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

153 results found

Eastwood J, Nakamura R, Turc L, Mejnertsen L, Hesse Met al., 2017, The scientific foundations of forecasting magnetospheric space weather, Space Science Reviews, Vol: 212, Pages: 1221-1252, ISSN: 1572-9672

The magnetosphere is the lens through which solar space weather phenomena are focused and directed towards the Earth. In particular, the non-linear interaction of the solar wind with the Earth’s magnetic field leads to the formation of highly inhomogenous electrical currents in the ionosphere which can ultimately result in damage to and problems with the operation of power distribution networks. Since electric power is the fundamental cornerstone of modern life, the interruption of power is the primary pathway by which space weather has impact on human activity and technology. Consequently, in the context of space weather, it is the ability to predict geomagnetic activity that is of key importance. This is usually stated in terms of geomagnetic storms, but we argue that in fact it is the substorm phenomenon which contains the crucial physics, and therefore prediction of substorm occurrence, severity and duration, either within the context of a longer-lasting geomagnetic storm, but potentially also as an isolated event, is of critical importance. Here we review the physics of the magnetosphere in the frame of space weather forecasting, focusing on recent results, current understanding, and an assessment of probable future developments.

Journal article

Øieroset M, Phan TD, Shay MA, Haggerty CC, Fujimoto M, Angelopoulos V, Eastwood JP, Mozer FSet al., 2017, THEMIS multispacecraft observations of a reconnecting magnetosheath current sheet with symmetric boundary conditions and a large guide field, Geophysical Research Letters, Vol: 44, Pages: 7598-7606, ISSN: 0094-8276

We report three spacecraft observations of a reconnecting magnetosheath current sheet with a guide field of unity, with THEMIS D (THD) and THEMIS E (THE)/THEMIS A (THA) observing oppositely directed reconnection exhausts, indicating the presence of an X line between the spacecraft. The near-constant convective speed of the magnetosheath current sheet allowed the direct translation of the observed time series into spatial profiles. THD observed asymmetries in the plasma density and temperature profiles across the exhaust, characteristics of symmetric reconnection with a guide field. The exhausts at THE and THA, on the other hand, were not the expected mirror image of the THD exhaust in terms of the plasma and field profiles. They consisted of a main outflow at the center of the current sheet, flanked by oppositely directed flows at the two edges of the current sheet, suggesting the presence of a second X line, whose outflow wraps around the outflow from the first X line.

Journal article

Moestl C, Isavnin A, Boakes PD, Kilpua EKJ, Davies JA, Harrison RA, Barnes D, Krupar V, Eastwood JP, Good SW, Forsyth RJ, Bothmer V, Reiss MA, Amerstorfer T, Winslow RM, Anderson BJ, Philpott LC, Rodriguez L, Rouillard AP, Gallagher P, Nieves-Chinchilla T, Zhang TLet al., 2017, Modeling observations of solar coronal mass ejections with heliospheric imagers verified with the Heliophysics System Observatory, Space Weather-the International Journal of Research and Applications, Vol: 15, Pages: 955-970, ISSN: 1539-4956

We present an advance toward accurately predicting the arrivals of coronal mass ejections (CMEs) at the terrestrial planets, including Earth. For the first time, we are able to assess a CME prediction model using data over two thirds of a solar cycle of observations with the Heliophysics System Observatory. We validate modeling results of 1337 CMEs observed with the Solar Terrestrial Relations Observatory (STEREO) heliospheric imagers (HI) (science data) from 8 years of observations by five in situ observing spacecraft. We use the self-similar expansion model for CME fronts assuming 60° longitudinal width, constant speed, and constant propagation direction. With these assumptions we find that 23%–35% of all CMEs that were predicted to hit a certain spacecraft lead to clear in situ signatures, so that for one correct prediction, two to three false alarms would have been issued. In addition, we find that the prediction accuracy does not degrade with the HI longitudinal separation from Earth. Predicted arrival times are on average within 2.6 ± 16.6 h difference of the in situ arrival time, similar to analytical and numerical modeling, and a true skill statistic of 0.21. We also discuss various factors that may improve the accuracy of space weather forecasting using wide-angle heliospheric imager observations. These results form a first-order approximated baseline of the prediction accuracy that is possible with HI and other methods used for data by an operational space weather mission at the Sun-Earth L5 point.

