Imperial College London

Dr Jonathan P. Eastwood

Faculty of Natural SciencesDepartment of Physics

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 8101jonathan.eastwood Website

 
 
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Location

 

6M63Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

176 results found

Mistry R, Eastwood JP, Haggerty CC, Shay MA, Phan TD, Hietala H, Cassak PAet al., 2016, Observations of Hall reconnection physics far downstream of the X-line, Physical Review Letters, Vol: 117, ISSN: 1079-7114

Observations made using the Wind spacecraft of Hall magnetic fields in solar wind reconnection exhausts are presented. These observations are consistent with the generation of Hall fields by a narrow ion inertial scale current layer near the separatrix, which is confirmed with an appropriately scaled particle-in-cell simulation that shows excellent agreement with observations. The Hall fields are observed thousands of ion inertial lengths downstream from the reconnection X line, indicating that narrow regions of kinetic dynamics can persist extremely far downstream.

Journal article

Vaivads A, Retino A, Soucek J, Khotjaintsev Y, Valentini F, Escoubet CP, Alexandrova O, Andrea M, Bale SD, Balikhin M, Burgess D, Camporeale E, Caprioli D, Chen CHK, Clacey E, Cully CM, De Keyser J, Eastwood, Fazakerley A, Eriksson S, Goldstein ML, Graham DB, Haaland S, Hoshino M, Ji J, Karimabadi H, Kucharek H, Lavraud B, Marcucci F, Matthaeus WH, Moore TE, Nakamura R, Narita Y, Nemecek Z, Norgren C, Opgenoorth H, Palmroth M, Perrone D, Pincon J-L, Rathsman P, Rothkaehl H, Sahraoui F, Servidio S, Sorriso-Valvo L, Vainio R, Voros Z, Wimmer-Schweingruber RFet al., 2016, Turbulence Heating ObserveR – satellite mission proposal, Journal of Plasma Physics, Vol: 82, ISSN: 1469-7807

The Universe is permeated by hot, turbulent, magnetized plasmas. Turbulent plasma is a major constituent of active galactic nuclei, supernova remnants, the intergalactic and interstellar medium, the solar corona, the solar wind and the Earth’s magnetosphere, just to mention a few examples. Energy dissipation of turbulent fluctuations plays a key role in plasma heating and energization, yet we still do not understand the underlying physical mechanisms involved. THOR is a mission designed to answer the questions of how turbulent plasma is heated and particles accelerated, how the dissipated energy is partitioned and how dissipation operates in different regimes of turbulence. THOR is a single-spacecraft mission with an orbit tuned to maximize data return from regions in near-Earth space – magnetosheath, shock, foreshock and pristine solar wind – featuring different kinds of turbulence. Here we summarize the THOR proposal submitted on 15 January 2015 to the ‘Call for a Medium-size mission opportunity in ESAs Science Programme for a launch in 2025 (M4)’. THOR has been selected by European Space Agency (ESA) for the study phase.

Journal article

Phan TD, Shay MA, Haggerty CC, Gosling JT, Eastwood JP, Fujimoto M, Malakit K, Mozer FS, Cassak PA, Oieroset M, Angelopoulos Vet al., 2016, Ion Larmor radius effects near a reconnection X line at the magnetopause: THEMIS observations and simulation comparison, Geophysical Research Letters, Vol: 43, Pages: 8844-8852, ISSN: 0094-8276

We report a Time History of Events and Macroscale Interactions during Substorms (THEMIS-D) spacecraft crossing of a magnetopause reconnection exhaust ~9 ion skin depths (di) downstream of an X line. The crossing was characterized by ion jetting at speeds substantially below the predicted reconnection outflow speed. In the magnetospheric inflow region THEMIS detected (a) penetration of magnetosheath ions and the resulting flows perpendicular to the reconnection plane, (b) ion outflow extending into the magnetosphere, and (c) enhanced electron parallel temperature. Comparison with a simulation suggests that these signatures are associated with the gyration of magnetosheath ions onto magnetospheric field lines due to the shift of the flow stagnation point toward the low-density magnetosphere. Our observations indicate that these effects, ~2–3 di in width, extend at least 9 di downstream of the X line. The detection of these signatures could indicate large-scale proximity of the X line but do not imply that the spacecraft was upstream of the electron diffusion region.

