Imperial College London

Emeritus ProfessorStevenSchwartz

Faculty of Natural SciencesDepartment of Physics

Distinguished Research Fellow
 
 
 
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Contact

 

+44 (0)20 7594 7660s.schwartz Website

 
 
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Location

 

6M58Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

234 results found

Wilder FD, Schwartz SJ, Ergun RE, Eriksson S, Ahmadi N, Chasapis A, Newman DL, Burch JL, Torbert RB, Strangeway RJ, Giles BLet al., 2020, Parallel Electrostatic Waves Associated With Turbulent Plasma Mixing in the Kelvin-Helmholtz Instability, GEOPHYSICAL RESEARCH LETTERS, Vol: 47, ISSN: 0094-8276

Journal article

Starkey M, Fuselier SA, Desai MI, Schwartz SJ, Gomez RG, Mukherjee J, Cohen IJ, Russell CTet al., 2020, MMS Observations of Accelerated Interstellar Pickup He(+)Ions at an Interplanetary Shock, ASTROPHYSICAL JOURNAL, Vol: 897, ISSN: 0004-637X

Journal article

Madanian H, Schwartz SJ, Halekas JS, Wilson LBet al., 2020, Nonstationary Quasiperpendicular Shock and Ion Reflection at Mars, GEOPHYSICAL RESEARCH LETTERS, Vol: 47, ISSN: 0094-8276

Journal article

Wilson LB, Chen L-J, Wang S, Schwartz SJ, Turner DL, Stevens ML, Kasper JC, Osmane A, Caprioli D, Bale SD, Pulupa MP, Salem CS, Goodrich KAet al., 2020, Electron Energy Partition across Interplanetary Shocks. III. Analysis, ASTROPHYSICAL JOURNAL, Vol: 893, ISSN: 0004-637X

Journal article

Gingell I, Schwartz SJ, Eastwood JP, Stawarz JE, Burch JL, Ergun RE, Fuselier SA, Gershman DJ, Giles BL, Khotyaintsev YV, Lavraud B, Lindqvist P, Paterson WR, Phan TD, Russell CT, Strangeway RJ, Torbert RB, Wilder Fet al., 2020, Statistics of reconnecting current sheets in the transition region of earth's bow shock, Journal of Geophysical Research: Space Physics, Vol: 125, Pages: 1-14, ISSN: 2169-9380

We have conducted a comprehensive survey of burst mode observations of Earth's bow shock by the Magnetospheric Multiscale mission to identify and characterize current sheets associated with collisionless shocks, with a focus on those containing fast electron outflows, a likely signature of magnetic reconnection. The survey demonstrates that these thin current sheets are observed within the transition region of approximately 40% of shocks within the burst mode data set of Magnetospheric Multiscale. With only small apparent bias toward quasi‐parallel shock orientations and high Alfvén Mach numbers, the results suggest that reconnection at shocks is a universal process, occurring across all shock orientations and Mach numbers. On examining the distributions of current sheet properties, we find no correlation between distance from the shock, sheet width, or electron jet speed, though the relationship between electron and ion jet speed supports expectations of electron‐only reconnection in the region. Furthermore, we find that robust heating statistics are not separable from background fluctuations, and thus, the primary consequence of reconnection at shocks is in relaxing the topology of the disordered magnetic field in the transition region.

Journal article

Hoilijoki S, Ergun RE, Schwartz SJ, Eriksson S, Wilder FD, Webster JM, Ahmadi N, Le Contel O, Burch JL, Torbert RB, Strangeway RJ, Giles BLet al., 2019, Electron-Scale Magnetic Structure Observed Adjacent to an Electron Diffusion Region at the Dayside Magnetopause, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 124, Pages: 10153-10169, ISSN: 2169-9380

Journal article

Ergun RE, Hoilijoki S, Ahmadi N, Schwartz SJ, Wilder FD, Burch JL, Torbert RB, Lindqvist P-A, Graham DB, Strangeway RJ, Le Contel O, Holmes JC, Stawarz JE, Goodrich KA, Eriksson S, Giles BL, Gershman D, Chen LJet al., 2019, Magnetic Reconnection in Three Dimensions: Observations of Electromagnetic Drift Waves in the Adjacent Current Sheet, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 124, Pages: 10104-10118, ISSN: 2169-9380

