Imperial College London

Dr Jonathan P. Eastwood

Faculty of Natural SciencesDepartment of Physics

Senior Lecturer



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




6M63Blackett LaboratorySouth Kensington Campus





Publication Type

176 results found

Eastwood J, Hapgood MA, Biffis E, Benedetti D, Bisi MM, Green L, Bentley RD, Burnett Cet al., 2019, Quantifying the economic value of space weather forecasting for power grids: An exploratory study, Space Weather, Vol: 16, Pages: 2052-2067, ISSN: 1539-4956

An accurate understanding of space weather socioeconomic impact is fundamental to the development of appropriate operational services, forecasting capabilities, and mitigation strategies. One way to approach this problem is by developing physics‐based models and frameworks that can lead to a bottom‐up estimate of risk and likely impact. Here we describe the development of a new framework to assess the economic impact of space weather on power distribution networks and the supply of electricity. In particular, we focus on the phenomenon of the geomagnetic substorm, which is relatively localized in time and space, and occurs multiple times with varying severity during a geomagnetic storm. The framework uses the AE index to characterize substorm severity, and the impact of the substorm is modulated by the resilience of the power grid and the nature of available forecast. Possible scenarios for substorm sequences during a 1‐in‐10‐, a 1‐in‐30‐, and a 1‐in‐100‐year geomagnetic storm events are generated based on the 2003, 1989, and 1859 geomagnetic storms. Economic impact, including international spill over, can then be calculated using standard techniques, based on the duration and the geographical footprint of the power outage. Illustrative calculations are made for the European sector, for a variety of forecast and resilience scenarios. However, currently available data are highly regionally inhomogeneous, frustrating attempts to define an overall global economic impact at the present time.

Journal article

Torbert RB, Burch JL, Phan TD, Hesse M, Argall MR, Shuster J, Ergun RE, Alm L, Nakamura R, Genestreti KJ, Gershman DJ, Paterson WR, Turner DL, Cohen I, Giles BL, Pollock CJ, Wang S, Chen L-J, Stawarz JE, Eastwood JP, Hwang KJ, Farrugia C, Dors I, Vaith H, Mouikis C, Ardakani A, Mauk BH, Fuselier SA, Russell CT, Strangeway RJ, Moore TE, Drake JF, Shay MA, Khotyaintsev YV, Lindqvist P-A, Baumjohann W, Wilder FD, Ahmadi N, Dorelli JC, Avanov LA, Oka M, Baker DN, Fennell JF, Blake JB, Jaynes AN, Le Contel O, Petrinec SM, Lavraud B, Saito Yet al., 2018, Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space., Science, Vol: 362, Pages: 1391-1395

Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvénic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.

Journal article

Hesse M, Norgren C, Tenfjord P, Burch JL, Liu YH, Chen LJ, Bessho N, Wang S, Nakamura R, Eastwood JP, Hoshino M, Torbert RB, Ergun REet al., 2018, On the role of separatrix instabilities in heating the reconnection outflow region, Physics of Plasmas, Vol: 25, ISSN: 1070-664X

A study of the role microinstabilities at the reconnection separatrix can play in heating the electrons during the transition from inflow to outflow is being presented. We find that very strong flow shears at the separatrix layer lead to counterstreaming electron distributions in the region around the separatrix, which become unstable to a beam-type instability. Similar to what has been seen in earlier research, the ensuing instability leads to the formation of propagating electrostatic solitons. We show here that this region of strong electrostatic turbulence is the predominant electron heating site when transiting from inflow to outflow. The heating is the result of heating generated by electrostatic turbulence driven by overlapping beams, and its macroscopic effect is a quasi-viscous contribution to the overall electron energy balance. We suggest that instabilities at the separatrix can play a key role in the overall electron energy balance in magnetic reconnection.

