoelectric Field Disturbances in Japan in Response to Different Geomagnetic Activities

AbstractAn increase in geomagnetically induced currents (GICs) is an inevitable result of geomagnetic field disturbances, and is harmful to the power grid, in particular, at high latitudes. At mid and low latitudes, the amplitude of the GICs is, in general, small, but large‐amplitude GICs are often observed during magnetic storms. It is of importance to understand major characteristics and extreme values of GICs at mid and low latitudes. For the geoelectric field disturbances ΔE observed at Kakioka (27.8° geomagnetic latitude) in Japan in 1996–2004, we performed superposed epoch analyses with respect to three types of geomagnetic disturbances: (a) storm sudden commencements (SSCs)/sudden impulses (SIs), (b) main phase of magnetic storms, and (c) bay disturbances. It is shown that the SSCs/SIs and the main phase of the magnetic storms are equally important for causing large‐amplitude disturbances of ΔE at Kakioka. GICs are thought to be amplified when the SIs and/or the bay disturbances occur during the magnetic storms. The maximum value of ΔE tends to be correlated with the maximum value of ΔH during the three types of events, where ΔH is the horizontal component of the geomagnetic field. Assuming that a quasi‐linear relationship between the maximum ΔE and the maximum ΔH is valid, we estimated GICs at three substations in Japan for an extreme SSCs/SIs, and the extreme magnetic storms. This scheme could be applicable to estimate roughly the GICs against extreme events, and to forecast the maximum GICs in a real‐time manner.

3D Modeling of Geomagnetically Induced Currents in Sweden—Validation and Extreme Event Analysis

AbstractRosenqvist and Hall (2019), https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018SW002084 developed a proof‐of‐concept modeling capability that incorporates a detailed 3D structure of Earth's electrical conductivity in a geomagnetically induced current estimation procedure (GIC‐SMAP). The model was verified based on GIC measurements in northern Sweden. The study showed that southern Sweden is exposed to stronger electric fields due to a combined effect of low crustal conductivity and the influence of the surrounding coast. This study aims at further verifying the model in this region. GIC measurements on a power line at the west coast of southern Sweden are utilized. The location of the transmission line was selected to include coast effects at the ocean‐land interface to investigate the importance of using 3D induction modeling methods. The model is used to quantify the hazard of severe GICs in this particular transmission line by using historic recordings of strong geomagnetic disturbances. To quantify a worst‐case scenario GICs are calculated from modeled magnetic disturbances by the Space Weather Modeling Framework based on estimates for an idealized extreme interplanetary coronal mass ejection. The observed and estimated GIC based on the 3D GIC‐SMAP procedure in the transmission line in southern Sweden are in good agreement. In contrast, 1D methods underestimate GICs by about 50%. The estimated GICs in the studied transmission line exceed 100 A for one of 14 historical geomagnetic storm intervals. The peak GIC during the sudden impulse phase of a “perfect” storm exceeds 300 A but depends on the locality of the station as the interplanetary magnetic cloud hits Earth.

Assessment of the predictive capabilities of NIGTEC model over Nigeria during geomagnetic storms

The Nigerian Total Electron Content (NIGTEC) is a regional neural network-based model developed by the Nigerian Centre for Atmospheric Research to predict the Total Electron Content (TEC) at any location over Nigeria. The addition of the disturbance storm time (Dst) index as one of NIGTEC's input layer neurons raises a question of its accuracy during geomagnetic storms. In this paper, the capability of NIGTEC in predicting the variability of TEC during geomagnetic storms has been assessed. TEC data predicted by NIGTEC is compared with those derived from Global Navigation Satellite System (GNSS) over Lagos (6.5oN, 3.4oE) and Toro (10.1oN, 9.12oE) during the intense storms in March 2012 and 2013. The model's predictive capability is evaluated in terms of Root Mean Square Error (RMSE). NIGTEC reproduced a fairly good storm time morphology in VTEC driven by the prompt penetration electric field and the increase in thermospheric O/N2. Nevertheless, it failed to predict the increase in TEC after the intense sudden impulse of 60 nT on 8 March 2012. And it could not capture the changes in VTEC driven by the storm time equatorward neutral wind especially during 18:00–24:00 UT. Consequently, the RMSEs were higher during this time window, and the highest RMSE value was obtained during the most intense storm in March 2012.

