Influence of the solar wind and IMF on Jupiter's magnetosphere: Results from global MHD simulations

Science.gov (United States)

Sarkango, Y.; Jia, X.; Toth, G.; Hansen, K. C.

2017-12-01

Due to its large size, rapid rotation and presence of substantial internal plasma sources, Jupiter's magnetosphere is fundamentally different from that of the Earth. How and to what extent do the external factors, such as the solar wind and interplanetary magnetic field (IMF), influence the internally-driven magnetosphere is an open question. In this work, we solve the 3D semi-relativistic magnetohydrodynamic (MHD) equations using a well-established code, BATSRUS, to model the Jovian magnetosphere and study its interaction with the solar wind. Our global model adopts a non-uniform mesh covering the region from 200 RJ upstream to 1800 RJ downstream with the inner boundary placed at a radial distance of 2.5 RJ. The Io plasma torus centered around 6 RJ is generated in our model through appropriate mass-loading terms added to the set of MHD equations. We perform systematic numerical experiments in which we vary the upstream solar wind properties to investigate the impact of solar wind events, such as interplanetary shock and IMF rotation, on the global magnetosphere. From our simulations, we extract the location of the magnetopause boundary, the bow shock and the open-closed field line boundary (OCB), and determine their dependence on the solar wind properties and the IMF orientation. For validation, we compare our simulation results, such as density, temperature and magnetic field, to published empirical models based on in-situ measurements.

Prospects for asteroseismology of rapidly rotating B-type stars

OpenAIRE

Saio, Hideyuki

2013-01-01

In rapidly rotating stars Coriolis forces and centrifugal deformations modify the properties of oscillations; the Coriolis force is important for low-frequency modes, while the centrifugal deformation affects mainly p-modes. Here, we discuss properties of g- and r-mode oscillations in rotating stars. Predicted frequency spectra of high-order g-modes (and r-modes) excited in rapidly rotating stars show frequency groupings associated with azimuthal order $m$. We compare such properties with obs...

A novel look at the pulsar force-free magnetosphere

Science.gov (United States)

Petrova, S. A.; Flanchik, A. B.

2018-03-01

The stationary axisymmetric force-free magnetosphere of a pulsar is considered. We present an exact dipolar solution of the pulsar equation, construct the magnetospheric model on its basis and examine its observational support. The new model has toroidal rather than common cylindrical geometry, in line with that of the plasma outflow observed directly as the pulsar wind nebula at much larger spatial scale. In its new configuration, the axisymmetric magnetosphere consumes the neutron star rotational energy much more efficiently, implying re-estimation of the stellar magnetic field, B_{new}0=3.3×10^{-4}B/P, where P is the pulsar period. Then the 7-order scatter of the magnetic field derived from the rotational characteristics of the pulsars observed appears consistent with the \\cotχ-law, where χ is a random quantity uniformly distributed in the interval [0,π/2]. Our result is suggestive of a unique actual magnetic field strength of the neutron stars along with a random angle between the magnetic and rotational axes and gives insight into the neutron star unification on the geometrical basis.

Magnetic absorption of VHE photons in the magnetosphere of the Crab pulsar

Science.gov (United States)

Bogovalov, S. V.; Contopoulos, I.; Prosekin, A.; Tronin, I.; Aharonian, F. A.

2018-05-01

The detection of the pulsed ˜1 TeV gamma-ray emission from the Crab pulsar reported by MAGIC and VERITAS collaborations demands a substantial revision of existing models of particle acceleration in the pulsar magnetosphere. In this regard model independent restrictions on the possible production site of the very high energy (VHE) photons become an important issue. In this paper, we consider limitations imposed by the process of conversion of VHE gamma-rays into e± pairs in the magnetic field of the pulsar magnetosphere. Photons with energies exceeding 1 TeV are effectively absorbed even at large distances from the surface of the neutron star. Our calculations of magnetic absorption in the force-free magnetosphere show that the twisting of the magnetic field due to the pulsar rotation makes the magnetosphere more transparent compared to the dipole magnetosphere. The gamma-ray absorption appears stronger for photons emitted in the direction of rotation than in the opposite direction. There is a small angular cone inside which the magnetosphere is relatively transparent and photons with energy 1.5 TeV can escape from distances beyond 0.1 light cylinder radius (Rlc). The emission surface from where photons can be emitted in the observer's direction further restricts the sites of VHE gamma-ray production. For the observation angle 57° relative to the Crab pulsar axis of rotation and the orthogonal rotation, the emission surface in the open field line region is located as close as 0.4 Rlc from the stellar surface for a dipole magnetic field, and 0.1 Rlc for a force-free magnetic field.

Transitions in rapidly rotating convection dynamos

Science.gov (United States)

Tilgner, A.

2013-12-01

It is commonly assumed that buoyancy in the fluid core powers the geodynamo. We study here the minimal model of a convection driven dynamo, which is a horizontal plane layer in a gravity field, filled with electrically conducting fluid, heated from below and cooled from above, and rotating about a vertical axis. Such a plane layer may be viewed as a local approximation to the geophysically more relevant spherical geometry. The numerical simulations have been run on graphics processing units with at least 960 cores. If the convection is driven stronger and stronger at fixed rotation rate, the flow behaves at some point as if it was not rotating. This transition shows in the scaling of the heat transport which can be used to distinguish slow from rapid rotation. One expects dynamos to behave differently in these two flow regimes. But even within the convection flows which are rapidly rotating according to this criterion, it will be shown that different types of dynamos exist. In one state, the magnetic field strength obeys a scaling indicative of a magnetostrophic balance, in which the Lorentz force is in equilibrium with the Coriolis force. The flow in this case is helical. A different state exists at higher magnetic Reynolds numbers, in which the magnetic energy obeys a different scaling law and the helicity of the flow is much reduced. As one increases the Rayleigh number, all other parameters kept constant, one may find both types of dynamos separated by an interval of Rayleigh numbers in which there are no dynamos at all. The effect of these transitions on energy dissipation and mean field generation have also been studied.

Jupiter's Magnetosphere: Plasma Description from the Ulysses Flyby.

Science.gov (United States)

Bame, S J; Barraclough, B L; Feldman, W C; Gisler, G R; Gosling, J T; McComas, D J; Phillips, J L; Thomsen, M F; Goldstein, B E; Neugebauer, M

1992-09-11

Plasma observations at Jupiter show that the outer regions of the Jovian magnetosphere are remarkably similar to those of Earth. Bow-shock precursor electrons and ions were detected in the upstream solar wind, as at Earth. Plasma changes across the bow shock and properties of the magnetosheath electrons were much like those at Earth, indicating that similar processes are operating. A boundary layer populated by a varying mixture of solar wind and magnetospheric plasmas was found inside the magnetopause, again as at Earth. In the middle magnetosphere, large electron density excursions were detected with a 10-hour periodicity as planetary rotation carried the tilted plasma sheet past Ulysses. Deep in the magnetosphere, Ulysses crossed a region, tentatively described as magnetically connected to the Jovian polar cap on one end and to the interplanetary magnetic field on the other. In the inner magnetosphere and lo torus, where corotation plays a dominant role, measurements could not be made because of extreme background rates from penetrating radiation belt particles.

The force-free magnetosphere of a rotating black hole

Directory of Open Access Journals (Sweden)

Contopoulos Ioannis

2013-12-01

Full Text Available We explore the analogy with pulsars and investigate the structure of the force-free magnetosphere around a Kerr black hole. We propose that the source of the black hole magnetic field is the Poynting-Robertson effect on the plasma electrons at the inner edge of the surrounding accretion disk, the so called Cosmic Battery. The magnetospheric solution is characterized by the distributions of the magnetic field angular velocity and the poloidal electric current. These are not arbitrary. They are determined self-consistently by requiring that magnetic field lines cross smoothly the two singular surfaces of the problem, the inner ‘light surface’ located inside the ergosphere, and the outer ‘light surface’ which is the generalization of the pulsar light cylinder. The black hole forms a relativistic jet only if it is surrounded by a thick disk and/or extended disk outflows.

The Force-Free Magnetosphere of a Rotating Black Hole

Science.gov (United States)

Contopoulos, Ioannis; Kazanas, Demosthenes; Papadopoulos, Demetrios B.

2013-01-01

We revisit the Blandford-Znajek process and solve the fundamental equation that governs the structure of the steady-state force-free magnetosphere around a Kerr black hole. The solution depends on the distributions of the magnetic field angular velocity and the poloidal electric current. These are not arbitrary. They are determined self-consistently by requiring that magnetic field lines cross smoothly the two singular surfaces of the problem: the inner "light surface" located inside the ergosphere and the outer "light surface" which is the generalization of the pulsar light cylinder.We find the solution for the simplest possible magnetic field configuration, the split monopole, through a numerical iterative relaxation method analogous to the one that yields the structure of the steady-state axisymmetric force-free pulsar magnetosphere. We obtain the rate of electromagnetic extraction of energy and confirm the results of Blandford and Znajek and of previous time-dependent simulations. Furthermore, we discuss the physical applicability of magnetic field configurations that do not cross both "light surfaces."

DISCOVERY OF TWO RARE RIGIDLY ROTATING MAGNETOSPHERE STARS IN THE APOGEE SURVEY

Energy Technology Data Exchange (ETDEWEB)

Eikenberry, Stephen S.; Garner, Alan [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Chojnowski, S. Drew; Majewski, Steven R.; Whelan, David G.; Borish, H. Jacob; Hearty, Fred; Li, Zhi-Yun; Nidever, David L.; Skrutskie, Michael [Department of Astronomy, University of Virginia, 530 McCormick Rd, Charlottesville, VA 22904 (United States); Wisniewski, John [Department of Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States); Shetrone, Matthew [University of Texas, McDonald Observatory, 3640 Dark Sky Drive, Fort Davis, TX (United States); Bizyaev, Dmitry; Ebelke, Garrett [Apache Point Observatory, 2001 Apache Point Rd, Sunspot, NM 88349 (United States); Davenport, James R. A. [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); Feuillet, Diane; Holtzman, Jon [Department of Astronomy, New Mexico State University, 1780 E University Ave, Las Cruces, NM 88003 (United States); Frinchaboy, Peter M. [Department of Physics and Astronomy, Texas Christian University, Box 298840, Fort Worth, TX 76129 (United States); Mészáros, Sz. [Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); and others

2014-04-01

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)—one of the Sloan Digital Sky Survey III programs—is using near-infrared (NIR) spectra of ∼100,000 red giant branch star candidates to study the structure of the Milky Way. In the course of the survey, APOGEE also acquires spectra of hot field stars to serve as telluric calibrators for the primary science targets. We report the serendipitous discovery of two rare, fast-rotating B-stars of the σ Ori E type among those blue field stars observed during the first year of APOGEE operations. Both of the discovered stars display the spectroscopic signatures of rigidly rotating magnetospheres (RRM) common to this class of highly magnetized (B ∼ 10 kGauss) stars, increasing the number of known RRM stars by ∼10%. One (HD 345439) is a main-sequence B-star with unusually strong He absorption (similar to σ Ori E), while the other (HD 23478) fits a ''He-normal'' B3IV classification. We combine the APOGEE discovery spectra with other optical and NIR spectra of these two stars, and of σ Ori E itself, to show how NIR spectroscopy can be a uniquely powerful tool for discovering more of these rare objects, which may show little/no RRM signatures in their optical spectra. We discuss the potential for further discovery of σ Ori E type stars, as well as the implications of our discoveries for the population of these objects and insights into their origin and evolution.

DISCOVERY OF TWO RARE RIGIDLY ROTATING MAGNETOSPHERE STARS IN THE APOGEE SURVEY

International Nuclear Information System (INIS)

Eikenberry, Stephen S.; Garner, Alan; Chojnowski, S. Drew; Majewski, Steven R.; Whelan, David G.; Borish, H. Jacob; Hearty, Fred; Li, Zhi-Yun; Nidever, David L.; Skrutskie, Michael; Wisniewski, John; Shetrone, Matthew; Bizyaev, Dmitry; Ebelke, Garrett; Davenport, James R. A.; Feuillet, Diane; Holtzman, Jon; Frinchaboy, Peter M.; Mészáros, Sz.; Schneider, Donald P.

2014-01-01

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)—one of the Sloan Digital Sky Survey III programs—is using near-infrared (NIR) spectra of ∼100,000 red giant branch star candidates to study the structure of the Milky Way. In the course of the survey, APOGEE also acquires spectra of hot field stars to serve as telluric calibrators for the primary science targets. We report the serendipitous discovery of two rare, fast-rotating B-stars of the σ Ori E type among those blue field stars observed during the first year of APOGEE operations. Both of the discovered stars display the spectroscopic signatures of rigidly rotating magnetospheres (RRM) common to this class of highly magnetized (B ∼ 10 kGauss) stars, increasing the number of known RRM stars by ∼10%. One (HD 345439) is a main-sequence B-star with unusually strong He absorption (similar to σ Ori E), while the other (HD 23478) fits a ''He-normal'' B3IV classification. We combine the APOGEE discovery spectra with other optical and NIR spectra of these two stars, and of σ Ori E itself, to show how NIR spectroscopy can be a uniquely powerful tool for discovering more of these rare objects, which may show little/no RRM signatures in their optical spectra. We discuss the potential for further discovery of σ Ori E type stars, as well as the implications of our discoveries for the population of these objects and insights into their origin and evolution

Single-particle motion in rapidly rotating nuclei

International Nuclear Information System (INIS)

Bengtsson, R.; Frisk, H.

1985-01-01

The motion of particles belonging to a single-j shell is described in terms of classical orbitals. The effects of rapid rotation and pairing correlations are discussed and the results are compared with the quantum mechanical orbitals. (orig.)

Quasiperiodic ULF-pulsations in Saturn's magnetosphere

Directory of Open Access Journals (Sweden)

G. Kleindienst

2009-02-01

Full Text Available Recent magnetic field investigations made onboard the Cassini spacecraft in the magnetosphere of Saturn show the existence of a variety of ultra low frequency plasma waves. Their frequencies suggest that they are presumably not eigenoscillations of the entire magnetospheric system, but excitations confined to selected regions of the magnetosphere. While the main magnetic field of Saturn shows a distinct large scale modulation of approximately 2 nT with a periodicity close to Saturn's rotation period, these ULF pulsations are less obvious superimposed oscillations with an amplitude generally not larger than 3 nT and show a package-like structure. We have analyzed these wave packages and found that they are correlated to a certain extent with the large scale modulation of the main magnetic field. The spatial localization of the ULF wave activity is represented with respect to local time and Kronographic coordinates. For this purpose we introduce a method to correct the Kronographic longitude with respect to a rotation period different from its IAU definition. The observed wave packages occur in all magnetospheric regions independent of local time, elevation, or radial distance. Independent of the longitude correction applied the wave packages do not occur in an accentuated Kronographic longitude range, which implies that the waves are not excited or confined in the same selected longitude ranges at all times or that their lifetime leads to a variable phase with respect to the longitudes where they have been exited.

A New Standard Pulsar Magnetosphere

Science.gov (United States)

Contopoulos, Ioannis; Kalapotharakos, Constantinos; Kazanas, Demosthenes

2014-01-01

In view of recent efforts to probe the physical conditions in the pulsar current sheet, we revisit the standard solution that describes the main elements of the ideal force-free pulsar magnetosphere. The simple physical requirement that the electric current contained in the current layer consists of the local electric charge moving outward at close to the speed of light yields a new solution for the pulsar magnetosphere everywhere that is ideal force-free except in the current layer. The main elements of the new solution are as follows: (1) the pulsar spindown rate of the aligned rotator is 23% larger than that of the orthogonal vacuum rotator; (2) only 60% of the magnetic flux that crosses the light cylinder opens up to infinity; (3) the electric current closes along the other 40%, which gradually converges to the equator; (4) this transfers 40% of the total pulsar spindown energy flux in the equatorial current sheet, which is then dissipated in the acceleration of particles and in high-energy electromagnetic radiation; and (5) there is no separatrix current layer. Our solution is a minimum free-parameter solution in that the equatorial current layer is electrostatically supported against collapse and thus does not require a thermal particle population. In this respect, it is one more step toward the development of a new standard solution. We discuss the implications for intermittent pulsars and long-duration gamma-ray bursts. We conclude that the physical conditions in the equatorial current layer determine the global structure of the pulsar magnetosphere.

On the paleo-magnetospheres of Earth and Mars

Science.gov (United States)

Scherf, Manuel; Khodachenko, Maxim; Alexeev, Igor; Belenkaya, Elena; Blokhina, Marina; Johnstone, Colin; Tarduno, John; Lammer, Helmut; Tu, Lin; Guedel, Manuel

2017-04-01

exobase of a nitrogen dominated atmosphere would most probably have been extended above the magnetopause, leading to enhanced atmospheric erosion, whereas a CO2-dominated atmosphere would have prevented atmospheric loss in such a scenario. Our simulations also show that the Martian paleo-magnetosphere during the early Noachian must have been comparable in size to the terrestrial paleo-magnetosphere, hence a CO2-rich atmosphere should have been protected by the magnetic field from rapid atmospheric erosion until the cessation of the Martian dipole field ˜4.0 billion years ago. Finally, our results favor the idea that the young Sun must have been a slow to moderate rotator. The solar wind and EUV flux from a fast rotating Sun would have been so intense, that most probably the ancient atmospheres of Mars and Earth would not have survived. Acknowledgments. The authors acknowledge the support of the FWF NFN project "Pathways to Habitability: From Disks to Active Stars, Planets and Life", in particular its related sub-projects S11604-N16, S11606-N16 and S11607-N16. This presentation is supported by the Austrian Science Fund (FWF) and the US NSF (EAR1015269 to JAT).

Seismology of rapidly rotating and solar-like stars

Science.gov (United States)

Reese, Daniel Roy

2018-05-01

A great deal of progress has been made in stellar physics thanks to asteroseismology, the study of pulsating stars. Indeed, asteroseismology is currently the only way to probe the internal structure of stars. The work presented here focuses on some of the theoretical aspects of this domain and addresses two broad categories of stars, namely solar-like pulsators (including red giants), and rapidly rotating pulsating stars. The work on solar-like pulsators focuses on setting up methods for efficiently characterising a large number of stars, in preparation for space missions like TESS and PLATO 2.0. In particular, the AIMS code applies an MCMC algorithm to find stellar properties and a sample of stellar models which fit a set of seismic and classic observational constraints. In order to reduce computation time, this code interpolates within a precalculated grid of models, using a Delaunay tessellation which allows a greater flexibility on the construction of the grid. Using interpolated models based on the outputs from this code or models from other forward modelling codes, it is possible to obtain refined estimates of various stellar properties such as the mean density thanks to inversion methods put together by me and G. Buldgen, my former PhD student. Finally, I show how inversion-type methods can also be used to test more qualitative information such as whether a decreasing rotation profile is compatible with a set of observed rotational splittings and a given reference model. In contrast to solar-like pulsators, the pulsation modes of rapidly rotating stars remain much more difficult to interpret due to the complexity of the numerical calculations needed to calculate such modes, the lack of simple frequency patterns, and the fact that it is difficult to predict mode amplitudes. The work described here therefore focuses on addressing the above difficulties one at a time in the hopes that it will one day be possible to carry out detailed asteroseismology in these

Current flow and pair creation at low altitude in rotation-powered pulsars' force-free magnetospheres: space charge limited flow

Science.gov (United States)

Timokhin, A. N.; Arons, J.

2013-02-01

We report the results of an investigation of particle acceleration and electron-positron plasma generation at low altitude in the polar magnetic flux tubes of rotation-powered pulsars, when the stellar surface is free to emit whatever charges and currents are demanded by the force-free magnetosphere. We apply a new 1D hybrid plasma simulation code to the dynamical problem, using Particle-in-Cell methods for the dynamics of the charged particles, including a determination of the collective electrostatic fluctuations in the plasma, combined with a Monte Carlo treatment of the high-energy gamma-rays that mediate the formation of the electron-positron pairs. We assume the electric current flowing through the pair creation zone is fixed by the much higher inductance magnetosphere, and adopt the results of force-free magnetosphere models to provide the currents which must be carried by the accelerator. The models are spatially one dimensional, and designed to explore the physics, although of practical relevance to young, high-voltage pulsars. We observe novel behaviour (a) When the current density j is less than the Goldreich-Julian value (0 electrically trapped particles with the same sign of charge as the beam. The voltage drops are of the order of mc2/e, and pair creation is absent. (b) When the current density exceeds the Goldreich-Julian value (j/jGJ > 1), the system develops high voltage drops (TV or greater), causing emission of curvature gamma-rays and intense bursts of pair creation. The bursts exhibit limit cycle behaviour, with characteristic time-scales somewhat longer than the relativistic fly-by time over distances comparable to the polar cap diameter (microseconds). (c) In return current regions, where j/jGJ generated pairs allow the system to simultaneously carry the magnetospherically prescribed currents and adjust the charge density and average electric field to force-free conditions. We also elucidate the conditions for pair creating beam flow to be

Rapidly rotating single late-type giants: New FK Comae stars?