Journal article

Mejnertsen L, Eastwood JP, Chittenden J, Masters Aet al., 2016, Global MHD Simulations of Neptune's Magnetosphere, Journal of Geophysical Research: Space Physics, Vol: 121, Pages: 7497-7513, ISSN: 2169-9380

A global magnetohydrodynamic (MHD) simulation has been performed in order to investigate the outer boundaries of Neptune's magnetosphere at the time of Voyager 2's flyby in 1989 and to better understand the dynamics of magnetospheres formed by highly inclined planetary dipoles. Using the MHD code Gorgon, we have implemented a precessing dipole to mimic Neptune's tilted magnetic field and rotation axes. By using the solar wind parameters measured by Voyager 2, the simulation is verified by finding good agreement with Voyager 2 magnetometer observations. Overall, there is a large-scale reconfiguration of magnetic topology and plasma distribution. During the “pole-on” magnetospheric configuration, there only exists one tail current sheet, contained between a rarefied lobe region which extends outward from the dayside cusp, and a lobe region attached to the nightside cusp. It is found that the tail current always closes to the magnetopause current system, rather than closing in on itself, as suggested by other models. The bow shock position and shape is found to be dependent on Neptune's daily rotation, with maximum standoff being during the pole-on case. Reconnection is found on the magnetopause but is highly modulated by the interplanetary magnetic field (IMF) and time of day, turning “off” and “on” when the magnetic shear between the IMF and planetary fields is large enough. The simulation shows that the most likely location for reconnection to occur during Voyager 2's flyby was far from the spacecraft trajectory, which may explain the relative lack of associated signatures in the observations.

Journal article

Plotnikov I, Rouillard AP, Davies JA, Bothmer V, Eastwood JP, Gallagher P, Harrison RA, Kilpua E, Möstl C, Perry CH, Rodriguez L, Lavraud B, Génot V, Pinto RF, Sanchez-Diaz Eet al., 2016, Long-Term Tracking of Corotating Density Structures Using Heliospheric Imaging, Solar Physics, Vol: 291, Pages: 1853-1875, ISSN: 0038-0938

The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalog listing the properties of 190 corotating structures well-observed in images taken by the Heliospheric Imager (HI) instruments onboard STEREO-A (ST-A). Based on this catalog, we present here one of very few long-term analyses of solar wind structures advected by the background solar wind. We concentrate on the subset of plasma density structures clearly identified inside corotating structures. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be (Formula presented.). Such a low mean value corresponds to the terminal speed of the slow solar wind rather than the speed of stream interfaces, which is typically intermediate between the slow and fast solar wind speeds ((Formula presented.)). Using our fitting technique, we predicted the arrival time of each corotating density structure at different probes in the inner heliosphere. We find that our derived speeds are systematically lower by (Formula presented.) than those measured in situ at the predicted impact times. Moreover, for cases when a stream interaction region is clearly detected in situ at the estimated impact time, we find that our derived speeds are lower than the speed of th

Journal article

Ergun RE, Goodrich KA, Wilder FD, Holmes JC, Stawarz JE, Eriksson S, Sturner AP, Malaspina DM, Usanova ME, Torbert RB, Lindqvist PA, Khotyaintsev Y, Burch JL, Strangeway RJ, Russell CT, Pollock CJ, Giles BL, Hesse M, Chen LJ, Lapenta G, Goldman MV, Newman DL, Schwartz SJ, Eastwood JP, Phan TD, Mozer FS, Drake J, Shay MA, Cassak PA, Nakamura R, Marklund Get al., 2016, Magnetospheric multiscale satellites observations of parallel electric fields associated with magnetic reconnection, Physical Review Letters, Vol: 116, ISSN: 1079-7114

We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E_{∥}) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E_{∥} events near the electron diffusion region have amplitudes on the order of 100  mV/m, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E_{∥} events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E_{∥} events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