Journal article

Eggington J, Mejnertsen L, Desai R, Eastwood J, Chittenden Jet al., 2018, Forging links in Earth's plasma environment, Astronomy and Geophysics, Vol: 59, Pages: 6.26-6.28, ISSN: 1366-8781

Journal article

Hwang KJ, Sibeck DG, Burch JL, Choi E, Fear RC, Lavraud B, Giles BL, Gershman D, Pollock CJ, Eastwood JP, Khotyaintsev Y, Escoubet P, Fu H, Toledo-Redondo S, Torbert RB, Ergun RE, Paterson WR, Dorelli JC, Avanov L, Russell CT, Strangeway RJet al., 2018, Small-scale flux transfer events formed in the reconnection exhaust region between two X lines, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 8473-8488, ISSN: 2169-9380

We report MMS observations of the ion-scale flux transfer events (FTEs) that may involve two main X lines and tearing instability between the two X lines. The four spacecraft detected multiple isolated regions with enhanced magnetic field strength and bipolar Bn signatures normal to the nominal magnetopause, indicating FTEs. The currents within the FTEs flow mostly parallel to B, and the magnetic tension force is balanced by the total pressure gradient force. During these events, the plasma bulk flow velocity was directed southward. Detailed analysis of the magnetic and electric field and plasma moments variations suggests that the FTEs were initially embedded within the exhaust region north of an X line but were later located southward/downstream of a subsequent X line. The cross sections of the individual FTEs are in the range of ~2.5–6.8 ion inertial lengths. The observations suggest the formation of multiple secondary FTEs. The presence of an X line in the exhaust region southward of a second X line results from the southward drift of an old X line and the reformation of a new X line. The current layer between the two X lines is unstable to the tearing instability, generating multiple ion-scale flux-rope-type secondary islands.

Journal article

Schwartz SJ, Avanov L, Turner D, Zhang H, Gingell I, Eastwood JP, Gershman DJ, Johlander A, Russell CT, Burch JL, Dorelli JC, Eriksson S, Ergun RE, Fuselier SA, Giles BL, Goodrich KA, Khotyaintsev YV, Lavraud B, Lindqvist PA, Oka M, Phan TD, Strangeway RJ, Trattner KJ, Torbert RB, Vaivads A, Wei H, Wilder Fet al., 2018, Ion kinetics in a hot flow anomaly: MMS observations, Geophysical Research Letters, Vol: 45, Pages: 11520-11529, ISSN: 0094-8276

Hot Flow Anomalies (HFAs) are transients observed at planetary bow shocks, formed by the shock interaction with a convected interplanetary current sheet. The primary interpretation relies on reflected ions channeled upstream along the current sheet. The short duration of HFAs has made direct observations of this process difficult. We employ high resolution measurements by NASA's Magnetospheric Multiscale Mission to probe the ion microphysics within a HFA. Magnetospheric Multiscale Mission data reveal a smoothly varying internal density and pressure, which increase toward the trailing edge of the HFA, sweeping up particles trapped within the current sheet. We find remnants of reflected or other backstreaming ions traveling along the current sheet, but most of these are not fast enough to out-run the incident current sheet convection. Despite the high level of internal turbulence, incident and backstreaming ions appear to couple gyro-kinetically in a coherent manner.

Journal article

Stawarz JE, Eastwood JP, Genestreti KJ, Nakamura R, Ergun RE, Burgess D, Burch JL, Fuselier SA, Gershamn DJ, Giles BL, Le Contel O, Lindqvist P-A, Russell CT, Torbert RBet al., 2018, Intense electric fields and electron‐scale substructure within magnetotail flux ropes as revealed by the Magnetospheric Multiscale mission, Geophysical Research Letters, Vol: 45, Pages: 8783-8792, ISSN: 0094-8276

Three flux ropes associated with near‐Earth magnetotail reconnection are analyzed using Magnetospheric Multiscale observations. The flux ropes are Earthward propagating with sizes from ∼3 to 11 ion inertial lengths. Significantly different axial orientations are observed, suggesting spatiotemporal variability in the reconnection and/or flux rope dynamics. An electron‐scale vortex, associated with one of the most intense electric fields (E) in the event, is observed within one of the flux ropes. This E is predominantly perpendicular to the magnetic field (B); the electron vortex is frozen‐in with E × B drifting electrons carrying perpendicular current and causing a small‐scale magnetic enhancement. The vortex is ∼16 electron gyroradii in size perpendicular to B and potentially elongated parallel to B. The need to decouple the frozen‐in vortical motion from the surrounding plasma implies a parallel E at the structure's ends. The formation of frozen‐in electron vortices within reconnection‐generated flux ropes may have implications for particle acceleration.

