153 results found
Eastwood J, 2015, Observing Magnetic Reconnection: The Influence of Jim Dungey, Magnetospheric Plasma Physics: The Impact of Jim Dungey’s Research, Editors: Southwood, Cowley, Mitton, Publisher: Springer, Pages: 181-197, ISBN: 9783319183589
This book makes good background reading for much of modern magnetospheric physics.
Horbury TS, Archer MO, Brown P, et al., 2015, The MAGIC of CINEMA: First in-flight science results from a miniaturised anisotropic magnetoresistive magnetometer, Annales Geophysicae, Vol: 33, Pages: 725-735, ISSN: 1432-0576
We present the first in-flight results from a novel miniaturised anisotropic magnetoresistive space magnetometer, MAGIC (MAGnetometer from Imperial College), aboard the first CINEMA (CubeSat for Ions, Neutrals, Electrons and MAgnetic fields) spacecraft in low Earth orbit. An attitude-independent calibration technique is detailed using the International Geomagnetic Reference Field (IGRF), which is temperature dependent in the case of the outboard sensor. We show that the sensors accurately measure the expected absolute field to within 2% in attitude mode and 1% in science mode. Using a simple method we are able to estimate the spacecraft's attitude using the magnetometer only, thus characterising CINEMA's spin, precession and nutation. Finally, we show that the outboard sensor is capable of detecting transient physical signals with amplitudes of ~ 20–60 nT. These include field-aligned currents at the auroral oval, qualitatively similar to previous observations, which agree in location with measurements from the DMSP (Defense Meteorological Satellite Program) and POES (Polar-orbiting Operational Environmental Satellites) spacecraft. Thus, we demonstrate and discuss the potential science capabilities of the MAGIC instrument onboard a CubeSat platform.
Eastwood JP, Hietala H, Toth G, et al., 2015, What Controls the Structure and Dynamics of Earth's Magnetosphere?, SPACE SCIENCE REVIEWS, Vol: 188, Pages: 251-286, ISSN: 0038-6308
Balogh A, Bykov A, Eastwood J, et al., 2015, Multi-scale Structure Formation and Dynamics in Cosmic Plasmas, SPACE SCIENCE REVIEWS, Vol: 188, Pages: 1-2, ISSN: 0038-6308
Eastwood JP, Goldman MV, Hietala H, et al., 2015, Ion reflection and acceleration near magnetotail dipolarization fronts associated with magnetic reconnection, Journal of Geophysical Research: Space Physics, Vol: 120, Pages: 511-525, ISSN: 2169-9402
Dipolarization fronts (DFs) are often associated with the leading edge of earthward bursty bulk flows in the magnetotail plasma sheet. Here multispacecraft Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations are used to show that a spatially limited region of counterpropagating ion beams, whose existence is not evident in either the plasma moments or the electric field, is observed on the low-density side of DFs. The THEMIS magnetic field data are used to establish appropriate comparison cuts through a particle-in-cell simulation of reconnection, and very good agreement is found between the observed and simulated ion distributions on both sides of the DF. Self-consistent back tracing shows that the ion beams originate from the thermal component of the preexisting high-density plasma into which the DF is propagating; they do not originate from the inflow region in the traditional sense. Forward tracing shows that some of these ions can subsequently overtake the DF and pass back into the high-density preexisting plasma sheet with an order-of-magnitude increase in energy; this process is distinct from other ion reflection processes that occur directly at the DF. The interaction of the reconnection jet with the preexisting plasma sheet therefore occurs over a macroscopic region, rather than simply being limited to the thin DF interface. A more general consequence of this study is the conclusion that reconnection jets are not simply fed by plasma inflow across the separatrices but are also fed by plasma from the region into which the jet is propagating; the implications of this finding are discussed.
Eastwood JP, Kiehas SA, 2015, Origin and Evolution of Plasmoids and Flux Ropes in the Magnetotails of Earth and Mars, Magnetotails in the Solar System, Pages: 269-287, ISBN: 9781118842348
© 2015 American Geophysical Union. All rights reserved. This chapter discusses the origin and evolution of plasmoids and flux ropes in Earth's magnetotail, providing an overview of author's current understanding based on recent multipoint and multimission data analysis. It also presents recent results concerning observations of flux ropes in the vicinity of Mars. Understanding the Mars solar wind interaction is very important for determining its atmospheric history, and recent discoveries show that magnetic reconnection-generated structures may play a significant role, particularly in the vicinity of the crustal field regions. The chapter briefly discusses some of the different terms used to describe reconnection-generated structures. It describes the production of islands, plasmoids, and secondary islands by antiparallel reconnection.