Journal article

Lavraud B, Liu Y, Segura K, He J, Qin G, Temmer M, Vial JC, Xiong M, Davies JA, Rouillard AP, Pinto R, Auchère F, Harrison RA, Eyles C, Gan W, Lamy P, Xia L, Eastwood JP, Kong L, Wang J, Wimmer-Schweingruber RF, Zhang S, Zong Q, Soucek J, An J, Prech L, Zhang A, Rochus P, Bothmer V, Janvier M, Maksimovic M, Escoubet CP, Kilpua EKJ, Tappin J, Vainio R, Poedts S, Dunlop MW, Savani N, Gopalswamy N, Bale SD, Li G, Howard T, DeForest C, Webb D, Lugaz N, Fuselier SA, Dalmasse K, Tallineau J, Vranken D, Fernández JGet al., 2016, A small mission concept to the Sun–Earth Lagrangian L5 point for innovative solar, heliospheric and space weather science, Journal of Atmospheric and Solar-Terrestrial Physics, Vol: 146, Pages: 171-185, ISSN: 1364-6826

We present a concept for a small mission to the Sun–Earth Lagrangian L5 point for innovative solar, heliospheric and space weather science. The proposed INvestigation of Solar-Terrestrial Activity aNd Transients (INSTANT) mission is designed to identify how solar coronal magnetic fields drive eruptions, mass transport and particle acceleration that impact the Earth and the heliosphere. INSTANT is the first mission designed to (1) obtain measurements of coronal magnetic fields from space and (2) determine coronal mass ejection (CME) kinematics with unparalleled accuracy. Thanks to innovative instrumentation at a vantage point that provides the most suitable perspective view of the Sun–Earth system, INSTANT would uniquely track the whole chain of fundamental processes driving space weather at Earth. We present the science requirements, payload and mission profile that fulfill ambitious science objectives within small mission programmatic boundary conditions.

Journal article

Phan TD, Eastwood JP, Cassak PA, Øieroset M, Gosling JT, Gershman DJ, Mozer FS, Shay MA, Fujimoto M, Daughton W, Drake JF, Burch JL, Torbert RB, Ergun RE, Chen LJ, Wang S, Pollock C, Dorelli JC, Lavraud B, Giles BL, Moore TE, Saito Y, Avanov LA, Paterson W, Strangeway RJ, Russell CT, Khotyaintsev Y, Lindqvist PA, Oka M, Wilder FDet al., 2016, MMS observations of electron-scale filamentary currents in the reconnection exhaust and near the X line, Geophysical Research Letters, Vol: 43, Pages: 6060-6069, ISSN: 0094-8276

We report Magnetospheric Multiscale observations of macroscopic and electron-scale current layers in asymmetric reconnection. By intercomparing plasma, magnetic, and electric field data at multiple crossings of a reconnecting magnetopause on 22 October 2015, when the average interspacecraft separation was ~10km, we demonstrate that the ion and electron moments are sufficiently accurate to provide reliable current density measurements at 30ms cadence. These measurements, which resolve current layers narrower than the interspacecraft separation, reveal electron-scale filamentary Hall currents and electron vorticity within the reconnection exhaust far downstream of the X line and even in the magnetosheath. Slightly downstream of the X line, intense (up to 3μA/m2) electron currents, a super-Alfvénic outflowing electron jet, and nongyrotropic crescent shape electron distributions were observed deep inside the ion-scale magnetopause current sheet and embedded in the ion diffusion region. These characteristics are similar to those attributed to the electron dissipation/diffusion region around the X line.

Journal article

Øieroset M, Phan TD, Haggerty C, Shay MA, Eastwood JP, Gershman DJ, Drake JF, Fujimoto M, Ergun RE, Mozer FS, Oka M, Torbert RB, Burch JL, Wang S, Chen LJ, Swisdak M, Pollock C, Dorelli JC, Fuselier SA, Lavraud B, Giles BL, Moore TE, Saito Y, Avanov LA, Paterson W, Strangeway RJ, Russell CT, Khotyaintsev Y, Lindqvist PA, Malakit Ket al., 2016, MMS observations of large guide field symmetric reconnection between colliding reconnection jets at the center of a magnetic flux rope at the magnetopause, Geophysical Research Letters, Vol: 43, Pages: 5536-5544, ISSN: 0094-8276

