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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
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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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
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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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
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  • 6
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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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    NASA TECHNICAL REPORTS
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