Journal article

Eastwood J, Mistry R, Phan TD, Schwartz SJ, Ergun RE, Drake JF, Oieroset M, Stawarz JE, Goldman MV, Haggerty C, Shay MA, Burch JL, Gershman DJ, Giles BL, LIndqvist PA, Torbert RB, Strangeway RJ, Russell CTet al., 2018, Guide field reconnection: exhaust structure and heating, Geophysical Research Letters, Vol: 45, Pages: 4569-4577, ISSN: 0094-8276

Magnetospheric Multiscale (MMS) observations are used to probe the structure and temperature profile of a guide field reconnection exhaust ~100 ion inertial lengths downstream from the X‐line in the Earth's magnetosheath. Asymmetric Hall electric and magnetic field signatures were detected, together with a density cavity confined near one edge of the exhaust and containing electron flow toward the X‐line. Electron holes were also detected both on the cavity edge and at the Hall magnetic field reversal. Predominantly parallel ion and electron heating was observed in the main exhaust but within the cavity, electron cooling and enhanced parallel ion heating was found. This is explained in terms of the parallel electric field, which inhibits electron mixing within the cavity on newly reconnected field lines, but accelerates ions. Consequently, guide field reconnection causes inhomogeneous changes in ion and electron temperature across the exhaust.

Journal article

Phan TD, Eastwood JP, Shay MA, Drake JF, Sonnerup BUO, Fujimoto M, Cassak PA, Øieroset M, Burch JL, Torbert RB, Rager AC, Dorelli JC, Gershman DJ, Pollock C, Pyakurel PS, Haggerty CC, Khotyaintsev Y, Lavraud B, Saito Y, Oka M, Ergun RE, Retino A, Le Contel O, Argall MR, Giles BL, Moore TE, Wilder FD, Strangeway RJ, Russell CT, Lindqvist PA, Magnes Wet al., 2018, Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath, Nature, Vol: 557, Pages: 202-206, ISSN: 0028-0836

© 2018 Macmillan Publishers Ltd., part of Springer Nature. Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region 1,2 . On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed 3-5 . Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region 6 . In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales 7-11 . However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

Journal article

Harrison RA, Davies JA, Barnes D, Byrne JP, Perry CH, Bothmer V, Eastwood JP, Gallagher PT, Kilpua EKJ, Moestl C, Rodriguez L, Rouillard AP, Odstril Det al., 2018, CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1, Solar Physics, Vol: 293, ISSN: 0038-0938

We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA’s twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS project. Here, we focus on the observational characteristics of CMEs imaged in the heliosphere by the inner (HI-1) cameras, while following papers will present analyses of CME propagation through the entire HI fields of view. More specifically, in this paper we present distributions of the basic observational parameters – namely occurrence frequency, central position angle (PA) and PA span – derived from nearly 2000 detections of CMEs in the heliosphere by HI-1 on STEREO-A or STEREO-B from the minimum between Solar Cycles 23 and 24 to the maximum of Cycle 24; STEREO-A analysis includes a further 158 CME detections from the descending phase of Cycle 24, by which time communication with STEREO-B had been lost. We compare heliospheric CME characteristics with properties of CMEs observed at coronal altitudes, and with sunspot number. As expected, heliospheric CME rates correlate with sunspot number, and are not inconsistent with coronal rates once instrumental factors/differences in cataloguing philosophy are considered. As well as being more abundant, heliospheric CMEs, like their coronal counterparts, tend to be wider during solar maximum. Our results confirm previous coronagraph analyses suggesting that CME launch sites do not simply migrate to higher latitudes with increasing solar activity. At solar minimum, CMEs tend to be launched from equatorial latitudes, while at maximum, CMEs appear to be launched over a much wider latitude range; this has implications for understanding the CME/solar source association. Our analysis provides some supporting evidence for the systematic dragging of CMEs to lower latitude