Science.gov (United States)

Fekel, Francis C.

1986-01-01

A group of rapidly rotating single late-type giants was found from surveys of chromospherically active stars. These stars have V sin I's ranging from 6 to 46 km/sec, modest ultraviolet emission line fluxes, and strong H alpha absorption lines. Although certainly chromospherically active, their characteristics are much less extreme than those of FK Com and one or two other similar systems. One possible explanation for the newly identified systems is that they have evolved from stars similar to FK Com. The chromospheric activity and rotation of single giant stars like FK Com would be expected to decrease with time as they do in single dwarfs. Alternatively, this newly identified group may have evolved from single rapidly rotating A, or early F stars.

Substorms in the earth's magnetosphere

International Nuclear Information System (INIS)

Baker, D.N.

1984-01-01

Magnetospheres are plasma regions of large scale in space dominated by magnetic field effects. The earth, and many planets in our solar system, are known to have magnetospheric regions around them. Magnetospheric substorms represent the intense, rapid dissipation of energy that has been extracted from the solar wind and stored temporarily in the terrestrial magnetotail. In this paper a widely, but not universally, accepted model of substorms is described. The energy budgets, time scales, and conversion efficiencies for substorms are presented. The primary forms of substorm energy dissipation are given along with the average levels of the dissipation. Aspects of particle acceleration and precipitation, Joule heating mechanisms, ring current formation, and plasmoid escape are illustrated based on in situ observations taken from the large available data base. A brief description is given of possible analogues of substorm-like behavior in other astrophysical systems. 27 references, 12 figures

Improving magnetosphere in situ observations using solar sails

Science.gov (United States)

Parsay, Khashayar; Schaub, Hanspeter; Schiff, Conrad; Williams, Trevor

2018-01-01

Past and current magnetosphere missions employ conventional spacecraft formations for in situ observations of the geomagnetic tail. Conventional spacecraft flying in inertially fixed Keplerian orbits are only aligned with the geomagnetic tail once per year, since the geomagnetic tail is always aligned with the Earth-Sun line, and therefore, rotates annually. Solar sails are able to artificially create sun-synchronous orbits such that the orbit apse line remains aligned with the geomagnetic tail line throughout the entire year. This continuous presence in the geomagnetic tail can significantly increase the science phase for magnetosphere missions. In this paper, the problem of solar sail formation design is explored using nonlinear programming to design optimal two-craft, triangle, and tetrahedron solar sail formations, in terms of formation quality and formation stability. The designed formations are directly compared to the formations used in NASA's Magnetospheric Multi-Scale mission.

The earth's palaeomagnetosphere as the third type of planetary magnetosphere

International Nuclear Information System (INIS)

Saito, T; Sakurai, T.; Yumoto, K.

1978-01-01

From the viewpoint of dynamical topology, planetary magnetospheres are classified into three: Types 1,2 and 3. When the rotation vector and dipole moment of a planet and the velocity vector of the solar wind are denoted as Ω,M, and V, respectively, the planetary magnetosphere with Ωparallel to M perpendicular to V is called Type 1. The magnetospheres of the present Earth, Jupiter, and Uranus at its equinoctial points belong to this type. The magnetosphere with Ωparallel to M parallel to V is called Type 2, which includes the Uranium magnetosphere at its solstitial points. The magnetosphere with Ωperpendicular M and perpendicular V is called Type 3. The Earth's palaeomagnetosphere is considered to have experienced Type 3 during excursions and transition stages of palaeomagnetic polarity reversals. In the Type 3 magnetosphere, drastic variations are expected in configurations of the dayside cusps, tail axis, neutral sheet, polar caps, and so on. A possible relation between the Type 3 palaeomagnetosphere and palaeoclimate of the Earth during polarity reversals and geomagnetic excursions is suggested. It is also suggested that the heliomagnetosphere during polarity reversals of the general field of the Sun exhibits a drastic configuration change similar to the Type 3 palaeomagnetosphere of the Earth. A relation between the perpendicular condition Ω perpendicular to M and magnetic variable stars and pulsars is briefly discussed. (author)

Rapidly rotating pulsar radiation in vacuum nonlinear electrodynamics

Energy Technology Data Exchange (ETDEWEB)

Denisov, V.I.; Pimenov, A.B.; Sokolov, V.A. [Moscow State University, Physics Department, Moscow (Russian Federation); Denisova, I.P. [Moscow Aviation Institute (National Research University), Moscow (Russian Federation)

2016-11-15

In this paper we investigate the corrections of vacuum nonlinear electrodynamics on rapidly rotating pulsar radiation and spin-down in the perturbative QED approach (post-Maxwellian approximation). An analytical expression for the pulsar's radiation intensity has been obtained and analyzed. (orig.)

A complex-plane strategy for computing rotating polytropic models - Numerical results for strong and rapid differential rotation

International Nuclear Information System (INIS)

Geroyannis, V.S.

1990-01-01

In this paper, a numerical method, called complex-plane strategy, is implemented in the computation of polytropic models distorted by strong and rapid differential rotation. The differential rotation model results from a direct generalization of the classical model, in the framework of the complex-plane strategy; this generalization yields very strong differential rotation. Accordingly, the polytropic models assume extremely distorted interiors, while their boundaries are slightly distorted. For an accurate simulation of differential rotation, a versatile method, called multiple partition technique is developed and implemented. It is shown that the method remains reliable up to rotation states where other elaborate techniques fail to give accurate results. 11 refs

Quantum measurement of a rapidly rotating spin qubit in diamond.

Science.gov (United States)

Wood, Alexander A; Lilette, Emmanuel; Fein, Yaakov Y; Tomek, Nikolas; McGuinness, Liam P; Hollenberg, Lloyd C L; Scholten, Robert E; Martin, Andy M

2018-05-01

A controlled qubit in a rotating frame opens new opportunities to probe fundamental quantum physics, such as geometric phases in physically rotating frames, and can potentially enhance detection of magnetic fields. Realizing a single qubit that can be measured and controlled during physical rotation is experimentally challenging. We demonstrate quantum control of a single nitrogen-vacancy (NV) center within a diamond rotated at 200,000 rpm, a rotational period comparable to the NV spin coherence time T 2 . We stroboscopically image individual NV centers that execute rapid circular motion in addition to rotation and demonstrate preparation, control, and readout of the qubit quantum state with lasers and microwaves. Using spin-echo interferometry of the rotating qubit, we are able to detect modulation of the NV Zeeman shift arising from the rotating NV axis and an external DC magnetic field. Our work establishes single NV qubits in diamond as quantum sensors in the physically rotating frame and paves the way for the realization of single-qubit diamond-based rotation sensors.

Particle Acceleration in Dissipative Pulsar Magnetospheres

Science.gov (United States)

Kazanas, Z.; Kalapotharakos, C.; Harding, A.; Contopoulos, I.

2012-01-01

Pulsar magnetospheres represent unipolar inductor-type electrical circuits at which an EM potential across the polar cap (due to the rotation of their magnetic field) drives currents that run in and out of the polar cap and close at infinity. An estimate ofthe magnitude of this current can be obtained by dividing the potential induced across the polar cap V approx = B(sub O) R(sub O)(Omega R(sub O)/c)(exp 2) by the impedance of free space Z approx eq 4 pi/c; the resulting polar cap current density is close to $n {GJ} c$ where $n_{GJ}$ is the Goldreich-Julian (GJ) charge density. This argument suggests that even at current densities close to the GJ one, pulsar magnetospheres have a significant component of electric field $E_{parallel}$, parallel to the magnetic field, a condition necessary for particle acceleration and the production of radiation. We present the magnetic and electric field structures as well as the currents, charge densities, spin down rates and potential drops along the magnetic field lines of pulsar magnetospheres which do not obey the ideal MHD condition $E cdot B = 0$. By relating the current density along the poloidal field lines to the parallel electric field via a kind of Ohm's law $J = sigma E_{parallel}$ we study the structure of these magnetospheres as a function of the conductivity $sigma$. We find that for $sigma gg OmegaS the solution tends to the (ideal) Force-Free one and to the Vacuum one for $sigma 11 OmegaS. Finally, we present dissipative magnetospheric solutions with spatially variable $sigma$ that supports various microphysical properties and are compatible with the observations.

Supernova seismology: gravitational wave signatures of rapidly rotating core collapse

Science.gov (United States)

Fuller, Jim; Klion, Hannah; Abdikamalov, Ernazar; Ott, Christian D.

2015-06-01

Gravitational waves (GW) generated during a core-collapse supernova open a window into the heart of the explosion. At core bounce, progenitors with rapid core rotation rates exhibit a characteristic GW signal which can be used to constrain the properties of the core of the progenitor star. We investigate the dynamics of rapidly rotating core collapse, focusing on hydrodynamic waves generated by the core bounce, and the GW spectrum they produce. The centrifugal distortion of the rapidly rotating proto-neutron star (PNS) leads to the generation of axisymmetric quadrupolar oscillations within the PNS and surrounding envelope. Using linear perturbation theory, we estimate the frequencies, amplitudes, damping times, and GW spectra of the oscillations. Our analysis provides a qualitative explanation for several features of the GW spectrum and shows reasonable agreement with non-linear hydrodynamic simulations, although a few discrepancies due to non-linear/rotational effects are evident. The dominant early post-bounce GW signal is produced by the fundamental quadrupolar oscillation mode of the PNS, at a frequency 0.70 ≲ f ≲ 0.80 kHz, whose energy is largely trapped within the PNS and leaks out on a ˜10-ms time-scale. Quasi-radial oscillations are not trapped within the PNS and quickly propagate outwards until they steepen into shocks. Both the PNS structure and Coriolis/centrifugal forces have a strong impact on the GW spectrum, and a detection of the GW signal can therefore be used to constrain progenitor properties.

Pleiades rapid rotators - evidence for an evolutionary sequence

International Nuclear Information System (INIS)

Butler, R.P.; Marcy, G.W.; Cohen, R.D.; Duncan, D.K.; California Univ., La Jolla; Space Telescope Science Institute, Baltimore, MD)

1987-01-01

Four rapidly rotating early-K dwarfs in the Pleiades are shown to contain an order of magnitude more Li than four slow rotators of the same spectral type, as would be expected if they were systematically younger. This supports the idea that late-type stars first arrive on the main sequence with V(rot) greater than about 100 km/s, that they spin down to V(rot) less than about 10 km/s in 10 to the 7th to 10 to the 8th yr, and that the Pleiades lower main sequence shows such an age spread. 14 references

Polarized curvature radiation in pulsar magnetosphere

Science.gov (United States)

Wang, P. F.; Wang, C.; Han, J. L.

2014-07-01

The propagation of polarized emission in pulsar magnetosphere is investigated in this paper. The polarized waves are generated through curvature radiation from the relativistic particles streaming along curved magnetic field lines and corotating with the pulsar magnetosphere. Within the 1/γ emission cone, the waves can be divided into two natural wave-mode components, the ordinary (O) mode and the extraordinary (X) mode, with comparable intensities. Both components propagate separately in magnetosphere, and are aligned within the cone by adiabatic walking. The refraction of O mode makes the two components separated and incoherent. The detectable emission at a given height and a given rotation phase consists of incoherent X-mode and O-mode components coming from discrete emission regions. For four particle-density models in the form of uniformity, cone, core and patches, we calculate the intensities for each mode numerically within the entire pulsar beam. If the corotation of relativistic particles with magnetosphere is not considered, the intensity distributions for the X-mode and O-mode components are quite similar within the pulsar beam, which causes serious depolarization. However, if the corotation of relativistic particles is considered, the intensity distributions of the two modes are very different, and the net polarization of outcoming emission should be significant. Our numerical results are compared with observations, and can naturally explain the orthogonal polarization modes of some pulsars. Strong linear polarizations of some parts of pulsar profile can be reproduced by curvature radiation and subsequent propagation effect.

Magnetosonic resonance in a dipole-like magnetosphere

Directory of Open Access Journals (Sweden)

A. S. Leonovich

2006-09-01

Full Text Available A theory of resonant conversion of fast magnetosonic (FMS waves into slow magnetosonic (SMS oscillations in a magnetosphere with dipole-like magnetic field has been constructed. Monochromatic FMS waves are shown to drive standing (along magnetic field lines SMS oscillations, narrowly localized across magnetic shells. The longitudinal and transverse structures, as well as spectrum of resonant SMS waves are determined. Frequencies of fundamental harmonics of standing SMS waves lie in the range of 0.1–1 mHz, and are about two orders of magnitude lower than frequencies of similar Alfvén field line resonance harmonics. This difference makes an effective interaction between these MHD modes impossible. The amplitude of SMS oscillations rapidly decreases along the field lines from the magnetospheric equator towards the ionosphere. In this context, magnetospheric SMS oscillations cannot be observed on the ground, and the ionosphere does not play any role either in their generation or dissipation. The theory developed can be used to interpret the occurrence of compressional Pc5 waves in a quiet magnetosphere with a weak ring current.

Closed model of the earth's magnetosphere

International Nuclear Information System (INIS)

Piddington, J.H.

1979-01-01

The existence of large-scale motions within the earth's magnetosphere and that of a long magnetotail were predicted in 1960 as results of a hypothetical frictional interaction between the solar wind and the geomagnetic field. The boundary layer model of this interaction involves the flow of magnetosheath plasma in a magnetospheric boundary layer. The flow is across magnetic field lines, and so the layer must be polarized, with a space charge field nearly balancing the induction field V x B. The space charge tends to discharge through the ionosphere, thus providing some magnetic and related activity as well as the Lorentz frictional force. This closed magnetosphere model has been largely neglected in favor of the reconnection model but is now strongly supported by observational results and their interpretation as follows. (1) The evidence for the reconnection model, increasing activity with a southward interplanetary field and invasion of the polar caps by flare particles, is shown to be equally compatible with the closed field model. (2) The magnetotail grows by the motions of closed flux tubes through the dawn and dusk meridians, a process which depends on the nature of the boundary between magnetosphere and magnetosheath plasmas and perhaps also on the solar wind dynamo. Both of these features depend, in turn, on the direction of the interplanetary magnetic field. (3) Closed field lines entering the tail may be stretched to a few tens of earth radii and then contract back to the corotating magnetosphere. Others enter the long tail and are stretched to hundreds of earth radii and so are pervious to fast solar particles. (4) A new model of the magnetospheric substorm involves the entry of closed field lines into the tail and their rapid return to the corotating magnetosphere. The return is due, first, to the release of their trapped plasma as it becomes electrically polarized and, second, to mounting magnetic and plasma stresses in the inflated magnetotail

Magnetosphere and ionosphere response to a positive-negative pulse pair of solar wind dynamic pressure

Science.gov (United States)

Tian, A.; Degeling, A. W.

2017-12-01

Simulations and observations had shown that single positive/negative solar wind dynamic pressure pulse would excite geomagnetic impulsive events along with ionosphere and/or magnetosphere vortices which are connected by field aligned currents(FACs). In this work, a large scale ( 9min) magnetic hole event in solar wind provided us with the opportunity to study the effects of positive-negative pulse pair (△p/p 1) on the magnetosphere and ionosphere. During the magnetic hole event, two traveling convection vortices (TCVs, anti-sunward) first in anticlockwise then in clockwise rotation were detected by geomagnetic stations located along the 10:30MLT meridian. At the same time, another pair of ionospheric vortices azimuthally seen up to 3 MLT first in clockwise then in counter-clockwise rotation were also appeared in the afternoon sector( 14MLT) and centered at 75 MLAT without obvious tailward propagation feature. The duskside vortices were also confirmed in SuperDARN radar data. We simulated the process of magnetosphere struck by a positive-negative pulse pair and it shows that a pair of reversed flow vortices in the magnetosphere equatorial plane appeared which may provide FACs for the vortices observed in ionosphere. Dawn dusk asymmetry of the vortices as well as the global geomagnetism perturbation characteristics were also discussed.

X-ray pulsar magnetosphere

International Nuclear Information System (INIS)

Lipunov, V.

1981-01-01

A pulsar consists of a close binary star system whose one component is a neutron star and the other a normal star. This supplies the neutron star with fuel in form of star wind or a gas stream. A hot plasma-like matter falls onto the neutron star, penetrates in its magnetic field and interacts with it. The matter coming from the normal star has a great rotational moment and forms a hot diamagnetic disk around the neutron star. The plasma penetrates in the internal parts of the magnetosphere where hard x radiation is formed as a result of the plasma impingement on the neutron star surface. (M.D.)

The magnetosphere

International Nuclear Information System (INIS)

Ratcliffe, J.A.

1977-01-01

The structure of the magnetosphere, deduced from observations in space craft, is described, together with some of the phenomena that occur in it. A simple non-mathematical outline is given of some of the processes involved. The effects of the magnetosphere on the aurora, and on the magnetic field observed at the ground, are described, and the way they change during magnetospheric storms is discussed. (author)

Rapidly rotating neutron stars with a massive scalar field—structure and universal relations

International Nuclear Information System (INIS)

Doneva, Daniela D.; Yazadjiev, Stoytcho S.

2016-01-01

We construct rapidly rotating neutron star models in scalar-tensor theories with a massive scalar field. The fact that the scalar field has nonzero mass leads to very interesting results since the allowed range of values of the coupling parameters is significantly broadened. Deviations from pure general relativity can be very large for values of the parameters that are in agreement with the observations. We found that the rapid rotation can magnify the differences several times compared to the static case. The universal relations between the normalized moment of inertia and quadrupole moment are also investigated both for the slowly and rapidly rotating cases. The results show that these relations are still EOS independent up to a large extend and the deviations from pure general relativity can be large. This places the massive scalar-tensor theories amongst the few alternative theories of gravity that can be tested via the universal I -Love- Q relations.

Rapidly rotating neutron stars with a massive scalar field—structure and universal relations

Energy Technology Data Exchange (ETDEWEB)

Doneva, Daniela D.; Yazadjiev, Stoytcho S., E-mail: daniela.doneva@uni-tuebingen.de, E-mail: yazad@phys.uni-sofia.bg [Theoretical Astrophysics, Eberhard Karls University of Tübingen, Tübingen 72076 (Germany)

2016-11-01

We construct rapidly rotating neutron star models in scalar-tensor theories with a massive scalar field. The fact that the scalar field has nonzero mass leads to very interesting results since the allowed range of values of the coupling parameters is significantly broadened. Deviations from pure general relativity can be very large for values of the parameters that are in agreement with the observations. We found that the rapid rotation can magnify the differences several times compared to the static case. The universal relations between the normalized moment of inertia and quadrupole moment are also investigated both for the slowly and rapidly rotating cases. The results show that these relations are still EOS independent up to a large extend and the deviations from pure general relativity can be large. This places the massive scalar-tensor theories amongst the few alternative theories of gravity that can be tested via the universal I -Love- Q relations.

Electron-positron plasma generation in a pulsar magnetosphere

International Nuclear Information System (INIS)

Gurevich, A.V.; Istomin, Ya.N.

1985-01-01

The generation of an electron-positron plasma in vacuum (vacuum ''breakdown'') in the presence of an inhomogeneous electric field and strong curvilinear magnetic field is considered. A situation of this type may occur in the magnetosphere of a rotating neutron star. A general set of kinetic equations for electrons, positrons and γ quanta in a curvilinear magnetic field is derived by taking into account electron-positron pair production and emission of curvicur and synchrotron photons. The conditions for appearance of ''breakdown'' are determined and the threshold value of the elec tric field discontinuity at the surface of the star is found. Multiplication of particles in the magnetosphere is investigated and the electron, positron and γ quantum distribution functions are found. The extinction limit of pulsars is determined. The theory is shown to be in accordance with the observation results

Concepts of magnetospheric convection

International Nuclear Information System (INIS)

Vasyliunas, V.M.

1975-01-01

Magnetospheric physics, which grew out of attempts to understand the space environment of the Earth, is becoming increasingly applicable to other systems in the Universe. Among the planets, in addition to the Earth, Jupiter, Mercury, Mars and (in a somewhat different way) Venus are now known to have magnetospheres. The magnetospheres of pulsars have been regarded as an essential part of the pulsar phenomenon. Other astrophysical systems, such as supernova remnant shells or magnetic stars and binary star systems, may be describable as magnetospheres. The major concepts of magnetospheric physics thus need to be formulated in a general way not restricted to the geophysical context in which they may have originated. Magnetospheric convection has been one of the most important and fruitful concepts in the study of the Earth's magnetosphere. This paper describes the basic theoretical notions of convection in a manner applicable to magnetospheres generally and discusses the relative importance of convective corotational motions, with particular reference to the comparison of the Earth and Jupiter. (Auth.)