Journal article

Ergun RE, Hoilijoki S, Ahmadi N, Schwartz SJ, Wilder FD, Drake JF, Hesse M, Shay MA, Ji H, Yamada M, Graham DB, Cassak PA, Swisdak M, Burch JL, Torbert RB, Holmes JC, Stawarz JE, Goodrich KA, Eriksson S, Strangeway RJ, LeContel Oet al., 2019, Magnetic Reconnection in Three Dimensions: Modeling and Analysis of Electromagnetic Drift Waves in the Adjacent Current Sheet, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 124, Pages: 10085-10103, ISSN: 2169-9380

Journal article

Wilson LB, Chen L-J, Wang S, Schwartz SJ, Turner DL, Stevens ML, Kasper JC, Osmane A, Caprioli D, Bale SD, Pulupa MP, Salem CS, Goodrich KAet al., 2019, Electron Energy Partition across Interplanetary Shocks. II. Statistics, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 245, ISSN: 0067-0049

Journal article

Schwartz SJ, Andersson L, Xu S, Mitchell DL, Akbari H, Ergun RE, Mazelle C, Thaller SA, Sales ARN, Horaites K, DiBraccio GA, Meziane Ket al., 2019, Collisionless Electron Dynamics in the Magnetosheath of Mars, GEOPHYSICAL RESEARCH LETTERS, Vol: 46, Pages: 11679-11688, ISSN: 0094-8276

Journal article

Starkey MJ, Fuselier SA, Desai M, Burch JL, Gomez RG, Mukherjee J, Russell CT, Lai H, Schwartz SJet al., 2019, Acceleration of Interstellar Pickup He+ at Earth's Perpendicular Bow Shock, GEOPHYSICAL RESEARCH LETTERS, Vol: 46, Pages: 10735-10743, ISSN: 0094-8276

Journal article

Fowler CM, Halekas J, Schwartz S, Goodrich KA, Gruesbeck JR, Benna Met al., 2019, The Modulation of Solar Wind Hydrogen Deposition in the Martian Atmosphere by Foreshock Phenomena, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 124, Pages: 7086-7097, ISSN: 2169-9380

Journal article

Shuster JR, Gershman DJ, Chen L-J, Wang S, Bessho N, Dorelli JC, da Silva DE, Giles BL, Paterson WR, Denton RE, Schwartz SJ, Norgred C, Wilder FD, Cassak PA, Swisdak M, Uritsky V, Schiff C, Rager AC, Smith S, Avanov LA, Vinas AFet al., 2019, MMS Measurements of the Vlasov Equation: Probing the Electron Pressure Divergence Within Thin Current Sheets, GEOPHYSICAL RESEARCH LETTERS, Vol: 46, Pages: 7862-7872, ISSN: 0094-8276

Journal article

Wilson LB, Chen L-J, Wang S, Schwartz SJ, Turner DL, Stevens ML, Kasper JC, Osmane A, Caprioli D, Bale SD, Pulupa MP, Salem CS, Goodrich KAet al., 2019, Electron Energy Partition across Interplanetary Shocks. I. Methodology and Data Product, ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 243, ISSN: 0067-0049

Journal article

Cohen IJ, Schwartz SJ, Goodrich KA, Ahmadi N, Ergun RE, Fuselier SA, Desai M, Christian ER, McComas DJ, Zank GP, Shuster JR, Vines SK, Mauk BH, Decker RB, Anderson BJ, Westlake JH, Le Contel O, Breuillard H, Giles BL, Torbert RB, Burch JLet al., 2019, High-Resolution Measurements of the Cross-Shock potential, Ion Reflection, and Electron Heating at an Interplanetary Shock by MMS, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 124, Pages: 3961-3978, ISSN: 2169-9380

Journal article

Goodrich KA, Ergun R, Schwartz SJ, Wilson LB, Johlander A, Newman D, Wilder FD, Holmes J, Burch J, Torbert R, Khotyaintsev Y, Lindqvist P-A, Strangeway R, Gershman D, Giles Bet al., 2019, Impulsively Reflected Ions: A Plausible Mechanism for Ion Acoustic Wave Growth in Collisionless Shocks, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 124, Pages: 1855-1865, ISSN: 2169-9380