We report evidence for reconnection between colliding reconnection jets in a compressed current sheet at the center of a magnetic flux rope at Earth's magnetopause. The reconnection involved nearly symmetric inflow boundary conditions with a strong guide field of two. The thin (2.5 ion-skin depth (di) width) current sheet (at ~12 di downstream of the X line) was well resolved by MMS, which revealed large asymmetries in plasma and field structures in the exhaust. Ion perpendicular heating, electron parallel heating, and density compression occurred on one side of the exhaust, while ion parallel heating and density depression were shifted to the other side. The normal electric field and double out-of-plane (bifurcated) currents spanned almost the entire exhaust. These observations are in good agreement with a kinetic simulation for similar boundary conditions, demonstrating in new detail that the structure of large guide field symmetric reconnection is distinctly different from antiparallel reconnection.

Journal article

Farrugia CJ, Lavraud B, Torbert RB, Argall M, Kacem I, Yu W, Alm L, Burch J, Russell CT, Shuster J, Dorelli J, Eastwood JP, Ergun RE, Fuselier S, Gershman D, Giles BL, Khotyaintsev YV, Lindqvist PA, Matsui H, Marklund GT, Phan TD, Paulson K, Pollock C, Strangeway RJet al., 2016, Magnetospheric Multiscale Mission observations and non-force free modeling of a flux transfer event immersed in a super-Alfvénic flow, Geophysical Research Letters, Vol: 43, Pages: 6070-6077, ISSN: 0094-8276

We analyze plasma, magnetic field, and electric field data for a flux transfer event (FTE) to highlight improvements in our understanding of these transient reconnection signatures resulting from high-resolution data. The ∼20 s long, reverse FTE, which occurred south of the geomagnetic equator near dusk, was immersed in super-Alfvénic flow. The field line twist is illustrated by the behavior of flows parallel/perpendicular to the magnetic field. Four-spacecraft timing and energetic particle pitch angle anisotropies indicate a flux rope (FR) connected to the Northern Hemisphere and moving southeast. The flow forces evidently overcame the magnetic tension. The high-speed flows inside the FR were different from those outside. The external flows were perpendicular to the field as expected for draping of the external field around the FR. Modeling the FR analytically, we adopt a non-force free approach since the current perpendicular to the field is nonzero. It reproduces many features of the observations.

Journal article

Eastwood J, Phan T, Cassak PA, Gershman DJ, Haggerty C, Malakit K, Shay MA, Mistry R, Oieroset M, Russell CT, Slavin JA, Argall MR, Avanov LA, Burch JL, Chen LJ, Dorelli JC, Ergun RE, Giles BL, Khotyaintsev Y, Lavraud B, Lindqvist PA, Moore TE, Nakamura R, Paterson W, Pollock C, Strangeway RJ, Torbert RB, Wang Set al., 2016, Ion-scale secondary flux-ropes generated by magnetopause reconnection as resolved by MMS, Geophysical Research Letters, Vol: 43, Pages: 4716-4724, ISSN: 1944-8007

New Magnetospheric Multiscale (MMS) observations of small-scale (~ 7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multi-spacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Inter-comparison of the plasma moments with electric and magnetic field measurements reveals structured non-frozen-in ion behavior. The data are further compared with a particle-in-cell simulation. It is concluded that these small-scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.

Journal article

Ergun RE, Holmes JC, Goodrich KA, Wilder FD, Stawarz JE, Eriksson S, Newman DL, Schwartz SJ, Goldman MV, Sturner AP, Malaspina DM, Usanova ME, Torbert RB, Argall M, Lindqvist PA, Khotyaintsev Y, Burch JL, Strangeway RJ, Russell CT, Pollock CJ, Giles BL, Dorelli JJC, Avanov L, Hesse M, Chen LJ, Lavraud B, Le Contel O, Retino A, Phan TD, Eastwood JP, Oieroset M, Drake J, Shay MA, Cassak PA, Nakamura R, Zhou M, Ashour-Abdalla M, André Met al., 2016, Magnetospheric Multiscale observations of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the magnetopause, Geophysical Research Letters, Vol: 43, Pages: 5626-5634, ISSN: 0094-8276