A Study of Vehicle Vibration with Multiple Degrees of Freedom Using OCTAVE and ANSYS

Vibration vehicle models provide a great opportunity to integrate vehicle-based vibrations into a mechanical engineering vibrations course. This paper documents and discusses an approach to a multiple-degree-of-freedom (MDOF) in regards to pitch and bounce of the vehicle body with dampening and stiffness observed. The approach utilizes hand calculations, OCTAVE, and ANSYS to solve speed-bump induced vibration and to calculate vibrations modes. The problem involves a bicycle-model approach to a vehicle’s response when subject to a speed bump, or a sudden impulse load upon the forward-face of the model. These responses are captured and analyzed on pitch and bounce of the model at the center-of-gravity and the front/rear sides of the model. Graphical models capture responses of the loading conditions and the modal equations of the model providing a method of studying and understanding vibrational responses under provided stiffness. Using ANSYS as an approach of the model to capture damping response, further graphical models can be captured and used to describe motions of the vehicle model’s center-of-gravity, frontward and rearward wheel assembly, and the pitch (rotation) of the center-of-gravity to the introduced responses. A successful study with analysis of each graphical element and further dissemination of the results is concluded.

Global Magnetosphere Response to Solar Wind Dynamic Pressure Pulses During Northward IMF Using the Heliophysics System Observatory

AbstractWe analyzed the magnetospheric global response to dynamic pressure pulses (DPPs) using the Heliophysics System Observatory (HSO) and ground magnetometers. During northward Interplanetary Magnetic Field (IMF) Bz conditions, the magnetosphere acts as a closed “cavity” and reacts to solar wind DPPs more simply than during southward IMF. In this study we use solar wind data collected by ACE and WIND together with magnetic field observations of Geotail, Cluster, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Magnetospheric Multiscale Mission (MMS), Van Allen Probes, GOES missions, and ground magnetometer arrays to observe the magnetosphere (dayside, nightside, inner magnetosphere, magnetotail, magnetosheath, etc.) and ionosphere response simultaneously in several local time sectors and regions. A total of 37 events were selected during the period between February 2007 to December 2017. We examine the global response of each event and identify systematic behavior of the magnetosphere due to DPPs' compression, such as MHD wave propagation, sudden impulses, and Ultra Low Frequency waves (ULF) in the Pc5 range. Our results confirm statistical studies with a more limited coverage that have been performed at different sectors and/or regions of the magnetosphere. We present observations of the different signatures generated in different regions that propagate through the magnetosphere. The signature of the tailward traveling DPP is observed to move at the same solar wind speed, and in superposition of other known magnetospheric perturbations. It is observed that the DPP also generates or increases the amplitude of Pc4‐5 waves observed in the inner magnetosphere, while similar waves are observed on the ground.

Numerical Simulations of the Geospace Response to the Arrival of an Idealized Perfect Interplanetary Coronal Mass Ejection

AbstractPreviously, Tsurutani and Lakhina (2014,https://doi.org/10.1002/2013GL058825) created estimates for a “perfect” interplanetary coronal mass ejection and performed simple calculations for the response of geospace, including. In this study, these estimates are used to drive a coupled magnetohydrodynamic‐ring current‐ionosphere model of geospace to obtain more physically accurate estimates of the geospace response to such an event. The sudden impulse phase is examined and compared to the estimations of Tsurutani and Lakhina (2014,https://doi.org/10.1002/2013GL058825). The physics‐based simulation yields similar estimates for Dst rise, magnetopause compression, and equatorialvalues as the previous study. However, results diverge away from the equator.values in excess of 30 nT/s are found as low asmagnetic latitude. Under southward interplanetary magnetic field conditions, magnetopause erosion combines with strong region one Birkeland currents to intensify theresponse. Values obtained here surpass those found in historically recorded events and set the upper threshold of extreme geomagnetically induced current activity at Earth.

Modelling the cardiac response to a mechanical stimulation using a low-order model of the heart.

