Geospace Environment Modeling 2008–2009 Challenge: Geosynchronous magnetic field

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94577/1/swe422.pd

CalcDeltaB: An efficient postprocessing tool to calculate ground‐level magnetic perturbations from global magnetosphere simulations

Ground magnetic field variations can induce electric currents on long conductor systems such as high‐voltage power transmission systems. The extra electric currents can interfere with normal operation of these conductor systems; and thus, there is a great need for better specification and prediction of the field perturbations. In this publication we present CalcDeltaB, an efficient postprocessing tool to calculate magnetic perturbations Δ B at any position on the ground from snapshots of the current systems that are being produced by first‐principle models of the global magnetosphere‐ionosphere system. This tool was developed during the recent “d B /d t ” modeling challenge at the Community Coordinated Modeling Center that compared magnetic perturbations and their derivative with observational results. The calculation tool is separate from each of the magnetosphere models and ensures that the Δ B computation method is uniformly applied, and that validation studies using Δ B compare the performance of the models rather than the combination of each model and a built‐in Δ B computation tool that may exist. Using the tool, magnetic perturbations on the ground are calculated from currents in the magnetosphere, from field‐aligned currents between magnetosphere and ionosphere, and the Hall and Pedersen currents in the ionosphere. The results of the new postprocessing tool are compared with Δ B calculations within the Space Weather Modeling Framework model and are in excellent agreement. We find that a radial resolution of 1/30 R E is fine enough to represent the contribution to Δ B from the region of field‐aligned currents. Key Points Developed tool to compute magnetic perturbations on the ground Too validated using existing SWMF implementation Model validation independent from Delta‐B calculation within each modelPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/1/Contributions_E4_highlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/2/AuxiliaryMaterial_README_v2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/3/Contributions_E1_highlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/4/Contributions_E2_highlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/5/Contributions_E3_midlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/6/Contributions_E2_midlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/7/Contributions_E1_midlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/8/Contributions_E3_highlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/9/Contributions_E5_midlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/10/Contributions_E4_midlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/11/Contributions_E6_midlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/12/swe20180.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/13/Contributions_E6_highlat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/109314/14/Contributions_E5_highlat.pd

Role of periodic loading‐unloading in the magnetotail versus interplanetary magnetic field B z flipping in the ring current buildup

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94813/1/jgra19183.pd

Community‐wide validation of geospace model ground magnetic field perturbation predictions to support model transition to operations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98787/1/swe20056.pd

Magnetic field topology during July 14–16 2000 (Bastille Day) solar CME event

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95295/1/grl15382.pd

Community‐wide validation of geospace model local K‐index predictions to support model transition to operations

We present the latest result of a community‐wide space weather model validation effort coordinated among the Community Coordinated Modeling Center (CCMC), NOAA Space Weather Prediction Center (SWPC), model developers, and the broader science community. Validation of geospace models is a critical activity for both building confidence in the science results produced by the models and in assessing the suitability of the models for transition to operations. Indeed, a primary motivation of this work is supporting NOAA/SWPC’s effort to select a model or models to be transitioned into operations. Our validation efforts focus on the ability of the models to reproduce a regional index of geomagnetic disturbance, the local K‐index. Our analysis includes six events representing a range of geomagnetic activity conditions and six geomagnetic observatories representing midlatitude and high‐latitude locations. Contingency tables, skill scores, and distribution metrics are used for the quantitative analysis of model performance. We consider model performance on an event‐by‐event basis, aggregated over events, at specific station locations, and separated into high‐latitude and midlatitude domains. A summary of results is presented in this report, and an online tool for detailed analysis is available at the CCMC.Key PointsReport community‐wide model validation resultsEvaluate ability of models to predict a local index of magnetic perturbationAnalysis directly led to selection of models to transition to operations at NOAA/SWPCPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134170/1/swe20333-sup-0001-supplementary.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134170/2/swe20333_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134170/3/swe20333.pd

A model for upper kHz QPO coherence of accreting neutron star

{We investigate the coherence of the twin kilohertz quasi-periodic oscillations (kHz QPOs) in the low-mass X-ray binary (LMXB) theoretically. The profile of upper kHz QPO, interpreted as Keplerian frequency, is ascribed to the radial extent of the kHz QPO emission region, associated with the transitional layer at the magnetosphere-disk boundary, which corresponds to the coherence of upper kHz QPO. The theoretical model for Q-factor of upper kHz QPO is applied to the observational data of five Atoll and five Z sources, and the consistence is implied.Comment: accepted by A&

Morphological analysis on the coherence of kHz QPOs

We take the recently published data of twin kHz quasi-period oscillations (QPOs) in neutron star (NS) lowmass X-ray binaries (LMXBs) as the samples, and investigate the morphology of the samples, which focuses on the quality factor, peak frequency of kHz QPOs, and try to infer their physical mechanism. We notice that: (1) The quality factors of upper kHz QPOs are low (2 ~ 20 in general) and increase with the kHz QPO peak frequencies for both Z and Atoll sources. (2) The distribution of quality factor versus frequency for the lower kHz QPOs are quite different between Z and Atoll sources. For most Z source samples, the quality factors of lower kHz QPOs are low (usually lower than 15) and rise steadily with the peak frequencies except for Sco X-1, which drop abruptly at the frequency of about 750 Hz. While for most Atoll sources, the quality factors of lower kHz QPOs are very high (from 2 to 200) and usually have a rising part, a maximum and an abrupt drop. (3) There are three Atoll sources (4U 1728-34, 4U 1636-53 and 4U 1608-52) of displaying very high quality factors for lower kHz QPOs. These three sources have been detected with the spin frequencies and sidebands, in which the source with higher spin frequency presents higher quality factor of lower kHz QPOs and lower difference between sideband frequency and lower kHz QPO frequency.Comment: 8 pages, 8 figures, publishe

Buildup of the ring current during periodic loading‐unloading cycles in the magnetotail driven by steady southward interplanetary magnetic field

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95239/1/jgra18825.pd