Journal article

Mistry R, Eastwood JP, Phan TD, Hietala Het al., 2017, Statistical properties of solar wind reconnection exhausts, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 5895-5909, ISSN: 2169-9380

The solar wind provides an excellent opportunity to study the exhausts that form as a result of symmetric guide field reconnection, where spacecraft rapidly cross the exhausts far downstream of the X line. We study the statistical properties of solar wind exhausts through a superposed epoch analysis of 188 events observed at 1 AU using the Wind spacecraft. These events span a range of guide fields of 0 to 10 times the reconnecting magnetic field and inflow region plasma beta of 0.1 to 6.6. This analysis reveals that the out-of-plane magnetic field is enhanced within solar wind exhausts. Furthermore, the amount by which the plasma density and ion temperature increase from inflow region to exhaust region is found to be a function of the inflow region plasma beta and reconnection guide field, which explains the lack of these enhancements in a subset of previous observations. This dependence is consistent with the scaling of ion heating with inflow region Alfven speed, which is measured to be consistent with previous observations in the solar wind and at the magnetopause.

Journal article

Innocenti ME, Cazzola E, Mistry R, Eastwood JP, Goldman MV, Newman DL, Markidis S, Lapenta Get al., 2017, Switch-off slow shock/rotational discontinuity structures in collisionless magnetic reconnection: What to look for in satellite observations, GEOPHYSICAL RESEARCH LETTERS, Vol: 44, Pages: 3447-3455, ISSN: 0094-8276

In Innocenti et al. (2015) we have observed and characterized for the first time Petschek-like switch-off slow shock/rotational discontinuity (SO-SS/RD) compound structures in a 2-D fully kinetic simulation of collisionless magnetic reconnection. Observing these structures in the solar wind or in the magnetotail would corroborate the possibility that Petschek exhausts develop in collisionless media as a result of single X point collisionless reconnection. Here we highlight their signatures in simulations with the aim of easing their identification in observations. The most notable signatures include a four-peaked ion current profile in the out-of-plane direction, associated ion distribution functions, increased electron and ion anisotropy downstream the SS, and increased electron agyrotropy downstream the RDs.

Journal article

Ergun RE, Chen L-J, Wilder FD, Ahmadi N, Eriksson S, Usanova ME, Goodrich KA, Holmes JC, Sturner AP, Malaspina DM, Newman DL, Torbert RB, Argall MR, Lindqvist P-A, Burch JL, Webster JM, Drake JF, Price L, Cassak PA, Swisdak M, Shay MA, Graham DB, Strangeway RJ, Russell CT, Giles BL, Dorelli JC, Gershman D, Avanov L, Hesse M, Lavraud B, Le Contel O, Retino A, Phan TD, Goldman MV, Stawarz JE, Schwartz SJ, Eastwood JP, Hwang K-J, Nakamura R, Wang Set al., 2017, Drift waves, intense parallel electric fields, and turbulence associated with asymmetric magnetic reconnection at the magnetopause, GEOPHYSICAL RESEARCH LETTERS, Vol: 44, Pages: 2978-2986, ISSN: 0094-8276

Observations of magnetic reconnection at Earth's magnetopause often display asymmetric structures that are accompanied by strong magnetic field (B) fluctuations and large-amplitude parallel electric fields (E||). The B turbulence is most intense at frequencies above the ion cyclotron frequency and below the lower hybrid frequency. The B fluctuations are consistent with a thin, oscillating current sheet that is corrugated along the electron flow direction (along the X line), which is a type of electromagnetic drift wave. Near the X line, electron flow is primarily due to a Hall electric field, which diverts ion flow in asymmetric reconnection and accompanies the instability. Importantly, the drift waves appear to drive strong parallel currents which, in turn, generate large-amplitude (~100 mV/m) E|| in the form of nonlinear waves and structures. These observations suggest that turbulence may be common in asymmetric reconnection, penetrate into the electron diffusion region, and possibly influence the magnetic reconnection process.

Journal article

Eastwood J, Biffis E, Hapgood MA, Green L, Bisi MM, Bentley RD, Wicks R, McKinnell LA, Gibbs M, Burnett Cet al., 2017, The economic impact of space weather – where do we stand?, Risk Analysis, Vol: 37, Pages: 206-218, ISSN: 0272-4332

Space weather describes the way in which the Sun, and conditions in space more generally, impact human activity and technology both in space and on the ground. It is now well understood that space weather represents a significant threat to infrastructure resilience, and is a source of risk which is wide-ranging in its impact and the pathways by which this impact may occur. Although space weather is growing rapidly as a field, work rigorously assessingthe overall economic cost of space weather appears to be in itsinfancy. Here we provide an initial literature review to gather and assess the quality of any published assessments of space weather impacts and socio-economic studies. Generally speaking there is a good volume of scientific peer-reviewed literature detailing the likelihood and statistics of different types of space weather phenomena. These phenomena all typically exhibit ‘power-law’ behaviour in their severity. The literature on documented impacts is not as extensive with many case studies, but few statistical studies. The literature on the economic impacts of space weather is rather sparse and not as well developed when compared to the other sections, most probably due to the somewhat limited data that is availablefrom end-users. The major risk is attached to power distribution systems and there is disagreement as to the severity of the technological footprint. This strongly controls the economic impact. Consequently, urgent work is required to better quantify the risk of future space weather events.