Magnetohydrodynamic calculations on pulsar magnetospheres

International Nuclear Information System (INIS)

Brinkmann, W.

1976-01-01

In this paper, the relativistic magnetohydrodynamic is presented in covariant form and applied to some problems in the field of pulsar magnetospheres. In addition, numerical methods to solve the resulting equations of motion are investigated. The theory of relativistic magnetohydrodynamic presented here is valid in the framework of the theory of general relativity, describing the interaction of electromagnetic fields with an ideal fluid. In the two-dimensional case, a Lax-Wendroff method is studied which should be optimally stable with the operator splitting of Strang. In the framework of relativistic magnetohydrodynamic also the model of a stationary aequatorial stellar pulsar wind as well as the parallel rotator is investigated. (orig.) [de

Outer magnetosphere

International Nuclear Information System (INIS)

Schardt, A.W.; Behannon, K.W.; Lepping, R.P.; Carbary, J.F.; Eviatar, A.; Siscoe, G.L.

1984-01-01

Similarities between the Saturnian and terrestrial outer magnetosphere are examined. Saturn, like earth, has a fully developed magnetic tail, 80 to 100 RS in diameter. One major difference between the two outer magnetospheres is the hydrogen and nitrogen torus produced by Titan. This plasma is, in general, convected in the corotation direction at nearly the rigid corotation speed. Energies of magnetospheric particles extend to above 500 keV. In contrast, interplanetary protons and ions above 2 MeV have free access to the outer magnetosphere to distances well below the Stormer cutoff. This access presumably occurs through the magnetotail. In addition to the H+, H2+, and H3+ ions primarily of local origin, energetic He, C, N, and O ions are found with solar composition. Their flux can be substantially enhanced over that of interplanetary ions at energies of 0.2 to 0.4 MeV/nuc

Dynamics of magnetospheric plasmas

International Nuclear Information System (INIS)

Horwitz, J.L.

1985-01-01

The dynamical behavior of the magnetospheric plasmas which control the electrostatic charging of spacecraft is the result of the complex interaction of a variety of production, loss, transport, and energization mechanisms in the magnetosphere. This paper is intended to provide the spacecraft engineer with a foundation in the basic morphology and controlling processes pertaining to magnetospheric plasma dynamics in the inner magnetosphere, including the synchronous orbit region. 32 references

Alteration of the magnetosphere of the Vela pulsar during a glitch.

Science.gov (United States)

Palfreyman, Jim; Dickey, John M; Hotan, Aidan; Ellingsen, Simon; van Straten, Willem

2018-04-01

As pulsars lose energy, primarily in the form of magnetic dipole radiation, their rotation slows down accordingly. For some pulsars, this spin-down is interrupted by occasional abrupt spin-up events known as glitches 1 . A glitch is hypothesized to be a catastrophic release of pinned vorticity 2 that provides an exchange of angular momentum between the superfluid outer core and the crust. This is manifested by a minute alteration in the rotation rate of the neutron star and its co-rotating magnetosphere, which is revealed by an abrupt change in the timing of observed radio pulses. Measurement of the flux density, polarization and single-pulse arrival times of the glitch with high time resolution may reveal the equation of state of the crustal superfluid, its drag-to-lift ratio and the parameters that describe its friction with the crust 3 . This has not hitherto been possible because glitch events happen unpredictably. Here we report single-pulse radio observations of a glitch in the Vela pulsar, which has a rotation frequency of 11.2 hertz. The glitch was detected on 2016 December 12 at 11:36 universal time, during continuous observations of the pulsar over a period of three years. We detected sudden changes in the pulse shape coincident with the glitch event: one pulse was unusually broad, the next pulse was missing (a 'null') and the following two pulses had unexpectedly low linear polarization. This sequence was followed by a 2.6-second interval during which pulses arrived later than usual, indicating that the glitch affects the magnetosphere.

Eigenmode frequency distribution of rapidly rotating neutron stars

International Nuclear Information System (INIS)

Boutloukos, Stratos; Nollert, Hans-Peter

2007-01-01

We use perturbation theory and the relativistic Cowling approximation to numerically compute characteristic oscillation modes of rapidly rotating relativistic stars which consist of a perfect fluid obeying a polytropic equation of state. We present a code that allows the computation of modes of arbitrary order. We focus here on the overall distribution of frequencies. As expected, we find an infinite pressure mode spectrum extending to infinite frequency. In addition we obtain an infinite number of inertial mode solutions confined to a finite, well-defined frequency range which depends on the compactness and the rotation frequency of the star. For nonaxisymmetric modes we observe how this range is shifted with respect to the axisymmetric ones, moving towards negative frequencies and thus making all m>2 modes unstable. We discuss whether our results indicate that the star's spectrum must have a continuous part, as opposed to simply containing an infinite number of discrete modes

Ab-initio Pulsar Magnetosphere: Particle Acceleration in Oblique Rotators and High-energy Emission Modeling

Science.gov (United States)

Philippov, Alexander A.; Spitkovsky, Anatoly

2018-03-01

We perform global particle-in-cell simulations of pulsar magnetospheres, including pair production, ion extraction from the surface, frame-dragging corrections, and high-energy photon emission and propagation. In the case of oblique rotators, the effects of general relativity increase the fraction of the open field lines that support active pair discharge. We find that the plasma density and particle energy flux in the pulsar wind are highly non-uniform with latitude. A significant fraction of the outgoing particle energy flux is carried by energetic ions, which are extracted from the stellar surface. Their energies may extend up to a large fraction of the open field line voltage, making them interesting candidates for ultra-high-energy cosmic rays. We show that pulsar gamma-ray radiation is dominated by synchrotron emission, produced by particles that are energized by relativistic magnetic reconnection close to the Y-point and in the equatorial current sheet. In most cases, the calculated light curves contain two strong peaks, which is in general agreement with Fermi observations. The radiative efficiency decreases with increasing pulsar inclination and increasing efficiency of pair production in the current sheet, which explains the observed scatter in L γ versus \\dot{E}. We find that the high-frequency cutoff in the spectra is regulated by the pair-loading of the current sheet. Our findings lay the foundation for quantitative interpretation of Fermi observations of gamma-ray pulsars.

Challenges Handling Magnetospheric and Ionospheric Signals in Internal Geomagnetic Field Modelling

DEFF Research Database (Denmark)

Finlay, Chris; Lesur, V.; Thébault, E.

2017-01-01

systems in the ionosphere and magnetosphere. In order to fully exploit magnetic data to probe the physical properties and dynamics of the Earth’s interior, field models with suitable treatments of external sources, and their associated induced signals, are essential. Here we review the methods presently......-by-track analysis to characterize magnetospheric field fluctuations, differences in internal field models that result from alternative treatments of the quiet-time ionospheric field, and challenges associated with rapidly changing, but spatially correlated, magnetic signatures of polar cap current systems. Possible...

Dynamical role of Ekman pumping in rapidly rotating convection

Science.gov (United States)

Stellmach, Stephan; Julien, Keith; Cheng, Jonathan; Aurnou, Jonathan

2015-04-01

The exact nature of the mechanical boundary conditions (i.e. no-slip versus stress-free) is usually considered to be of secondary importance in the rapidly rotating parameter regime characterizing planetary cores. While they have considerable influence for the Ekman numbers achievable in today's global simulations, for planetary values both the viscous Ekman layers and the associated secondary flows are generally expected to become negligibly small. In fact, usually the main purpose of using stress-free boundary conditions in numerical dynamo simulations is to suppress unrealistically large friction and pumping effects. In this study, we investigate the influence of the mechanical boundary conditions on core convection systematically. By restricting ourselves to the idealized case of rapidly rotating Rayleigh-Bénard convection, we are able to combine results from direct numerical simulations (DNS), laboratory experiments and asymptotic theory into a coherent picture. Contrary to the general expectation, we show that the dynamical effects of Ekman pumping increase with decreasing Ekman number over the investigated parameter range. While stress-free DNS results converge to the asymptotic predictions, both no-slip simulations and laboratory experiments consistently reveal increasingly large deviations from the existing asymptotic theory based on dynamically passive Ekman layers. The implications of these results for core dynamics are discussed briefly.

Venus magnetosphere

International Nuclear Information System (INIS)

Podgornyj, I.M.

1983-01-01

Some peculiarities of the structure of the Venus magnetosphere are considered. A Swedish scientist H. Alfven supposes that nebular bodies with ionospheric shelles of the type of Venus atmosphere possess induced magnetospheres with dragged magnetic tails. In the Institute of Space Research of the USSR Academy of Sciences experiments on the modelling of such magnetosphere are performed. The possibility of formation of the shock wave in the body with plasma shell in the absence of the proper magnetic shell is proved. The cosmic ''Pioneer-Venus'' equipment is used to obtain such a distribution of the magnetic field depending on the distance to Venus as it was predicted by the laboratory model

Self-consistent equilibria in the pulsar magnetosphere

International Nuclear Information System (INIS)

Endean, V.G.

1976-01-01

For a 'collisionless' pulsar magnetosphere the self-consistent equilibrium particle distribution functions are functions of the constants of the motion ony. Reasons are given for concluding that to a good approximation they will be functions of the rotating frame Hamiltonian only. This is shown to result in a rigid rotation of the plasma, which therefore becomes trapped inside the velocity of light cylinder. The self-consistent field equations are derived, and a method of solving them is illustrated. The axial component of the magnetic field decays to zero at the plasma boundary. In practice, some streaming of particles into the wind zone may occur as a second-order effect. Acceleration of such particles to very high energies is expected when they approach the velocity of light cylinder, but they cannot be accelerated to very high energies near the star. (author)

WHY ARE RAPIDLY ROTATING M DWARFS IN THE PLEIADES SO (INFRA)RED? NEW PERIOD MEASUREMENTS CONFIRM ROTATION-DEPENDENT COLOR OFFSETS FROM THE CLUSTER SEQUENCE

Energy Technology Data Exchange (ETDEWEB)

Covey, Kevin R. [Department of Physics and Astronomy, Western Washington University, Bellingham WA 98225-9164 (United States); Agüeros, Marcel A.; Liu, Jiyu [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255 (United States); Ahmadi, Aida [Max Planck Institute for Radioastronomy, Auf dem Hügel 69, D-53121 Bonn (Germany); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Levitan, David [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Sesar, Branimir, E-mail: kevin.covey@wwu.edu [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

2016-05-10

Stellar rotation periods ( P {sub rot}) measured in open clusters have proved to be extremely useful for studying stars’ angular momentum content and rotationally driven magnetic activity, which are both age- and mass-dependent processes. While P {sub rot} measurements have been obtained for hundreds of solar-mass members of the Pleiades, measurements exist for only a few low-mass (<0.5 M {sub ⊙}) members of this key laboratory for stellar evolution theory. To fill this gap, we report P {sub rot} for 132 low-mass Pleiades members (including nearly 100 with M ≤ 0.45 M {sub ⊙}), measured from photometric monitoring of the cluster conducted by the Palomar Transient Factory in late 2011 and early 2012. These periods extend the portrait of stellar rotation at 125 Myr to the lowest-mass stars and re-establish the Pleiades as a key benchmark for models of the transport and evolution of stellar angular momentum. Combining our new P {sub rot} with precise BVIJHK photometry reported by Stauffer et al. and Kamai et al., we investigate known anomalies in the photometric properties of K and M Pleiades members. We confirm the correlation detected by Kamai et al. between a star's P {sub rot} and position relative to the main sequence in the cluster's color–magnitude diagram. We find that rapid rotators have redder ( V − K ) colors than slower rotators at the same V , indicating that rapid and slow rotators have different binary frequencies and/or photospheric properties. We find no difference in the photometric amplitudes of rapid and slow rotators, indicating that asymmetries in the longitudinal distribution of starspots do not scale grossly with rotation rate.

Mercury's Dynamic Magnetosphere

Science.gov (United States)

Imber, S. M.

2018-05-01

The global dynamics of Mercury's magnetosphere will be discussed, focussing on observed asymmetries in the magnetotail and on the precipitation of particles of magnetospheric origin onto the nightside planetary surface.

New Understanding of Mercury's Magnetosphere from MESSENGER'S First Flyby

Science.gov (United States)

Slavin, James A.; Acuna, Mario H.; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Gloeckler, George; Gold, Robert E.; Ho, George C.; Killen, M.; Korth, Haje;

Identifying Cassini's Magnetospheric Location Using Magnetospheric Imaging Instrument (MIMI) Data and Machine Learning

Science.gov (United States)

Vandegriff, J. D.; Smith, G. L.; Edenbaum, H.; Peachey, J. M.; Mitchell, D. G.

2017-12-01

We analyzed data from Cassini's Magnetospheric Imaging Instrument (MIMI) and Magnetometer (MAG) and attempted to identify the region of Saturn's magnetosphere that Cassini was in at a given time using machine learning. MIMI data are from the Charge-Energy-Mass Spectrometer (CHEMS) instrument and the Low-Energy Magnetospheric Measurement System (LEMMS). We trained on data where the region is known based on a previous analysis of Cassini Plasma Spectrometer (CAPS) plasma data. Three magnetospheric regions are considered: Magnetosphere, Magnetosheath, and Solar Wind. MIMI particle intensities, magnetic field values, and spacecraft position are used as input attributes, and the output is the CAPS-based region, which is available from 2004 to 2012. We then use the trained classifier to identify Cassini's magnetospheric regions for times after 2012, when CAPS data is no longer available. Training accuracy is evaluated by testing the classifier performance on a time range of known regions that the classifier has never seen. Preliminary results indicate a 68% accuracy on such test data. Other techniques are being tested that may increase this performance. We present the data and algorithms used, and will describe the latest results, including the magnetospheric regions post-2012 identified by the algorithm.

Hydromagnetic quasi-geostrophic modes in rapidly rotating planetary cores

DEFF Research Database (Denmark)

Canet, E.; Finlay, Chris; Fournier, A.

2014-01-01

The core of a terrestrial-type planet consists of a spherical shell of rapidly rotating, electrically conducting, fluid. Such a body supports two distinct classes of quasi-geostrophic (QG) eigenmodes: fast, primarily hydrodynamic, inertial modes with period related to the rotation time scale...... decreases toward the outer boundary in a spherical shell, QG modes tend to be compressed towards the outer boundary. Including magnetic dissipation, we find a continuous transition from diffusionless slow magnetic modes into quasi-free decay magnetic modes. During that transition (which is controlled......, or shorter than, their oscillation time scale.Based on our analysis, we expect Mercury to be in a regime where the slow magnetic modes are of quasi-free decay type. Earth and possibly Ganymede, with their larger Elsasser numbers, may possess slow modes that are in the transition regime of weak diffusion...

Magnetosphere of Uranus: plasma sources, convection, and field configuration

International Nuclear Information System (INIS)

Voigt, G.; Hill, T.W.; Dessler, A.J.

1983-01-01

At the time of the Voyager 2 flyby of Uranus, the planetary rotational axis will be roughly antiparallel to the solar wind flow. If Uranus has a magnetic dipole moment that is approximately aligned with its spin axis, and if the heliospheric shock has not been encountered, we will have the rare opportunity to observe a ''pole-on'' magnetosphere as discussed qualitatively by Siscoe. Qualitative arguments based on analogy with Earth, Jupiter, and Saturn suggest that the magnetosphere of Uranus may lack a source of plasma adequate to produce significant internal currents, internal convection, and associated effects. In order to provide a test of this hypothesis with the forthcoming Voyager measurements, we have constructed a class of approximately self-consistent quantitative magnetohydrostatic equilibrium configurations for a pole-on magnetosphere with variable plasma pressure parameters. Given a few simplifying assumptions, the geometries of the magnetic field and of the tail current sheet can be computed for a given distribution of trapped plasma pressure. The configurations have a single funnel-shaped polar cusp that points directly into the solar wind and a cylindrical tail plasma sheet whose currents close within the tail rather than on the tail magnetopause, and whose length depends on the rate of decrease of thermal plasma pressure down the tail. Interconnection between magnetospheric and interplanetary fields results in a highly asymmetric tail-field configuration. These features were predicted qualtitatively by Siscoe; the quantitative models presented here may be useful in the interpretation of Voyager encounter results

Solar wind energy transfer through the magnetopause of an open magnetosphere

International Nuclear Information System (INIS)

Lee, L.C.; Roederer, J.G.

1982-01-01

An expression for the total power P/sub T/ transferred from the solar wind to an ''open'' magnetopause with a nonzero normal component of the magnetic field, which is identified as a rotational discontinuity. The total power P/sub T/ consists of (1) the power P/sub EM/ representing the electromagnetic energy transfer and (2) the power P/sub KE/ representing the rate of kinetic energy carried by particles penetrating into the magnetosphere. It is found that P/sub EM/approx. =V/sub SW/ B/sub SW/psi, P/sub KE/approx. =(1/2 M/sub A/-1) P/sub EM/ and P/sub T/approx. =1/2M/sub A/P/sub EM/, where V/sub SW/, B/sub SW/, and M/sub A/ are the velocity, magnetic field, and the Alfven--Mach number in the solar wind, respectively, and Psi is the open magnetic flux in the magnetosphere. The Alfven--Mach number of flow at the magnetopause determines the nature of the local energy transfer; the power per unit area transferred from the solar wind to the magnetosphere consists mainly of kinetic energy. The electromagnetic energy rate P/sub EM/ controls the near-earth magnetospheric activity, whereas the kinetic energy rate P/sub KE/(approx. =3--4 P/sub EM/) should dominate the dynamics of the distant magnetotail

The Warm Plasma Composition in the Inner Magnetosphere during 2012-2015

Science.gov (United States)

Jahn, J. M.; Goldstein, J.; Reeves, G. D.; Fernandes, P. A.; Skoug, R. M.; Larsen, B.; Spence, H. E.

2017-12-01

Ionospheric heavy ions play an important role in the dynamics of Earth's magnetosphere. The greater mass and gyro radius of ionospheric oxygen differentiates its behavior from protons at the same energies. Oxygen may have an impact on tail reconnection processes, and it can at least temporarily dominate the energy content of the ring current during geomagnetic storms. At sub-keV energies, multi-species ion populations in the inner magnetosphere form the warm plasma cloak, occupying the energy range between the plasmasphere and the ring current. Lastly, cold lighter ions from the mid-latitude ionosphere create the co-rotating plasmasphere whose outer regions can interact with the plasma cloak, plasma sheet, ring current, and outer electron belt. In this paper we present a statistical view of warm, cloak-like ion populations in the inner magnetosphere, contrasting in particular the warm plasma composition during quiet and active times. We study the relative abundances and absolute densities of warm plasma measured by the Van Allen Probes, whose two spacecraft cover the inner magnetosphere from plasmaspheric altitudes close to Earth to just inside geostationary orbit. We observe that warm (> 30 eV) oxygen is most abundant closer to the plasmasphere boundary whereas warm hydrogen dominates closer to geostationary orbit. Warm helium is usually a minor constituent, but shows a noticeable enhancement in the near-Earth dusk sector.

Rapid determination of Faraday rotation in optical glasses by means of secondary Faraday modulator.

Science.gov (United States)

Sofronie, M; Elisa, M; Sava, B A; Boroica, L; Valeanu, M; Kuncser, V

2015-05-01

A rapid high sensitive method for determining the Faraday rotation of optical glasses is proposed. Starting from an experimental setup based on a Faraday rod coupled to a lock-in amplifier in the detection chain, two methodologies were developed for providing reliable results on samples presenting low and large Faraday rotations. The proposed methodologies were critically discussed and compared, via results obtained in transmission geometry, on a new series of aluminophosphate glasses with or without rare-earth doping ions. An example on how the method can be used for a rapid examination of the optical homogeneity of the sample with respect to magneto-optical effects is also provided.

Precession of a rapidly rotating cylinder flow: traverse through resonance

Science.gov (United States)

Lopez, Juan; Marques, Francisco

2014-11-01

The flow in a rapidly rotating cylinder that is titled and also rotating around another axis can undergo sudden transitions to turbulence. Experimental observations of this have been associated with triadic resonances. The experimental and theoretical results are well-established in the literature, but there remains a lack of understanding of the physical mechanisms at play in the sudden transition from laminar to turbulent flow with very small variations in the governing parameters. Here, we present direct numerical simulations of a traverse in parameter space through an isolated resonance, and describe in detail the bifurcations involved in the sudden transition. U.S. National Science Foundation Grant CBET-1336410 and Spanish Ministry of Education and Science Grant (with FEDER funds) FIS2013-40880.