Journal article

Krupar V, Maksimovic M, Kontar EP, Zaslavsky A, Santolik O, Soucek J, Kruparova O, Eastwood JP, Szabo Aet al., 2018, Interplanetary Type III Bursts and Electron Density Fluctuations in the Solar Wind, ASTROPHYSICAL JOURNAL, Vol: 857, ISSN: 0004-637X

Type III bursts are generated by fast electron beams originated from magnetic reconnection sites of solar flares. As propagation of radio waves in the interplanetary medium is strongly affected by random electron density fluctuations, type III bursts provide us with a unique diagnostic tool for solar wind remote plasma measurements. Here, we performed a statistical survey of 152 simple and isolated type III bursts observed by the twin-spacecraft Solar TErrestrial RElations Observatory mission. We investigated their time–frequency profiles in order to retrieve decay times as a function of frequency. Next, we performed Monte Carlo simulations to study the role of scattering due to random electron density fluctuations on time–frequency profiles of radio emissions generated in the interplanetary medium. For simplification, we assumed the presence of isotropic electron density fluctuations described by a power law with the Kolmogorov spectral index. Decay times obtained from observations and simulations were compared. We found that the characteristic exponential decay profile of type III bursts can be explained by the scattering of the fundamental component between the source and the observer despite restrictive assumptions included in the Monte Carlo simulation algorithm. Our results suggest that relative electron density fluctuations $\langle \delta {n}_{{\rm{e}}}\rangle /{n}_{{\rm{e}}}$ in the solar wind are 0.06–0.07 over wide range of heliospheric distances.

Journal article

Ergun RE, Goodrich KA, Wilder FD, Ahmadi N, Holmes JC, Eriksson S, Stawarz JE, Nakamura R, Genestreti KJ, Hesse M, Burch JL, Torbert RB, Phan TD, Schwartz SJ, Eastwood JP, Strangeway RJ, Le Contel O, Russell CT, Argall MR, Lindqvist PA, Chen LJ, Cassak PA, Giles BL, Dorelli JC, Gershman D, Leonard TW, Lavraud B, Retino A, Matthaeus W, Vaivads Aet al., 2018, Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail, Geophysical Research Letters, Vol: 45, Pages: 3338-3347, ISSN: 0094-8276

We report observations of turbulent dissipation and particle acceleration from large-amplitude electric fields (E) associated with strong magnetic field (B) fluctuations in the Earth's plasma sheet. The turbulence occurs in a region of depleted density with anti-earthward flows followed by earthward flows suggesting ongoing magnetic reconnection. In the turbulent region, ions and electrons have a significant increase in energy, occasionally > 100 keV, and strong variation. There are numerous occurrences of |E| > 100 mV/m including occurrences of large potentials ( > 1 kV) parallel to B and occurrences with extraordinarily large J · E (J is current density). In this event, we find that the perpendicular contribution of J · E with frequencies near or below the ion cyclotron frequency (f ci ) provide the majority net positive J · E. Large-amplitude parallel E events with frequencies above f ci to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration.

Journal article

Good SW, Forsyth RJ, Eastwood JP, Möstl Cet al., 2018, Correlation of ICME magnetic fields at radially aligned spacecraft, Solar Physics, Vol: 293, ISSN: 0038-0938

The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7° in heliographic latitude. Both ICMEs took approximately two days to travel between the spacecraft. The ICME magnetic field profiles observed at MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of one hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east–west and north–south directed components, with Pearson’s correlation coefficients of approximately 0.85 and 0.95, respectively; microscale features with timescales of one minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the magnetic field profiles may be interpreted in two ways. If the spacecraft sampled the same region of each ICME (i.e. if the spacecraft angular separations are neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors w

