176 results found
Eastwood JP, Brain DA, Halekas JS, et al., 2008, Evidence for collisionless magnetic reconnection at Mars, GEOPHYSICAL RESEARCH LETTERS, Vol: 35, ISSN: 0094-8276
Dunlop MW, Eastwood JP, 2008, The curlometer and other gradient based methods, Multi-spacecraft Analysis Methods Revisited, Editors: Paschmann, Daly, Noordwijk, The Netherlands, Publisher: ESA Communications, Pages: 17-25
Phan TD, Drake JF, Shay MA, et al., 2007, Evidence for an elongated (> 60 ion skin depths) electron diffusion region during fast magnetic reconnection, PHYSICAL REVIEW LETTERS, Vol: 99, ISSN: 0031-9007
Eastwood JP, Bale SD, Mozer FS, et al., 2007, Contributions to the cross shock electric field at a quasiperpendicular collisionless shock, GEOPHYSICAL RESEARCH LETTERS, Vol: 34, ISSN: 0094-8276
Phan TD, Paschmann G, Twitty C, et al., 2007, Evidence for magnetic reconnection initiated in the magnetosheath, GEOPHYSICAL RESEARCH LETTERS, Vol: 34, ISSN: 0094-8276
Eastwood JP, Phan T-D, Mozer FS, et al., 2007, Multi-point observations of the Hall electromagnetic field and secondary island formation during magnetic reconnection, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 112, ISSN: 2169-9380
Kucharek H, Moebius E, Scholer M, et al., 2006, On the ion reflection properties of the quasi-perpendicular earth's bow shock, European Space Agency, (Special Publication) ESA SP, Pages: 299-304, ISSN: 0379-6566
Recent multiple spacecraft observations by Cluster revealed that field-aligned ion beams appear to emerge from the gyrating ions in the ramp of a quasiperpendicular shock created by the same reflection process. A closer look at recent findings show that effective scattering in pitch angle within the shock ramp during the reflection may also be needed to produce these beams at higher shock normal angles. Obviously, ion reflection, transmission and wave particle scattering depend on shock parameters, such as Mach number, plasma beta and shock angle. However, how important are these parameters relative to each other for these processes? Furthermore, the internal dynamics, structure of the shock and the cross-shock potential may also be important. A better understanding would provide very useful information about the ion reflection and transmission process at perpendicular shocks in general for other disciplines such as astrophysics. A survey of shock crossings for a wide range of plasma conditions such as shock normal angle, Mach number, and plasma beta has been compiled and investigated in detail in order to determine the major controlling parameters. In this database we included information about the cross shock potential and magnetic field profile at the shock, as well as the global dynamics of the shock. We will report on dependence of variability of different ion distributions such as the gyration and escaping ions on these various parameters.
Eastwood JP, Sibeck DG, Slavin JA, et al., 2006, Observations of flux ropes and X-lines in the near earth magnetotail, European Space Agency, (Special Publication) ESA SP, Pages: 59-66, ISSN: 0379-6566
Magnetic reconnection in the Earth's magnetotail plays a key role in controlling the dynamics of the Earth's magnetosphere. Recent results based on Cluster multi-spacecraft analysis have raised important questions about the traditional interpretation of reconnection-associated phenomena observed by single spacecraft. Cluster has shown that observations conventionally interpreted as a single X-line can correspond to multiple X-line structure . Single point observations cannot distinguish between these two possibilities, and previous interpretations have invoked the simpler picture. This case study is put into a wider context by examining the plasma dynamics following this particular event. Within this picture, one can make the hypothesis that further loop-like structures - small flux ropes - ought to be observed in conjunction with this event. We present such evidence here, and in particular use the curlometer technique to analyse the observations.
Eastwood JP, Balogh A, Lucek EA, et al., 2005, Quasi-monochromatic ULF foreshock waves as observed by the four-spacecraft Cluster mission: 1. Statistical properties, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 110, ISSN: 0148-0227
Eastwood JP, Balogh A, Lucek EA, et al., 2005, Quasi-monochromatic ULF foreshock waves as observed by the four-spacecraft Cluster mission: 2. Oblique propagation, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 110, ISSN: 2169-9380
Tanskanen EI, Slavin JA, Tanskanen AJ, et al., 2005, Magnetospheric substorms are strongly modulated by interplanetary high-speed streams, GEOPHYSICAL RESEARCH LETTERS, Vol: 32, ISSN: 0094-8276
Eastwood JP, Sibeck DG, Slavin JA, et al., 2005, Observations of multiple X-line structure in the Earth's magnetotail current sheet: A Cluster case study, GEOPHYSICAL RESEARCH LETTERS, Vol: 32, ISSN: 0094-8276
Zheng Y, Le G, Slavin JA, et al., 2005, Cluster observation of continuous reconnection at dayside magnetopause in the vicinity of cusp, ANNALES GEOPHYSICAE, Vol: 23, Pages: 2199-2215, ISSN: 0992-7689
Eastwood JP, Balogh A, Mazelle C, et al., 2004, Oblique propagation of 30 s period fast magnetosonic foreshock waves: A Cluster case study, GEOPHYSICAL RESEARCH LETTERS, Vol: 31, ISSN: 0094-8276
Meziane K, Mazelle C, Wilber M, et al., 2004, Bow shock specularly reflected ions in the presence of low-frequency electromagnetic waves: a case study, Annales Geophysicae, Vol: 22, Pages: 2325-2335
An energetic ion (E less than or equal to40 keV) event observed by the CLUSTER/CIS experiment upstream of the Earth's bow shock is studied in detail. The ion event is observed in association with quasi-monochromatic ULF MHD-like waves, which we show modulate the ion fluxes. According to three statistical bow shock position models, the Cluster spacecrafts are located at similar to0.5 R-E from the shock and the averaged bow shock theta(Bno) is about similar to30degrees. The analysis of the three-dimensional angular distribution indicates that ions propagating roughly along the magnetic field direction are observed at the onset of the event. Later on, the angular distribution is gyrophase-bunched and the pitch-angle distribution is peaked at alpha(o)similar totheta(Bno), consistent with the specular reflection production mechanism. The analysis of the waves shows that they are left-handed in the spacecraft frame of reference (right-handed in the solar wind frame) and propagate roughly along the ambient magnetic field; we have found that they are in cyclotron-resonance with the field-aligned beam observed just upstream. Using properties of the waves and particles, we explain the observed particle flux-modulation in the context Of theta(Bn) changes at the shock caused by the convected ULF waves. We have found that the high count rates coincide with particles leaving the shock when theta(Bn) angles are less than similar to40degrees, consistent with the specular reflection hypothesis as the production mechanism of ions.