Magnetic Inflation and Stellar Mass. II. On the Radii of Single, Rapidly Rotating, Fully Convective M-Dwarf Stars

Science.gov (United States)

Kesseli, Aurora Y.; Muirhead, Philip S.; Mann, Andrew W.; Mace, Greg

2018-06-01

Main-sequence, fully convective M dwarfs in eclipsing binaries are observed to be larger than stellar evolutionary models predict by as much as 10%–15%. A proposed explanation for this discrepancy involves effects from strong magnetic fields, induced by rapid rotation via the dynamo process. Although, a handful of single, slowly rotating M dwarfs with radius measurements from interferometry also appear to be larger than models predict, suggesting that rotation or binarity specifically may not be the sole cause of the discrepancy. We test whether single, rapidly rotating, fully convective stars are also larger than expected by measuring their R\\sin i distribution. We combine photometric rotation periods from the literature with rotational broadening (v\\sin i) measurements reported in this work for a sample of 88 rapidly rotating M dwarf stars. Using a Bayesian framework, we find that stellar evolutionary models underestimate the radii by 10 % {--}15{ % }-2.5+3, but that at higher masses (0.18 theory is 13%–18%, and we argue that the discrepancy is unlikely to be due to effects from age. Furthermore, we find no statistically significant radius discrepancy between our sample and the handful of M dwarfs with interferometric radii. We conclude that neither rotation nor binarity are responsible for the inflated radii of fully convective M dwarfs, and that all fully convective M dwarfs are larger than models predict.

Phenomenological aspects of new gravitational forces. I. Rapidly rotating compact objects

International Nuclear Information System (INIS)

Nieto, M.M.; Goldman, T.; Hughes, R.J.

1987-01-01

A general phenomenological feature of theories of quantum gravity is the existence of spin-1 and spin-0 partners of the graviton, which are expected to be massive (have finite ranges). In the static limit, the forces associated with these partners could almost cancel for particle-particle interactions and yet still produce dramatic effects for antiparticle-particle interactions (such as the gravitational attraction of antiprotons to Earth). However, at relativistic velocities the new forces could become significant even for particle-particle interactions. In this paper we show how these partners could modify the dynamics of particles at the surface of rotating, compact objects, specifically, rapidly rotating pulsars

Pulsar magnetospheres

International Nuclear Information System (INIS)

Kennel, C.F.; Fujimura, F.S.; Pellat, R.

1979-01-01

The structure of both the interior and exterior pulsar magnetospehere depends upon the strength of its plasma source near the surface of the star. We review magnetospheric models in the light of a vacuum pair-production source model proposed by Sturrock, and Ruderman and Sutherland. This model predicts the existence of a cutoff, determined by the neutron star's spin rate and magnetic field strength, beyond which coherent radio emission is no longer possible. The observed distribution of pulsar spin periods and period derivates, and the distribution of pulsars with missing radio pulses, is quantitatively consistent with the pair production threshold, when its variation of neutron star radius and moment of interia with mass is taken into account. All neutron stars observed as pulsars can have relativistic magneto-hydrodynamic wind exterior magnetospheres. The properties of the wind can be directly related to those of the pair production source. Radio pulsars cannot have relativistic plasma wave exterior magnetospheres. On the other hand, most erstwhile pulsars in the galaxy are probably halo objects that emit weak fluxes of energetic photons that can have relativistic wave exterior magnetospheres. Extinct pulsars have not been yet observed. (orig.)

Terrestrial magnetosphere

International Nuclear Information System (INIS)

Pande, D.C.; Agarwal, D.C.

1982-01-01

This paper presents a review about terrestrial magnetosphere. During the last few years considerable investigation have been carried out about the properties of Solar Wind and its interaction with planetary magnetic fields. It is therefore of high importance to accumulate all the investigations in a comprehensive form. The paper reviews the property of earth's magnetosphere, magnetosheath, magneto pause, polar cusps, bow shook and plasma sheath. (author)

Saturn's outer magnetosphere

Science.gov (United States)

Schardt, A. W.; Behannon, K. W.; Carbary, J. F.; Eviatar, A.; Lepping, R. P.; Siscoe, G. L.

1983-01-01

Similarities between the Saturnian and terrestrial outer magnetosphere are examined. Saturn, like Earth, has a fully developed magnetic tail, 80 to 100 RS in diameter. One major difference between the two outer magnetospheres is the hydrogen and nitrogen torus produced by Titan. This plasma is, in general, convected in the corotation direction at nearly the rigid corotation speed. Energies of magnetospheric particles extend to above 500 keV. In contrast, interplanetary protons and ions above 2 MeV have free access to the outer magnetosphere to distances well below the Stormer cutoff. This access presumably occurs through the magnetotail. In addition to the H+, H2+, and H3+ ions primarily of local origin, energetic He, C, N, and O ions are found with solar composition. Their flux can be substantially enhanced over that of interplanetary ions at energies of 0.2 to 0.4 MeV/nuc.

The Hawking evaporation process of rapidly-rotating black holes: an almost continuous cascade of gravitons

International Nuclear Information System (INIS)

Hod, Shahar

2015-01-01

It is shown that rapidly-rotating Kerr black holes are characterized by the dimensionless ratio τ gap /τ emission = O(1), where τ gap is the average time gap between the emissions of successive Hawking quanta and τ emission is the characteristic timescale required for an individual Hawking quantum to be emitted from the black hole. This relation implies that the Hawking cascade from rapidly-rotating black holes has an almost continuous character. Our results correct some inaccurate claims that recently appeared in the literature regarding the nature of the Hawking black-hole evaporation process. (orig.)

The Hawking evaporation process of rapidly-rotating black holes: an almost continuous cascade of gravitons

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emek Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

2015-07-15

It is shown that rapidly-rotating Kerr black holes are characterized by the dimensionless ratio τ{sub gap}/τ{sub emission} = O(1), where τ{sub gap} is the average time gap between the emissions of successive Hawking quanta and τ{sub emission} is the characteristic timescale required for an individual Hawking quantum to be emitted from the black hole. This relation implies that the Hawking cascade from rapidly-rotating black holes has an almost continuous character. Our results correct some inaccurate claims that recently appeared in the literature regarding the nature of the Hawking black-hole evaporation process. (orig.)

MESSENGER: Exploring Mercury's Magnetosphere

Science.gov (United States)

Slavin, James A.

2008-01-01

The MESSENGER mission to Mercury offers our first opportunity to explore this planet's miniature magnetosphere since Mariner 10's brief fly-bys in 1974-5. Mercury's magnetosphere is unique in many respects. The magnetosphere of Mercury is the smallest in the solar system with its magnetic field typically standing off the solar wind only - 1000 to 2000 km above the surface. For this reason there are no closed dri-fi paths for energetic particles and, hence, no radiation belts; the characteristic time scales for wave propagation and convective transport are short possibly coupling kinetic and fluid modes; magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere allowing solar wind ions to directly impact the dayside regolith; inductive currents in Mercury's interior should act to modify the solar In addition, Mercury's magnetosphere is the only one with its defining magnetic flux tubes rooted in a planetary regolith as opposed to an atmosphere with a conductive ionosphere. This lack of an ionosphere is thought to be the underlying reason for the brevity of the very intense, but short lived, approx. 1-2 min, substorm-like energetic particle events observed by Mariner 10 in Mercury's magnetic tail. In this seminar, we review what we think we know about Mercury's magnetosphere and describe the MESSENGER science team's strategy for obtaining answers to the outstanding science questions surrounding the interaction of the solar wind with Mercury and its small, but dynamic magnetosphere.

Upper ionosphere and magnetospheric-ionospheric coupling

International Nuclear Information System (INIS)

Manzano, J.R.

1989-02-01

After a presentation of the ionospheric physics and of the earth magnetosphere morphology, generation and dynamics, the magnetosphere-ionosphere coupling in quiet and perturbed conditions is discussed. Some summary information about other planetary magnetospheres, particularly Venus and Jupiter magnetospheres, are finally given. 41 refs, 24 figs

SUN-LIKE MAGNETIC CYCLES IN THE RAPIDLY ROTATING YOUNG SOLAR ANALOG HD 30495

International Nuclear Information System (INIS)

Egeland, Ricky; Metcalfe, Travis S.; Hall, Jeffrey C.; Henry, Gregory W.

2015-01-01

A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial (∼2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, a ∼1 Gyr old G1.5 V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at ∼1.7 years and a long cycle of ∼12 years. We measure three individual long-period cycles and find durations ranging from 9.6 to 15.5 years. We find the short-term variability to be intermittent, but present throughout the majority of the time series, though its occurrence and amplitude are uncorrelated with the longer cycle. These essentially solar-like variations occur in a Sun-like star with more rapid rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence

Report of the magnetospheric physics panel

International Nuclear Information System (INIS)

Burch, J.L.; Potemra, T.A.; Ashourabdalla, M.; Baker, D.N.; Cattell, C.A.; Chang, A.F.; Frank, L.A.; Goertz, C.K.; Kivelson, M.G.; Lee, Lou-Chuang

1991-01-01

Magnetospheric research is a relatively new area in the study of the Earth's environment. The present report attempts to overview past and future research on this topic. The goals of magnetospheric research are numerous, and include: understanding large scale magnetospheres of the Earth and other planets; understanding the plasma physical processes operating within the various magnetospheres; to understand how mass, energy and momentum are transmitted from the solar wind; to understand quantitatively the coupling between magnetospheres and their ionospheres; and to understand the magnetospheric mechanisms which accelerate particles to high energies, as well as the ultimate fate of these particles. The report continues on to summarize a number of proposed space missions aimed at data acquisition. Finally, there is a brief discussion of the theory and modeling of magnetospheres

Production of an electron-positron plasma in a pulsar magnetosphere

International Nuclear Information System (INIS)

Gurevich, A.V.; Istomin, Y.N.

1985-01-01

A study is made of the production of electron-positron plasma in the vacuum state (''breakdown'' of the vacuum) in the presence of an inhomogeneous electric field and a strong curvilinear magnetic field. Such conditions are encountered in the magnetosphere of a rotating neutron star. A general system of kinetic equations is derived for the electrons, positrons, and γ photons in the curvilinear magnetic field with allowance for the production of electron-positron pairs and the emission of curvature and synchrotron photons. The conditions of occurrence of ''breakdown'' are determined, and the threshold value of the jump in the value of the electric field at the surface of the star is found. The process of multiplication of particles in the magnetosphere is investigated, and the distribution functions of the electrons, positrons, and photons are found. The extinction limit of pulsars is determined. It is shown that the theory is in agreement with observational data

Magnetosphere energetics during substorm events IMP 8 and Geotail observations

CERN Document Server

Belehaki, A

2001-01-01

Magnetospheric energetics during substorm events is studied in this paper. Three events were selected, a weak substorm, a large isolated one and finally a prolonged period of substorm activity with multiple intensifications. It is assumed that the energy, that entered the magnetosphere due to electromagnetic coupling with the solar wind, is described by the epsilon parameter, proposed by Perreault and Akasofu (1978). High resolution, magnetic field and plasma data from the MGF and LEP experiments on board Geotail were analyzed to determine the timing of plasmoid release, its dimensions, its convection velocity and finally the energy carried by each plasmoid. Plasmoids were defined as structures with rotating magnetic fields and enhanced total pressure. Tailward plasmoid bulk speed in the distant tail varied from 350 to 750 km/s. Their dimensions in the X/sub GSM/ direction was found to be from 4.5 to 28 R/sub E/, and their duration did not exceed 5 min. The average energy carried by each plasmoid in the dista...

A Comet Engulfs Mars: MAVEN Observations of Comet Siding Spring's Influence on the Martian Magnetosphere

Science.gov (United States)

Espley, Jared R.; Dibraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper S.; Combi, Michael; Luhmann, Janet; Ma, Yingjuan

2015-01-01

The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000?km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

Production of a rapidly rotating plasma by cross-field injection of gun-produced plasma

International Nuclear Information System (INIS)

Ohzu, Akira; Ikehata, Takashi; Tanabe, Toshio; Mase, Hiroshi

1984-01-01

Cross-field plasma injection with use of a JxB plasma gun is described as a method to produce rapidly rotating plasma in a crossed electric and magnetic field system. The rotational velocity of the plasma is seriously limited by neutrals surrounding the plasma through strong interactions at the boundary layer. The concentration of neutrals can be reduced by the injection of fully or partially ionized plasma into the discharge volume instead of filling the volume with an operating gas. With use of this method, it is observed that the rotational velocity increases by a factor of 2 to 3 when compared with the conventional method of stationary gas-filling. (author)

M-dwarf rapid rotators and the detection of relatively young multiple M-star systems

International Nuclear Information System (INIS)

Rappaport, S.; Joss, M.; Sanchis-Ojeda, R.

2014-01-01

We have searched the Kepler light curves of ∼3900 M-star targets for evidence of periodicities that indicate, by means of the effects of starspots, rapid stellar rotation. Several analysis techniques, including Fourier transforms, inspection of folded light curves, 'sonograms', and phase tracking of individual modulation cycles, were applied in order to distinguish the periodicities due to rapid rotation from those due to stellar pulsations, eclipsing binaries, or transiting planets. We find 178 Kepler M-star targets with rotation periods, P rot , of <2 days, and 110 with P rot < 1 day. Some 30 of the 178 systems exhibit two or more independent short periods within the same Kepler photometric aperture, while several have 3 or more short periods. Adaptive optics imaging and modeling of the Kepler pixel response function for a subset of our sample support the conclusion that the targets with multiple periods are highly likely to be relatively young physical binary, triple, and even quadruple M star systems. We explore in detail the one object with four incommensurate periods all less than 1.2 days, and show that two of the periods arise from one of a close pair of stars, while the other two arise from the second star, which itself is probably a visual binary. If most of these M-star systems with multiple periods turn out to be bound M stars, this could prove a valuable way discovering young hierarchical M-star systems; the same approach may also be applicable to G and K stars. The ∼5% occurrence rate of rapid rotation among the ∼3900 M star targets is consistent with spin evolution models that include an initial contraction phase followed by magnetic braking, wherein a typical M star can spend several hundred Myr before spinning down to periods longer than 2 days.

Does the Magnetosphere go to Sleep?

Science.gov (United States)

Hesse, M.; Moretto, T.; Friis-Christensen, E. A.; Kuznetsova, M.; Østgaard, N.; Tenfjord, P.; Opgenoorth, H. J.

2017-12-01

An interesting question in magnetospheric research is related to the transition between magnetospheric configurations under substantial solar wind driving, and a putative relaxed state after the driving ceases. While it is conceivable that the latter state may be unique and only dependent on residual solar wind driving, a more likely scenario has magnetospheric memory playing a key role. Memory processes may be manifold: constraints from conservation of flux tube entropy to neutral wind inertia in the upper atmosphere may all contribute. In this presentation, we use high-resolution, global, MHD simulations to begin to shed light on this transition, as well as on the concept of a quiet state of the magnetosphere. We will discuss key elements of magnetospheric memory, and demonstrate their influence, as well as the actual memory time scale, through simulations and analytical estimates. Finally, we will point out processes with the potential to effect magnetospheric memory loss.

Further determination of the characteristics of magnetospheric plasma vortices with Isee 1 and 2

International Nuclear Information System (INIS)

Hones, E.W. Jr.; Birn, J.; Bame, S.J.; Asbridge, J.R.; Paschmann, G.; Sckopke, N.; Haerendel, G.

1981-01-01

Further studies of the vortices in magnetospheric plasma flow with the Los Alamos Scientific Laboratory/Max-Planck-Institut (LASL/MPI) fast plasma experiment on Isee 1 and 2 have revealed that the pattern of vortical flow has a wavelength of approx.20-40 R/sub E/ and moves tailward through the magnetosphere at speed of several hundred kilometers per second. The tendency toward vorticity pervades the total breadth of the plasma sheet tailward of the dawn-dusk meridian. The sense of rotation of the plasma flow (as viewed from above the ecliptic plane) is clockwise in the morningside of the plasma sheet and counterclockwise in the eveningside. The sense of rotation in the morning and evening boundary layers is reversed from that in the contiguous regions of the plasma sheet. The occurrence of vortical flow is independent of the level of geomagnetic activity but is associated with long-period geomagnetic pulsations. We believe that the source of the vortical motion is a Kelvin-Helmholtz instability of the plasma boundary layer's inner surface (i.e., the interface between the plasma sheet and the boundary layer) that has recently been proposed by Sonnerup [1980

Pulsar magnetosphere-wind or wave

International Nuclear Information System (INIS)

Kennel, C.F.

1979-01-01

The structure of both the interior and exterior pulsar magnetosphere depends upon the strength of its plasma source near the surface of the star. We review wave models of exterior pulsar magnetospheres in the light of a vacuum pair-production source model proposed by Sturrock, and Ruderman and Sutherland. This model predicts the existence of a cutoff, determined by the neutron star's spin rate and magnetic field strenght, beyond which coherent radio emission is no longer possible. Since the observed distribution of pulsar spin periods and period derivatives, and the distribution of pulsars with missing radio pulses, is consistent with the pair production threshold, those neutron stars observed as radio pulsars can have relativistic magnetohydrodynamic wind exterior magnetospheres, and cannot have relativistic plasma wave exterior magnetospheres. On the other hand, most erstwhile pulsars in the galaxy are probably halo objects that emit weak fluxes of energetic photons that can have relativistic wave exterior magnetospheres. Extinct pulsars have not been yet observed

Low-Cost Rotating Experimentation in Compressor Aerodynamics Using Rapid Prototyping

Directory of Open Access Journals (Sweden)

Mathias Michaud

2016-01-01

Full Text Available With the rapid evolution of additive manufacturing, 3D printed parts are no longer limited to display purposes but can also be used in structural applications. The objective of this paper is to show that 3D prototyping can be used to produce low-cost rotating turbomachinery rigs capable of carrying out detailed flow measurements that can be used, among other things, for computational fluid dynamics (CFD code validation. A fully instrumented polymer two-stage axial-mixed flow compressor test rig was designed and fabricated with stereolithography (SLA technology by a team of undergraduate students as part of a senior-year design course. Experiments were subsequently performed on this rig to obtain both the overall pressure rise characteristics of the compressor and the stagnation pressure distributions downstream of the blade rows for comparison with CFD simulations. In doing so, this work provides a first-of-a-kind assessment of the use of polymer additive technology for low-cost rotating turbomachinery experimentation with detailed measurements.

Ionospheric control of the magnetosphere: conductance

Directory of Open Access Journals (Sweden)

A. J. Ridley

2004-01-01

Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function. Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

The Magnetospheric Cusps Structure and Dynamics

CERN Document Server

Fritz, Theodore A

2005-01-01

This collection of papers will address the question "What is the Magnetospheric Cusp?" and what is its role in the coupling of the solar wind to the magnetosphere as well as its role in the processes of particle transport and energization within the magnetosphere. The cusps have traditionally been described as narrow funnel-shaped regions that provide a focus of the Chapman-Ferraro currents that flow on the magnetopause, a boundary between the cavity dominated by the geomagnetic field (i.e., the magnetosphere) and the external region of the interplanetary medium. Measurements from a number of recent satellite programs have shown that the cusp is not confined to a narrow region near local noon but appears to encompass a large portion of the dayside high-latitude magnetosphere and it appears that the cusp is a major source region for the production of energetic charged particles for the magnetosphere. Audience: This book will be of interest to space science research organizations in governments and industries, ...

A rapid decrease in the rotation rate of comet 41P/Tuttle-Giacobini-Kresák.

Science.gov (United States)

Bodewits, Dennis; Farnham, Tony L; Kelley, Michael S P; Knight, Matthew M

2018-01-10

Cometary outgassing can produce torques that change the spin state of the cometary nucleus, which in turn influences the evolution and lifetime of the comet. If these torques increase the rate of rotation to the extent that centripetal forces exceed the material strength of the nucleus, the comet can fragment. Torques that slow down the rotation can cause the spin state to become unstable, but if the torques persist the nucleus can eventually reorient itself and the rotation rate can increase again. Simulations predict that most comets go through a short phase of rapid changes in spin state, after which changes occur gradually over longer times. Here we report observations of comet 41P/Tuttle-Giacobini-Kresák during its close approach to Earth (0.142 astronomical units, approximately 21 million kilometres, on 1 April 2017) that reveal a rapid decrease in rotation rate. Between March and May 2017, the apparent rotation period of the nucleus increased from 20 hours to more than 46 hours-a rate of change of more than an order of magnitude larger than has hitherto been measured. This phenomenon must have been caused by the gas emission from the comet aligning in such a way that it produced an anomalously strong torque that slowed the spin rate of the nucleus. The behaviour of comet 41P/Tuttle-Giacobini-Kresák suggests that it is in a distinct evolutionary state and that its rotation may be approaching the point of instability.