Heart diseases are one of the leading causes of death worldwide, and a dysfunction of the cardiac electrical mechanisms is responsible for a significant portion of these deaths. One of these mechanisms, the mechano-electric feedback (MEF), is the electrical response of the heart to local mechanical changes in the environment. This electrical response, in turn, leads to macroscopic changes in heart function. In this paper, we demonstrate that the MEF plays a crucial role in mechanical generation and recovery from arrhythmia which has been observed in experimental studies. To this end, we investigate the cardiac response to a mechanical stimulation using a minimal, multiscale model of the heart which couples the organ level dynamics (left ventricular pressure and volume) and contractile dynamics. By including a mechanical stimulation into the model as a (short, sudden) impulse in the muscle microscale stress, we investigate how the timing, amplitude and duration of the impulse affect the cardiac cycle. In particular, when introduced in the diastolic period of the cardiac cycle, the pulse rate can be stabilised, and ectopic beats and bifurcation can be eliminated, either temporarily or permanently. The stimulation amplitude is a key indicator to this response. We find an optimal value of the impulse amplitude above or below which the impulse maximises the stabilisation. As a result a dysfunction of the MEF can be helped using a mechanical stimulation, by allowing the heart to recover its pumping power. On the other hand, when the mechanical stimulation is introduced towards the end of systole, arrhythmia can be generated.

Optimization of Micro-Thruster Cold Gas Propulsion System Design for Space Applications

Comparing the complexity of the hardware and the control system, cold gas micro thrusters are much more simplified than other propulsion thrusters. Numerical calculation was carried out for mass requirement, mass flow rate, valves, feed system and computational fluid dynamics with finite element analysis was used for tank, pipe and nozzle design. Four different materials: Structural steel, Stainless steel, Aluminum and Titanium, were considered for tank design. They were subjected to the same conditions for four different tank geometries. The propulsion system was designed to be able to produce between 1 and 2 minutes of continuous thrust and the sudden impulses of between 0.8 and 1 seconds of gas expulsion, with over 20 impulses as desired thrust time. The mass and the volume needed for multiple tank geometries, concepts, and materials were determined. The main performance characteristics of the micro thrusters evaluated were Pressure Distribution, Velocity Profile, Temperature Distribution, Nozzle Efficiency and the corresponding Mach Number Distribution. This work is to provide a stable and controllable platform for testing equipment that can be ultimately applied to space applications.

Numerical investigation of sloshing in a three-dimensional square tank under excitation using CFD code

ABSTRACT A numerical analysis and experimental validation of sloshing phenomenon in three-dimensional square tank with varying resonant frequency and amplitude of excitation is carried out in this study. Numerical simulations using fluid-structure interaction (FSI) was carried out and validated with experimental result. Square tank is numerically simulated with 50, 100 and 200 mm of water height excited at its 25%, 50%, 75% and 100% of resonance frequencies. Numerical study has been extended to study sloshing phenomenon at different ratio of resonance frequencies to that of varying amplitudes 30, 40 and 60 mm. Pressure of liquid in container during excitation were recorded at specific intervals of time and analysed. Increase in amplitude and frequency of excitation is directly proportional to pressure of liquid in tank. Sudden impulse of velocity of tank has an impact over the pressure built inside tank. The sloshing phenomenon in vertical and horizontal baffle configuration is also examined.

The Complex Space Weather Events of 2017 September

Abstract Interplanetary coronal mass ejections (ICMEs), magnetic clouds (MCs), sheaths, corotating interaction regions (CIRs), solar wind high-speed streams (HSSs), fast forward shocks (FSs), reverse waves (RWs), stream interfaces, and heliospheric current sheet crossings detected upstream of the Earth and their geoeffectiveness are studied during 2017 September. The most intense geomagnetic storm (SYM-H peak = −146 nT) starting on September 7 had a three-step main phase. A compound interplanetary structure resulting from an FS encountering and compressing the upstream MC southward interplanetary magnetic fields (IMFs) caused the first two steps of the storm. A magnetospheric supersubstorm (SSS; SML peak = −3712 nT) led to the third and most intense step. An MC portion of an ICME created an intense storm (SYM-H peak = −115 nT) on September 8. A second SSS (SML peak = −2642 nT) occurred during the main phase of this storm. Intense geomagnetically induced currents (GICs) occurred during the SSSs. Two moderate magnetic storms with peak SYM-H indices of −65 and −74 nT occurring on September 13 and 27 were caused by sheath and CIR southward IMFs, respectively. Six FSs and their associated sheaths caused sudden impulses (SI+s) of magnitude ranging from +11 to +56 nT. The shocks/sheaths led to magnetospheric relativistic electron flux decreases. The RWs caused SI−s and substorm recoveries by reducing southward IMFs. The high-intensity long-duration continuous AE activities (HILDCAAs) caused by the HSSs were related to the increase/acceleration of relativistic electron fluxes.