Journal article

Gingell I, Schwartz SJ, Eastwood JP, Burch JL, Ergun RE, Fuselier S, Gershman DJ, Giles BL, Khotyaintsev Y, Lavraud B, Lindqvist P-A, Paterson WR, Phan TD, Russell CT, Stawarz JE, Strangeway RJ, Torbert RB, Wilder Fet al., 2019, Observations of magnetic reconnection in the ransition region of quasi-parallel hocks, Geophysical Research Letters, Vol: 46, Pages: 1177-1184, ISSN: 0094-8276

Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the quasi‐parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron‐only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub‐ion time scales. We also discuss the impact of electron heating in shocks via reconnection.

Journal article

Johlander A, Vaivads A, Khotyaintsev YV, Gingell I, Schwartz SJ, Giles BL, Torbert RB, Russell CTet al., 2018, Shock ripples observed by the MMS spacecraft: ion reflection and dispersive properties, PLASMA PHYSICS AND CONTROLLED FUSION, Vol: 60, ISSN: 0741-3335

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

Goodrich KA, Ergun R, Schwartz SJ, Wilson LB, Newman D, Wilder FD, Holmes J, Johlander A, Burch J, Torbert R, Khotyaintsev Y, Lindqvist P-A, Strangeway R, Russell C, Gershman D, Giles B, Andersson Let al., 2018, MMS Observations of Electrostatic Waves in an Oblique Shock Crossing, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 123, Pages: 9430-9442, ISSN: 2169-9380

Journal article

Bandyopadhyay R, Chasapis A, Chhiber R, Parashar TN, Maruca BA, Matthaeus WH, Schwartz SJ, Eriksson S, Le Contel O, Breuillard H, Burch JL, Moore TE, Pollock CJ, Giles BL, Paterson WR, Dorelli J, Gershman DJ, Torbert RB, Russell CT, Strangeway RJet al., 2018, Solar Wind Turbulence Studies Using MMS Fast Plasma Investigation Data, ASTROPHYSICAL JOURNAL, Vol: 866, ISSN: 0004-637X

Journal article

Turner DL, Wilson LB, Liu TZ, Cohen IJ, Schwartz SJ, Osmane A, Fennell JF, Clemmons JH, Blake JB, Westlake J, Mauk BH, Jaynes AN, Leonard T, Baker DN, Strangeway RJ, Russell CT, Gershman DJ, Avanov L, Giles BL, Torbert RB, Broll J, Gomez RG, Fuselier SA, Burch JLet al., 2018, Autogenous and efficient acceleration of energetic ions upstream of Earth's bow shock, NATURE, Vol: 561, Pages: 206-+, ISSN: 0028-0836

Journal article

Gingell IL, Schwartz SJ, Gershman DJ, Paterson WR, Desai RT, Giles BL, Pollock CJ, Avanov LAet al., 2018, Production of negative hydrogen ions within MMS Fast Plasma Investigation due to solar wind bombardment, Journal of Geophysical Research: Space Physics, Vol: 123, Pages: 6161-6170, ISSN: 2169-9380

The particle data delivered by Fast Plasma Investigation (FPI) instrument aboard NASA's Magnetospheric Multiscale (MMS) mission allows for exceptionally high-resolution examination of the electron and ion phase space in the near-Earth plasma environment. It is necessary to identify populations which originate from instrumental effects. Using FPI's Dual Electron Spectrometers (DES) we isolate a high energy (~keV) beam, present while the spacecraft are in the solar wind, which exhibits an azimuthal drift with period associated with the spacecraft spin. We show that this population is consistent with negative hydrogen ions H- generated by a double charge exchange interaction between the incident solar wind H+ ions and the metallic surfaces within the instrument. This interaction is likely to occur at the deflector plates close to the instrument aperture. The H- density is shown to be approximately 0.2-0.4% of the solar wind ion density, and the energy of the negative ion population is shown to be 70% of the incident solar wind energy. These negative ions may introduce errors in electron velocity moments on the order of 0.2-0.4% of the solar wind velocity, and significantly higher errors in the electron temperature.