A rapid decrease in the rotation rate of comet 41P/Tuttle–Giacobini–Kresák

Science.gov (United States)

Bodewits, Dennis; Farnham, Tony L.; Kelley, Michael S. P.; Knight, Matthew M.

2018-01-01

Cometary outgassing can produce torques that change the spin state of the cometary nucleus, which in turn influences the evolution and lifetime of the comet. If these torques increase the rate of rotation to the extent that centripetal forces exceed the material strength of the nucleus, the comet can fragment. Torques that slow down the rotation can cause the spin state to become unstable, but if the torques persist the nucleus can eventually reorient itself and the rotation rate can increase again. Simulations predict that most comets go through a short phase of rapid changes in spin state, after which changes occur gradually over longer times. Here we report observations of comet 41P/Tuttle–Giacobini–Kresák during its close approach to Earth (0.142 astronomical units, approximately 21 million kilometres, on 1 April 2017) that reveal a rapid decrease in rotation rate. Between March and May 2017, the apparent rotation period of the nucleus increased from 20 hours to more than 46 hours—a rate of change of more than an order of magnitude larger than has hitherto been measured. This phenomenon must have been caused by the gas emission from the comet aligning in such a way that it produced an anomalously strong torque that slowed the spin rate of the nucleus. The behaviour of comet 41P/Tuttle–Giacobini–Kresák suggests that it is in a distinct evolutionary state and that its rotation may be approaching the point of instability.

Terrestrial magnetosphere and comparison with Jupiter's

International Nuclear Information System (INIS)

Michel, F.C.

1974-01-01

A review of the characteristics of Jupiter's magnetosphere, with comparisons to the earth's is given. Radio observations of Jupiter indicate that energetic electrons are trapped in its magnetic field. The interaction of the trapped radiation with the satellite Io and the centrifugal instability of Jupiter's magnetosphere are discussed. Jupiter's outer magnetosphere is constantly accreting plasma at an uncertain rate. Various mechanisms for supplying ions to the outer magnetosphere are discussed, including: gravitational and centrifugal forces acting on corotating particles; field-line diffusion; photoelectron injection; excitation by Io or other satellites; and viscous interaction with the solar wind. The over-all morphology of the Jovian magnetosphere seems to be highly distorted by centrifugal forces and is easily compressed or deflected by the solar wind

A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907

Science.gov (United States)

Leto, P.; Trigilio, C.; Oskinova, L. M.; Ignace, R.; Buemi, C. S.; Umana, G.; Ingallinera, A.; Leone, F.; Phillips, N. M.; Agliozzo, C.; Todt, H.; Cerrigone, L.

2018-05-01

We present new radio/millimeter measurements of the hot magnetic star HR 5907 obtained with the VLA and ALMA interferometers. We find that HR 5907 is the most radio luminous early type star in the cm-mm band among those presently known. Its multi-wavelength radio light curves are strongly variable with an amplitude that increases with radio frequency. The radio emission can be explained by the populations of the non-thermal electrons accelerated in the current sheets on the outer border of the magnetosphere of this fast-rotating magnetic star. We classify HR 5907 as another member of the growing class of strongly magnetic fast-rotating hot stars where the gyro-synchrotron emission mechanism efficiently operates in their magnetospheres. The new radio observations of HR 5907 are combined with archival X-ray data to study the physical condition of its magnetosphere. The X-ray spectra of HR 5907 show tentative evidence for the presence of non-thermal spectral component. We suggest that non-thermal X-rays originate a stellar X-ray aurora due to streams of non-thermal electrons impacting on the stellar surface. Taking advantage of the relation between the spectral indices of the X-ray power-law spectrum and the non-thermal electron energy distributions, we perform 3-D modelling of the radio emission for HR 5907. The wavelength-dependent radio light curves probe magnetospheric layers at different heights above the stellar surface. A detailed comparison between simulated and observed radio light curves leads us to conclude that the stellar magnetic field of HR 5907 is likely non-dipolar, providing further indirect evidence of the complex magnetic field topology of HR 5907.

Ionospheric control of the magnetosphere: conductance

Directory of Open Access Journals (Sweden)

A. J. Ridley

2004-01-01

Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function.

Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

Boundary layers of the earth's outer magnetosphere

Science.gov (United States)

Eastman, T. E.; Frank, L. A.

1984-01-01

The magnetospheric boundary layer and the plasma-sheet boundary layer are the primary boundary layers of the earth's outer magnetosphere. Recent satellite observations indicate that they provide for more than 50 percent of the plasma and energy transport in the outer magnetosphere although they constitute less than 5 percent by volume. Relative to the energy density in the source regions, plasma in the magnetospheric boundary layer is predominantly deenergized whereas plasma in the plasma-sheet boundary layer has been accelerated. The reconnection hypothesis continues to provide a useful framework for comparing data sampled in the highly dynamic magnetospheric environment. Observations of 'flux transfer events' and other detailed features near the boundaries have been recently interpreted in terms of nonsteady-state reconnection. Alternative hypotheses are also being investigated. More work needs to be done, both in theory and observation, to determine whether reconnection actually occurs in the magnetosphere and, if so, whether it is important for overall magnetospheric dynamics.

Boundary layers of the earth's outer magnetosphere

International Nuclear Information System (INIS)

Eastman, T.E.; Frank, L.A.

1984-01-01

The magnetospheric boundary layer and the plasma-sheet boundary layer are the primary boundary layers of the earth's outer magnetosphere. Recent satellite observations indicate that they provide for more than 50 percent of the plasma and energy transport in the outer magnetosphere although they constitute less than 5 percent by volume. Relative to the energy density in the source regions, plasma in the magnetospheric boundary layer is predominantly deenergized whereas plasma in the plasma-sheet boundary layer has been accelerated. The reconnection hypothesis continues to provide a useful framework for comparing data sampled in the highly dynamic magnetospheric environment. Observations of flux transfer events and other detailed features near the boundaries have been recently interpreted in terms of nonsteady-state reconnection. Alternative hypotheses are also being investigated. More work needs to be done, both in theory and observation, to determine whether reconnection actually occurs in the magnetosphere and, if so, whether it is important for overall magnetospheric dynamics. 30 references

Magnetosphere imager science definition team: Executive summary

Science.gov (United States)

Armstrong, T. P.; Gallagher, D. L.; Johnson, C. L.

1995-01-01

For three decades, magnetospheric field and plasma measurements have been made by diverse instruments flown on spacecraft in many different orbits, widely separated in space and time, and under various solar and magnetospheric conditions. Scientists have used this information to piece together an intricate, yet incomplete view of the magnetosphere. A simultaneous global view, using various light wavelengths and energetic neutral atoms, could reveal exciting new data and help explain complex magnetospheric processes, thus providing a clear picture of this region of space. This report summarizes the scientific rationale for such a magnetospheric imaging mission and outlines a mission concept for its implementation.

Magnetosphere imager science definition team interim report

Science.gov (United States)

Armstrong, T. P.; Johnson, C. L.

1995-01-01

For three decades, magnetospheric field and plasma measurements have been made by diverse instruments flown on spacecraft in may different orbits, widely separated in space and time, and under various solar and magnetospheric conditions. Scientists have used this information to piece together an intricate, yet incomplete view of the magnetosphere. A simultaneous global view, using various light wavelengths and energetic neutral atoms, could reveal exciting new data nd help explain complex magnetospheric processes, thus providing a clear picture of this region of space. This report documents the scientific rational for such a magnetospheric imaging mission and provides a mission concept for its implementation.

Subcritical thermal convection of liquid metals in a rapidly rotating sphere

Science.gov (United States)

Cardin, P.; Schaeffer, N.; Guervilly, C.; Kaplan, E.

2017-12-01

Planetary cores consist of liquid metals (low Prandtl number Pr) that convect as the core cools. Here we study nonlinear convection in a rotating (low Ekman number Ek) planetary core using a fully 3D direct (down to Ek=10-7) and a quasi geostrophic (down to Ek=10-10) numerical simulations. Near the critical thermal forcing (Rayleigh number Ra), convection onsets as thermal Rossby waves, but as Ra increases, this state is superceded by one dominated by advection. At moderate rotation, these states (here called the weak branch and strong branch, respectively) are continuously connected. As the planetary core rotates faster, the continuous transition is replaced by hysteresis cycles and subcriticality until the weak branch disappears entirely and the strong branch onsets in a turbulent state at Ekforcing decreases well below the linear onset of convection (Ra 0.4Racrit in this study for Ek=10-10 and Pr=0.01). We highlight the importance of the Reynolds stress, which is required for convection to persist below the linear onset. We further note the presence of a strong zonal flow that is nonetheless unimportant to the convective subcritical state. Our study suggests that, in the asymptotic regime of rapid rotation relevant for planetary interiors, thermal convection of liquid metals in a sphere onsets and shuts down through a subcritical bifurcation. This scenario may be relevant to explain the lunar and martian dynamo extinctions.

Featured Image: Making a Rapidly Rotating Black Hole

Science.gov (United States)

Kohler, Susanna

2017-10-01

These stills from a simulation show the evolution (from left to right and top to bottom) of a high-mass X-ray binary over 1.1 days, starting after the star on the right fails to explode as a supernova and then collapses into a black hole. Many high-mass X-ray binaries like the well-known Cygnus X-1, the first source widely accepted to be a black hole host rapidly spinning black holes. Despite our observations of these systems, however, were still not sure how these objects end up with such high rotation speeds. Using simulations like that shown above, a team of scientists led by Aldo Batta (UC Santa Cruz) has demonstrated how a failed supernova explosion can result in such a rapidly spinning black hole. The authors work shows that in a binary where one star attempts to explode as a supernova and fails it doesnt succeed in unbinding the star the large amount of fallback material can interact with the companion star and then accrete onto the black hole, spinning it up in the process. You can read more about the authors simulations and conclusions in the paper below.CitationAldo Batta et al 2017 ApJL 846 L15. doi:10.3847/2041-8213/aa8506

Electric fields in the magnetosphere

International Nuclear Information System (INIS)

Faelthammar, C.G.

1989-12-01

The electric field plays an important role in the complex plasma system called the magnetosphere. In spite of this, direct measurement of this quantity are still scarce except in its lowest-altitude part, i.e. the ionosphere. The large scale ionospheric electric field has been determined from measurement on the ground and in low satellite orbit. For most of the magnetosphere, our concepts of the electric field have mostly been based on theoretical considerations and extrapolations of the ionspheric electric field. Direct, in situ, electric field measurements in the outer parts of the magnetosphere have been made only relatively recently. A few satellite missions. most recently the Viking mission, have extended the direct empirical knowledge so as to include major parts of the magnetosphere. These measurements have revealed a number of unexpected features. The actual electric field has been found to have unexpectedly strong space and time variations, which reflect the dynamic nature of the system. Examples are give of measured electric fields in the plasmasphere, the plasmasheet, the neutral sheet, the magnetotail, the flanks of the magnetosphere, the dayside magnetopause and the auroral acceleration region. (author)

Late-time dynamics of rapidly rotating black holes

International Nuclear Information System (INIS)

Glampedakis, K.; Andersson, N.

2001-01-01

We study the late-time behaviour of a dynamically perturbed rapidly rotating black hole. Considering an extreme Kerr black hole, we show that the large number of virtually undamped quasinormal modes (that exist for nonzero values of the azimuthal eigenvalue m) combine in such a way that the field (as observed at infinity) oscillates with an amplitude that decays as 1/t at late times. For a near extreme black hole, these modes, collectively, give rise to an exponentially decaying field which, however, is considerably 'long-lived'. Our analytic results are verified using numerical time-evolutions of the Teukolsky equation. Moreover, we argue that the physical mechanism behind the observed behaviour is the presence of a 'superradiance resonance cavity' immediately outside the black hole. We present this new feature in detail, and discuss whether it may be relevant for astrophysical black holes. (author)

Magnetospheric plasma physics

International Nuclear Information System (INIS)

Bingham, R.

1989-09-01

The discovery of the earth's radiation belts in 1957 by Van Allen marked the beginning of what is now known as magnetospheric physics. In this study of plasma physics in the magnetosphere, we shall take the magnetosphere to be that part of the earth's ionized atmosphere which is formed by the interaction of the solar wind with the earth's dipole-like magnetic field. It extends from approximately 100km above the earth's surface where the proton-neutral atom collision frequency is equal to the proton gyrofrequency to about ten earth radii (R E ∼ 6380km) in the sunward direction and to several hundred earth radii in the anti-sunward direction. The collision dominated region is called the ionosphere and is sometimes considered separate from the collisionless plasma region. In the ionosphere ion-neutral collisions are dominant and one may think of the ionosphere as a frictional boundary layer ∼ 1000km thick. Other planets are also considered. (author)

The Taylor-Proudman column in a rapidly-rotating compressible fluid I. energy transports

International Nuclear Information System (INIS)

Park, Jun Sang

2014-01-01

A theoretical study is made of the steady flow of a compressible fluid in a rapidly rotating finite cylinder. Flow is generated by imposing mechanical and/or thermal disturbances at the rotating endwall disks. Both the Ekman and Rossby numbers are small. An examination is made of the energy budget for a control volume in the Ekman boundary layer. A combination of physical variables, which is termed the energy flux content, consisting of temperature and modified angular momentum, emerges to be relevant. The distinguishing features of a compressible fluid, in contrast to those of an incompressible fluid, are noted. A plausible argument is given to explain the difficulty in achieving the Taylor-Proudman column in a compressible rotating fluid. For the Taylor-Proudman column to be sustained, in the interior, it is shown that the net energy transport between the solid disk wall and the interior fluid should vanish. Physical rationalizations are facilitated by resorting to the concept of the afore-stated energy flux content.

Bounds on heat transport in rapidly rotating Rayleigh–Bénard convection

International Nuclear Information System (INIS)

Grooms, Ian; Whitehead, Jared P

2015-01-01

The heat transport in rotating Rayleigh–Bénard convection is considered in the limit of rapid rotation (small Ekman number E) and strong thermal forcing (large Rayleigh number Ra). The analysis proceeds from a set of asymptotically reduced equations appropriate for rotationally constrained dynamics; the conjectured range of validity for these equations is Ra ≲ E −8/5 . A rigorous bound on heat transport of Nu ⩽ 20.56Ra 3 E 4 is derived in the limit of infinite Prandtl number using the background method. We demonstrate that the exponent in this bound cannot be improved on using a piece-wise monotonic background temperature profile like the one used here. This is true for finite Prandtl numbers as well, i.e. Nu ≲ Ra 3 is the best upper bound for this particular setup of the background method. The feature that obstructs the availability of a better bound in this case is the appearance of small-scale thermal plumes emanating from (or entering) the thermal boundary layer. The derived upper bound is consistent with, although significantly higher than the observed behaviour in simulations of the reduced equations, which find at most Nu ∼ Ra 2 E 8/3 . (paper)

Electromagnetic and Radiative Properties of Neutron Star Magnetospheres

Science.gov (United States)

Li, Jason G.

2014-05-01

luminosity with orbital angular velocity varies between the power 4 for nonspinning stars and the power 1.5 for rapidly spinning millisecond pulsars near contact. Our derived scalings and magnetospheres can be used to help understand electromagnetic signatures from merging neutron stars to be observed by Advanced LIGO.

Significance of Dungey-cycle flows in Jupiter's and Saturn's magnetospheres, and their identification on closed equatorial field lines

Directory of Open Access Journals (Sweden)

S. V. Badman

2007-05-01

Full Text Available We consider the contribution of the solar wind-driven Dungey-cycle to flux transport in Jupiter's and Saturn's magnetospheres, the associated voltages being based on estimates of the magnetopause reconnection rates recently derived from observations of the interplanetary medium in the vicinity of the corresponding planetary orbits. At Jupiter, the reconnection voltages are estimated to be ~150 kV during several-day weak-field rarefaction regions, increasing to ~1 MV during few-day strong-field compression regions. The corresponding values at Saturn are ~25 kV for rarefaction regions, increasing to ~150 kV for compressions. These values are compared with the voltages associated with the flows driven by planetary rotation. Estimates of the rotational flux transport in the "middle" and "outer" magnetosphere regions are shown to yield voltages of several MV and several hundred kV at Jupiter and Saturn respectively, thus being of the same order as the estimated peak Dungey-cycle voltages. We conclude that under such circumstances the Dungey-cycle "return" flow will make a significant contribution to the flux transport in the outer magnetospheric regions. The "return" Dungey-cycle flows are then expected to form layers which are a few planetary radii wide inside the dawn and morning magnetopause. In the absence of significant cross-field plasma diffusion, these layers will be characterized by the presence of hot light ions originating from either the planetary ionosphere or the solar wind, while the inner layers associated with the Vasyliunas-cycle and middle magnetosphere transport will be dominated by hot heavy ions originating from internal moon/ring plasma sources. The temperature of these ions is estimated to be of the order of a few keV at Saturn and a few tens of keV at Jupiter, in both layers.

Geomagnetic response to sudden expansions of the magnetosphere

International Nuclear Information System (INIS)

Araki, Tohru; Nagano, Hiroshi

1988-01-01

The geomagnetic response to five successive sudden expansions of the magnetosphere was examined by the use of magnetic data observed on the ground and by satellites. At the geosynchronous orbit between 0800 and 1100 LT the magnetic field component parallel to Earth's rotation axis decreased successively. The amplitude and the fall time of each decrease were 20-30 nT and 2.5-3.5 min, respectively. The decrease was propagated about 10 min later to the distance of about 31 R E from Earth in the antisunward direction, indicating propagation speed of about 300 km/s. The H component of ground magnetograms from low-latitude stations showed decreases with waveform similar to that at the geosynchronous orbit, but each decrease at the dayside equator was greatly enhanced and preceded by a short small positive impulse. Each of the corresponding geomagnetic variations at high latitude stations consisted of two successive sharp pulses of opposite sense with 2-3 min duration. The dominant component and the sense of these high-latitude pulses were highly dependent upon local time and latitude. The distribution of equivalent ionospheric current arrows for each high-latitude pulse showed clear twin vortices centered at 70-76 degree geomagnetic latitude in the dayside and was approximately symmetric with respect to the noon meridian. The current direction of the vortices was reversed from the first pulse to the second. it suggests successive appearance of a dawn-to-dusk and then a dusk-to-dawn electric field, both of which were transmitted from the magnetosphere to the polar ionosphere. The effect of ionospheric currents due to these polar electric fields was superposed on the simple magnetic decrease produced by an expansion of the whole magnetosphere and produced the complex waveform distribution on the ground

Impulsive Alfven coupling between the magnetosphere and ionosphere

International Nuclear Information System (INIS)

Reddy, R.V.; Watanabe, K.; Sato, T.; Watanabe, T.H.

1994-04-01

Basic properties of the impulsive Alfven interaction between the magnetosphere and ionosphere have been studied by means of a three-dimensional self-consistent simulation of the coupled magnetosphere and ionosphere system. It is found that the duration time of an impulsive perturbation at the magnetospheric equator, the latitudinal distribution of the Alfven propagation time along the field lines, and the ratio between the magnetospheric impedance and the ionospheric resistance is the main key factors that determine the propagation dynamics and the ionospheric responses for an impulsive MHD perturbation in the magnetosphere. (author)

Axi-symmetric models of auroral current systems in Jupiter's magnetosphere with predictions for the Juno mission

Directory of Open Access Journals (Sweden)

S. W. H. Cowley

2008-12-01

Full Text Available We develop two related models of magnetosphere-ionosphere coupling in the jovian system by combining previous models defined at ionospheric heights with magnetospheric magnetic models that allow system parameters to be extended appropriately into the magnetosphere. The key feature of the combined models is thus that they allow direct connection to be made between observations in the magnetosphere, particularly of the azimuthal field produced by the magnetosphere-ionosphere coupling currents and the plasma angular velocity, and the auroral response in the ionosphere. The two models are intended to reflect typical steady-state sub-corotation conditions in the jovian magnetosphere, and transient super-corotation produced by sudden major solar wind-induced compressions, respectively. The key simplification of the models is that of axi-symmetry of the field, flow, and currents about the magnetic axis, limiting their validity to radial distances within ~30 R_J of the planet, though the magnetic axis is appropriately tilted relative to the planetary spin axis and rotates with the planet. The first exploration of the jovian polar magnetosphere is planned to be undertaken in 2016–2017 during the NASA New Frontiers Juno mission, with observations of the polar field, plasma, and UV emissions as a major goal. Evaluation of the models along Juno planning orbits thus produces predictive results that may aid in science mission planning. It is shown in particular that the low-altitude near-periapsis polar passes will generally occur underneath the corresponding auroral acceleration regions, thus allowing brief examination of the auroral primaries over intervals of ~1–3 min for the main oval and ~10 s for narrower polar arc structures, while the "lagging" field deflections produced by the auroral current systems on these passes will be ~0.1°, associated with azimuthal fields above the ionosphere of a few hundred nT.

