Browsing by Author "Hartinger, Michael D."
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- The Atmospheric-Ionospheric-Magnetospheric Responses to the 2015 St. Patrick's Day Geomagnetic Storm at High LatitudesXu, Z.; Clauer, C. Robert; Chu, Xinzhao; Hartinger, Michael D.; Zhao, Jian (2016-12-15)The atmospheric-ionospheric-magnetospheric (AIM) system response to extreme solar wind conditions depends on the solar wind driving conditions, ionospheric configurations, and neutral atmospheric transportation. The 17 March 2015 geomagnetic storms driven by coronal mass ejections (CME) provide an opportunity to investigate how the global AIM response depends on the solar wind inputs. In this study, multiple instruments, including lidars, magnetometers, HF radars, satellites, and others, are combined to provide global, coordinated coverage in the AIM system. First, we examined the ionospheric responses at high latitude regions in both the northern and southern hemispheres, by using the conjugate West Greenland and Antarctic magnetometer chains to remotely sense several current systems. There were dramatic differences between the intensity, duration, and spatial structure of the current systems between hemispheres. Then, we examined the neutral atmospheric response and its connection with the MI systems in the high latitude regions with the Fe Boltzmann Lidar observations at the McMurdo station in Antarctica. The neutral Fe layer observed by Lidar from abnormally high altitudes (nearly 160km) is enhanced during the storm. It should be associated with not only the neutral atmospheric factors but also MI factors such as Joule heating and ionospheric electromagnetic drifting. These multiple instrument observations present an overall picture and help understand the AIM coupling mechanisms better.
- Characteristics and Sources of Intense Geoelectric Fields in the United States: Comparative Analysis of Multiple Geomagnetic StormsShi, Xueling; Hartinger, Michael D.; Baker, Joseph B. H.; Murphy, Benjamin S.; Bedrosian, Paul A.; Kelbert, Anna; Rigler, Erin Joshua (American Geophysical Union, 2022-04)Intense geoelectric fields during geomagnetic storms drive geomagnetically induced currents in power grids and other infrastructure, yet there are limited direct measurements of these storm-time geoelectric fields. Moreover, most previous studies examining storm-time geoelectric fields focused on single events or small geographic regions, making it difficult to determine the typical source(s) of intense geoelectric fields. We perform the first comparative analysis of (a) the sources of intense geoelectric fields over multiple geomagnetic storms, (b) using 1-s cadence geoelectric field measurements made at (c) magnetotelluric survey sites distributed widely across the United States. Temporally localized intense perturbations in measured geoelectric fields with prominences (a measure of the relative amplitude of geoelectric field enhancement above the surrounding signal) of at least 500 mV/km were detected during geomagnetic storms with Dst minima (Dst(min)) of less than -100 nT from 2006 to 2019. Most of the intense geoelectric fields were observed in resistive regions with magnetic latitudes greater than 55 degrees even though we have 167 sites located at lower latitudes during geomagnetic storms of -200 nT <= Dst(min) < -100 nT. Our study indicates intense short-lived (<1 min) and geoelectric field perturbations with periods on the order of 1-2 min are common. Most of these perturbations cannot be resolved with 1-min data because they correspond to higher frequency or impulsive phenomena that vary on timescales shorter than that sampling interval. The sources of geomagnetic perturbations inducing these intense geoelectric fields include interplanetary shocks, interplanetary magnetic field turnings, substorms, and ultralow frequency waves.
- Characterization of multi-scale ionospheric irregularities using ground-based and space-based GNSS observationsPeng, YuXiang; Scales, Wayne A.; Hartinger, Michael D.; Xu, Zhonghua; Coyle, Shane (2021-07-12)Ionospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). However, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregularities for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observation technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.
