Search

RBSPA observations suggest that the inner radiation belt high energy proton fluxes drop significantly during the storm main phase and recover in parallel to as the SYM-H index [Xu et al., 2019]. A natural problem arises: are these storm‐time proton flux variations in response to the magnetic field modifications adiabatic? Based on Liouville's theorem and conservation of the first and third adiabatic invariants, the fully adiabatic effects of high energy protons in the inner radiation belt have been quantitatively evaluated. Two case studies show that theoretically calculated, adiabatic flux decreases are in good agreement with RBSPA observations. Statistical survey of 67 geomagnetic storms which occurred in 2013–2016 has been conducted. The results confirm that the fully adiabatic response constitutes the main contribution 90 % to the changes in high energy protons in inner radiation belt during the storm main and recovery phases. It indicates that adiabatic invariants of the inner belt high energy protons are well preserved for majority of storms. Phase space density results also support adiabatic effect controls the varication of high energy protons especially for small and medium geomagnetic storms. Non-adiabatic effects could play important role for the most intense storms with fast changes in magnetic configuration.

We present a series of electron holes observed simultaneously on four Magnetospheric Multiscale spacecraft in the plasma sheet boundary layer. The multispacecraft probing shows that the electron ho ...

The unique magnetic structure of the terrestrial aurora as a conduit of information between the ionosphere and magnetosphere can be utilized as a laboratory for physical processes at similar magnetic configurations and applied to various evolutionary phases of the solar (stellar) system. The most spectacular heliospheric abundance enhancement involves the 3He isotope and selective heavy elements in impulsive solar flares. In situ observations of electromagnetic waves on active aurora are extrapolated to flaring corona in an analysis of solar acceleration processes of 3He, the only element that may resonate strongly with the waves, as well as heavy ions with specific charge-to-mass ratios, which may resonate weaker via their higher gyroharmonics. These results are applied to two observed anomalous astrophysical abundances: (1) enhanced abundance of 3He and possibly 13C in the late stellar evolutionary stages of planetary nebulae; and (2) enhanced abundance of the observed fossil element 26Mg in meteorites as a decay product of radioactive 26Al isotope due to interaction with the flare-energized 3He in the early solar system.

Recent observations from satellites crossing regions of magnetic-field-aligned electron streams reveal solitary potential structures that move at speeds much greater than the ion acoustic/thermal velocity. The structures appear as positive potential pulses rapidly drifting along the magnetic field, and are electrostatic in their rest frame. We interpret them as BGK electron holes supported by a drifting population of trapped electrons. Using Laplace transforms, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron distribution functions are self-consistent and compatible with the field and particle data associated with the observed pulses. In particular, the spatial width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulation code with open boundaries. We consider a strongly magnetized parameter regime in which the bounce frequency of the trapped electrons is much less than their gyrofrequency. Our investigation includes the influence of the ions, which in the frame of the hole appear as an incident beam, and impinge on the BGK potential with considerable energy. The nonlinear structure is remarkably resilient

The analogy between magnetohydrodynamics (MHD) and knot theory is utilized in presenting a new method for an analysis of stability and evolution of complex magnetic heliospheric flux tubes. Planar projection of a three-dimensional magnetic configuration depicts the structure as a two-dimensional diagram with crossings, to which one may assign mathematical operations leading to robust topological invariants. These invariants enrich the topological information of magnetic configurations beyond helicity. It is conjectured that the field which emerges from the solar photosphere is structured as one of the simplest knots—unknot or prime knot—and these flux ropes are then stretched while carried by the solar wind into the interplanetary medium. Preservation of invariants for small diffusivity and large cross section of the emerging magnetic flux makes them impervious to large scale reconnection, allowing us to predict the observed structures at 1 AU as elongated prime knots. Similar structures may be observed in magnetic clouds which got disconnected from their footpoints and in ion drop-out configurations from a compact flare source in solar impulsive solar events. Observation of small scale magnetic features consistent with prime knots may indicate spatial intermittency and non-Gaussian statistics in the turbulent cascade process. For flux tubes with higher resistivity, magnetic energy decay rate should decrease with increased knot complexity as the invariants are then harder to be violated. These observations could be confirmed if adjacent satellites happen to measure distinctly oriented magnetic fields with directionally varying suprathermal particle fluxes.

The argument that multipolar international systems are less stable because certain states have an incentive to externalize the costs of defense to other states has been built on interpretations of the behavior of France, Russia, and especially Great Britain between the two World Wars. This article addresses flaws in both the use of the French and Russian cases, but is most tightly focused on the British case, which was the strongest, prima facie, of the three. This article demonstrates how the British scheme for defense against Germany was not a policy of attempted externalization on either the political or military level. Consequently, the long debate over the relationship between systemic structure and systemic stability, which has been heavily influenced by the belief in the existence of an incentive to externalize defense costs under multipolarity, must be re-examined, with new tests run and new conclusions explored.