Collinear velocity relaxation of two spheres in a viscous incompressible fluid.

Collinear velocity relaxation of two spheres immersed in a viscous incompressible fluid is studied on the basis of an approximate expression for the retarded hydrodynamic interaction. After a sudden impulse applied to one sphere, the other one instantaneously starts to move as well, with amplitude determined by the added mass effect. The velocities of both spheres eventually decay with a t^{-3/2} long-time tail, but the relative velocity decays with a t^{-5/2} long-time tail. The three relaxation functions are approximated by simple expressions involving only a small number of poles in the complex square root of frequency plane.

Unprecedented Hemispheric Asymmetries During a Surprise Ionospheric Storm: A Game of Drivers

AbstractThe geomagnetic storm occurred on 25–26 August 2018 as a surprise to forecasters. The arrival of a weak coronal mass ejection did not show a sudden impulse in the magnetic data; however, when the Interplanetary magnetic field Bz turned southward, it intensified and further remained unchangeably negative for the next 9 hr, causing a major storm with the minimum SYM‐H excursion of −205 nT. In this work, we study the thermospheric, ionospheric, and electrodynamic behavior during this storm. We use a set of space‐borne (the Swarm constellation, GUVI/TIMED) and ground‐based (GPS receivers, magnetometers, SuperDARN) instruments. We particularly focus on storm effects in the American and East Pacific sectors, where unprecedented hemispheric asymmetries occurred in the thermosphere and ionosphere during the main and the recovery phases of the storm. At the beginning of the storm, a strong positive ionospheric storm was observed in the Northern Hemisphere, while in the Southern Hemisphere, surprisingly, no storm effect occurred. During the recovery phase, the thermospheric composition ratio O/N2 showed an extreme expansion of the bulge into the opposite hemisphere. Our analysis shows that in each case the asymmetry was produced by a unique combination of drivers that acted at particular moment of time and in particular place. The seasonal asymmetry in the high‐latitude plasma and neutral mass density distributions along with the asymmetries in the geomagnetic field and the timing of these impacts played the decisive role.

Антропоморфизация японского государства и его эмоциональная жизнь (вторая половина XIXв. – 1945 г.)

Вторая половина XIX в. – 1945 г. время радикальных перемен в японском обществе, эпоха создания общенационального государства и японской империи, основанной на единении всех обитателей Японии. Политические реформы и идеология этого периода достаточно подробно изучены в историографии. Исследований, посвященных тому, как изменились сами японцы и их мировосприятие, гораздо меньше. Статья посвящена изучению эмоциональных трансформаций японцев, произошедших в этот период. Материалом исследования послужили официальные исторические документы, публицистика, поэзия и проза. Изменения оказались настолько быстрыми, что японская психика не выдерживала, в период Мэйдзи резко увеличилось количество душевных заболеваний и самоубийств. Общая экзальтация была характерной чертой эпохи, важнейшие государственные решения принимались под влиянием эмоций. Литература (в особенности новая поэзия синтай) играла важную роль в возбуждении народных чувств, в ней открыто транслировалась ксенофобия. Вера в то, что японский дух сильнее материи, диктовала безумные с военно-практической точки зрения решения. В 1941 г. Япония напала на главную военно-морскую базу США на Тихом океане – Пёрл-Харбор. Решение, которое привело к краху империи.