Eastwood JP, 2003, The terrestrial foreshock as observed by the multi-spacecraft Cluster mission
Mazelle C, Meziane K, LeQueau D, et al., 2003, Production of gyrating ions from nonlinear wave-particle interaction upstream from the Earth's bow shock: A case study from Cluster-CIS, PLANETARY AND SPACE SCIENCE, Vol: 51, Pages: 785-795, ISSN: 0032-0633
Eastwood JP, Balogh A, Lucek EA, et al., 2003, On the existence of Alfven waves in the terrestrial foreshock, ANNALES GEOPHYSICAE, Vol: 21, Pages: 1457-1465, ISSN: 0992-7689
Eastwood JP, Balogh A, Dunlop MW, et al., 2002, Cluster observations of fast magnetosonic waves in the terrestrial foreshock, GEOPHYSICAL RESEARCH LETTERS, Vol: 29, ISSN: 0094-8276
Eastwood JP, Balogh A, Dunlop MW, et al., 2002, Cluster observations of the heliospheric current sheet and an associated magnetic flux rope and comparisons with ACE, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 107, ISSN: 0148-0227
Horbury TS, Cargill PJ, Lucek EA, et al., 2002, Four spacecraft measurements of the quasiperpendicular terrestrial bow shock: Orientation and motion, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 107, ISSN: 0148-0227
Eggington J, Coxon J, Shore R, et al., Timescales of Ionospheric Field-Aligned Currents during a Geomagnetic Storm: Global Magnetospheric Simulations
<jats:p> &lt;p&gt;Geomagnetic storms generate a complex and highly time-dependent response in the magnetosphere-ionosphere system. Enhancement in field-aligned currents (FACs) can be very localised, and so accurately predicting the stormtime response of the ionosphere is crucial in forecasting the potential impacts of a severe space weather event at a given location on the Earth. Global MHD simulations provide a means to model ionospheric conditions in real-time for a given geomagnetic storm, allowing direct comparison to space- and ground-based observations from which the observations can be placed in global context to better understand the physical drivers behind the system's response.&amp;#160;&amp;#160; &amp;#160; &amp;#160; &amp;#160; &amp;#160; &amp;#160; &amp;#160; &amp;#160; &amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;Using the Gorgon MHD code and driving with upstream data from the ACE spacecraft, we simulate the state of the magnetosphere-ionosphere system during a geomagnetic storm commencing on 3&lt;sup&gt;rd&lt;/sup&gt; May 2014. To elucidate the characteristic timescales of the system response during this event, we adopt a novel approach originally applied by Shore et al. (2019) to ground magnetic field data from SuperMAG, and by Coxon et al. (2019) to FAC data from AMPERE. In this method the simulated FAC at each point on the ionospheric grid is cross-correlated with solar wind time-series for time lags of up to several hours, and the lag with the strongest correlation is identified.&lt;/p&gt;&lt;p&gt;From this we construct maps of the characteristic response timescale and strength of correlation in the ionosphere to IMF B&lt;sub&gt;y&lt;/sub&gt; and B&lt;sub&gt;z&lt;/sub&gt;, and int
Stawarz JE, Matteini L, Parashar TN, et al., Generalized Ohm's Law Decomposition of the Electric Field in Magnetosheath Turbulence: Magnetospheric Multiscale Observations
Goldman MV, Newman DL, Eastwood JP, et al., Multi-beam Energy Moments of Multibeam Particle Velocity Distributions
High resolution electron and ion velocity distributions, f(v), which consistof N effectively disjoint beams, have been measured by NASA's MagnetosphericMulti-Scale Mission (MMS) observatories and in reconnection simulations.Commonly used standard velocity moments generally assume a singlemean-flow-velocity for the entire distribution, which can lead tocounterintuitive results for a multibeam f(v). An example is the (false)standard thermal energy moment of a pair of equal and opposite cold particlebeams, which is nonzero even though each beam has zero thermal energy. Bycontrast, a multibeam moment of two or more beams has no false thermal energy.A multibeam moment is obtained by taking a standard moment of each beam andthen summing over beams. In this paper we will generalize these notions,explore their consequences and apply them to an f(v) which is sum oftri-Maxwellians. Both standard and multibeam energy moments have coherent andincoherent forms. Examples of incoherent moments are the thermal energydensity, the pressure and the thermal energy flux (enthalpy flux plus heatflux). Corresponding coherent moments are the bulk kinetic energy density, theRAM pressure and the bulk kinetic energy flux. The false part of an incoherentmoment is defined as the difference between the standard incoherent moment andthe corresponding multibeam moment. The sum of a pair of corresponding coherentand incoherent moments will be called the undecomposed moment. Undecomposedmoments are independent of whether the sum is standard or multibeam andtherefore have advantages when studying moments of measured f(v).
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.