The (near) relativistic electrons, emanating from the solar corona in long-lasting, gradual events, are generally observed at 1 AU as delayed vs the less energetic, type-III beams. The observations are consistent with the delayed electrons being energized along the stretched post-CME coronal field lines, when the tail of an anisotropic seed population, which is injected in conjunction to the observed radioheliograph bursts, interacts with the self-excited whistler waves (bootstrap mechanism). These bursts indicate efficient processes where suprathermal seed electrons are injected as a result of magnetic reconnection at the marginally stable coronal configuration left behind the emerging CME. The dependence of the bootstrap mechanism on the electron injection raises the general question of the MHD description and its deviation over the small electron skin-depth scale. The similarity between MHD and knot theories allows one to characterize any turbulent magnetic configuration through topological invariants, while deviation over electron skin-depth scale, characterized by the generalized vorticity, which is enhanced due to density inhomogeneity, creates the conditions for the potential injection sites.

This article argues that Israel experiences a unique perception of the perils of anarchy that drives it to a strategic preference for disproportionately offensive action against rivals and enemies. Actions taken pursuant to that doctrine have caused serious inconvenience to U.S. foreign policy in the Mideast for over four decades. This article argues that by reassuring Israel, both diplomatically and with arms sales, that the United States is committed to its survival, the United States has obtained significant measures of strategic restraint on Israel’s part. That restraint has brought significant benefit to the United States as it seeks to guarantee regular access to the vital resources of the Middle East. This article provides examples of both successful reassurance and reassurance denied to illustrate the argument that U.S. support produces tangible strategic benefits for the United States.

In situ and remote observations indicate that relativistic or ultra relativistic electrons are formed at various magnetized configurations. It is suggested that a specific bootstrap mechanism operates in some of these environments. The mechanism applies to (a) relativistic electrons observed on localized field lines in outer radiation belt - through a process initiated at a distant substorm injection; (b) relativistic electrons observed at the interplanetary medium - through a process initiated via coronal injection, at large distances from flares or propagating CME; (c) ultra-relativistic electrons deduced at the galactic jets - through a process initiated via local injection at the small-scale magnetic field. The injected nonisotropic electrons excite whistler waves which boost efficiently the tail of the electron distribution.

This article uses the case of King Saul, David, and the Philistines, drawn from the Hebrew Bible (books 1 and 2 Samuel), to argue that leaders of states with contested or immature authority structures often elect to prioritize threats to their personal rule over external threats to the integrity and welfare of the states which they lead in a manner not predicted by neo-Realist international relations theory. In making this argument, this article not only makes a contribution to the Realist literature on threat prioritization but introduces a new, novel, and ancient data set which can be used both to generate new theories and to test existing theories within international relations.

The existence of non-thermal electrons in the solar atmosphere and along the heliospheric field lines is deduced through emission of electromagnetic waves and via direct in situ measurements at 1 AU. The relation between the in situ electrons, their spectral shapes and the relative timing with respect to imaging and spectrographic observations are important in identifying potential acceleration sites and in understanding of the processes which control the formation of the delayed, (mildly) relativistic electrons which are observed in conjunction with flares or coronal mass ejections (CMEs). In contrast to previously suggested paradigms of acceleration of relativistic electrons around the CME shocks or at the flare site, it is suggested here that the delayed acceleration occurs along the stretched, closed coronal field lines, when an anisotropic seed population of low-energy electrons is injected in conjunction with the high frequency coronal radio bursts behind the large CME, as recorded by radioheliographs. The energization proceeds as a bootstrap process due to interaction with oblique whistler waves. The flare serves mainly as a time reference for the electromagnetic emissions, while the propagating CME subsequently opens an access for the relativistic electrons to the interplanetary medium.

Direct observations or deduced analysis indicate clearly that formation of intense fluxes of relativistic electrons is an important ingredient in the evolution of numerous active magnetized plasma systems. Examples of relativistic electron energization include the recovery phase of a planetary magnetic storm, post solar flare coronal activity and the afterglow of gamma ray bursts. It is suggested that there exists a universal mechanism, which may explain electron energization at the vastly different magnetized plasma environments. The favorite configuration consists of an inhomogeneous magnetic field anchored at a given magnetic structure and excitation of whistler waves due to external injection of low-energy non-isotropic electrons. The energization proceeds as a bootstrap process due to interaction with the propagating whistler waves along the inhomogeneous magnetic field.

This essay identifies a difference of opinion over the role of nuclear weapons as an absolute deterrent as the basis for the theoretical disagreement between Kenneth Waltz and John Mearsheimer regarding whether security is attained through the maintenance of the status quo or through the aggressive elimination of potential rivals. The essay traces the writings of both scholars over a period of decades to demonstrate how Waltz has come to regard nuclear weapons as making conquest so unprofitable that possessing them provides absolute security. It also shows how Mearsheimer holds a more ambiguous position on the deterrent strength of nuclear weapons, which helps to explain why he believes that states still seek security through offensive action. The essay offers a guide to show how these important theories influence and shape current policy debates over the proliferation of nuclear weapons to both state and nonstate actors.