The structure of standing Alfvén waves in a dipole magnetosphere with moving plasma

Directory of Open Access Journals (Sweden)

D. A. Kozlov

2006-03-01

Full Text Available The structure and spectrum of standing Alfvén waves were theoretically investigated in a dipole magnetosphere with moving plasma. Plasma motion was simulated with its azimuthal rotation. The model's scope allowed for describing a transition from the inner plasmasphere at rest to the outer magnetosphere with convecting plasma and, through the magnetopause, to the moving plasma of the solar wind. Solutions were found to equations describing longitudinal and transverse (those formed, respectively, along field lines and across magnetic shells structures of standing Alfvén waves with high azimuthal wave numbers m>>1. Spectra were constructed for a number of first harmonics of poloidal and toroidal standing Alfvén waves inside the magnetosphere. For charged particles with velocities greatly exceeding the velocity of the background plasma, an effective parallel wave component of the electric field appears in the region occupied by such waves. This results in structured high-energy-particle flows and in the appearance of multiband aurorae. The transverse structure of the standing Alfvén waves' basic harmonic was shown to be analogous to the structure of a discrete auroral arc.

The Magnetospheric Multiscale Magnetometers

Science.gov (United States)

Russell, C. T.; Anderson, B. J.; Baumjohann, W.; Bromund, K. R.; Dearborn, D.; Fischer, D.; Le, G.; Leinweber, H. K.; Leneman, D.; Magnes, W.;

Theories of magnetospheres around accreting compact objects

International Nuclear Information System (INIS)

Vasyliunas, V.M.

1979-01-01

A wide class of galactic X-ray sources are believed to be binary systems where mass is flowing from a normal star to a companion that is a compact object, such as a neutron star. The strong magnetic fields of the compact object create a magnetosphere around it. We review the theoretical models developed to describe the properties of magnetospheres in such accreting binary systems. The size of the magnetosphere can be estimated from pressure balance arguments and is found to be small compared to the over-all size of the accretion region but large compared object if the latter is a neutron star. In the early models the magnetosphere was assumed to have open funnels in the polar regions, through which accreting plasma could pour in. Later, magnetically closed models were developed, with plasma entry made possible by instabilities at the magnetosphere boundary. The theory of plasma flow inside the magnetosphere has been formulated in analogy to a stellar wind with reversed flow; a complicating factor is the instability of the Alfven critical point for inflow. In the case of accretion via a well-defined disk, new problems if magnetospheric structure appear, in particular the question to what extent and by what process the magnetic fields from the compact object can penetrate into the acretion disk. Since the X-ray emission is powered by the gravitational energy released in the accretion process, mass transfer into the magnetosphere is of fundamental importance; the various proposed mechanisms are critically examined. (orig.)

Possible mechanism of the interplanetary medium effect on the diurnal rotation rate of the Earth

International Nuclear Information System (INIS)

Krymskij, P.F.

1993-01-01

Mechanism is proposed for effect of the solar wind and interplanetary magnetic field on the Earth rotation. In the mechanism base is Hall current generation in the plasma layer of the magnetosphere tail

Fast hisslers: a form of magnetospheric radio emissions

International Nuclear Information System (INIS)

Siren, J.C.

1974-01-01

Auroral radio hiss bursts in the frequency range 2-18 kHz have been observed, with rise or turn-on-times of 20-50 ms, and fall or turn-off times of 20-80 ms. These time scales are too brief to reconcile with the Cerenkov radiation emission mechanism often proposed as the transducer that converts precipitating auroral electron kinetic energy into very-low-frequency radio wave energy. The auroral hiss bursts, called here ''fast hisslers,'' are observed to be ''dispersed,', that is, their arrival time at the receiving site is not simultaneous at all frequencies, but depends on frequency in a way that is consistent with propagation in the whistler mode of electromagnetic wave propagation. Since whistler mode wave propagation at these frequencies occurs only in the earth' magnetosphere, it is inferred that these fast hisslers are of magnetospheric origin. On the assumption that all the observed dispersion results from whistler mode dispersion at high latitudes, altitudes of origin of 1800 km to 30,000 km are calculated for these emissions. Fine details of some of the amplitude spectra of fast hisslers have been examined. Potential double layers have been investigated as a highly localized region of acceleration of the auroral electrons that are believed to be the source of energy of the fast hisslers. Evidence is strong that a plasma instability exists which rapidly converts electron kinetic energies into whistler-mode wave energy traveling in the same direction relative to the rest frame of the thermal magnetospheric plasma

The inner magnetosphere imager mission

International Nuclear Information System (INIS)

Johnson, L.; Herrmann, M.

1993-01-01

After 30 years of in situ measurements of the Earth's magnetosphere, scientists have assembled an incomplete picture of its global composition and dynamics. Imaging the magnetosphere from space will enable scientists to better understand the global shape of the inner magnetosphere, its components and processes. The proposed inner magnetosphere imager (IMI) mission will obtain the first simultaneous images of the component regions of the inner magnetosphere and will enable scientists to relate these global images to internal and external influences as well as local observations. To obtain simultaneous images of component regions of the inner magnetosphere, measurements will comprise: the ring current and inner plasma sheet using energetic neutral atoms; the plasmasphere using extreme ultraviolet; the electron and proton auroras using far ultraviolet (FUV) and x rays; and the geocorona using FUV. The George C. Marshall Space Flight Center (MSFC) is performing a concept definition study of the proposed mission. NASA's Office of Space Science and Applications has placed the IMI third in its queue of intermediate-class missions for launch in the 1990's. An instrument complement of approximately seven imagers will fly in an elliptical Earth orbit with a seven Earth Radii (R E ) altitude apogee and approximately 4,800-kin altitude perigee. Several spacecraft concepts were examined for the mission. The first concept utilizes a spinning spacecraft with a despun platform. The second concept splits the instruments onto a spin-stabilized spacecraft and a complementary three-axis stabilized spacecraft. Launch options being assessed for the spacecraft range from a Delta 11 for the single and dual spacecraft concepts to dual Taurus launches for the two smaller spacecraft. This paper will address the mission objectives, the spacecraft design considerations, the results of the MSFC concept definition study, and future mission plans

3-D Force-balanced Magnetospheric Configurations

International Nuclear Information System (INIS)

Sorin Zaharia; Cheng, C.Z.; Maezawa, K.

2003-01-01

The knowledge of plasma pressure is essential for many physics applications in the magnetosphere, such as computing magnetospheric currents and deriving magnetosphere-ionosphere coupling. A thorough knowledge of the 3-D pressure distribution has however eluded the community, as most in-situ pressure observations are either in the ionosphere or the equatorial region of the magnetosphere. With the assumption of pressure isotropy there have been attempts to obtain the pressure at different locations by either (a) mapping observed data (e.g., in the ionosphere) along the field lines of an empirical magnetospheric field model or (b) computing a pressure profile in the equatorial plane (in 2-D) or along the Sun-Earth axis (in 1-D) that is in force balance with the magnetic stresses of an empirical model. However, the pressure distributions obtained through these methods are not in force balance with the empirical magnetic field at all locations. In order to find a global 3-D plasma pressure distribution in force balance with the magnetospheric magnetic field, we have developed the MAG-3D code, that solves the 3-D force balance equation J x B = (upside-down delta) P computationally. Our calculation is performed in a flux coordinate system in which the magnetic field is expressed in terms of Euler potentials as B = (upside-down delta) psi x (upside-down delta) alpha. The pressure distribution, P = P(psi,alpha), is prescribed in the equatorial plane and is based on satellite measurements. In addition, computational boundary conditions for y surfaces are imposed using empirical field models. Our results provide 3-D distributions of magnetic field and plasma pressure as well as parallel and transverse currents for both quiet-time and disturbed magnetospheric conditions

Global Particle-in-Cell Simulations of Mercury's Magnetosphere

Science.gov (United States)

Schriver, D.; Travnicek, P. M.; Lapenta, G.; Amaya, J.; Gonzalez, D.; Richard, R. L.; Berchem, J.; Hellinger, P.

2017-12-01

Spacecraft observations of Mercury's magnetosphere have shown that kinetic ion and electron particle effects play a major role in the transport, acceleration, and loss of plasma within the magnetospheric system. Kinetic processes include reconnection, the breakdown of particle adiabaticity and wave-particle interactions. Because of the vast range in spatial scales involved in magnetospheric dynamics, from local electron Debye length scales ( meters) to solar wind/planetary magnetic scale lengths (tens to hundreds of planetary radii), fully self-consistent kinetic simulations of a global planetary magnetosphere remain challenging. Most global simulations of Earth's and other planet's magnetosphere are carried out using MHD, enhanced MHD (e.g., Hall MHD), hybrid, or a combination of MHD and particle in cell (PIC) simulations. Here, 3D kinetic self-consistent hybrid (ion particle, electron fluid) and full PIC (ion and electron particle) simulations of the solar wind interaction with Mercury's magnetosphere are carried out. Using the implicit PIC and hybrid simulations, Mercury's relatively small, but highly kinetic magnetosphere will be examined to determine how the self-consistent inclusion of electrons affects magnetic reconnection, particle transport and acceleration of plasma at Mercury. Also the spatial and energy profiles of precipitating magnetospheric ions and electrons onto Mercury's surface, which can strongly affect the regolith in terms of space weathering and particle outflow, will be examined with the PIC and hybrid codes. MESSENGER spacecraft observations are used both to initiate and validate the global kinetic simulations to achieve a deeper understanding of the role kinetic physics play in magnetospheric dynamics.

Three-dimensional simulations of rapidly rotating core-collapse supernovae: finding a neutrino-powered explosion aided by non-axisymmetric flows

Science.gov (United States)

Takiwaki, Tomoya; Kotake, Kei; Suwa, Yudai

2016-09-01

We report results from a series of three-dimensional (3D) rotational core-collapse simulations for 11.2 and 27 M⊙ stars employing neutrino transport scheme by the isotropic diffusion source approximation. By changing the initial strength of rotation systematically, we find a rotation-assisted explosion for the 27 M⊙ progenitor , which fails in the absence of rotation. The unique feature was not captured in previous two-dimensional (2D) self-consistent rotating models because the growing non-axisymmetric instabilities play a key role. In the rapidly rotating case, strong spiral flows generated by the so-called low T/|W| instability enhance the energy transport from the proto-neutron star (PNS) to the gain region, which makes the shock expansion more energetic. The explosion occurs more strongly in the direction perpendicular to the rotational axis, which is different from previous 2D predictions.

Magnetospheric plasma waves

International Nuclear Information System (INIS)

Shawhan, S.D.

1977-01-01

A brief history of plasma wave observations in the Earth's magnetosphere is recounted and a classification of the identified plasma wave phenomena is presented. The existence of plasma waves is discussed in terms of the characteristic frequencies of the plasma, the energetic particle populations and the proposed generation mechanisms. Examples are given for which plasmas waves have provided information about the plasma parameters and particle characteristics once a reasonable theory has been developed. Observational evidence and arguments by analogy to the observed Earth plasma wave processes are used to identify plasma waves that may be significant in other planetary magnetospheres. The similarities between the observed characteristics of the terrestrial kilometric radiation and radio bursts from Jupiter, Saturn and possibly Uranus are stressed. Important scientific problems concerning plasma wave processes in the solar system and beyond are identified and discussed. Models for solar flares, flare star radio outbursts and pulsars include elements which are also common to the models for magnetospheric radio bursts. Finally, a listing of the research and development in terms of instruments, missions, laboratory experiments, theory and computer simulations needed to make meaningful progress on the outstanding scientific problems of plasma wave research is given. (Auth.)

The GLAaS algorithm for portal dosimetry and quality assurance of RapidArc, an intensity modulated rotational therapy

International Nuclear Information System (INIS)

Nicolini, Giorgia; Vanetti, Eugenio; Clivio, Alessandro; Fogliata, Antonella; Korreman, Stine; Bocanek, Jiri; Cozzi, Luca

2008-01-01

To expand and test the dosimetric procedure, known as GLAaS, for amorphous silicon detectors to the RapidArc intensity modulated arc delivery with Varian infrastructures and to test the RapidArc dosimetric reliability between calculation and delivery. The GLAaS algorithm was applied and tested on a set of RapidArc fields at both low (6 MV) and high (18 MV) beam energies with a PV-aS1000 detector. Pilot tests for short arcs were performed on a 6 MV beam associated to a PV-aS500. RapidArc is a novel planning and delivery method in the category of intensity modulated arc therapies aiming to deliver highly modulated plans with variable MLC shapes, dose rate and gantry speed during rotation. Tests were repeated for entire (360 degrees) gantry rotations on composite dose plans and for short partial arcs (of ~6 or 12 degrees) to assess GLAaS and RapidArc mutual relationships on global and fine delivery scales. The gamma index concept of Low and the Modulation Index concept of Webb were applied to compare quantitatively TPS dose matrices and dose converted PV images. The Gamma Agreement Index computed for a Distance to Agreement of 3 mm and a Dose Difference (ΔD) of 3% was, as mean ± 1 SD, 96.7 ± 1.2% at 6 MV and 94.9 ± 1.3% at 18 MV, over the field area. These findings deteriorated slightly is ΔD was reduced to 2% (93.4 ± 3.2% and 90.1 ± 3.1%, respectively) and improved with ΔD = 4% (98.3 ± 0.8% and 97.3 ± 0.9%, respectively). For all tests a grid of 1 mm and the AAA photon dose calculation algorithm were applied. The spatial resolution of the PV-aS1000 is 0.392 mm/pxl. The Modulation Index for calculations resulted 17.0 ± 3.2 at 6 MV and 15.3 ± 2.7 at 18 MV while the corresponding data for measurements were: 18.5 ± 3.7 and 17.5 ± 3.7. Partial arcs findings were (for ΔD = 3%): GAI = 96.7 ± 0.9% for 6° rotations and 98.0 ± 1.1% for 12° rotations. The GLAaS method can be considered as a valid Quality Assurance tool for the verification of RapidArc fields

Pulsar Magnetospheres and Pulsar Winds

OpenAIRE

Beskin, Vasily S.

2016-01-01

Surprisingly, the chronology of nearly 50 years of the pulsar magnetosphere and pulsar wind research is quite similar to the history of our civilization. Using this analogy, I have tried to outline the main results obtained in this field. In addition to my talk, the possibility of particle acceleration due to different processes in the pulsar magnetosphere is discussed in more detail.

Inner Magnetospheric Physics

Science.gov (United States)

Gallagher, Dennis

2018-01-01

Outline - Inner Magnetosphere Effects: Historical Background; Main regions and transport processes: Ionosphere, Plasmasphere, Plasma sheet, Ring current, Radiation belt; Geomagnetic Activity: Storms, Substorm; Models.

Photometric light curves for seven rapidly-rotating K dwarfs in the Pleiades and Alpha Persei clusters

Science.gov (United States)

Stauffer, John R.; Schild, Rudolph A.; Baliunas, Sallie L.; Africano, John L.

1987-01-01

Light curves and period estimates were obtained for several Pleiades and Alpha Persei cluster K dwarfs which were identified as rapid rotators in earlier spectroscopic studies. A few of the stars have previously-published light curves, making it possible to study the long-term variability of the light-curve shapes. The general cause of the photometric variability observed for these stars is an asymmetric distribution of photospheric inhomogeneities (starspots). The presence of these inhomogeneities combined with the rotation of the star lead to the light curves observed. The photometric periods derived are thus identified with the rotation period of the star, making it possible to estimate equatorial rotational velocities for these K dwarfs. These data are of particular importance because the clusters are sufficiently young that stars of this mass should have just arrived on the main sequence. These data could be used to estimate the temperatures and sizes of the spot groups necessary to produce the observed light curves for these stars.

Pulsars Magnetospheres

Science.gov (United States)

Timokhin, Andrey

2012-01-01

Current density determines the plasma flow regime. Cascades are non-stationary. ALWAYS. All flow regimes look different: multiple components (?) Return current regions should have particle accelerating zones in the outer magnetosphere: y-ray pulsars (?) Plasma oscillations in discharges: direct radio emission (?)

Auroral kilometric radiation and magnetospheric substorm

International Nuclear Information System (INIS)

Morioka, Akira; Oya, Hiroshi

1980-01-01

The auroral kilometric radiation (AKR) and its relation to the development of the magnetospheric substorm have been studied based on the data obtained by JIKIKEN (EXOS-B) satellite. The occurrence of AKR is closely correlated to the intense UHR emission outside the plasmapause at the satellite position; the evidence clearly suggests that the development of the field aligned current system is associated with AKR generated at the upward current region and with the UHR emission at the downward current region. The drifting plasma due to the electric field that is generated in the magnetosphere at the moment of the magnetospheric substorm is derived from the frequency change of the plasma waves. The enhancement of the westward electric field in the duskside magnetosphere is detected simultaneously with the appearence of AKR. The altitude of the center of the AKR source region varies with intimate relation to the substorm activity suggesting that the generation of AKR is taking place in the region where the polar ionosphere and the magnetosphere are predominantly coupling through the precipitating or up going particles. From the fine structure of the dynamic spectra of AKR, it is suggested that the source of AKR might be closely related to the double layer type electric field along the magnetic field. (author)

Magnetosphere Modeling: From Cartoons to Simulations

Science.gov (United States)

Gombosi, T. I.

2017-12-01

Over the last half a century physics-based global computer simulations became a bridge between experiment and basic theory and now it represents the "third pillar" of geospace research. Today, many of our scientific publications utilize large-scale simulations to interpret observations, test new ideas, plan campaigns, or design new instruments. Realistic simulations of the complex Sun-Earth system have been made possible by the dramatically increased power of both computing hardware and numerical algorithms. Early magnetosphere models were based on simple E&M concepts (like the Chapman-Ferraro cavity) and hydrodynamic analogies (bow shock). At the beginning of the space age current system models were developed culminating in the sophisticated Tsyganenko-type description of the magnetic configuration. The first 3D MHD simulations of the magnetosphere were published in the early 1980s. A decade later there were several competing global models that were able to reproduce many fundamental properties of the magnetosphere. The leading models included the impact of the ionosphere by using a height-integrated electric potential description. Dynamic coupling of global and regional models started in the early 2000s by integrating a ring current and a global magnetosphere model. It has been recognized for quite some time that plasma kinetic effects play an important role. Presently, global hybrid simulations of the dynamic magnetosphere are expected to be possible on exascale supercomputers, while fully kinetic simulations with realistic mass ratios are still decades away. In the 2010s several groups started to experiment with PIC simulations embedded in large-scale 3D MHD models. Presently this integrated MHD-PIC approach is at the forefront of magnetosphere simulations and this technique is expected to lead to some important advances in our understanding of magnetosheric physics. This talk will review the evolution of magnetosphere modeling from cartoons to current systems

Observations of Heavy Ions in the Magnetosphere

Science.gov (United States)

Kistler, L. M.

2017-12-01

There are two sources for the hot ions in the magnetosphere: the solar wind and the ionosphere. The solar wind is predominantly protons, with about 4% He++ and less than 1% other high charge state heavy ions. The ionospheric outflow is also predominantly H+, but can contain a significant fraction of heavy ions including O+, N+, He+, O++, and molecular ions (NO+, N2+, O2+). The ionospheric outflow composition varies significantly both with geomagnetic activity and with solar EUV. The variability in the contribution of the two sources, the variability in the ionospheric source itself, and the transport paths of the different species are all important in determining the ion composition at a given location in the magnetosphere. In addition to the source variations, loss processes within the magnetosphere can be mass dependent, changing the composition. In particular, charge exchange is strongly species dependent, and can lead to heavy ion dominance at some energies in the inner magnetosphere. In this talk we will review the current state of our understanding of the composition of the magnetosphere and the processes that determine it.