We report observations from the Magnetospheric Multiscale satellites of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the Earth's magnetopause. The observed waves have parallel electric fields (E||) with amplitudes on the order of 100 mV/m and display nonlinear characteristics that suggest a possible net E||. These waves are observed within the ion diffusion region and adjacent to (within several electron skin depths) the electron diffusion region. They are in or near the magnetosphere side current layer. Simulation results support that the strong electrostatic linear and nonlinear wave activities appear to be driven by a two stream instability, which is a consequence of mixing cold (<10 eV) plasma in the magnetosphere with warm (~100 eV) plasma from the magnetosheath on a freshly reconnected magnetic field line. The frequent observation of these waves suggests that cold plasma is often present near the magnetopause.

Journal article

Krupar V, Eastwood JP, Kruparova O, Santolik O, Soucek J, Magdalenić J, Vourlidas A, Maksimovic M, Bonnin X, Bothmer V, Mrotzek N, Pluta A, Barnes D, Davies JA, Oliveros JCM, Bale SDet al., 2016, An analysis of interplanetary solar radio emissions associated with a coronal mass ejection, Astrophysical Journal Letters, Vol: 823, ISSN: 2041-8205

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma that may cause severe geomagnetic storms if Earth directed. Here, we report a rare instance with comprehensive in situ and remote sensing observations of a CME combining white-light, radio, and plasma measurements from four different vantage points. For the first time, we have successfully applied a radio direction-finding technique to an interplanetary type II burst detected by two identical widely separated radio receivers. The derived locations of the type II and type III bursts are in general agreement with the white-light CME reconstruction. We find that the radio emission arises from the flanks of the CME and are most likely associated with the CME-driven shock. Our work demonstrates the complementarity between radio triangulation and 3D reconstruction techniques for space weather applications.

Journal article

Burch J, Torbert RB, Phan TD, Chen LJ, Moore TE, Ergun RE, Eastwood J, Gerschman DJ, Cassak PA, Argall MR, Wang S, Hesse M, Pollock CJ, Giles BL, Nakamura R, Mauk BH, Fuselier SA, Russell CT, Strangeway RJ, Drake JF, Shay MA, Khotyaintsev YV, Lindqvist PA, Marklund G, Wilder FD, Young DT, Torkar K, Goldstein J, Dorelli JC, Avanov LA, Oka M, Baker DN, Jaynes AN, Goodrich KA, Cohen IJ, Turner DL, Fennell JF, Blake JB, Clemmons J, Goldman M, Newman D, Petrinec SM, Trattner KJ, Lavraud B, Reiff PH, Baumjohann W, Magnes W, Steller M, Lewis W, Saito Y, Coffey V, Chandler Met al., 2016, Electron-scale measurements of magnetic reconnection in space, Science, Vol: 352, ISSN: 1095-9203

Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using very high time resolution measurements, NASA’s Magnetospheric Multiscale Mission (MMS) has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth’s magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy, (ii) measured the electric field and current, which together cause the dissipation of magnetic energy, and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

Journal article

Lavraud B, Zhang YC, Vernisse Y, Gershman DJ, Dorelli J, Cassak PA, Dargent J, Pollock C, Giles B, Aunai N, Argall M, Avanov L, Barrie A, Burch J, Chandler M, Chen LJ, Clark G, Cohen I, Coffey V, Eastwood JP, Egedal J, Eriksson S, Ergun R, Farrugia CJ, Fuselier SA, Génot V, Graham D, Grigorenko E, Hasegawa H, Jacquey C, Kacem I, Khotyaintsev Y, Macdonald E, Magnes W, Marchaudon A, Mauk B, Moore TE, Mukai T, Nakamura R, Paterson W, Penou E, Phan TD, Rager A, Retino A, Rong ZJ, Russell CT, Saito Y, Sauvaud JA, Schwartz SJ, Shen C, Smith S, Strangeway R, Toledo-Redondo S, Torbert R, Turner DL, Wang S, Yokota Set al., 2016, Currents and associated electron scattering and bouncing near the diffusion region at Earth's magnetopause, Geophysical Research Letters, Vol: 43, Pages: 3042-3050, ISSN: 1944-8007