Observations of energetic ions of solar origin in the heliosphere suggest the existence of two main energization sites with different physical mechanisms: (1) impulsive mechanism on the flaring coronal magnetic field – via resonant interaction, presumably with low-frequency electromagnetic waves; (2) gradual mechanism around the propagating, interplanetary shock – by interaction with quasi-static inhomogeneous electromagnetic structure and low-frequency Alfvenic turbulence. While the coronal process enhances a subset of rare elements, the interplanetary interaction energizes most of the elements of coronal/solar wind origin. In the impulsive events, according to recent models, a significant fraction of heavy elements which reside on the active flaring flux rope is energized; the resonant interaction operates mainly on Fe and other heavy elements with high charge states. In the gradual events main energization occurs close to the Sun at low Mach numbers; significant interplanetary enhancement of energetic ion fluxes requires a narrow scale length in the propagating shock. Coupling of both processes results in the final heliospheric distribution function of the heavy elements. The enhanced energetic heavy ion population may have a profound impact on human space exploration in the interplanetary space as well as in the resulting trapped radiation in the magnetosphere.

Substorm injections bring energetic particles to the inner magnetosphere. But the role of the injected population in building up the storm time ring current is not well understood. By surveying Los Alamos National Laboratory geosynchronous data during 34 storm main phases, we show evidence that at least some substorm injections can contribute to substorm-time scale SYM-H/Dst depressions in the main phase of storms. For event studies, we analyze two typical events in which the main-phase SYM-H index exhibited stepwise depressions that are correlated with particle flux enhancement due to injections and with AL index. A statistical study is performed based on 95 storm time injection events. The flux increases of the injected population (50–400 keV) are found proportional to the sharp SYM-H depressions during the injection interval. By identifying dispersionless and dispersive injection signals, we estimate the azimuthal extent of the substorm injection. Statistical results show that the injection regions of these storm time substorms are characterized with an azimuthal extent larger than 06:00 magnetic local time. These results suggest that at least some substorm injections may mimic the large-scale enhanced convection and contribute to sharp decreases of Dst in the storm main phase.

The variations in the fluxes of the relativistic electrons in the planetary radiation belts are due to a set of different physical processes which violate one or more of the adiabatic invariants. We survey the mechanisms which break down these invariants and investigate the time scales for the processes and the resulting effects on the observed fluxes. The mechanisms include (a) sudden deformation of the magnetic field configuration, (b) radial diffusion due to low-frequency electromagnetic oscillations, (c) transit-time damping due to fast waves and (d) diffusion due to electromagnetic ion-cyclotron (emic) or whistler waves. It is indicated how the waves which interact resonantly with the relativistic electrons are responsible for enhancement in the radiative spectra of the gyrosynchrotron emissions in the GHz frequency range and the X-ray bremsstrahlung emissions at the MeV energy range.

A model is presented for a new type of fast solitary waves which is observed in downward current regions of the auroral zone. The three-dimensional, coherent structures are electrostatic, have a positive potential, and move along the magnetic field lines with speeds on the order of the electron drift. Their parallel potential profile is flattened and cannot fit to the Gaussian shape used in previous work. We develop a detailed BGK model which includes a flattened potential and an assumed cylindrical symmetry around a centric magnetic field line. The model envisions concentric shells of trapped electrons slowly drifting azimuthally while bouncing back and forth in the parallel direction. The electron dynamics is analysed in terms of three basic motions that occur on different time scales characterized by the cyclotron frequency We , the bounce frequency wb , and the azimuthal drift frequency wg. The ordering We >> wb >> wg is required. Self-consistent distribution functions are calculated in terms of approximate constants of motion. Constraints on the parameters characterizing the amplitude and shape of the stretched solitary wave are discussed.

Electron phase space holes or vortices (EHs) are electrostatic solitary waves with a bipolar parallel (magnetic field-aligned) electric field. They are formed in a nonlinear stage of electron streaming type instabilities and exist due to electrons trapped within the EH electrostatic potential. The background plasma density gradients, characteristic for both space and laboratory plasmas, can affect the evolution of EHs. In this paper, we use a one-dimensional electrostatic Vlasov–Ampere code (ions are immobile) with periodic boundary conditions to study the evolution of a single EH in inhomogeneous plasmas. We find that the EH propagating along a positive (negative) plasma density gradient is accelerated (decelerated) and narrowed (widened). EH propagating along a positive density gradient results in the acceleration of a relatively small population of trapped electrons to suprathermal energies. Interestingly, a decelerating EH is reflected at the point with the plasma density value dependent only on EH pa...