Magnetopause reconnection rate estimates for Jupiter's magnetosphere based on interplanetary measurements at ~5AU

Directory of Open Access Journals (Sweden)

J. D. Nichols

2006-03-01

Full Text Available We make the first quantitative estimates of the magnetopause reconnection rate at Jupiter using extended in situ data sets, building on simple order of magnitude estimates made some thirty years ago by Brice and Ionannidis (1970 and Kennel and Coroniti (1975, 1977. The jovian low-latitude magnetopause (open flux production reconnection voltage is estimated using the Jackman et al. (2004 algorithm, validated at Earth, previously applied to Saturn, and here adapted to Jupiter. The high-latitude (lobe magnetopause reconnection voltage is similarly calculated using the related Gérard et al. (2005 algorithm, also previously used for Saturn. We employ data from the Ulysses spacecraft obtained during periods when it was located near 5AU and within 5° of the ecliptic plane (January to June 1992, January to August 1998, and April to October 2004, along with data from the Cassini spacecraft obtained during the Jupiter flyby in 2000/2001. We include the effect of magnetospheric compression through dynamic pressure modulation, and also examine the effect of variations in the direction of Jupiter's magnetic axis throughout the jovian day and year. The intervals of data considered represent different phases in the solar cycle, such that we are also able to examine solar cycle dependency. The overall average low-latitude reconnection voltage is estimated to be ~230 kV, such that the average amount of open flux created over one solar rotation is ~500 GWb. We thus estimate the average time to replenish Jupiter's magnetotail, which contains ~300-500 GWb of open flux, to be ~15-25 days, corresponding to a tail length of ~3.8-6.5 AU. The average high-latitude reconnection voltage is estimated to be ~130 kV, associated with lobe "stirring". Within these averages, however, the estimated voltages undergo considerable variation. Generally, the low-latitude reconnection voltage exhibits a "background" of ~100 kV that is punctuated by one or two significant

Ground observations of magnetospheric boundary layer phenomena

International Nuclear Information System (INIS)

McHenry, M.A.; Clauer, C.R.; Friis-Christensen, E.; Newell, P.T.; Kelly, J.D.

1990-01-01

Several classes of traveling vortices in the dayside ionospheric convection have been detected and tracked using the Greenland magnetometer chain (Friis-Christensen et al., 1988, McHenry et al., 1989). One class observed during quiet times consists of a continuous series of vortices moving generally anti-sunward for several hours at a time. The vortices strength is seen to be approximately steady and neighboring vortices rotate in opposite directions. Sondrestrom radar observations show that the vortices are located at the ionospheric convection reversal boundary. Low altitude DMSP observations indicate the vortices are on field lines which map to the inner edge of the low latitude boundary layer. Because the vortices are conjugate to the boundary layer, repeat in a regular fashion and travel antisunward, the authors argue that this class of vortices is caused by the Kelvin-Helmholtz instability of the inner edge of the magnetospheric boundary layer

Analysis of synchronous excitation of the Pi 2 geomagnetic pulsations in the night and day magnetosphere

International Nuclear Information System (INIS)

Petlenko, A.V.; Raspopov, O.M.; Shumilov, O.I.

1998-01-01

Analysis of the Pi 2 characteristics shows appearance of Pi 2 at the auroral stations of the western and eastern hemispheres. Direction of Pi 2 polarization vector rotation changes at the day side in the latitude range of 58-63 deg. These data permit to interpret the Pi 2 appearance at the day side by formation of an oscillating three-dimensional current system. Pi 2 synchronism is explained by pulse switching and decay of the magnetospheric substorm currents

VARIABILITY IN HOT CARBON-DOMINATED ATMOSPHERE (HOT DQ) WHITE DWARFS: RAPID ROTATION?

Energy Technology Data Exchange (ETDEWEB)

Williams, Kurtis A.; Bierwagen, Michael [Department of Physics and Astrophysics, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX, 75429 (United States); Montgomery, M. H.; Winget, D. E.; Falcon, Ross E., E-mail: Kurtis.Williams@tamuc.edu [Department of Astronomy, University of Texas, 1 University Station C1400, Austin, TX, 78712 (United States)

2016-01-20

Hot white dwarfs (WDs) with carbon-dominated atmospheres (hot DQs) are a cryptic class of WDs. In addition to their deficiency of hydrogen and helium, most of these stars are highly magnetic, and a large fraction vary in luminosity. This variability has been ascribed to nonradial pulsations, but increasing data call this explanation into question. We present studies of short-term variability in seven hot DQ WDs. Three (SDSS J1426+5752, SDSS J2200−0741, and SDSS J2348−0942) were known to be variable. Their photometric modulations are coherent over at least two years, and we find no evidence for variability at frequencies that are not harmonics. We present the first time-series photometry for three additional hot DQs (SDSS J0236−0734, SDSS J1402+3818, and SDSS J1615+4543); none are observed to vary, but the signal-to-noise is low. Finally, we present high speed photometry for SDSS J0005−1002, known to exhibit a 2.1-day photometric variation; we do not observe any short-term variability. Monoperiodicity is rare among pulsating WDs, so we contemplate whether the photometric variability is due to rotation rather than pulsations; similar hypotheses have been raised by other researchers. If the variability is due to rotation, then hot DQ WDs as a class contain many rapid rotators. Given the lack of companions to these stars, the origin of any fast rotation is unclear—both massive progenitor stars and double degenerate merger remnants are possibilities. We end with suggestions of future work that would best clarify the nature of these rare, intriguing objects.

Measurement and Finite Element Model Validation of Immature Porcine Brain-Skull Displacement during Rapid Sagittal Head Rotations.

Science.gov (United States)

Pasquesi, Stephanie A; Margulies, Susan S

2018-01-01

Computational models are valuable tools for studying tissue-level mechanisms of traumatic brain injury, but to produce more accurate estimates of tissue deformation, these models must be validated against experimental data. In this study, we present in situ measurements of brain-skull displacement in the neonatal piglet head ( n  = 3) at the sagittal midline during six rapid non-impact rotations (two rotations per specimen) with peak angular velocities averaging 51.7 ± 1.4 rad/s. Marks on the sagittally cut brain and skull/rigid potting surfaces were tracked, and peak values of relative brain-skull displacement were extracted and found to be significantly less than values extracted from a previous axial plane model. In a finite element model of the sagittally transected neonatal porcine head, the brain-skull boundary condition was matched to the measured physical experiment data. Despite smaller sagittal plane displacements at the brain-skull boundary, the corresponding finite element boundary condition optimized for sagittal plane rotations is far less stiff than its axial counterpart, likely due to the prominent role of the boundary geometry in restricting interface movement. Finally, bridging veins were included in the finite element model. Varying the bridging vein mechanical behavior over a previously reported range had no influence on the brain-skull boundary displacements. This direction-specific sagittal plane boundary condition can be employed in finite element models of rapid sagittal head rotations.

Measurement and Finite Element Model Validation of Immature Porcine Brain–Skull Displacement during Rapid Sagittal Head Rotations

Science.gov (United States)

Pasquesi, Stephanie A.; Margulies, Susan S.

2018-01-01

Computational models are valuable tools for studying tissue-level mechanisms of traumatic brain injury, but to produce more accurate estimates of tissue deformation, these models must be validated against experimental data. In this study, we present in situ measurements of brain–skull displacement in the neonatal piglet head (n = 3) at the sagittal midline during six rapid non-impact rotations (two rotations per specimen) with peak angular velocities averaging 51.7 ± 1.4 rad/s. Marks on the sagittally cut brain and skull/rigid potting surfaces were tracked, and peak values of relative brain–skull displacement were extracted and found to be significantly less than values extracted from a previous axial plane model. In a finite element model of the sagittally transected neonatal porcine head, the brain–skull boundary condition was matched to the measured physical experiment data. Despite smaller sagittal plane displacements at the brain–skull boundary, the corresponding finite element boundary condition optimized for sagittal plane rotations is far less stiff than its axial counterpart, likely due to the prominent role of the boundary geometry in restricting interface movement. Finally, bridging veins were included in the finite element model. Varying the bridging vein mechanical behavior over a previously reported range had no influence on the brain–skull boundary displacements. This direction-specific sagittal plane boundary condition can be employed in finite element models of rapid sagittal head rotations. PMID:29515995

Circular Polarizations of Gravitational Waves from Core-Collapse Supernovae: A Clear Indication of Rapid Rotation.

Science.gov (United States)

Hayama, Kazuhiro; Kuroda, Takami; Nakamura, Ko; Yamada, Shoichi

2016-04-15

We propose to employ the circular polarization of gravitational waves emitted by core-collapse supernovae as an unequivocal indication of rapid rotation deep in their cores just prior to collapse. It has been demonstrated by three dimensional simulations that nonaxisymmetric accretion flows may develop spontaneously via hydrodynamical instabilities in the postbounce cores. It is not surprising, then, that the gravitational waves emitted by such fluid motions are circularly polarized. We show, in this Letter, that a network of the second generation detectors of gravitational waves worldwide may be able to detect such polarizations up to the opposite side of the Galaxy as long as the rotation period of the core is shorter than a few seconds prior to collapse.

The solar wind-magentosphere energy coupling and magnetospheric disturbances

International Nuclear Information System (INIS)

Akasofu, S.I.

1980-01-01

The recent finding of the solar wind-magnetosphere energy coupling function epsilon has advanced significantly our understanding of magnetosphere disturbances. It is shown that the magnetosphere-ionosphere coupling system responds somewhat differently to three different input energy flux levels of epsilon. As epsilon increases from 17 erg s -1 to >10 19 erg s -1 , typical responses of the magnetosphere-ionosphere coupling system are: (1) epsilon 17 erg s -1 : an enhancement of the Ssub(q)sup(p), etc. (2) epsilon approximately 10 18 erg s -1 : substorm onset. (3) 10 18 erg s -1 19 erg s -1 : a typical substorm. (4) epsilon >10 19 erg s -1 : an abnormal growth of the ring current belt, resulting in a magnetospheric storm. It is stressed that the magnetospheric substorm results as a direct response of the magnetosphere to a rise and fall of epsilon above approximately 10 18 erg s -1 , so that it is not caused by a sudden conversion of magnetic energy accumulated prior to substorm onset. The variety of the development of the main phase of geomagnetic storms is also primarily controlled by epsilon. (author)

Quadrupole collective excitations in rapidly rotating nuclej

International Nuclear Information System (INIS)

Mikhajlov, I.N.

1983-01-01

The spectrum of collective quadrupole excitations in nuclei is investigated. The average nucleus field has the axial symmetry and rotation occurs relatively to this axis. Dependences of the spectrum of quadrupole oscillations on rotation rate for classic liquid drop (CLD) and for a drop of fermi-liquid (DFL) with fissionability parameter X=0.62 ( 154 Er) are presented. The dependence of probabilities of E2-transitions between single-phonon and phonon-free states on rotation rate for CLD and DFL with fussionability parameter X=0.62 ( 154 Er) is also presented. It is shown that for CLD collective E2-transition of states of yrast-consequence is absolutely forbidden. For DFL transitions are possible that lead to decay of phonon-free state with the excitation of phonons of γ-modes and decrease of angular momentum

Scientists Detect Radio Emission from Rapidly Rotating Cosmic Dust Grains

Science.gov (United States)

2001-11-01

Astronomers have made the first tentative observations of a long-speculated, but never before detected, source of natural radio waves in interstellar space. Data from the National Science Foundation's 140 Foot Radio Telescope at the National Radio Astronomy Observatory in Green Bank, W.Va., show the faint, tell-tale signals of what appear to be dust grains spinning billions of times each second. This discovery eventually could yield a powerful new tool for understanding the interstellar medium - the immense clouds of gas and dust that populate interstellar space. The NRAO 140 Foot Radio Telescope The NRAO 140-Foot Radio Telescope "What we believe we have found," said Douglas P. Finkbeiner of Princeton University's Department of Astrophysics, "is the first hard evidence for electric dipole emission from rapidly rotating dust grains. If our studies are confirmed, it will be the first new source of continuum emission to be conclusively identified in the interstellar medium in nearly the past 20 years." Finkbeiner believes that these emissions have the potential in the future of revealing new and exciting information about the interstellar medium; they also may help to refine future studies of the Cosmic Microwave Background Radiation. The results from this study, which took place in spring 1999, were accepted for publication in Astrophysical Journal. Other contributors to this paper include David J. Schlegel, department of astrophysics, Princeton University; Curtis Frank, department of astronomy, University of Maryland; and Carl Heiles, department of astronomy, University of California at Berkeley. "The idea of dust grains emitting radiation by rotating is not new," comments Finkbeiner, "but to date it has been somewhat speculative." Scientists first proposed in 1957 that dust grains could emit radio signals, if they were caused to rotate rapidly enough. It was believed, however, that these radio emissions would be negligibly small - too weak to be of any impact to

The Earth's magnetosphere is 165 R(sub E) long: Self-consistent currents, convection, magnetospheric structure, and processes for northward interplanetary magnetic field

Science.gov (United States)

Fedder, J. A.; Lyon, J. G.

1995-01-01

The subject of this paper is a self-consistent, magnetohydrodynamic numerical realization for the Earth's magnetosphere which is in a quasi-steady dynamic equilibrium for a due northward interplanetary magnetic field (IMF). Although a few hours of steady northward IMF are required for this asymptotic state to be set up, it should still be of considerable theoretical interest because it constitutes a 'ground state' for the solar wind-magnetosphere interaction. Moreover, particular features of this ground state magnetosphere should be observable even under less extreme solar wind conditions. Certain characteristics of this magnetosphere, namely, NBZ Birkeland currents, four-cell ionospheric convection, a relatively weak cross-polar potential, and a prominent flow boundary layer, are widely expected. Other characteristics, such as no open tail lobes, no Earth-connected magnetic flux beyond 155 R(sub E) downstream, magnetic merging in a closed topology at the cusps, and a 'tadpole' shaped magnetospheric boundary, might not be expected. In this paper, we will present the evidence for this unusual but interesting magnetospheric equilibrium. We will also discuss our present understanding of this singular state.

RADII OF RAPIDLY ROTATING STARS, WITH APPLICATION TO TRANSITING-PLANET HOSTS

International Nuclear Information System (INIS)

Brown, Timothy M.

2010-01-01

The currently favored method for estimating radii and other parameters of transiting-planet host stars is to match theoretical models to observations of the stellar mean density ρ * , the effective temperature T eff , and the composition parameter [Z]. This explicitly model-dependent approach is based on readily available observations, and results in small formal errors. Its performance will be central to the reliability of results from ground-based transit surveys such as TrES, HAT, and SuperWASP, as well as to the space-borne missions MOST, CoRoT, and Kepler. Here, I use two calibration samples of stars (eclipsing binaries (EBs) and stars for which asteroseismic analyses are available) having well-determined masses and radii to estimate the accuracy and systematic errors inherent in the ρ * method. When matching to the Yonsei-Yale stellar evolution models, I find the most important systematic error results from selection bias favoring rapidly rotating (hence probably magnetically active) stars among the EB sample. If unaccounted for, this bias leads to a mass-dependent underestimate of stellar radii by as much as 4% for stars of 0.4 M sun , decreasing to zero for masses above about 1.4 M sun . Relative errors in estimated stellar masses are three times larger than those in radii. The asteroseismic sample suggests (albeit with significant uncertainty) that systematic errors are small for slowly rotating, inactive stars. Systematic errors arising from failings of the Yonsei-Yale models of inactive stars probably exist, but are difficult to assess because of the small number of well-characterized comparison stars having low mass and slow rotation. Poor information about [Z] is an important source of random error, and may be a minor source of systematic error as well. With suitable corrections for rotation, it is likely that systematic errors in the ρ * method can be comparable to or smaller than the random errors, yielding radii that are accurate to about 2% for

GAMERA - The New Magnetospheric Code

Science.gov (United States)

Lyon, J.; Sorathia, K.; Zhang, B.; Merkin, V. G.; Wiltberger, M. J.; Daldorff, L. K. S.

2017-12-01

The Lyon-Fedder-Mobarry (LFM) code has been a main-line magnetospheric simulation code for 30 years. The code base, designed in the age of memory to memory vector ma- chines,is still in wide use for science production but needs upgrading to ensure the long term sustainability. In this presentation, we will discuss our recent efforts to update and improve that code base and also highlight some recent results. The new project GAM- ERA, Grid Agnostic MHD for Extended Research Applications, has kept the original design characteristics of the LFM and made significant improvements. The original de- sign included high order numerical differencing with very aggressive limiting, the ability to use arbitrary, but logically rectangular, grids, and maintenance of div B = 0 through the use of the Yee grid. Significant improvements include high-order upwinding and a non-clipping limiter. One other improvement with wider applicability is an im- proved averaging technique for the singularities in polar and spherical grids. The new code adopts a hybrid structure - multi-threaded OpenMP with an overarching MPI layer for large scale and coupled applications. The MPI layer uses a combination of standard MPI and the Global Array Toolkit from PNL to provide a lightweight mechanism for coupling codes together concurrently. The single processor code is highly efficient and can run magnetospheric simulations at the default CCMC resolution faster than real time on a MacBook pro. We have run the new code through the Athena suite of tests, and the results compare favorably with the codes available to the astrophysics community. LFM/GAMERA has been applied to many different situations ranging from the inner and outer heliosphere and magnetospheres of Venus, the Earth, Jupiter and Saturn. We present example results the Earth's magnetosphere including a coupled ring current (RCM), the magnetospheres of Jupiter and Saturn, and the inner heliosphere.

On the mapping of ionospheric convection into the magnetosphere

International Nuclear Information System (INIS)

Hesse, M.; Birn, J.; Hoffman, R.A.

1997-01-01

Under steady state conditions and in the absence of parallel electric fields, ionospheric convection is a direct map of plasma and magnetic flux convection in the magnetosphere, and quantitative estimates can be obtained from the mapping along magnetic field lines of electrostatic ionospheric electric fields. The resulting magnetospheric electrostatic potential distribution then provides the convection electric field in various magnetospheric regions. We present a quantitative framework for the investigation of the applicability and limitations of this approach based on an analytical theory derived from first principles. Particular emphasis is on the role of parallel electric field regions and on inductive effects, such as expected during the growth and expansive phases of magnetospheric substorms. We derive quantitative estimates for the limits in which either effect leads to a significant decoupling between ionospheric and magnetospheric convection and provide an interpretation of ionospheric convection which is independent of the presence of inductive electric fields elsewhere in the magnetosphere. Finally, we present a study of the relation between average and instantaneous convection, using two periodic dynamical models. The models demonstrate and quantify the potential mismatch between the average electric fields in the ionosphere and the magnetosphere in strongly time-dependent cases that may exist even when they are governed entirely by ideal MHD

Particle tracing in the magnetosphere: New algorithms and results

International Nuclear Information System (INIS)

Sheldon, R.B.; Gaffey, J.D. Jr.

1993-01-01

The authors present new algorithms for calculating charged-particle trajectories in realistic magnetospheric fields in fast and efficient manners. The scheme is based on a hamiltonian energy conservation principle. It requires that particles conserve the first two adiabatic invariants, and thus also conserve energy. It is applicable for particles ranging in energy from 0.01 to 100 keV, having arbitrary charge, and pitch angle. In addition to rapid particle trajectory calculations, it allows topological boundaries to be located efficiently. The results can be combined with fluid models to provide quantitative models of the time development of the whole convecting plasma model

An astrophysical interpretation of the remarkable g-mode frequency groups of the rapidly rotating γ Dor star, KIC 5608334

Science.gov (United States)

Saio, Hideyuki; Bedding, Timothy R.; Kurtz, Donald W.; Murphy, Simon J.; Antoci, Victoria; Shibahashi, Hiromoto; Li, Gang; Takata, Masao

2018-06-01

The Fourier spectrum of the γ-Dor variable KIC 5608334 shows remarkable frequency groups at ˜3, ˜6, ˜9, and 11-12 d-1. We explain the four frequency groups as prograde sectoral g modes in a rapidly rotating star. Frequencies of intermediate-to-high radial order prograde sectoral g modes in a rapidly rotating star are proportional to |m| (i.e. ν ∝ |m|) in the corotating frame as well as in the inertial frame. This property is consistent with the frequency groups of KIC 5608334 as well as the period versus period-spacing relation present within each frequency group, if we assume a rotation frequency of 2.2 d-1, and that each frequency group consists of prograde sectoral g modes of |m| = 1, 2, 3, and 4, respectively. In addition, these modes naturally satisfy near-resonance conditions νi ≈ νj + νk with mi = mj + mk. We even find exact resonance frequency conditions (within the precise measurement uncertainties) in many cases, which correspond to combination frequencies.