Journal article

Chen L-J, Wang S, Wilson LB, Schwartz S, Bessho N, Moore T, Gershman D, Giles B, Malaspina D, Wilder FD, Ergun RE, Hesse M, Lai H, Russell C, Strangeway R, Torbert RB, F-Vinas A, Burch J, Lee S, Pollock C, Dorelli J, Paterson W, Ahmadi N, Goodrich K, Lavraud B, Le Contel O, Khotyaintsev YV, Lindqvist P-A, Boardsen S, Wei H, Le A, Avanov Let al., 2018, Electron Bulk Acceleration and Thermalization at Earth's Quasiperpendicular Bow Shock., Phys Rev Lett, Vol: 120

Electron heating at Earth's quasiperpendicular bow shock has been surmised to be due to the combined effects of a quasistatic electric potential and scattering through wave-particle interaction. Here we report the observation of electron distribution functions indicating a new electron heating process occurring at the leading edge of the shock front. Incident solar wind electrons are accelerated parallel to the magnetic field toward downstream, reaching an electron-ion relative drift speed exceeding the electron thermal speed. The bulk acceleration is associated with an electric field pulse embedded in a whistler-mode wave. The high electron-ion relative drift is relaxed primarily through a nonlinear current-driven instability. The relaxed distributions contain a beam traveling toward the shock as a remnant of the accelerated electrons. Similar distribution functions prevail throughout the shock transition layer, suggesting that the observed acceleration and thermalization is essential to the cross-shock electron heating.

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

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

Gershman DJ, F-Vinas A, Dorelli JC, Goldstein ML, Shuster J, Avanov LA, Boardsen SA, Stawarz JE, Schwartz SJ, Schiff C, Lavraud B, Saito Y, Paterson WR, Giles BL, Pollock CJ, Strangeway RJ, Russell CT, Torbert RB, Moore TE, Burch JLet al., 2018, Energy partitioning constraints at kinetic scales in low-beta turbulence, PHYSICS OF PLASMAS, Vol: 25, ISSN: 1070-664X

Journal article

Broll JM, Fuselier SA, Trattner KJ, Schwartz SJ, Burch JL, Giles BL, Anderson BJet al., 2018, MMS Observation of Shock-Reflected He++ at Earth's Quasi-Perpendicular Bow Shock, GEOPHYSICAL RESEARCH LETTERS, Vol: 45, Pages: 49-55, ISSN: 0094-8276

Journal article

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

Gingell IL, Schwartz SJ, Burgess D, Johlander A, Russell CT, Burch JL, Ergun RE, Fuselier S, Gershman DJ, Giles BL, Goodrich KA, Khotyaintsev YV, Lavraud B, Lindqvist P-A, Strangeway RJ, Trattner K, Torbert RB, Wei H, Wilder Fet al., 2017, MMS observations and hybrid simulations of surface ripples at a marginally quasi-parallel shock, Journal of Geophysical Research: Space Physics, Vol: 122, Pages: 11003-11017, ISSN: 2169-9380

Simulations and observations of collisionless shocks have shown that deviations of the nominal local shock normal orientation, i.e. surface waves or ripples, are expected to propagate in the ramp and overshoot of quasi-perpendicular shocks. Here, we identify signatures of a surface ripple propagating during a crossing of Earth's marginally quasi-parallel (θBn∼45∘) or quasi-parallel bow shock shock on 2015-11-27 06:01:44 UTC by the Magnetospheric Multiscale (MMS) mission, and determine the ripple's properties using multi-spacecraft methods. Using two-dimensional hybrid simulations, we confirm that surface ripples are a feature of marginally quasi-parallel and quasi-parallel shocks under the observed solar wind conditions. In addition, since these marginally quasi-parallel and quasi-parallel shocks are expected to undergo a cyclic reformation of the shock front, we discuss the impact of multiple sources of non-stationarity on shock structure. Importantly, ripples are shown to be transient phenomena, developing faster than an ion gyroperiod and only during the period of the reformation cycle when a newly developed shock ramp is unaffected by turbulence in the foot. We conclude that the change in properties of the ripple observed by MMS is consistent with the reformation of the shock front over a timescale of an ion gyro-period.

Journal article

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