Brown P, Whiteside BJ, Beek TJ, et al., 2014, Space magnetometer based on an anisotropic magnetoresistive hybrid sensor, Review of Scientific Instruments, Vol: 85, ISSN: 1089-7623
Mistry R, Eastwood JP, Hietala H, 2014, Detection of small-scale folds at a solar wind reconnection exhaust, Journal of Geophysical Research: Space Physics, Vol: 120, Pages: 30-42, ISSN: 2169-9402
Observations of reconnection in the solar wind over the last few years appear to indicate that the majority of large-scale reconnecting current sheets are roughly planar, and that reconnection itself is quasi-steady. Most studies of solar wind exhausts have used spacecraft with large separations and relatively low time cadence ion measurements. Here we present multipoint Cluster observations of a reconnection exhaust and the associated current sheet at ACE and Wind, enabling it to be studied on multiple length scales and at high time resolution. While analysis shows that on large scales the current sheet is planar, detailed measurements using the four closely spaced Cluster spacecraft show that the trailing edge of the reconnection jet is nonplanar with folds orthogonal to the reconnection plane, with length scales of approximately 230 ion inertial lengths. Our findings thus suggest that while solar wind current sheets undergoing reconnection may be planar on large scales, they may also exhibit complex smaller-scale structure. Such structure is difficult to observe and has rarely been detected because exhausts are rapidly convected past the spacecraft in a single cut; there is therefore a limited set of spacecraft trajectories through the exhaust which would allow the nonplanar features to be intercepted. We consider how such nonplanar reconnection current sheets can form and the processes which may have generated the 3-D structure that was observed.
Archer MO, Turner DL, Eastwood JP, et al., 2014, Global impacts of a Foreshock Bubble: Magnetosheath, magnetopause and ground-based observations, Planetary and Space Science, Vol: 106, Pages: 56-66, ISSN: 1873-5088
Using multipoint observations we show, for the first time, that Foreshock Bubbles (FBs) have a global impact on Earth׳s magnetosphere. We show that an FB, a transient kinetic phenomenon due to the interaction of backstreaming suprathermal ions with a discontinuity, modifies the total pressure upstream of the bow shock showing a decrease within the FB׳s core and sheath regions. Magnetosheath plasma is accelerated towards the intersection of the FB׳s current sheet with the bow shock resulting in fast, sunward, flows as well as outward motion of the magnetopause. Ground-based magnetometers also show signatures of this magnetopause motion simultaneously across at least 7 h of magnetic local time, corresponding to a distance of 21.5RE transverse to the Sun–Earth line along the magnetopause. These observed global impacts of the FB are in agreement with previous simulations and in stark contrast to the known localised, smaller scale effects of Hot Flow Anomalies (HFAs).
Genestreti KJ, Fuselier SA, Goldstein J, et al., 2014, The location and rate of occurrence of near-Earth magnetotail reconnection as observed by Cluster and Geotail, JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS, Vol: 121, Pages: 98-109, ISSN: 1364-6826
Phan TD, Drake JF, Shay MA, et al., 2014, Ion bulk heating in magnetic reconnection exhausts at Earth's magnetopause: Dependence on the inflow Alfven speed and magnetic shear angle, GEOPHYSICAL RESEARCH LETTERS, Vol: 41, Pages: 7002-7010, ISSN: 0094-8276
Archer MO, Turner DL, Eastwood JP, et al., 2014, The role of pressure gradients in driving sunward magnetosheath flows and magnetopause motion, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 8117-8125, ISSN: 2169-9380
Oieroset M, Sundkvist D, Chaston CC, et al., 2014, Observations of plasma waves in the colliding jet region of amagnetic flux rope flanked by two active X lines at the subsolar magnetopause, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, ISSN: 2169-9380
Jackman CM, Slavin JA, Kivelson MG, et al., 2014, Saturn's dynamic magnetotail: A comprehensive magnetic field and plasma survey of plasmoids and traveling compression regions and their role in global magnetospheric dynamics, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 119, Pages: 5465-5494, ISSN: 2169-9380
Selzer LA, Hnat B, Osman KT, et al., 2014, TEMPERATURE ANISOTROPY IN THE PRESENCE OF ULTRA LOW FREQUENCY WAVES IN THE TERRESTRIAL FORESHOCK, ASTROPHYSICAL JOURNAL LETTERS, Vol: 788, ISSN: 2041-8205
Hietala H, Eastwood JP, Isavnin A, 2014, Sequentially released tilted flux ropes in the Earth's magnetotail, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 56, ISSN: 0741-3335
Goldman MV, Newman DL, Lapenta G, et al., 2014, Cerenkov Emission of Quasiparallel Whistlers by Fast Electron Phase-Space Holes during Magnetic Reconnection, PHYSICAL REVIEW LETTERS, Vol: 112, ISSN: 0031-9007
Eastwood JP, Phan TD, Oieroset M, et al., 2013, Influence of asymmetries and guide fields on the magnetic reconnection diffusion region in collisionless space plasmas, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 55, ISSN: 0741-3335
© Springer Science+Business Media New York 2014. All rights are reserved. NASA's two spacecraft ARTEMIS mission will address both heliospheric and planetary research questions, first while in orbit about the Earth with the Moon and subsequently while in orbit about the Moon. Heliospheric topics include the structure of the Earth's magnetotail; reconnection, particle acceleration, and turbulence in the Earth's magnetosphere, at the bow shock, and in the solar wind; and the formation and structure of the lunar wake. Planetary topics include the lunar exosphere and its relationship to the composition of the lunar surface, the effects of electric fields on dust in the exosphere, internal structure of the Moon, and the lunar crustal magnetic field. This paper describes the expected contributions of ARTEMIS to these baseline scientific objectives.