A model describing (1) short time scale increases in Jovian synchrotron radiation and (2) emissions from high Jovian latitudes is presented. In the present model resonant interaction between oblique whistler waves and relativistic electrons diffuses the energy and the pitch angle of electrons which bounce along the Jovian magnetic field. The resonant interaction violates the first two adiabatic invariants and the energy diffusion results in hardening of the electron spectrum and in intensification of the synchrotron radiation. This model complements the radial diffusion process which (a) violates the third adiabatic invariant of a seed population via interaction with low-frequency magnetospheric oscillations and (b) increases the flux of energetic electrons at low L -shells over long time scales by conserving the first adiabatic invariant. The high-latitude emissions indicate also acceleration of bouncing electrons and radiation in the region of the strongest magnetic field. The seed particles and whistler waves determine the form of the electron distribution tail. This tail enhances the high-latitude synchrotron radiation observed at Earth. The resulting emissivities of the nonthermal radio waves in the ordinary/extraordinary modes of propagation, the polarization and the intensity spectrum observed at Earth due to these high-energy populations are calculated.

The stability of the fast solitary structures which were observed onboard several auroral crossing satellites is analyzed as a dynamical system and investigated numerically. These large-amplitude potential spikes are supported by trapped electron populations. For parameters of low and mid-altitude auroral passes with gyro-to-bounce frequency ratios significantly larger than unity, the potential spikes are very resilient, while for lower magnetic fields, at ratios below unity, they develop unstable undulations in the transverse direction. The evolution of the solitary structures is related to changes in the trajectories of the trapped electrons. It is shown here that the coupling of the parallel and perpendicular dynamics is stronger when the above ratio decreases, resulting in a bifurcation of trajectories. The addition of a small perturbation to the large amplitude structure leads to a very different response of the trapped electrons in the two configurations. The electron behavior reflects the lack of spike stability at small gyro-to-bounce frequency ratios.

We report on FAST observations of large amplitude (up to 500 mV m−1) envelope solitary waves at the edges of the AKR source region. These edges are characterized by the presence of two electron populations: a dominant hot (∼keV) component and a minority cold (

Recent observations from satellites crossing active magnetic field lines have revealed solitary potential structures that move at speeds substantially greater than the ion thermal velocity. The structures appear as positive potential pulses rapidly drifting along the magnetic field. We interpret them as BGK electron holes supported by a population of trapped and passing electrons. Using Laplace transform techniques, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron distribution functions are self-consistent and compatible with the field and particle data associated with the observed pulses. In particular, the spatial width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulation code with open boundaries. We also use our code to briefly investigate the influence of the ions. The nonlinear structure appears to be remarkably resilient.

The Nuclear Taboo: The United States and the Non-Use of Nuclear Weapons Since 1945. Edited by Nina Tannenwald. New York: Cambridge University Press, 2007. 449 pp., $34.99 paper (ISBN-13: 978-0521524285). Nina Tannenwald's provocative book, The Nuclear Taboo , issues a direct, well reasoned, richly detailed and forcefully argued challenge to the domain of international relations on which realism has long had exclusive claim. That domain is explanations for the non-use of nuclear weapons. The core argument of The Nuclear Taboo is that the non-use of nuclear weapons by the United States since the end of World War II is not attributable to deterrence, as realists, particularly structural realists, have traditionally argued, but rather to the existence of a taboo against their use. In identifying a social norm against the use of nuclear weapons as the causal variable, and not the material considerations of anticipated loss which lie at the heart of deterrence theory, Tannenwald challenges the primacy of realism as the most powerful paradigm for understanding the so-called “High Politics” of security. Tannenwald's conclusions on the existence of a powerful social norm that controls the use of nuclear arms are reached by researching a key puzzle of modern history: Why have nuclear weapons not been used in situations where acute forms of deterrence, like the Cold War's Mutual Assured Destruction, did not apply (pp. 1, 3). According to Tannenwald, a careful search of the historical record, including both archival primary documents and secondary sources, shows that the policy discourse within the inner sanctum of power on whether to use nuclear weapons during the crisis situations where their use might be anticipated was not centered on questions of the military utility of the weapons. Rather it tended to focus on the inhumanity inherent in their …

The resonant wave-particle effects which enhance spectacularly the abundance of the 3 He isotope and heavy elements in impulsive solar flares are analyzed. Primordial nucleosynthesis and galactic evolution confines the coronal ratio of the He isotopes, 3 He 4 He , to several times 10 −4 ; this ratio is enhanced during impulsive flares by up to four orders of magnitude due to interaction with electromagnetic ion cyclotron (emic) waves. The heavy elements, which are produced during galactic evolution and which are not fully ionized at coronal temperatures, are also accelerated by emic waves through higher gyroharmonic resonances. The oblique emic waves, which propagate undamped over large distances, are observed on auroral field lines in conjunction with dynamically evolving electron fluxes, and, analogously, are postulated on coronal field lines in conjunction with the X-ray emitting electrons. Quasilinear simulations show that the dynamically evolving electron velocity distribution consisting of a core, halo and beam can enhance the low-frequency modes, while quenching the high-frequency Langmuir waves and preserving some positive slope. This positive slope may drive the low-frequency electromagnetic waves. The acceleration of 3 He by the emic waves and the enrichment of specific elements and charge states, at different coronal conditions, is described.

