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  • 1
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    Violation of Field Line Conservation and Associated Spatial Scales in Particle-in-Cell Simulations and MMS Data (2018)
    American Geophysical Union
    Details
    Publication Date: 2018-03-13
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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    PAPER CURRENT
  • 2
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    Magnetopause reconnection impact parameters from multiple spacecraft magnetic field measurements (2009)
    American Geophysical Union
    Details
    Publication Date: 2009-10-30
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by American Geophysical Union
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    PAPER CURRENT
  • 3
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    Searching for Turbulent Spectra in Mutliple Spacecraft Observations (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: The subject of magnetohydrodynamic simulations in the 1980's, magnetic turbulence has reemerged as a favored explanation for the production of fast magnetic reconnection. Recent three-dimensional simulations reveal the formation of secondary islands that serve to shorten the current sheet and increase the accelerating electric field, while both simulations and observations witness electron holes whose collapse energizes electrons. However, little work has been done to investigate the presence of turbulent magnetic and electric field spectra in association with in situ reconnection observations in space. In this study we address this deficiency by analyzing the wavelength spectra of two reconnection events established by multiple spacecraft observations in previous publications. We apply a k-filtering analysis to determine the wave vectors. To optimize the quality of the k-filtering analysis and minimize aliasing, we select multi-spacecraft observations having optimal spacecraft tetrahedral geometry and dimensions that resolve wavelengths within the ion diffusion region. We have chosen one dayside and one nightside reconnection event each observed by the Cluster spacecraft. Spatial correlation between the reconnecting current sheet and a turbulent magnetic spectrum supports an association between turbulence and reconnection in space. The k-filtering method, a wavelet time-frequency spectrum, and a polarization analysis serve to identify wave modes associated with the turbulence. A calculation of the reconnection electric field based on the normal component of the reconnecting magnetic field provides an estimate of the reconnection rate.
    Keywords: Astrophysics
    Type: 2010 Meeting of the Americas; Aug 08, 2010 - Aug 13, 2010; Foz do Iguacu; Brazil
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  • 4
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    Multiple Spacecraft Study of the Impact of Turbulence on Reconnection Rates (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Magnetic turbulence and secondary island formation have reemerged as possible explanations for fast reconnection. Recent three-dimensional simulations reveal the formation of secondary islands that serve to shorten the current sheet and increase the accelerating electric field, while both simulations and observations witness electron holes whose collapse energizes electrons. However, few data studies have explicitly investigated the effect of turbulence and islands on the reconnection rate. We present a more comprehensive analysis of the effect of turbulence and islands on reconnection rates observed in space. Our approach takes advantage of multiple spacecraft to find the location of the spacecraft relative to the inflow and the outflow, to estimate the reconnection electric field, to indicate the presence and size of islands, and to determine wave vectors indicating turbulence. A superposed epoch analysis provides independent estimates of spatial scales and a reconnection electric field. We apply k-filtering and a new method adopted from seismological analyses to identify the wavevectors. From several case studies of reconnection events, we obtain preliminary estimates of the spectral scaling law, identify wave modes, and present a method for finding the reconnection electric field associated with the wave modes.
    Keywords: Geophysics
    Type: Geophysical Research Abstracts; 13|European Geosciences Union General Assembly 2011; Jan 01, 2011; United States
    Format: application/pdf
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  • 5
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    Violation of Field Line Conservation and Associated Spatial Scales in Particle-In-Cell Simulations and MMS Data (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: For the first time, space flight technology exists to detect, in situ, violation of magnetic field line conservation. The violation of magnetic line conservation on scales smaller than the system size is a necessary and sufficient condition for finite magnetic field reconnection. We demonstrate that violation of line conservation produces a detectable, structured signature both in particle-in-cell simulations of reconnection and in data from the Magnetospheric Multi-Scale mission. In particle-in-cell simulations of asymmetric reconnection, the quantity-which we call M-that identifies this violation achieves significant values in electron skin depth-scale layers that extend away from the separator, with higher values emerging on the low-density, high-magnetic-field side of the current sheet. At the separator, M owes largely to perpendicular gradients in the parallel electric field, while it attains its highest values away from the separator in dispersed, layered structures associated with gradients in the perpendicular nonideal electric field and electron transport. Sub-ion scale bipolar forms of the quantity also appear further from the separator. In two MMS burst data intervals detecting the electron diffusion region, we find that M exceeds measurement uncertainties both at the separator and near the separatrices. One interval has highly sheared reconnecting fields and the other a stronger guide field. For one event, we determine the location and scale of M and the inner electron diffusion region relative to electron outflows and the magnetic separatrices. The measure can therefore serve as a potent diagnostic for magnetic reconnection in space measurements.
    Keywords: General
    Type: GSFC-E-DAA-TN58342 , Journal of Geophysical Research: Space Physics (ISSN 2169-9402) (e-ISSN 2169-9402); 123; 3; 1853-1884
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  • 6
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    Magnetopause Reconnection Impact Parameters from Multiple Spacecraft Magnetic Field Measurements (2009)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: We present a novel technique that exploits multiple spacecraft data to determine the impact parameters of the most general form of magnetic reconnection at the magnetopause. The method consists of a superposed epoch of multiple spacecraft magnetometer measurements that yields the instantaneous magnetic spatial gradients near a magnetopause reconnection site. The gradients establish the instantaneous positions of the spacecraft relative to the reconnection site. The analysis is well suited to evaluating the spatial scales of singular field line reconnection, which is characterized by a two-dimensional x-type topology adjacent and perpendicular to a reconnecting singular field line. Application of the method to Cluster data known to lie in the vicinity of a northward IMF reconnection site establishes a field topology consistent with singular field line reconnection and a normal magnetic field component of 20 nT. The corresponding current structure consists of a 130 km sheet possibly embedding a thinner. bifurcated sheet.