- Conjugate observations of electromagnetic ion cyclotron waves associated with traveling convection vortex eventsKim, Hyomin; Clauer, C. Robert; Gerrard, Andrew J.; Engebretson, Mark J.; Hartinger, Michael D.; Lessard, Marc R.; Matzka, Juergen; Sibeck, David G.; Singer, Howard J.; Stolle, Claudia; Weimer, Daniel R.; Xu, Zhonghua (2017-07)We report on simultaneous observations of electromagnetic ion cyclotron (EMIC) waves associated with traveling convection vortex (TCV) events caused by transient solar wind dynamic pressure (P-d) impulse events. The Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft located near the magnetopause observed radial fluctuations of the magnetopause, and the GOES spacecraft measured sudden compressions of the magnetosphere in response to sudden increases in Pd. During the transient events, EMIC waves were observed by interhemispheric conjugate ground-based magnetometer arrays as well as the GOES spacecraft. The spectral structures of the waves appear to be well correlated with the fluctuating motion of the magnetopause, showing compression-associated wave generation. In addition, the wave features are remarkably similar in conjugate hemispheres in terms of bandwidth, quasiperiodic wave power modulation, and polarization. Proton precipitation was also observed by the DMSP spacecraft during the wave events, from which the wave source region is estimated to be 72 degrees-74 degrees in magnetic latitude, consistent with the TCV center. The confluence of space-borne and ground instruments including the interhemispheric, high-latitude, fluxgate/induction coil magnetometer array allows us to constrain the EMIC source region while also confirming the relationship between EMIC waves and the TCV current system.
- Dayside Magnetospheric and Ionospheric Responses to a Foreshock Transient on 25 June 2008: 1. FLR Observed by Satellite and Ground-Based MagnetometersShen, Xiao-Chen; Shi, Quanqi; Wang, Boyi; Zhang, Hui; Hudson, Mary K.; Nishimura, Yukitoshi; Hartinger, Michael D.; Tian, Anmin; Zong, Qiu-Gang; Rae, I. J.; Degeling, Alexander W. (2018-08)As one type of driver of magnetospheric Alfven waves, foreshock transients have received less attention than, for example, the Kelvin-Helmholtz instability, discrete and broadband frequency solar wind dynamic pressure oscillations, and interplanetary shocks. Previous works show that foreshock transients can induce both Alfven mode and compressional mode Pc 3-5 ULF waves inside the magnetosphere. However, to our knowledge, none of these reported Pc 3-5 waves, induced by foreshock transients, are proved to be localized in the magnetosphere. In this paper, using in situ and ground-based observations, we report the generation of localized magnetospheric compressional waves and field line resonances (FLRs) by a foreshock transient. Both the foreshock transient and Pc 5 ULF waves were found on the duskside; while on the morning side of the magnetosphere, no clear wave signatures were captured. Our results demonstrate that in addition to the global effects of foreshock transients on the magnetosphere reported earlier, foreshock transients can also generate localized magnetospheric responses in the Pc 5 range with clear dawn-dusk asymmetry. A suite of eight dayside spacecraft plus ground magnetometer measurements make possible the determination of the foreshock transient driver and dawn-dusk asymmetry of the magnetospheric response not previously reported with such a complete data set.
- Direct observations of a surface eigenmode of the dayside magnetopauseArcher, M.O.; Hietala, H.; Hartinger, Michael D.; Plaschke, F.; Angelopoulos, Vassilis (Nature Publishing Group, 2019-02-12)The abrupt boundary between a magnetosphere and the surrounding plasma, the magnetopause, has long been known to support surface waves. It was proposed that impulses acting on the boundary might lead to a trapping of these waves on the dayside by the ionosphere, resulting in a standing wave or eigenmode of the magnetopause surface. No direct observational evidence of this has been found to date and searches for indirect evidence have proved inconclusive, leading to speculation that this mechanism might not occur. By using fortuitous multipoint spacecraft observations during a rare isolated fast plasma jet impinging on the boundary, here we show that the resulting magnetopause motion and magnetospheric ultra-low frequency waves at well-defined frequencies are in agreement with and can only be explained by the magnetopause surface eigenmode. We therefore show through direct observations that this mechanism, which should impact upon the magnetospheric system globally, does in fact occur. © 2019, The Author(s).