Phan TD, Shay MA, Gosling JT, et al., 2013, Electron bulk heating in magnetic reconnection at Earth's magnetopause: Dependence on the inflow Alfven speed and magnetic shear, GEOPHYSICAL RESEARCH LETTERS, Vol: 40, Pages: 4475-4480, ISSN: 0094-8276
Carr J, Cassak PA, Galante M, et al., 2013, Spontaneous ion beam formation in the laboratory, space, and simulation, PHYSICS OF PLASMAS, Vol: 20, ISSN: 1070-664X
Eastwood JP, Phan TD, Drake JF, et al., 2013, Energy Partition in Magnetic Reconnection in Earth's Magnetotail, PHYSICAL REVIEW LETTERS, Vol: 110, ISSN: 0031-9007
Zhong J, Pu ZY, Dunlop MW, et al., 2013, Three-dimensional magnetic flux rope structure formed by multiple sequential X-line reconnection at the magnetopause, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 118, Pages: 1904-1911, ISSN: 2169-9380
Archer MO, Horbury TS, Eastwood JP, et al., 2013, Magnetospheric response to magnetosheath pressure pulses: A low pass filter effect, Journal of Geophysical Research, Vol: 118, Pages: 5454-5466
Abstract. We present observations from the magnetopause to the ground during periods of large amplitude, transient dynamic pressure pulses in the magnetosheath. While individual magnetosheath pulses are sharp and impulsive, the magnetospheric response is much smoother with frequencies in the Pc5-6 range being excited in the compressional and poloidal components of the magnetic field. We show that the magnetopause acts like a low pass filter, suppressing timescales shorter than a few minutes. Further filtering appears to occur locally within the magnetosphere, which may be due to the unusual field line resonance frequency profile on this day. Ground magnetometer and radar data along with equivalent ionospheric currents show signatures of travelling convection vortices, similar to the response from pressure variations of solar wind origin. However, the signatures are associated with groups of magnetosheath pulses rather than individual ones due to the impulsive nature of the pressure variations. Thus the scale-dependent magnetospheric response to these transient pressure variations, results in coherent signatures on longer timescales than any individual pulse.
Moestl C, Farrugia CJ, Kilpua EKJ, et al., 2012, MULTI-POINT SHOCK AND FLUX ROPE ANALYSIS OF MULTIPLE INTERPLANETARY CORONAL MASS EJECTIONS AROUND 2010 AUGUST 1 IN THE INNER HELIOSPHERE, ASTROPHYSICAL JOURNAL, Vol: 758, ISSN: 0004-637X
Eastwood JP, Phan TD, Fear RC, et al., 2012, Survival of flux transfer event (FTE) flux ropes far along the tail magnetopause, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 117, ISSN: 2169-9380
Archer MO, Horbury TS, Eastwood JP, 2012, Magnetosheath pressure pulses: Generation downstream of the bow shock from solar wind discontinuities, Journal of Geophyical Research, Vol: 117, ISSN: 0148-0227
We present multipoint Time History of Events and Macroscale Interactions duringSubstorms (THEMIS) observations of transient dynamic pressure pulses in themagnetosheath 3–10 times the background in amplitude, due to enhancements in both theion density and velocity. Their spatial dimensions are of the order of 1 RE parallel tothe flow and 0.2–0.5 RE perpendicular to it, inferred from the difference in theamplitudes observed by the different spacecraft. For the first time, simultaneousobservations of the solar wind and foreshock are also shown, proving no similar dynamicpressure enhancements exist upstream of the bow shock and that the majority of pulsesare downstream of the quasi-parallel shock. By considering previously suggestedmechanisms for their generation, we show that the pressure pulses cannot be caused byreconnection, hot flow anomalies, or short, large-amplitude magnetic structures andthat at least some of the pressure pulses appear to be consistent with previoussimulations of solar wind discontinuities interacting with the bow shock. Thesesimulations predict large-amplitude pulses when the local geometry of the shock changesfrom quasi-perpendicular to quasi-parallel, while the opposite case should also producenotable pulses but typically of lower amplitude. Therefore, in a given region of themagnetosheath, some of the discontinuities in the solar wind should generate pressurepulses, whereas others are expected not to. There is also evidence that the pulses canimpinge upon the magnetopause, causing its motion.
Harrison RA, Davies JA, Moestl C, et al., 2012, AN ANALYSIS OF THE ORIGIN AND PROPAGATION OF THE MULTIPLE CORONAL MASS EJECTIONS OF 2010 AUGUST 1, ASTROPHYSICAL JOURNAL, Vol: 750, ISSN: 0004-637X
Masters A, Eastwood JP, Swisdak M, et al., 2012, The importance of plasma beta conditions for magnetic reconnection at Saturn's magnetopause, GEOPHYSICAL RESEARCH LETTERS, Vol: 39, ISSN: 0094-8276
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.