We present detailed observations of electromagnetic waves and particle distributions from the Fast Auroral SnapshoT (FAST) satellite which reveal many important properties of large-amplitude, spatially-coherent plasma structures known as "fast solitary structures" or "electron phase space holes". Similar structures have been observed in several regions of the magnetosphere including the auroral zone, plasma sheet boundary layer, and bow shock. There has been rapid theoretical progress in understanding these structures. Solitary structures can develop from bidirectional electron beams. Once developed, the one-dimensional properties parallel to the magnetic field can be adequately described by analytical treatment as BGK structures. There remains, however, several unanswered questions. The origin of the bidirectional electron beams, the development of two-or three-dimensional structures, and the observed association with the ion cyclotron frequency are not well understood.

We report the first detection of a terrestrial X-ray burst extending up to MeV energies, made by a liquid-nitrogen-cooled germanium detector (∼2 keV FWHM resolution) on a high-altitude balloon at 65.5° magnetic latitude (L=5.7) in the late afternoon (1815 MLT) during low geomagnetic activity. The burst occurred at 1532–1554 UT on August 20, 1996, and consisted of seven peaks of ∼60–90 s duration, spaced by ∼100–200 s, with quasi-periodic (∼10–20 s) modulation of the peak count rates. The very hard X-ray spectrum extends to the instrumental limit of 1.4 MeV, and is consistent with bremsstrahlung emission from monoenergetic, ∼1.7 MeV, precipitating electrons. Since the trapped relativistic electrons showed a steeply falling energy spectrum from 0.6 to 4 MeV (at L=6.6), the precipitation mechanism appears to be highly energy selective. The modulation frequencies suggest scattering of the MeV electrons due to gyro-resonance with Doppler-shifted electromagnetic ion cyclotron waves, but either equatorial proton densities a factor of ∼10² higher than typical for the plasmasphere or significant O+ densities would be required.

The spectacular enrichment of 3He and the smaller enrichments of heavy ions in impulsive flares is discussed in the context of a resonant interaction with the same electromagnetic ion cyclotron waves. The observed abundances are used to delineate the coronal thermodynamic conditions, the scalings of the enhancements with the coronal parameters and the frequency range of the resonant waves.

Simulation of the March 24, 1991 storm sudden commencement (SSC) has illuminated the rapid formation of new radiation belts on the particle drift time scale. While this event was the most dramatic in terms of radiation belt effects of the last solar maximum, comparable signatures of such events were seen in 1962 by Explorer 15 and in 1986 by DMSP. Several smaller MeV proton events with comparable particle morphology, but less radial transport and energization, were observed during the lifetime of the CRRES satellite (July 1990 – October 1991), which was well instrumented for both particle and field measurements inside geosynchronous orbit. Typically a solar proton event is accompanied by an SSC in the CRRES data set, while the converse is not always true. An SSC accompanied by solar protons produces a trapped population which remains on closed drift orbits until ring current buildup disrupts trapping, either by violation of the adiabatic trapping criterion or generation of waves whose frequency is comparable to periodic particle motion. Thus, new radiation belts formed around L = 4 by SSC injection are short-lived compared to the March 24, 1991 storm, wherein solar protons were transported radially inward to L = 2.5, with greater energization corresponding to first adiabatic invariant conservation than for the weaker events.

Unanswered Threats: Political Constraints on the Balance of Power. By Randall Schweller. Princeton: Princeton University Press, 2006. $29.95 (ISBN: 0-691-12425-6). Berating Kenneth Waltz for his “balancing proposition's” lack of predictive specificity has become a cottage industry among international relations theorists. What started with sympathetic emendations from Stephen Walt (1987) has blossomed into a scathing series of critiques of this core Waltzian proposition that the anarchic structure of the international system conditions states to respond to any accumulation of power by forming balancing coalitions. A recent volume edited by John Vasquez and Colin Elman (2003) is dedicated to exploring the validity of the balancing proposition. In it, Vasquez (2003), among others, contends that the lack of predictive specificity in Waltz serves to render the whole enterprise of structural neorealism into a degenerative research program—that is, one that provides no new knowledge but only creates loopholes that allow the agenda to survive another day. Unanswered Threats , by Randall Schweller, joins this cavalcade of voices criticizing Waltz, but it does so in a more constructive manner. Unlike other recent criticisms, Schweller posits an alternative theoretical explanation for state behavior in these situations. Schweller's explanation is less parsimonious than Waltz's original balancing proposition, but it has the merit of not only explaining previous anomalies in structural neorealism, but of offering testable hypotheses of its own. The core question in Unanswered Threats is why, despite the frequency of unbalanced power, does power balancing happen so infrequently. In other words, why do states “underbalance”? Schweller's answer goes beyond the specifics of this question to explore the question of effective resource mobilization more broadly. He argues that …