- Effect of Interplanetary Shock Impact Angle on the Occurrence Rate and Properties of Pc5 Waves Observed by High-Latitude Ground MagnetometersBaker, Andrew Ballard (Virginia Tech, 2019-06-21)The effects of interplanetary shock impact angles have the potential to have far reaching consequences. By their nature, interplanetary shocks are a direct consequence of a variety of solar events including both Coronal Mass Ejections (CMEs) and Co-rotating Interaction Regions (CIRs). They have the ability to move the magnetopause, the boundary between the Earth's magnetosphere and the surrounding plasma, leading to ionospheric current systems and an enhanced ring current. Their association with a time-varying EMF also makes them potentially dangerous at a human level. This EMF can couple to electrical currents in technological infrastructure that can overload transformers, communication cables, and power grids. As IP shocks have the potential to have a large impact on our society, research to further our understanding of these events is prudent. We know that shocks can couple to currents and ULF waves in the magnetosphere-ionosphere system. Much of the current research into their behaviors has been focused on models and simulations and has indicated that the shock impact angle should affect the properties of the waves. To investigate the potential influence of the impact angle, data from a series of Antarctic magnetometers was collected and compared to a database of known interplanetary shocks to determine when the response to different shocks was detected at the magnetometer. For this investigation, we were concerned with determining what impact if any, the impact angle of the IP shock had on the generation of Pc5 waves. To that end, the power spectra both before and after the shock was calculated. This information was then combined with the shock impact angle to determine what effects if any, the shock impact angle had on Pc5 wave occurrence rates. From our research, it was determined that the impact angle of the interplanetary shock had a significant impact on the occurrence rate and properties of Pc5 waves observed by high-latitude ground magnetometers.
- Geomagnetic Disturbances That Cause GICs: Investigating Their Interhemispheric Conjugacy and Control by IMF OrientationEngebretson, Mark J.; Simms, Laura E.; Pilipenko, Viacheslav A.; Bouayed, Lilia; Moldwin, Mark B.; Weygand, James M.; Hartinger, Michael D.; Xu, Zhonghua; Clauer, C. Robert; Coyle, Shane; Willer, Anna N.; Freeman, Mervyn P.; Gerrard, Andy J. (American Geophysical Union, 2022-10-01)Nearly all studies of impulsive geomagnetic disturbances (GMDs, also known as magnetic perturbation events MPEs) that can produce dangerous geomagnetically induced currents (GICs) have used data from the northern hemisphere. In this study, we investigated GMD occurrences during the first 6 months of 2016 at four magnetically conjugate high latitude station pairs using data from the Greenland West Coast magnetometer chain and from Antarctic stations in the conjugate AAL-PIP magnetometer chain. Events for statistical analysis and four case studies were selected from Greenland/AAL-PIP data by detecting the presence of >6 nT/s derivatives of any component of the magnetic field at any of the station pairs. For case studies, these chains were supplemented by data from the BAS-LPM chain in Antarctica as well as Pangnirtung and South Pole in order to extend longitudinal coverage to the west. Amplitude comparisons between hemispheres showed (a) a seasonal dependence (larger in the winter hemisphere), and (b) a dependence on the sign of the By component of the interplanetary magnetic field (IMF): GMDs were larger in the north (south) when IMF By was >0 (<0). A majority of events occurred nearly simultaneously (to within ±3 min) independent of the sign of By as long as |By| ≤ 2 |Bz|. As has been found in earlier studies, IMF Bz was <0 prior to most events. When IMF data from Geotail, Themis B, and/or Themis C in the near-Earth solar wind were used to supplement the time-shifted OMNI IMF data, the consistency of these IMF orientations was improved.
- The impact and resolution of the GPS week number rollover of April 2019 on autonomous geophysical instrument platformsCoyle, Shane; Clauer, C. Robert; Hartinger, Michael D.; Xu, Zhonghua; Peng, Yuxiang (2021-07-28)Instrument platforms the world over often rely on GPS or similar satellite constellations for accurate timekeeping and synchronization. This reliance can create problems when the timekeeping counter aboard a satellite overflows and begins a new epoch. Due to the rarity of these events (19.6 years for GPS), software designers may be unaware of such circumstance or may choose to ignore it for development complexity considerations. Although it is impossible to predict every fault that may occur in a complicated system, there are a few "best practices" that can allow for graceful fault recovery and restorative action. These guiding principles are especially pertinent for instrument platforms operating in space or in remote locations like Antarctica, where restorative maintenance is both difficult and expensive. In this work, we describe how these principles apply to a communications failure on autonomous adaptive low-power instrument platforms (AAL-PIP) deployed in Antarctica. In particular, we describe how code execution patterns were subtly altered after the GPS week number rollover of April 2019, how this led to Iridium satellite communications and data collection failures, and how communications and data collection were ultimately restored. Finally, we offer some core tenets of instrument platform design as guidance for future development.