An Improved Empirical Mode Decomposition Based on Adaptive Weighted Rational Quartic Spline for Rolling Bearing Fault Diagnosis

As a powerful time-frequency signal analysis technique, empirical mode decomposition (EMD) has been commonly applied in fault diagnosis. However, the cubic spline-curve often causes outstanding over and undershoot problem, which significantly limits the performance of conventional EMD. To address this problem, an improved EMD (I-EMD) based on adaptive weighted rational quartic spline is proposed. Firstly, the original cubic spline interpolation in conventional EMD is replaced with the weighted rational quartic spline interpolation (WRQSI) which has two adjustable shape control parameters. Secondly, a novel parameter selection criterion termed envelope characteristic frequency ratio (ECFR) is designed to guide the construction of the optimal local envelope. And simulation analysis proved that ECFR is not only sensitive to the characteristic information but also robust to the weak noise and sudden impulses. Subsequently, the optimal shape control parameter can be searched by grasshopper optimization algorithm (GOA) using the maximum ECFR as the objective function. Then the sensitive modes selected via weighted Kurtosis index are employed for further Hilbert envelope spectrum analysis. Finally, two case studies on rolling bearing fault diagnosis are constructed to verify the rationality and effectiveness of the I-EMD method. The results show that I-EMD method can evidently solve the over and undershoot problem and restrain the mode mixing phenomenon. Moreover, I-EMD also performs better fault feature extraction ability under the same conditions compared with EMD, VMD and CEEMDAN. So it is expected that I-EMD will serve as a potential improvement for signal processing, fault feature extraction and fault diagnosis.

Geoelectric Field Evaluation During the September 2017 Geomagnetic Storm: MA.I.GIC. Model

AbstractThe space environment near Earth is constantly subjected to changes in the solar wind flow generated at the Sun. Examples of this variability are the occurrence of powerful solar disturbances, such as coronal mass ejections (CMEs). The impact of CMEs on the Earth's magnetosphere perturbs the geomagnetic field causing the occurrence of geomagnetic storms. Such extremely variable geomagnetic fields trigger geomagnetic effects measurable not only in the geospace but also in the ionosphere, upper atmosphere, and on the ground. For example, during extreme events, rapidly changing geomagnetic fields generate intense geomagnetically induced currents (GICs). In recent years, GIC impact on the power networks at middle and low latitudes has attracted attention due to the expansion of large‐scale power networks into these regions. This paper presents a new model, called MA.I.GIC. (Magnetosphere‐Ionosphere‐Ground‐Induced Current), to derive the geoelectric field used to determine the magnitude of GICs. In addition, we discuss the results of the MA.I.GIC. model applied to the September 2017 Geomagnetic Storm with particular focus on the two sudden impulses occurring on 6 and 7 September 2017, and the two main phases on 7 and 8 September 2017.

Field-aligned currents (FACs) behaviour during the arrival of interplanetary magnetic shock

In this paper, our study is focused on the FACs behavior during the SC event. SC consists of two events which are storm sudden commencement (SSC) and sudden impulse (SI) event. The difference between these two events is that the interplanetary shock due to SSC leads to geomagnetic storm while during SI event, there is no geomagnetic storm afterward. We performed the statistical analysis between the FACs value and the temporal variation of SYMH index (dSYMH/dt) during SC events from 2008 until 2015. The dSYMH/dt describe the interplanetary shock signature during the SC events. The results showed that the dSYMH/dt during SSC event has a better correlation than the dSYMH/dt during SI events. It suggested that during the SSC onset, there is the magnetic reconnection process between magnetosphere and ionosphere. So, the enhancement of ground magnetic field is contributed by both magnetospheric and ionospheric currents. However, during the SI onset, least connection process happen between magnetosphere and ionosphere thus, the ground magnetic disturbance was mainly associated with the magnetospheric current.