Journal article

Genestreti KJ, Varsani A, Burch JL, Cassak PA, Torbert RB, Nakamura R, Ergun RE, Phan TD, Toledo-Redondo S, Hesse M, Wang S, Giles BL, Russell CT, Vörös Z, Hwang KJ, Eastwood JP, Lavraud B, Escoubet CP, Fear RC, Khotyaintsev Y, Nakamura TKM, Webster JM, Baumjohann Wet al., 2018, MMS observation of asymmetric reconnection supported by 3-D electron pressure divergence, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 1806-1821, ISSN: 2169-9380

We identify the electron diffusion region (EDR) of a guide field dayside reconnection site encountered by the Magnetospheric Multiscale (MMS) mission and estimate the terms in generalized Ohm's law that controlled energy conversion near the X-point. MMS crossed the moderate-shear (∼130°) magnetopause southward of the exact X-point. MMS likely entered the magnetopause far from the X-point, outside the EDR, as the size of the reconnection layer was less than but comparable to the magnetosheath proton gyroradius, and also as anisotropic gyrotropic "outflow" crescent electron distributions were observed. MMS then approached the X-point, where all four spacecraft simultaneously observed signatures of the EDR, for example, an intense out-of-plane electron current, moderate electron agyrotropy, intense electron anisotropy, nonideal electric fields, and nonideal energy conversion. We find that the electric field associated with the nonideal energy conversion is (a) well described by the sum of the electron inertial and pressure divergence terms in generalized Ohms law though (b) the pressure divergence term dominates the inertial term by roughly a factor of 5:1, (c) both the gyrotropic and agyrotropic pressure forces contribute to energy conversion at the X-point, and (d) both out-of-the-reconnection-plane gradients (∂/∂M) and in-plane (∂/∂L,N) in the pressure tensor contribute to energy conversion near the X-point. This indicates that this EDR had some electron-scale structure in the out-of-plane direction during the time when (and at the location where) the reconnection site was observed.

Journal article

Kacem I, Jacquey C, Génot V, Lavraud B, Vernisse Y, Marchaudon A, Le Contel O, Breuillard H, Phan TD, Hasegawa H, Oka M, Trattner KJ, Farrugia CJ, Paulson K, Eastwood JP, Fuselier SA, Turner D, Eriksson S, Wilder F, Russell CT, Øieroset M, Burch J, Graham DB, Sauvaud JA, Avanov L, Chandler M, Coffey V, Dorelli J, Gershman DJ, Giles BL, Moore TE, Saito Y, Chen LJ, Penou Eet al., 2018, Magnetic reconnection at a thin current sheet separating two interlaced flux tubes at the Earth's magnetopause, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 1779-1793, ISSN: 2169-9380

The occurrence of spatially and temporally variable reconnection at the Earth's magnetopause leads to the complex interaction of magnetic fields from the magnetosphere and magnetosheath. Flux transfer events (FTEs) constitute one such type of interaction. Their main characteristics are (1) an enhanced core magnetic field magnitude and (2) a bipolar magnetic field signature in the component normal to the magnetopause, reminiscent of a large-scale helicoidal flux tube magnetic configuration. However, other geometrical configurations which do not fit this classical picture have also been observed. Using high-resolution measurements from the Magnetospheric Multiscale mission, we investigate an event in the vicinity of the Earth's magnetopause on 7 November 2015. Despite signatures that, at first glance, appear consistent with a classic FTE, based on detailed geometrical and dynamical analyses as well as on topological signatures revealed by suprathermal electron properties, we demonstrate that this event is not consistent with a single, homogenous helicoidal structure. Our analysis rather suggests that it consists of the interaction of two separate sets of magnetic field lines with different connectivities. This complex three-dimensional interaction constructively conspires to produce signatures partially consistent with that of an FTE. We also show that, at the interface between the two sets of field lines, where the observed magnetic pileup occurs, a thin and strong current sheet forms with a large ion jet, which may be consistent with magnetic flux dissipation through magnetic reconnection in the interaction region.