International audience; The mechanisms for accelerating electrons from thermal to relativistic energies in the terrestrial magnetosphere, on the sun, and in many astrophysical environments have never been verified. We present the first direct observation of two processes that, in a chain, cause this acceleration in Earth's outer radiation belt. The two processes are parallel acceleration from electron-volt to kilovolt energies by parallel electric fields in time-domain structures (TDS), after which the parallel electron velocity becomes sufficiently large for Doppler-shifted upper band whistler frequencies to be in resonance with the electron gyration frequency, even though the electron energies are kilovolts and not hundreds of kilovolts. The electrons are then accelerated by the whistler perpendicular electric field to relativistic energies in several resonant interactions. TDS are packets of electric field spikes, each spike having duration of a few hundred microseconds and containing a local parallel electric field. The TDS of interest resulted from nonlinearity of the parallel electric field component in oblique whistlers and consisted of ∼0.1 msec pulses superposed on the whistler waveform with each such spike containing a net parallel potential the order of 50 V. Local magnetic field compression from remote activity provided the free energy to drive the two processes. The expected temporal correlations between the compressed magnetic field, the nonlinear whistlers with their parallel electric field spikes, the electron flux and the electron pitch angle distributions were all observed. Rapid acceleration of electrons up to relativistic energies occurs in different plasma configuration on all scales from the laboratory to astrophysics. The Van Allen radiation belts around Earth contain such relativistic electrons that are trapped in Earth's magnetic field. Because of intrinsic interest in the acceleration mechanism, because these electrons may be prototypical of relativistic electron acceleration in other environments, and because they present a danger to space travelers and spacecraft, it is important to understand their origin and acceleration. Two possible sources of these electrons that have been discussed are injections into the local environment of electrons that were energized by moving earthward from the tail into a stronger magnetic field while conserving their first two adiabatic invariants [1], and local acceleration in the region of the satellite measurements. While both mechanisms occur, the local acceleration mechanism has been shown to be more important, at least for major, rapid, relativistic flux increases [2–4]. Simulations of rela-tivistic electron acceleration via the whistler mode resonance have produced relativistic electrons from seed populations of hundreds of keV electrons [5,6]. This work has left open the question of the source of such seed populations. Meanwhile, observations have been made in Earth's radiation belts of parallel (to the local magnetic field) electric fields in the form of packets of spikes, each spike having a duration the order of 100 msec, and each packet containing hundreds of such spikes [7]. These spikes, dubbed time-domain structures, have at least five different forms that satisfy the above description and they have been suggested as the mechanism for producing the ∼100 keV electrons that are the seed population for whistler wave acceleration to highly relativistic energies [7]. This suggestion has not been verified by detailed comparison of particles and fields before the studies described in this Letter that show, for the first time, both that low energy electrons can be accelerated up to keV energies by the parallel electric fields in time-domain structures and that such keV electrons can be further accelerated to relativistic energies via the whistler mode resonance even though their initial energies are significantly less than ∼100 keV. The data in this Letter were collected on May 2, 2013 on Van Allen probe B (VAP-B) by the electric field experiment [8], the magnetic field experiment [9], and the Energetic particle, Composition, and Thermal plasma (RBSP-ECT) Suite experiments [10–12]. The spacecraft was at a magnetic latitude of 2°, a magnetic local time of midnight, and a geocentric radial distance of 5.8 Earth radii during these measurements. Figure 1 illustrates three components of the electric and magnetic fields in the background-magnetic-field-aligned coordinate system during a 20 msec interval in which two packets of nonlinear whistlers were observed. Panels 1(a) and 1(b) give the two perpendicular (to the background magnetic

This paper investigates how the various waves of the whistler resonance cone compete for the free energy available in field-aligned fluxes of precipitating electrons in the auroral ionosphere. A two-dimensional numerical simulation code, based on the coupled pair of quasi-linear equations, is used for the investigation. The description provided by these equations allows us to follow the nonlinear development of the instability and analyze the interplay between the modes as mediated by the changing distribution function. We present results for a parameter regime corresponding to altitudes probed by sounding rockets, around 103 km and Ωe ≳ ωp. The presence of a halo of energetic electrons significantly affects the evolution of the turbulence. The spectrum is shown to shift with time toward increasingly oblique propagation angles including a substantial share of quasi perpendicular, short-wavelength modes close to the lower hybrid frequency.