- Impact Angle Control of Local Intense dB/dt Variations During Shock-Induced SubstormsOliveira, Denny M.; Weygand, James M.; Zesta, Eftyhia; Ngwira, Chigomezyo M.; Hartinger, Michael D.; Xu, Zhonghua; Giles, Barbara L.; Gershman, Daniel J.; Silveira, Marcos V. D.; Souza, Vítor M. (American Geophysical Union, 2021-12-01)The impact of interplanetary shocks on the magnetosphere can trigger magnetic substorms that intensify auroral electrojet currents. These currents enhance ground magnetic field perturbations (dB/dt), which in turn generate geomagnetically induced currents (GICs) that can be detrimental to power transmission infrastructure. We perform a comparative study of dB/dt variations in response to two similarly strong shocks, but with one being nearly frontal and the other highly inclined. Multi-instrument analyses by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Los Alamos National Laboratory spacecraft show that nightside substorm-time energetic particle injections are more intense and occur faster in the case of the nearly head-on impact. The same trend is observed in dB/dt variations recorded by THEMIS ground magnetometers. THEMIS all-sky imager data show a fast and clear poleward auroral expansion in the first case, which does not clearly occur in the second case. Strong field-aligned currents computed with the spherical elementary current system (SECS) technique occur in both cases, but the current variations resulting from the inclined shock impact are weaker and slower compared to the nearly frontal case. SECS analyses also reveal that geographic areas with dB/dt surpassing the thresholds 1.5 and 5 nT/s, usually linked to high-risk GICs, are larger and occur earlier due to the symmetric compression caused by the nearly head-on impact. These results, with profound space weather implications, suggest that shock impact angles affect the geospace driving conditions and the location and intensity of the subsequent dB/dt variations during substorm activity.
- Interhemispheric Asymmetries in the Ground Magnetic Response to Interplanetary Shocks: The Role of Shock Impact AngleXu, Z.; Hartinger, Michael D.; Oliveira, Denny M.; Coyle, Shane; Clauer, C. Robert; Weimer, Daniel R.; Edwards, T. R. (2020-03)Interplanetary (IP) shocks drive magnetosphere-ionosphere (MI) current systems that in turn are associated with ground magnetic perturbations. Recent work has shown that IP shock impact angle plays a significant role in controlling the subsequent geomagnetic activity and magnetic perturbations; for example, highly inclined shocks drive asymmetric MI responses due to interhemispherical asymmetric magnetospheric compressions, while almost head-on shocks drive more symmetric MI responses. However, there are few observations confirming that inclined shocks drive such asymmetries in the high-latitude ground magnetic response. We use data from a chain of Antarctic magnetometers, combined with magnetically conjugate stations on the west coast of Greenland, to test these model predictions (Oliveira & Raeder, 2015, https://doi.org/10.1002/2015JA021147; Oliveira, 2017, https://doi.org/10.1007/s13538-016-0472-x). We calculate the time derivative of the magnetic field (partial derivative B/partial derivative t) in each hemisphere separately. Next, we examine the ratio of Northern to Southern Hemisphere partial derivative B/partial derivative t intensities and the time differences between the maximum. partial derivative B/partial derivative t immediately following the impact of IP shocks. We order these results according to shock impact angles obtained from a recently published database with over 500 events and discuss how shock impact angles affect north-south hemisphere asymmetries in the ground magnetic response. We find that the hemisphere the shock strikes first usually has (1) the first response in partial derivative B/partial derivative t and (2) the most intense response in partial derivative B/partial derivative t. Additionally, we show that highly inclined shocks can generate high-latitude ground magnetic responses that differ significantly from predictions based on models that assume symmetric driving conditions.