Journal article

Akhavan-Tafti M, Slavin JA, Le G, Eastwood JP, Strangeway RJ, Russell CT, Nakamura R, Baumjohann W, Torbert RB, Giles BL, Gershman DJ, Burch JLet al., 2018, MMS examination of FTEs at the earth's subsolar magnetopause, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 1224-1241, ISSN: 2169-9380

Determining the magnetic field structure, electric currents, and plasma distributions within flux transfer event (FTE)-type flux ropes is critical to the understanding of their origin, evolution, and dynamics. Here the Magnetospheric Multiscale mission's high-resolution magnetic field and plasma measurements are used to identify FTEs in the vicinity of the subsolar magnetopause. The constant-α flux rope model is used to identify quasi-force free flux ropes and to infer the size, the core magnetic field strength, the magnetic flux content, and the spacecraft trajectories through these structures. Our statistical analysis determines a mean diameter of 1,700 ± 400 km (~30 ± 9 d i ) and an average magnetic flux content of 100 ± 30 kWb for the quasi-force free FTEs at the Earth's subsolar magnetopause which are smaller than values reported by Cluster at high latitudes. These observed nonlinear size and magnetic flux content distributions of FTEs appear consistent with the plasmoid instability theory, which relies on the merging of neighboring, small-scale FTEs to generate larger structures. The ratio of the perpendicular to parallel components of current density, R J , indicates that our FTEs are magnetically force-free, defined as R J < 1, in their core regions ( < 0.6 R flux rope ). Plasma density is shown to be larger in smaller, newly formed FTEs and dropping with increasing FTE size. It is also shown that parallel ion velocity dominates inside FTEs with largest plasma density. Field-aligned flow facilitates the evacuation of plasma inside newly formed FTEs, while their core magnetic field strengthens with increasing FTE size.

Journal article

Zabori B, Hirn A, Eastwood J, Brown P, Palla C, Oddy T, Nolbert D, Santin G, Nieminen P, Marosy Get al., 2018, Space radiation and magnetic field environment specification for the Radcube space weather related CubeSat mission, ISSN: 0074-1795

Copyright © 2018 by the International Astronautical Federation (IAF). All rights reserved. To study space weather environment in space, as a first step, it is necessary to develop and establish an advanced, real-time monitoring system. Such a monitoring system may be able to provide scientific data on space radiation (electron and proton spectra, flux of heavier ions) and the status of the magnetosphere in order to gain the possibility for a reliable forecast capability. The expansion of the CubeSat/SmallSat industry will make it possible in the near future to launch orbital constellations with relevant, miniaturised instrumentation in order to study the space weather environment in near real-time. Thus the development of RADCUBE, a 3U CubeSat demonstration mission lead by a Hungarian company, called C3S LLC, for space weather monitoring purpose, has begun within the European Space Agency (ESA) CubeSat programme. As part of the development a new, combined, space weather monitoring instrument package (called RadMag) has been initiated at the Centre for Energy Research, Hungarian Academy of Sciences in the framework of ESA General Support Technology Programme (GSTP) in collaboration with Imperial College London and Astronika. The RadMag measurement capabilities were defined by reconstructing the expected space radiation and magnetic field environments for different orbit scenarios. The space radiation environment was analyzed considering the following parameters: flux of Galactic Cosmic Rays, trapped protons and electrons, solar particle events, corresponding Linear Energy Transfer (LET) spectra and Total Ionizing Dose (TID) levels. The expected magnetic field environment was modeled with the IGRF2015 + Tsyganenko-96 model both for quiet and stormy conditions. This paper addresses the results of these radiation and magnetic field environment reconstruction and calculations for the different possible orbital parameters of the RADCUBE mission in order to characteri

Conference paper

Mejnertsen L, Eastwood J, Hietala H, Chittenden Jet al., 2017, Global MHD simulations of the Earth's bow shock shape and motion under variable solar wind conditions, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 259-271, ISSN: 2169-9380