The acceleration of 3He and heavy ions by electromagnetic hydrogen cyclotron waves in a direct single-stage process in impulsive solar flares is investigated analytically and with the help of test particle simulations. We illustrate in detail the mechanism by which a single monochromatic wave can accelerate such ions to MeV and even GeV energies. While somewhat idealized, a monochromatic wave well illustrates the importance of the background magnetic field gradient in the acceleration process. An interesting result of our analysis shows that the acceleration rate is proportional to the magnitude of the magnetic field gradient and is independent of the wave amplitude, while the maximum energy gained increases with decreasing magnetic field gradient and increasing wave amplitude. Heavy ions can also be accelerated by these electromagnetic hydrogen cyclotron waves in a single-stage process by the second or higher harmonic resonance. The acceleration of heavier ions by the same mechanism raises the question of their low enrichment in comparison to much higher enrichment of 3He. The solution is related to the initial small acceleration of the thermal heavy ions at the higher harmonic resonances. The enrichment of the heavy ions increases with the amplitude of the electromagnetic waves and decreases with the plasma density due to Coulomb collisions and absorption of wave energy. Comparison between the rate of cooling of thermal heavy ions due to collisions and heating by waves gives wave intensity and heavy ion ratios which are consistent with observations. The relation between the accelerated heavy ion abundances and their gyrofrequencies in the corona is used to estimate the temperature in the acceleration region. The existence of electromagnetic hydrogen cyclotron waves in flare plasmas is supported by observations in auroral plasmas and by solution of the dispersion relation, which shows that such waves can propagate over long distances along coronal magnetic fields.

MHD fields from a global three-dimensional simulation of the great March 24, 1991, storm sudden commencement (SSC) are used to follow the trajectories of particles in a guiding center test particle simulation of radiation belt formation during this event. Modeling of less intense events during the lifetime of the CRRES satellite, with similar morphology but less radial transport and energization, is also presented. In all cases analyzed, a solar proton event was followed by an SSC, leading to the formation of a new proton belt earthward of solar proton penetration. The effect on particle energization of varying solar wind and model pulse parameters is investigated. Both a seed population of solar protons and the SSC shock-induced compression of the magnetosphere are necessary conditions for the formation of a new proton belt. The outer boundary of the inner zone protons can be affected by an SSC and a newly formed belt can be affected by the ensuing or a subsequent storm, which may occur in rapid succession, as was the case in June and July 1991. The acceleration process is effective for both northward and southward IMF, with more energization and inward radial transport for the southward case for otherwise comparable solar wind parameters, because of the initially more compressed magnetopause in the southward case. The inner boundary and stability of the newly formed belt depends on the magnitude of radial transport at the time of formation and subsequent ring current perturbation of adiabatic trapping.

Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth's outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230 000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1 000 000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer speed of $3100\text{ }\text{ }\mathrm{km}/\mathrm{s}$ is the order of the electron acoustic speed (and not the ion acoustic speed) of a 25 eV plasma, the double layers may result from a new electron acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects.

Kinetic localization of beam-driven Langmuir waves is studied for parameters relevant to the electron foreshock environment. Particle-in-cell simulations of the interaction occurring between energetic electrons and Langmuir waves are performed. It is shown that the nonlinearities in the resonant electrons lead to the formation of packets growing out of the noise. The characteristic spatial scale depends upon the beam velocity and has a weak dependence on the wave amplitude. The mechanism takes place within shorter timescales and for smaller amplitudes than the classic nonlinearities due to bulk electrons and ions. As an example, we apply the results to observations made in the Earth and Jovian foreshocks.

One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

The trajectories of ions in the Tsyganenko magnetic field model with a convection electric field have been compared to the trajectories when a perturbation electric field based on ISEE-1 and Geotail observations of lower hybrid frequency waves is included. The inclusion of waves dramatically modifies the characteristics of the ion trajectories. For example, initial conditions which result in adiabatic orbits in the absence of waves are often non-adiabatic when waves are included. In addition, both the regions of space accessible to the particles and the energization are changed. Although only individual trajectories were examined in this study, it is argued that the effect of the waves is to mix previously distinct regions of phase space.

The rapid formation of a new proton radiation belt at L approximately = 2.5 following the March 24, 1991 Storm Sudden Commencement (SSC) observed at the Combined Release and Radiation Effects Satellite (CRRES) satellite is modeled using a relativistic guiding center test particle code. The SSC is modeled by a bipolar electric field and associated compression and relaxation in the magnetic field, superimposed on a dipole magnetic field. The source population consists of both solar and trapped inner zone protons. The simulations show that while both populations contribute to drift echoes in the 20-80 MeV range, primary conditions is from the solar protons. Proton acceleration by the SSC differs from relativistic electron acceleration in that different source populations contribute and nonrelativistic conservation of the first adiabatic invariation leads to greater energization of protons for a given decrease in L. Model drift echoes and flux distribution in L at the time of injection compare well with CRRES observations.