    Keywords: Geophysics
    Format: text
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  • 7
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    Mission Oriented Support and Theory (MOST) for MMS -- The Goddard Space Flight Center/University of California Los Angeles Interdisciplinary Science Program (2015)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The MOST IDS team was tasked with focusing on two general areas: The first was to participate with the Fast Plasma Investigation (FPI) team in the development of virtual detectors that model the instrument responses of the MMS FPI sensors. The virtual instruments can be 'flown through' both simulation data (from magnetohydrodynamic, hybrid, and kinetic simulations) and Cluster and THEMIS spacecraft data. The goal is to determine signatures of magnetic reconnection expected during the MMS mission. Such signatures can serve as triggers for selection of burst mode downloads. The chapter contributed by the FPI team covers that effort in detail and, therefore, most of that work has not been included here. The second area of emphasis, and the one detailed in this chapter, was to build on past and present knowledge of magnetic reconnection and its physical signatures. Below we describe intensive analyses of Cluster and THEMIS data together with theoretical models and simulations that delineate the plasma signatures that surround sites of reconnection, including the effects of turbulence as well as the detailed kinetic signatures that indicate proximity to reconnection sites. In particular, we point out that particles are energized in several regions, not only at the actual site of reconnection.
    Keywords: Geophysics; Computer Programming and Software
    Type: GSFC-E-DAA-TN41233 , Space Science Reviews (ISSN 0038-6308) (e-ISSN 1572-9672); 199; 1; 689-719
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  • 8
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    Turbulent Reconnection Rates from Cluster Observations in the Magnetosheath (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: The role of turbulence in producing fast reconnection rates is an important unresolved question. Scant in situ analyses exist. We apply multiple spacecraft techniques to a case of nonlinear turbulent reconnection in the magnetosheath to test various theoretical results for turbulent reconnection rates. To date, in situ estimates of the contribution of turbulence to reconnection rates have been calculated from an effective electric field derived through linear wave theory. However, estimates of reconnection rates based on fully nonlinear turbulence theories and simulations exist that are amenable to multiple spacecraft analyses. Here we present the linear and nonlinear theories and apply some of the nonlinear rates to Cluster observations of reconnecting, turbulent current sheets in the magnetosheath. We compare the results to the net reconnection rate found from the inflow speed. Ultimately, we intend to test and compare linear and nonlinear estimates of the turbulent contribution to reconnection rates and to measure the relative contributions of turbulence and the Hall effect.
    Keywords: Geophysics
    Type: GSFC.ABS.5498.2011 , GSFC.ABS.5393.2011 , GSFC.ABS.5709.2011 , Arcetri 2011 Workshop on Plasma Astrophysics; Oct 17, 2011 - Oct 21, 2011; Florence; Italy|American Geophysical Union 2011 Fall Meeting (AGU2011); Dec 05, 2011 - Dec 10, 2011; San Francisco, CA; United States
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  • 9
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    Turbulent Reconnection Rates from Cluster Observations in the Magneto sheath (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: The role of turbulence in producing fast reconnection rates is an important unresolved question. Scant in situ analyses exist. We apply multiple spacecraft techniques to a case of nonlinear turbulent reconnection in the magnetosheath to test various theoretical results for turbulent reconnection rates. To date, in situ estimates of the contribution of turbulence to reconnection rates have been calculated from an effective electric field derived through linear wave theory. However, estimates of reconnection rates based on fully nonlinear turbulence theories and simulations exist that are amenable to multiple spacecraft analyses. Here we present the linear and nonlinear theories and apply some of the nonlinear rates to Cluster observations of reconnecting, turbulent current sheets in the magnetos heath. We compare the results to the net reconnection rate found from the inflow speed. Ultimately, we intend to test and compare linear and nonlinear estimates of the turbulent contribution to reconnection rates and to measure the relative contributions of turbulence and the Hall effect.
    Keywords: Geosciences (General)
    Type: GSFC.ABS.4739.2011 , Joint CEDAR/GEM (Coupling, Energetics and Dynamics of Atmospheric Regions - Geospace Environment Modeling) 2011 Summer Workshop; Jun 26, 2011 - Jul 01, 2011; Santa Fe, NM; United States
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  • 10
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    Impact of Magnetic Draping, Convection, and Field Line Tying on Magnetopause Reconnection Under Northward IMF (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: We simulate a northward IMF cusp reconnection event at the magnetopause using the OpenGGCM resistive MHD code. The ACE input data, solar wind parameters, and dipole tilt belong to a 2002 reconnection event observed by IMAGE and Cluster. Based on a fully three-dimensional skeleton separators, nulls, and parallel electric fields, we show magnetic draping, convection, ionospheric field line tying play a role in producing a series of locally reconnecting nulls with flux ropes. The flux ropes in the cusp along the global separator line of symmetry. In 2D projection, the flux ropes the appearance of a tearing mode with a series of 'x's' and 'o's' but bearing a kind of 'guide field' that exists only within the magnetopause. The reconnecting field lines in the string of ropes involve IMF and both open and closed Earth magnetic field lines. The observed magnetic geometry reproduces the findings of a superposed epoch impact parameter study derived from the Cluster magnetometer data for the same event. The observed geometry has repercussions for spacecraft observations of cusp reconnection and for the imposed boundary conditions reconnection simulations.
    Keywords: Solar Physics
    Type: 2010 Meeting of the Americas/American Geophysical Union; Aug 08, 2010 - Aug 13, 2010; Foz do Iguacu; Brazil|13176-10-ST Yosemite 2010 Interdisciplinary Workshop; Feb 07, 2010 - Feb 14, 2010; San Francisco, CA; United States
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