Journal article

Fu HS, Vaivads A, Khotyaintsev YV, André M, Cao JB, Olshevsky V, Eastwood JP, Retinò Aet al., 2017, Intermittent energy dissipation by turbulent reconnection, Geophysical Research Letters, Vol: 44, Pages: 37-43, ISSN: 1944-8007

Magnetic reconnection—the process responsible for many explosive phenomena in both nature and laboratory—is efficient at dissipating magnetic energy into particle energy. To date, exactly how this dissipation happens remains unclear, owing to the scarcity of multipoint measurements of the “diffusion region” at the sub-ion scale. Here we report such a measurement by Cluster—four spacecraft with separation of 1/5 ion scale. We discover numerous current filaments and magnetic nulls inside the diffusion region of magnetic reconnection, with the strongest currents appearing at spiral nulls (O-lines) and the separatrices. Inside each current filament, kinetic-scale turbulence is significantly increased and the energy dissipation, E′ ⋅ j, is 100 times larger than the typical value. At the jet reversal point, where radial nulls (X-lines) are detected, the current, turbulence, and energy dissipations are surprisingly small. All these features clearly demonstrate that energy dissipation in magnetic reconnection occurs at O-lines but not X-lines.

Journal article

Kubicka M, Mostl C, Amerstorfer T, Boakes PD, Feng L, Eastwood J, Tormanen Oet al., 2016, Prediction of geomagnetic storm strength from inner heliospheric in situ observations, Astrophysical Journal, Vol: 833, ISSN: 1538-4357

Prediction of the effects of coronal mass ejections (CMEs) on Earth strongly depends on knowledge of the interplanetary magnetic field southward component, B z . Predicting the strength and duration of B z inside a CME with sufficient accuracy is currently impossible, forming the so-called B z problem. Here, we provide a proof-of-concept of a new method for predicting the CME arrival time, speed, B z , and resulting disturbance storm time (Dst) index on Earth based only on magnetic field data, measured in situ in the inner heliosphere (<1 au). On 2012 June 12–16, three approximately Earthward-directed and interacting CMEs were observed by the Solar Terrestrial Relations Observatory imagers and Venus Express (VEX) in situ at 0.72 au, 6° away from the Sun–Earth line. The CME kinematics are calculated using the drag-based and WSA–Enlil models, constrained by the arrival time at VEX, resulting in the CME arrival time and speed on Earth. The CME magnetic field strength is scaled with a power law from VEX to Wind. Our investigation shows promising results for the Dst forecast (predicted: −96 and −114 nT (from 2 Dst models); observed: −71 nT), for the arrival speed (predicted: 531 ± 23 km s−1; observed: 488 ± 30 km s−1), and for the timing (6 ± 1 hr after the actual arrival time). The prediction lead time is 21 hr. The method may be applied to vector magnetic field data from a spacecraft at an artificial Lagrange point between the Sun and Earth or to data taken by any spacecraft temporarily crossing the Sun–Earth line.

Journal article

Stawarz JE, Eriksson S, Wilder FD, Ergun RE, Schwartz SJ, Pouquet A, Burch JL, Giles BL, Khotyaintsev Y, Le Contel O, Lindqvist PA, Magnes W, Pollock CJ, Russell CT, Strangeway RJ, Torbert RB, Avanov LA, Dorelli JC, Eastwood JP, Gershman DJ, Goodrich KA, Malaspina DM, Marklund GT, Mirioni L, Sturner APet al., 2016, Observations of turbulence in a Kelvin-Helmholtz event on September 8, 2015 by the Magnetospheric Multiscale Mission, Journal of Geophysical Research: Space Physics, Vol: 121, Pages: 11021-11034, ISSN: 2169-9380

Spatial and high-time-resolution properties of the velocities,magnetic eld, and 3D electric eld within plasma turbulence are examined observationally using data from the Magnetospheric Multiscale Mission. Observations from a Kelvin-Helmholtz instability (KHI) on the Earth's magnetopause are examined, which both provides a series of repeatable intervals to analyze, giving better statistics, and provides a rst look at the properties of turbulence in the KHI. For the rst time direct observations of both the high-frequency ion and electron velocity spectra are examined, showing differing ion and electron behavior at kinetic scales. Temporal spectra ex-hibit power law behavior with changes in slope near the ion gyrofrequency and lower-hybrid frequency. The work provides the rst observational evi-dence for turbulent intermittency and anisotropy consistent with quasi-two-dimensional turbulence in association with the KHI. The behavior of kinetic scale intermittency is found to have di erences from previous studies of solar wind turbulence, leading to novel insights on the turbulent dynamics inthe KHI.

Journal article

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

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