- Listening to the Magnetosphere: How Best to Make ULF Waves AudibleArcher, Martin O.; Cottingham, Marek; Hartinger, Michael D.; Shi, Xueling; Coyle, Shane; Hill, Ethan ''Duke''; Fox, Michael F. J.; Masongsong, Emmanuel V. (Frontiers, 2022-06-08)Observations across the heliosphere typically rely on in situ spacecraft observations producing time-series data. While often this data is analysed visually, it lends itself more naturally to our sense of sound. The simplest method of converting oscillatory data into audible sound is audification-a one-to-one mapping of data samples to audio samples-which has the benefit that no information is lost, thus is a true representation of the original data. However, audification can make some magnetospheric ULF waves observations pass by too quickly for someone to realistically be able to listen to effectively. For this reason, we detail various existing audio time scale modification techniques developed for music, applying these to ULF wave observations by spacecraft and exploring how they affect the properties of the resulting audio. Through a public dialogue we arrive at recommendations for ULF wave researchers on rendering these waves audible and discuss the scientific and educational possibilities of these new methods.
- Modeling geomagnetic induction in submarine cablesChakraborty, Shibaji; Boteler, David H.; Shi, Xueling; Murphy, Benjamin S.; Hartinger, Michael D.; Wang, Xuan; Lucas, Greg; Baker, Joseph B. H. (Frontiers, 2022-10)Submarine cables have become a vital component of modern infrastructure, but past submarine cable natural hazard studies have mostly focused on potential cable damage from landslides and tsunamis. A handful of studies examine the possibility of space weather effects in submarine cables. The main purpose of this study is to develop a computational model, using Python, of geomagnetic induction on submarine cables. The model is used to estimate the induced voltage in the submarine cables in response to geomagnetic disturbances. It also utilizes newly acquired knowledge from magnetotelluric studies and associated investigations of geomagnetically induced currents in power systems. We describe the Python-based software, its working principle, inputs/outputs based on synthetic geomagnetic field data, and compare its operational capabilities against analytical solutions. We present the results for different model inputs, and find: 1) the seawater layer acts as a shield in the induction process: the greater the ocean depth, the smaller the seafloor geoelectric field; and 2) the model is sensitive to the Ocean-Earth layered conductivity structure.
- Simultaneous Observations of Geoelectric and Geomagnetic Fields Produced by Magnetospheric ULF WavesHartinger, Michael D.; Shi, X.; Lucas, G. M.; Murphy, B. S.; Kelbert, A.; Baker, Joseph B. H.; Rigler, E. J.; Bedrosian, P. A. (2020-09-28)Geomagnetic perturbations (B-GEO) related to magnetospheric ultralow frequency (ULF) waves induce electric fields within the conductive Earth-geoelectric fields (E-GEO)-that in turn drive geomagnetically induced currents. Though numerous past studies have examined ULF waveB(GEO)from a space weather perspective, few studies have linked ULF waves withE(GEO). Using recently available magnetotelluric impedance andE(GEO)measurements in the contiguous United States, we explore the relationship between ULF waves andE(GEO). We use satellite, ground-based radar,B-GEO, andE(GEO)measurements in a case study of a plasmaspheric virtual resonance (PVR), demonstrating that the PVRE(GEO)has significant spatial variation in contrast to a relatively uniformB(GEO), consistent with spatially varying Earth conductivity. We further show ULF waveE(GEO)measurements during two moderate storms of similar to 1 V/km. We use both results to highlight the need for more research characterizing ULF waveE(GEO).
- ULF Wave Modeling, Effects, and Applications: Accomplishments, Recent Advances, and FutureHartinger, Michael D.; Takahashi, Kazue; Drozdov, Alexander Y.; Shi, Xueling; Usanova, Maria E.; Kress, Brian (Frontiers, 2022-04-14)Ultra Low Frequency (ULF) waves play important roles in magnetosphere-ionosphere coupling, ring current and radiation belt dynamics, and modulation of higher frequency wave modes and energetic particle precipitation. The "ULF wave modeling, effects, and applications" (UMEA) focus group - part of the Geospace Environment Modeling effort from 2016 to 2021 - sought to improve understanding of the physics of ULF waves and their specification in geospace models. Through a series of in person and virtual meetings the UMEA focus group brought modelers and experimentalists together to compare ULF wave outputs in different models, plan observation campaigns focused on ULF waves, discuss recent advances in ULF wave research, and identify unresolved ULF wave science questions. This article summarizes major discussion points and accomplishments in the UMEA focus group over the last 6 years, recent advances and their connection to Richard Thorne and Peter Gary's significant contributions to ULF wave research, and the future of ULF wave research.