PC index as a proxy of the solar wind energy that entered into the magnetosphere: 4. Relationship between the solar wind dynamic pressure (PSW) impulses and PC, AL indices

The solar wind dynamic pressure (PSW) impulses impacting on the magnetosphere were separated on the basis of solar wind parameters measured in the point of libration L1 in 1998–2017. Comparison of the “estimated” PSW impulses reduced to the Earth's magnetopause with the appropriate sudden impulses (SI), revealed in the ground-based 1-min SymH index, showed that features of the really observed sudden impulses (moment of beginning, time evolution, intensity) can be significantly different from characteristics of the estimated PSW impulses. Because of this the preference was given to the real SI events over the estimated PSW impulses. Only the events with sudden impulses starting against the background of steady quiet pressure levels were taken for the analysis (N = 143). Relationship between the positive (leaps) and negative (drops) SI events, on the one hand, and PC and AL indices, on the other hand, were examined under the various solar wind conditions, such as: growing and steady solar wind speed at negative and positive values of the IMF BZ component, fluctuating BZ and solar wind speed, steady solar wind speed and BZ = 0. Analysis of SI events showed that the solar wind dynamic pressure impulses themselves are not promote (or insignificantly promote) the solar wind energy input into the magnetosphere, which is controlled by the interplanetary electric field EKL = Vsw*(BY2+BZ2)1/2 and is displayed by the polar cap magnetic activity PC index. When the PSW impulses (leaps or drops) are accompanied by the corresponding changes in EKL field, the PC index correlates (increases or decreases) with the PSW changes. Inconsistency between the PSW and PC behavior becomes evident as soon as the EKL and PSW courses start to diverge. Development of magnetic disturbances (AL index) is governed only by the EKL field and PC index increase irrespective of the PSW impulses magnitude and time evolution.

Два типа отклика магнитосферы в геомагнитных пульсациях PSc на взаимодействие с межпланетными ударными волнами

Using the June 22, 2015 event as an example, we present new data confirming the presence of a precursor of the sudden magnetic impulse caused by a powerful interplanetary shock wave (ISW). The precursor in the form of a train of oscillations (broadband pulse) with a falling frequency in the range 0.25÷11 Hz with a duration of ~20 s, which had a spectral resonance structure, was recorded globally by a network of induc-tion magnetometers at 18:33:27 UT. No significant phase delays of the signals were detected in four fre-quency bands at widely spaced observatories. It is sug-gested that the impulse can be excited in the Earth — ionosphere waveguide by a pulsed electric field which occurs in the ionosphere due to the short-term impact of ISW on the magnetosphere.

Magnetospheric response of two types in PSc geomagnetic pulsations to interaction with interplanetary shock waves

Using the June 22, 2015 event as an example, we present new data confirming the presence of a precursor of the sudden magnetic impulse caused by a powerful interplanetary shock wave (ISW). The precursor in the form of a train of oscillations (broadband pulse) with a falling frequency in the range 0.25÷11 Hz with a duration of ~20 s, which had a spectral resonance structure, was recorded globally by a network of induction magnetometers at 18:33:27 UT. No significant phase delays of the signals were detected in four frequency bands at widely spaced observatories. It is suggested that the impulse can be excited in the Earth – ionosphere waveguide by a pulsed electric field which occurs in the ionosphere due to the short-term impact of ISW on the magnetosphere.

How do interplanetary shock impact angles control the size of the geoeffective magnetosphere?

In this paper, we investigate temporal and spatial magnetosphere response to the impact of interplanetary (IP) shocks with different inclinations and speeds on the Earth’s magnetosphere. A data set with more than 500 IP shocks is used to identify positive sudden impulse (SI+) events as expressed by the SuperMAG partial ring current index. The SI+ rise time (RT), defined as the time interval between compression onset and maximum SI+ signature, is obtained for each event. We use RT and a model suggested by Takeuchi et al. (2002) to calculate the geoeffective magnetospheric distance (GMD) in the shock propagation direction as a function of shock impact angle and speed for each event. GMD is a generalization of the geoeffective magnetosphere length (GML) suggested by Takeuchi et al. (2002), defined from the subsolar point along the X line toward the tail. We estimate statistical GMD and GML values which are then reported for the first time. We also show that, similarly to well-known results for RT, the highest correlation coefficient for the GMD and impact angle is found for shocks with high speeds and small impact angles, and the faster and more frontal the shock, the smaller the GMD. This result indicates that the magnetospheric response depends heavily on shock impact angle. With these results, we argue that the prediction and forecasting of space weather events, such as those caused by coronal mass ejections, will not be accurately accomplished if the disturbances’ angles of impact are not considered as an important parameter within model and observation scheme capabilities.