Empirical models of the Earth's bow shock are often used to place in situ measurements in context and to understand the global behavior of the foreshock/bow shock system. They are derived statistically from spacecraft bow shock crossings and typically treat the shock surface as a conic section parameterized according to a uniform solar wind ram pressure, although more complex models exist. Here a global magnetohydrodynamic simulation is used to analyze the variability of the Earth's bow shock under real solar wind conditions. The shape and location of the bow shock is found as a function of time, and this is used to calculate the shock velocity over the shock surface. The results are compared to existing empirical models. Good agreement is found in the variability of the subsolar shock location. However, empirical models fail to reproduce the two-dimensional shape of the shock in the simulation. This is because significant solar wind variability occurs on timescales less than the transit time of a single solar wind phase front over the curved shock surface. Empirical models must therefore be used with care when interpreting spacecraft data, especially when observations are made far from the Sun-Earth line. Further analysis reveals a bias to higher shock speeds when measured by virtual spacecraft. This is attributed to the fact that the spacecraft only observes the shock when it is in motion. This must be accounted for when studying bow shock motion and variability with spacecraft data.

Journal article

Farrugia CJ, Lugaz N, Alm L, Vasquez B, Argall MR, Kucharek H, Matsui H, Torbert RB, Lavraud B, LeContel O, Cohen IJ, Burch JL, Russell CT, Strangeway RJ, Shuster J, Dorelli JC, Eastwood JP, Ergun RE, Fuselier SA, Gershman DJ, Giles BL, Khotyaintsev YV, Lindqvist PA, Marklund GT, Paulson KW, Petrinec SM, Phan TD, Pollock CJet al., 2017, MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub-Alfvénic Flow, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 9934-9951, ISSN: 2169-9380

We present MMS observations during two dayside magnetopause crossings under hithertounexamined conditions: (i) when the bow shock is weakening and the solar wind transitioning tosub-Alfvénic flow and (ii) when it is reforming. Interplanetary conditions consist of a magnetic cloud with (i)a strongB(∼20 nT) pointing south and (ii) a density profile with episodic decreases to values of∼0.3 cm−3followed by moderate recovery. During the crossings the magnetosheath magnetic field is stronger thanthe magnetosphere field by a factor of∼2.2. As a result, during the outbound crossing through the iondiffusion region, MMS observed an inversion of the relative positions of the X and stagnation (S) lines fromthat typically the case: the S line was closer to the magnetosheath side. The S line appears in the form of aslow expansion fan near which most of the energy dissipation is taking place. While in the magnetospherebetween the crossings, MMS observed strong field and flow perturbations, which we argue to be due tokinetic Alfvén waves. During the reconnection interval, whistler mode waves generated by an electrontemperature anisotropy (Te⟂>Te∥) were observed. Another aim of the paper is to distinguish bowshock-induced field and flow perturbations from reconnection-related signatures. The high-resolutionMMS data together with 2-D hybrid simulations of bow shock dynamics helped us to distinguish betweenthe two sources. We show examples of bow shock-related effects (such as heating) and reconnectioneffects such as accelerated flows satisfying the Walén relation.

Journal article

Stawarz JE, Eastwood JP, Varsani A, Ergun RE, Shay MA, Nakamura R, Phan TD, Burch JL, Gershman DJ, Giles BL, Goodrich KA, Khotyaintsev YV, Lindqvist P-A, Russell CT, Strangeway RJ, Torbert RBet al., 2017, Magnetospheric Multiscale analysis of intense field-aligned Poynting flux near the Earth's plasma sheet boundary, Geophysical Research Letters, Vol: 44, Pages: 7106-7113, ISSN: 1944-8007

The Magnetospheric Multiscale mission is employed to examine intense Poynting flux directed along the background magnetic field toward Earth, which reaches amplitudes of nearly 2 mW/m2. The event is located within the plasma sheet but likely near the boundary at a geocentric distance of 9 RE in association with bulk flow signatures. The fluctuations have wavelengths perpendicular to the magnetic field of 124–264 km (compared to an ion gyroradius of 280 km), consistent with highly kinetic Alfvén waves. While the wave vector remains highly perpendicular to the magnetic field, there is substantial variation of the direction in the perpendicular plane. The field-aligned Poynting flux may be associated with kinetic Alfvén waves released along the separatrix by magnetotail reconnection and/or the radiation of waves excited by bursty bulk flow braking and may provide a means through which energy released by magnetic reconnection is transferred to the auroral region.

Journal article

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

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