Based on high-resolution measurements from NASA's Magnetospheric Multiscale mission, we present the dynamics of electrons associated with current systems observed near the diffusion region of magnetic reconnection at Earth's magnetopause. Using pitch angle distributions (PAD) and magnetic curvature analysis, we demonstrate the occurrence of electron scattering in the curved magnetic field of the diffusion region down to energies of 20eV. We show that scattering occurs closer to the current sheet as the electron energy decreases. The scattering of inflowing electrons, associated with field-aligned electrostatic potentials and Hall currents, produces a new population of scattered electrons with broader PAD which bounce back and forth in the exhaust. Except at the center of the diffusion region the two populations are collocated and appear to behave adiabatically: the inflowing electron PAD focuses inward (toward lower magnetic field), while the bouncing population PAD gradually peaks at 90° away from the center (where it mirrors owing to higher magnetic field and probable field-aligned potentials).

Journal article

Phan TD, Shay MA, Eastwood JP, Angelopoulos V, Oieroset M, Oka M, Fujimoto Met al., 2016, Establishing the Context for Reconnection Diffusion Region Encounters and Strategies for the Capture and Transmission of Diffusion Region Burst Data by MMS, Space Science Reviews, Vol: 199, Pages: 631-650, ISSN: 0038-6308

© 2015, The Author(s). This paper describes the efforts of our Inter-Disciplinary Scientist (IDS) team to (a) establish the large-scale context for reconnection diffusion region encounters by MMS at the magnetopause and in the magnetotail, including the distinction between X-line and O-line encounters, that would help the identification of diffusion regions in spacecraft data, and (b) devise possible strategies that can be used by MMS to capture and transmit burst data associated with diffusion region candidates. At the magnetopause we suggest the strategy of transmitting burst data from all magnetopause crossings so that no magnetopause reconnection diffusion regions encountered by the spacecraft will be missed. The strategy is made possible by the MMS mass memory and downlink budget. In the magnetotail, it is estimated that MMS will be able to transmit burst data for all diffusion regions, all reconnection jet fronts (a.k.a. dipolarization fronts) and separatrix encounters, but less than 50 % of reconnection exhausts encountered by the spacecraft. We also discuss automated burst trigger schemes that could capture various reconnection-related phenomena. The identification of candidate diffusion region encounters by the burst trigger schemes will be verified and improved by a Scientist-In-The-Loop (SITL). With the knowledge of the properties of the region surrounding the diffusion region and the combination of automated burst triggers and further optimization by the SITL, MMS should be able to capture most diffusion regions it encounters.

Journal article

Mistry R, Eastwood JP, Hietala H, 2015, Development of bifurcated current sheets in solar wind reconnection exhausts, Geophysical Research Letters, Vol: 42, Pages: 10513-10520, ISSN: 1944-8007

Petschek-type reconnection is expected to result in bifurcations of reconnection current sheets. In contrast, Hall reconnection simulations show smooth changes in the reconnecting magnetic field. Here we study three solar wind reconnection events where different spacecraft sample oppositely directed reconnection exhausts from a common reconnection site. The spacecraft's relative separations and measurements of the exhaust width are used to geometrically calculate each spacecraft's distance from the X line. We find that in all cases spacecraft farthest from the X line observe clearly bifurcated reconnection current sheets, while spacecraft nearer to the X line do not. These observations suggest that clear bifurcations of reconnection current sheets occur at large distances from the X line (~1000 ion skin depths) and that Petschek-type signatures are less developed close to the reconnection site. This may imply that fully developed bifurcations of reconnection current sheets are unlikely to be observed in the near-Earth magnetotail.