A substorm dispersionless injection event observed during the storm recovery phase on 11 March 1998 at geosynchronous orbit is carefully studied. The event shows the notable characteristics that for energetic ions the flux enhancement ratio before and after injection increases and remains elevated with increasing energy, while for energetic electrons it tends to decrease with increasing energy. In order to explain the unique injection feature, the authors propose a possible mechanism that velocity space diffusion in common to electric acceleration adjusts the particle injection state. Spectral characteristics of four different phases (pregrowth phase, the growth phase, the substorm expansion phase, and the recovery phase) have been investigated. The differential fluxes of electrons from 50 keV to 1.5 Mev and ions from 50 keV to 1.2 MeV measured by Synchronous Orbit Plasma Analyzer (SOPA) instrument onboard LANL satellite 1991-080 are found to be best fitted with the three-parameter kappa distribution function (f similar to A(0) . E[1 + E / (kappa E-0)](-kappa-1)) by Levenberg-Marquardt and Universal Global Optimization methods. The evolutions of the three parameters in the above kappa distribution in different substorm phases have been depicted for both electrons and ions. In each phase, E-0 and kappa show an approximately linear relationship kappa(E-0) = kappa(0) + eta E-0. This linear relationship can be obtained by solving the velocity space diffusion equation with an initial superthermal kappa distribution. Ion and electron are found to have opposite trend of parameters kappa(0) and eta in each phase, which indicates that the different species of particles exert different velocity space diffusion processes so that their flux enhancement ratios before and after injection are rather different. This implies that not only electric field acceleration, but also velocity space diffusion plays a very important role in the particle injection.

An analytical model of the interaction between a localized wave packet and energetic electrons is presented. Electrostatic packets of tens to a hundred wavelengths are considered in order to emulate the Langmuir waves observed in the auroral zone and in the solar wind. The phase information is retained, so the results can be applied to wave–particle correlator measurements. The perturbed distribution function is explicitly calculated and is shown to be bounded over all phase space due to a broadening of resonance ascribable to the finite extent of the packet. Its resistive part (in phase or 180° out of phase with the electric field) maximizes for v=ω/k, so that the associated bunching of electrons enables assessment of the characteristic wavelength. The changes in the wave profile due to the interaction with the energetic electrons are calculated. Broad wave packets grow or decay ‘‘self‐similarly’’ with a rate given by the standard expression for a plane wave. Narrow, growing packets, on the other hand, q...

[1] Satellite observations near the X line are required to understand electromagnetic energy conversion and particle acceleration resulting from magnetic field reconnection. More than 900 orbits of Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft across the low-latitude dayside magnetopause, involving more than 4000 magnetopause crossings and 5000 h of data, were searched for examples of magnetic field reconnection within a few electron skin depths of the X line. Evidence that the X line was crossed in the best of these events comes from observations of DC electric and magnetic fields, electrostatic and electromagnetic lower hybrid waves, magnetosheath electrons flowing along the separatricies, and a super-Alfvenic electron jet flowing perpendicular to the magnetic field. A dispersion analysis identifies properties of the wave that are in agreement with the experiment. Neither these waves nor the DC electric field were sufficient to account for acceleration of the electron jet. The anomalous drag was not an important source of the observed DC electric field. The observed pressure gradient is a possible candidate for maintaining the electric field.

We present multi-satellite observations indicating a strong correlation between large amplitude radiation belt whistler-mode waves and relativistic electron precipitation. On separate occasions during the Wind petal orbits and STEREO phasing orbits, Wind and STEREO recorded intense whistler-mode waves in the outer nightside equatorial radiation belt with peak-to-peak amplitudes exceeding 300 mV/m. During these intervals of intense wave activity, SAMPEX recorded relativistic electron microbursts in near magnetic conjunction with Wind and STEREO. The microburst precipitation exhibits a bursty temporal structure similar to that of the observed large amplitude wave packets, suggesting a connection between the two phenomena. Simulation studies corroborate this idea, showing that nonlinear wave--particle interactions may result in rapid energization and scattering on timescales comparable to those of the impulsive relativistic electron precipitation.

A variety of in‐situ measurements in space plasmas point out to an intermittent formation of distribution functions with elongated tails and power‐law at high energies. Power‐laws form ubiquitous signature of many complex systems, plasma being a good example of a non‐Boltzmann behavior for distribution functions of energetic particles. Particles, which either undergo mutual collisions or are scattered in phase space by electromagnetic fluctuations, exhibit statistical properties, which are determined by the transition probability density function of a single interaction, while their non‐asymptotic evolution may determine the observed high‐energy populations. It is shown that relaxation of the Brownian motion assumptions leads to non‐analytical characteristic functions and to generalization of the Fokker‐Planck equation with fractional derivatives that result in power law solutions parameterized by the probability density function.