Browsing by Author "Murphy, Benjamin S."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- 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.
- 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.