Journal article

Arridge CS, Eastwood J, Jackman CM, Poh GK, Slavin JA, Thomsen MF, Andre N, Jia X, Kidder A, Lamy L, Radioti A, Reisenfeld DB, Sergis N, Volwerk M, Walsh AP, Zarka P, Coates AJ, Dougherty MKet al., 2015, Cassini in situ observations of long duration magnetic reconnection in Saturn’s magnetotail, Nature Physics, Vol: 12, Pages: 268-271, ISSN: 1745-2481

Magnetic reconnection is a fundamental process in solar system and astrophysical plasmas, through which stored magnetic energy associated with current sheets is converted into thermal, kinetic and wave energy1, 2, 3, 4. Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field5, 6. The region where magnetic fields reconnect is known as the diffusion region and in this letter we report on the first encounter of the Cassini spacecraft with a diffusion region in Saturn’s magnetotail. The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn6. This counters the view of reconnection as a transient method of internal plasma loss at Saturn5, 7. These results, although directly relating to the magnetosphere of Saturn, have applications in the understanding of other rapidly rotating magnetospheres, including that of Jupiter and other astrophysical bodies.

Journal article

Palmroth M, Archer M, Vainio R, Hietala H, Pfau-Kempf Y, Hoilijoki S, Hannuksela O, Ganse U, Sandroos A, von Alfthan S, Eastwood JPet al., 2015, ULF foreshock under radial IMF: THEMIS observations and global kinetic simulation Vlasiator results compared, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 120, Pages: 8782-8798, ISSN: 2169-9380

Journal article

Hietala H, Drake JF, Phan TD, Eastwood J, McFadden JPet al., 2015, Ion temperature anisotropy across a magnetotail reconnection jet, Geophysical Research Letters, Vol: 42, Pages: 7239-7247, ISSN: 1944-8007

A significant fraction of the energy released by magnetotail reconnection appears to go into ion heating, but this heating is generally anisotropic. We examine ARTEMIS dual-spacecraft observations of a long-duration magnetotail exhaust generated by anti-parallel reconnection in conjunction with Particle-In-Cell simulations, showing spatial variations in the anisotropy across the outflow far (> 100di) downstream of the X-line. A consistent pattern is found in both the spacecraft data and the simulations: Whilst the total temperature across the exhaust is rather constant, near the boundaries Ti,|| dominates. The plasma is well-above the firehose threshold within patchy spatial regions at |BX| ∈ [0.1, 0.5]B0, suggesting that the drive for the instability is strong and the instability is too weak to relax the anisotropy. At the mid-plane (|BX|0.1 B0), Ti,⊥ > Ti,|| and ions undergo Speiser-like motion despite the large distance from the X-line.

Journal article

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.

Book chapter

Horbury TS, Archer MO, Brown P, Eastwood JP, Oddy TM, Whiteside BJ, Sample JGet 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.

Journal article

Eastwood JP, Hietala H, Toth G, Phan TD, Fujimoto Met al., 2015, What Controls the Structure and Dynamics of Earth's Magnetosphere?, SPACE SCIENCE REVIEWS, Vol: 188, Pages: 251-286, ISSN: 0038-6308

Journal article

Balogh A, Bykov A, Eastwood J, Kaastra Jet al., 2015, Multi-scale Structure Formation and Dynamics in Cosmic Plasmas, SPACE SCIENCE REVIEWS, Vol: 188, Pages: 1-2, ISSN: 0038-6308

Journal article

Eastwood JP, Goldman MV, Hietala H, Newman DL, Mistry R, Lapenta Get 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.

Journal article

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.

Book chapter

Eastwood JP, Kataria DO, McInnes CR, Barnes NC, Mulligan Pet al., 2015, Sunjammer, WEATHER, Vol: 70, Pages: 27-30, ISSN: 0043-1656

Journal article

Brown P, Whiteside BJ, Beek TJ, Fox P, Horbury TS, Oddy TM, Archer MO, Eastwood JP, Sanz-Hernndez D, Sample JG, Cupido E, O'Brien H, Carr CMet al., 2014, Space magnetometer based on an anisotropic magnetoresistive hybrid sensor, Review of Scientific Instruments, Vol: 85, ISSN: 1089-7623

Journal article

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.

Journal article

Archer MO, Turner DL, Eastwood JP, Schwartz SJ, Horbury TSet 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).

Journal article

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