Physical conditions in the reconnection layer in pulsar magnetospheres

Energy Technology Data Exchange (ETDEWEB)

Uzdensky, Dmitri A. [Center for Integrated Plasma Studies, Physics Department, University of Colorado, UCB 390, Boulder, CO 80309-0390 (United States); Spitkovsky, Anatoly, E-mail: uzdensky@colorado.edu, E-mail: anatoly@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2014-01-01

The magnetosphere of a rotating pulsar naturally develops a current sheet (CS) beyond the light cylinder (LC). Magnetic reconnection in this CS inevitably dissipates a nontrivial fraction of the pulsar spin-down power within a few LC radii. We develop a basic physical picture of reconnection in this environment and discuss its implications for the observed pulsed gamma-ray emission. We argue that reconnection proceeds in the plasmoid-dominated regime, via a hierarchical chain of multiple secondary islands/flux ropes. The inter-plasmoid reconnection layers are subject to strong synchrotron cooling, leading to significant plasma compression. Using the conditions of pressure balance across these current layers, the balance between the heating by magnetic energy dissipation and synchrotron cooling, and Ampere's law, we obtain simple estimates for key parameters of the layers—temperature, density, and layer thickness. In the comoving frame of the relativistic pulsar wind just outside of the equatorial CS, these basic parameters are uniquely determined by the strength of the reconnecting upstream magnetic field. For the case of the Crab pulsar, we find them to be of order 10 GeV, 10{sup 13} cm{sup –3}, and 10 cm, respectively. After accounting for the bulk Doppler boosting due to the pulsar wind, the synchrotron and inverse-Compton emission from the reconnecting CS can explain the observed pulsed high-energy (GeV) and very high energy (∼100 GeV) radiation, respectively. Also, we suggest that the rapid relative motions of the secondary plasmoids in the hierarchical chain may contribute to the production of the pulsar radio emission.

From the Solar Wind to the Magnetospheric Substorm

Institute of Scientific and Technical Information of China (English)

E.A. Ponomarev; P.A. Sedykh; O.V. Mager

2005-01-01

This paper gives a brief outline of the progression from the first substorm model developed in Ref.[4] and [8] based on Kennel's ideas[3], to the present views about the mechanism by which solar wind kinetic energy is converted to electromagnetic energy at the Bow Shock and by which this energy is transferred to the magnetosphere in the form of current; about the transformation of the energy of this current to gas kinetic energy of convecting plasma tubes, and, finally, the back transformation of gas kinetic energy to electromagnetic energy in secondary magnetospheric MHD generators. The questions of the formation of the magnetospheric convection system, the nature of substorm break-up, and of the matching of currents in the magnetosphere-ionosphere system are discussed.

Research in magnetospheric wave phenomena

International Nuclear Information System (INIS)

Barfield, J.N.

1975-01-01

During the last 4 years a number of developments have occurred which have led to an increased understanding of the role of wave phenomena in the physical processes of the magnetosphere. While the studies span the frequency regime from millihertz to the electron gyrofrequency, the developments to be discussed in this paper have in common that they have added substantially to the understanding of the controlling processes, regions, and boundaries in the magnetosphere. The topics discussed are the increased awareness and documentation of the role of the plasmapause in micropulsation generation and propagation; the establishment of the role of ion cyclotron waves in the wave-particle interactions at the plasmapause; the discovery of magnetospheric electrostatic waves with ω = (3/2)Ω/sub -/; the discovery and preliminary identification of the source of plasmaspheric hiss; and the analysis of storm time Pc 5 waves as observed on the satellites ATS 1 and Explorer 45. (auth)

Plasma in Saturn's nightside magnetosphere and the implications for global circulation

International Nuclear Information System (INIS)

Mcandrews, Hazel J.; Thomsen, Michelle F.; Wilson, Robert J.; Henderson, Michael G.; Tokar, Robert L.; Arridge, Chris S.; Jackman, Caitriona M.; Khurana, Krishan K.; Sittler, Edward C.; Coates, Andrew J.; Dougherty, Michele K.

2008-01-01

We present a bulk ion flow map from the nightside, equatorial region of Saturn's magnetosphere derived from the Cassini CAPS ion mass spectrometer data. The map clearly demonstrates the dominance of corotation flow over radial flow and suggests that the flux tubes sampled are still closed and attached to the planet up to distances of 50 RS. The plasma characteristics in the near-midnight region are described and indicate a transition between the region of the magnetosphere containing plasma on closed drift paths and that containing flux tubes which may not complete a full rotation around the planet. Data from the electron spectrometer reveal two plasma states of high and low density. These are attributed either to the sampling of mass-loaded and depleted flux tubes, respectively, or to the latitudinal structure of the plasma sheet. Depleted, returning flux tubes are not, in general, directly observed in the ions, although the electron observations suggest that such a process must take place in order to produce the low density population. An example of such a low-density interval containing hot electrons with a dipolarised, swept-forward field configuration is described and strongly suggests that reconnection must have occurred planetward of Cassini. Flux tube content is conserved below a limit defined by the mass-loading and magnetic field strength and indicates that the flux tubes sampled may survive their passage through the tail. The conditions for mass release are evaluated using measured densities, angular velocities and magnetic field strength. The results suggest that for the relatively dense ion populations detectable by IMS, the condition for flux-tube breakage has not yet been exceeded. However, the low-density regimes observed in the electron data suggest that loaded flux tubes at greater distances do exceed the threshold for mass loss and subsequently return to the inner magnetosphere significantly depleted of plasma.

Impacts of Earth rotation parameters on GNSS ultra-rapid orbit prediction: Derivation and real-time correction

Science.gov (United States)

Wang, Qianxin; Hu, Chao; Xu, Tianhe; Chang, Guobin; Hernández Moraleda, Alberto

2017-12-01

Analysis centers (ACs) for global navigation satellite systems (GNSSs) cannot accurately obtain real-time Earth rotation parameters (ERPs). Thus, the prediction of ultra-rapid orbits in the international terrestrial reference system (ITRS) has to utilize the predicted ERPs issued by the International Earth Rotation and Reference Systems Service (IERS) or the International GNSS Service (IGS). In this study, the accuracy of ERPs predicted by IERS and IGS is analyzed. The error of the ERPs predicted for one day can reach 0.15 mas and 0.053 ms in polar motion and UT1-UTC direction, respectively. Then, the impact of ERP errors on ultra-rapid orbit prediction by GNSS is studied. The methods for orbit integration and frame transformation in orbit prediction with introduced ERP errors dominate the accuracy of the predicted orbit. Experimental results show that the transformation from the geocentric celestial references system (GCRS) to ITRS exerts the strongest effect on the accuracy of the predicted ultra-rapid orbit. To obtain the most accurate predicted ultra-rapid orbit, a corresponding real-time orbit correction method is developed. First, orbits without ERP-related errors are predicted on the basis of ITRS observed part of ultra-rapid orbit for use as reference. Then, the corresponding predicted orbit is transformed from GCRS to ITRS to adjust for the predicted ERPs. Finally, the corrected ERPs with error slopes are re-introduced to correct the predicted orbit in ITRS. To validate the proposed method, three experimental schemes are designed: function extrapolation, simulation experiments, and experiments with predicted ultra-rapid orbits and international GNSS Monitoring and Assessment System (iGMAS) products. Experimental results show that using the proposed correction method with IERS products considerably improved the accuracy of ultra-rapid orbit prediction (except the geosynchronous BeiDou orbits). The accuracy of orbit prediction is enhanced by at least 50

Advances in magnetospheric physics, 1971--1974: energetic particles

International Nuclear Information System (INIS)

West, H.I. Jr.

1974-12-01

An account is given of energetic particle research in magnetospheric physics for the time period 1971--1974. Emphasis is on relating the various aspects of energetic particles to magnetospheric processes. 458 refs. (U.S.)

Nonlinear dynamics of the magnetosphere and space weather

Science.gov (United States)

Sharma, A. Surjalal

1996-01-01

The solar wind-magnetosphere system exhibits coherence on the global scale and such behavior can arise from nonlinearity on the dynamics. The observational time series data were used together with phase space reconstruction techniques to analyze the magnetospheric dynamics. Analysis of the solar wind, auroral electrojet and Dst indices showed low dimensionality of the dynamics and accurate prediction can be made with an input/output model. The predictability of the magnetosphere in spite of the apparent complexity arises from its dynamical synchronism with the solar wind. The electrodynamic coupling between different regions of the magnetosphere yields its coherent, low dimensional behavior. The data from multiple satellites and ground stations can be used to develop a spatio-temporal model that identifies the coupling between different regions. These nonlinear dynamical models provide space weather forecasting capabilities.

Substorms - Future of magnetospheric substorm-storm research

International Nuclear Information System (INIS)

Akasofu, S.I.

1989-01-01

Seven approaches and/or areas of magnetospheric substorm and storm science which should be emphasized in future research are briefly discussed. They are: the combining of groups of researchers who study magnetic storms and substorms in terms of magnetic reconnection with those that do not, the possible use of a magnetosphere-ionosphere coupling model to merge the groups, the development of improved input-output relationships, the complementing of satellite and ground-based observations, the need for global imaging of the magnetosphere, the complementing of observations with computer simulations, and the need to study the causes of changes in the north-south component of the IMF. 36 refs

Advances in magnetospheric storm and substorm research: 1989-1991

International Nuclear Information System (INIS)

Fairfield, D.H.

1992-01-01

Geomagnetic storms represent the magnetospheric response to fast solar wind and unusually large southward interplanetary magnetic fields that are caused by solar processes and resulting dynamics in the interplanetary medium. The solar wind/magnetosphere interaction is, however, more commonly studied via smaller, more common, magnetospheric substorms. Accumulating evidence suggests that two separate magnetospheric current systems are important during magnetospheric substorms. Currents directly driven by the solar wind/magnetosphere interaction produce magnetic field variations that make important contributions to the AE index but have little relation to the many effects traditionally associated with sudden substorm onsets. Currents driven by energy unloaded from the magnetotail form the nightside current wedge and are associated with onset effects such as auroral breakup, field dipolarization, and particle acceleration. Observations are gradually leading to a coherent picture of the interrelations among these various onset phenomena, but their cause remains a controversial question. The abrupt nature of substorm onsets suggests a magnetospheric instability, but doubt remains as to its nature and place of origin. Measurements increasingly suggest the region of 7-10 R E near midnight as the likely point of origin, but it is not clear that the long-popular tearing mode can go unstable this close to the Earth, where it may be stabilized by a small northward field component. Also the tailward flows that would be expected tailward of a near-Earth neutral line are seldom seen inside of 19 R E . The changing magnetic field configuration during substorms means that existing static models cannot be used to map phenomena between the magnetosphere and the ground at these interesting times

Observations & modeling of solar-wind/magnetospheric interactions

Science.gov (United States)

Hoilijoki, Sanni; Von Alfthan, Sebastian; Pfau-Kempf, Yann; Palmroth, Minna; Ganse, Urs

2016-07-01

The majority of the global magnetospheric dynamics is driven by magnetic reconnection, indicating the need to understand and predict reconnection processes and their global consequences. So far, global magnetospheric dynamics has been simulated using mainly magnetohydrodynamic (MHD) models, which are approximate but fast enough to be executed in real time or near-real time. Due to their fast computation times, MHD models are currently the only possible frameworks for space weather predictions. However, in MHD models reconnection is not treated kinetically. In this presentation we will compare the results from global kinetic (hybrid-Vlasov) and global MHD simulations. Both simulations are compared with in-situ measurements. We will show that the kinetic processes at the bow shock, in the magnetosheath and at the magnetopause affect global dynamics even during steady solar wind conditions. Foreshock processes cause an asymmetry in the magnetosheath plasma, indicating that the plasma entering the magnetosphere is not symmetrical on different sides of the magnetosphere. Behind the bow shock in the magnetosheath kinetic wave modes appear. Some of these waves propagate to the magnetopause and have an effect on the magnetopause reconnection. Therefore we find that kinetic phenomena have a significant role in the interaction between the solar wind and the magnetosphere. While kinetic models cannot be executed in real time currently, they could be used to extract heuristics to be added in the faster MHD models.

Photometric light curves for ten rapidly rotating stars in Alpha Persei, the Pleiades, and the field

Science.gov (United States)

Prosser, Charles F.; Schild, Rudolph E.; Stauffer, John R.; Jones, Burton F.

1993-01-01

We present the results from a photometric monitoring program of ten rapidly rotating stars observed during 1991 using the FLWO 48-in. telescope. Brightness variations for an additional six cluster stars observed with the Lick 40-in. telescope are also given. The periods and light curves for seven Alpha Persei members, two Pleiades members, and one naked T Tauri field star are reported.

Global Current Circuit Structure in a Resistive Pulsar Magnetosphere Model

Science.gov (United States)

Kato, Yugo. E.

2017-12-01

Pulsar magnetospheres have strong magnetic fields and large amounts of plasma. The structures of these magnetospheres are studied using force-free electrodynamics. To understand pulsar magnetospheres, discussions must include their outer region. However, force-free electrodynamics is limited in it does not handle dissipation. Therefore, a resistive pulsar magnetic field model is needed. To break the ideal magnetohydrodynamic (MHD) condition E\\cdot B=0, Ohm’s law is used. This work introduces resistivity depending upon the distance from the star and obtain a self-consistent steady state by time integration. Poloidal current circuits form in the magnetosphere while the toroidal magnetic field region expands beyond the light cylinder and the Poynting flux radiation appears. High electric resistivity causes a large space scale poloidal current circuit and the magnetosphere radiates a larger Poynting flux than the linear increase outside of the light cylinder radius. The formed poloidal-current circuit has width, which grows with the electric conductivity. This result contributes to a more concrete dissipative pulsar magnetosphere model.

Hydromagnetic wave coupling in the magnetosphere

International Nuclear Information System (INIS)

Lee, D.

1990-01-01

The hydromagnetic wave phenomena in the magnetosphere has been an area of space physics and plasma physics where theory has been successful in explaining many features in satellite experiments and ground-based observations. Magnetohydrodynamic (MHD) waves, which are composed of transverse Alven waves and compressional waves, are usually coupled in space due to an inhomogeneous plasma density and curved magnetic field lines. In addition to these effects, hot temperature plasmas invoke various ultra low frequency (ULF) wave phenomena via macroscopic wave instabilities or wave particle resonant interactions. These properties of the coupling between the two different MHD waves were analytically and numerically studied in a simplified model such as the box model with straight field lines. However, the real magnetosphere is rather close to a dipole field, even though the night side of the magnetosphere is significantly distorted from dipole geometry. The curvature of field lines plays an important role in understanding hydromagnetic wave coupling in the magnetosphere since the MHD wave propagation depends strongly on the curved magnetic fields. The study of the hydromagnetic wave properties on an inhomogeneous and curved magnetic field system by considering realistic geometry is emphasized. Most of the current theories are reviewed and a number of observations are introduced according to the wave excitation mechanism. Studies are also performed with the development of numerical models such as the two and three dimensional MHD dipole models. An attempt is made to understand and classify the hydromagnetic wave behavior in inhomogeneous and hot plasmas with respect to the energy sources and their frequency band in the magnetosphere. Therefore, various excitation mechanisms for hydromagnetic waves are examined to compare analytical and numerical results with the observations

Interactions of planetary magnetospheres with icy satellite surfaces

International Nuclear Information System (INIS)

Cheng, A.F.; Haff, P.K.; Johnson, R.E.; Lanzerotti, L.J.

1986-01-01

When natural satellites and ring particles are embedded within magnetospheric plasmas, the charged particles interact with the surfaces of these solid bodies. These interactions have important implications for the surface, the atmosphere of the parent body, and the magnetosphere as a whole. Significant erosion of the surface by sputtering, as well as redeposition of sputter ejecta, can occur over geologic time. The surface can also be chemically modified. Sputter ejecta can make important contributions to the atmosphere; sputtering provides a lower limit to the atmospheric column density even for arbitrarily cold satellite surfaces. Sputter ejecta escaping from the parent body can form extensive neutral clouds within the magnetosphere. Ionization and dissociation within these neutral clouds can be dominant sources of low-energy plasma. The importance of these processes is discussed for the satellites and magnetospheres of Jupiter, Saturn and Uranus

Solar wind and its interaction with the Earth magnetosphere

International Nuclear Information System (INIS)

Grib, S.A.

1978-01-01

A critical review is given regarding the research of the stationary and non-stationary interaction of the solar wind with the Earth magnetosphere. Highlighted is the significance of the interplanetary magnetic field in the non-stationary movement of the solar wind flux. The problem of the solar wind shock waves interaction with the ''bow wave-Earth's magnetosphere'' system is being solved. Considered are the secondary phenomena, as a result of which the depression-type wave occurs, that lowers the pressure on the Earth's maanetosphere. The law, governing the movement of the magnetosphere subsolar point during the abrupt start of a geomagnetic storm has been discovered. Stationary circumvention of the magnetosphere by the solar wind flux is well described by the gas dynamic theory of the hypersonic flux. Non-stationary interaction of the solar wind shock waves with the magnetosphere is magnetohydrodynamic. It is pointed out, that the problems under consideration are important for the forecasting of strong geomagnetic perturbations on the basis of cosmic observations

Energetic Nitrogen Ions within the Inner Magnetosphere of Saturn

Science.gov (United States)

Sittler, E. C.; Johnson, R. E.; Richardson, J. D.; Jurac, S.; Moore, M.; Cooper, J. F.; Mauk, B. H.; Smith, H. T.; Michael, M.; Paranicus, C.; Armstrong, T. P.; Tsurutani, B.; Connerney, J. E. P.

2003-05-01

Titan's interaction with Saturn's magnetosphere will result in the energetic ejection of atomic nitrogen atoms into Saturn's magnetosphere due to dissociation of N2 by electrons, ions, and UV photons. The ejection of N atoms into Saturn's magnetosphere will form a nitrogen torus around Saturn with mean density of about 4 atoms/cm3 with source strength of 4.5x1025 atoms/sec. These nitrogen atoms are ionized by photoionization, electron impact ionization and charge exchange reactions producing an N+ torus of 1-4 keV suprathermal ions centered on Titan's orbital position. We will show Voyager plasma observations that demonstrate presence of a suprathermal ion component within Saturn's outer magnetosphere. The Voyager LECP data also reported the presence of inward diffusing energetic ions from the outer magnetosphere of Saturn, which could have an N+ contribution. If so, when one conserves the first and second adiabatic invariant the N+ ions will have energies in excess of 100 keV at Dione's L shell and greater than 400 keV at Enceladus' L shell. Energetic charged particle radial diffusion coefficients are also used to constrain the model results. But, one must also consider the solar wind as another important source of keV ions, in the form of protons and alpha particles, for Saturn's outer magnetosphere. Initial estimates indicate that a solar wind source could dominate in the outer magnetosphere, but various required parameters for this estimate are highly uncertain and will have to await Cassini results for confirmation. We show that satellite sweeping and charged particle precipitation within the middle and outer magnetosphere will tend to enrich N+ ions relative to protons within Saturn's inner magnetosphere as they diffuse radially inward for radial diffusion coefficients that do not violate observations. Charge exchange reactions within the inner magnetosphere can be an important loss mechanism for O+ ions, but to a lesser degree for N+ ions. Initial LECP

The use of iron charge state changes as a tracer for solar wind entry and energization within the magnetosphere

Directory of Open Access Journals (Sweden)

T. A. Fritz

Full Text Available The variation of the charge state of iron [Fe] ions is used to trace volume elements of plasma in the solar wind into the magnetosphere and to determine the time scales associated with the entry into and the action of the magnetospheric energization process working on these plasmas. On 2–3 May 1998 the Advanced Composition Explorer (ACE spacecraft located at the L1 libration point observed a series of changes to the average charge state of the element Fe in the solar wind plasma reflecting variation in the coronal temperature of their original source. Over the period of these two days the average Fe charge state was observed to vary from + 15 to + 6 both at the Polar satellite in the high latitude dayside magnetosphere and at ACE. During a period of southward IMF the observations at Polar inside the magnetosphere of the same Fe charge state were simultaneous with those at ACE delayed by the measured convection speed of the solar wind to the subsolar magnetopause. Comparing the phase space density as a function of energy at both ACE and Polar has indicated that significant energization of the plasma occurred on very rapid time scales. Energization at constant phase space density by a factor of 5 to 10 was observed over a range of energy from a few keV to about 1 MeV. For a detector with a fixed energy threshold in the range from 10 keV to a few hundred keV this observed energization will appear as a factor of ~10³ increase in its counting rate. Polar observations of very energetic O⁺ ions at the same time indicate that this energization process must be occurring in the high latitude cusp region inside the magnetosphere and that it is capable of energizing ionospheric ions at the same time.

Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetospheric configuration and dynamics; solar wind-magnetosphere interactions

Auroral vortex street formed by the magnetosphere-ionosphere coupling instability

Science.gov (United States)

Hiraki, Y.

2015-02-01

By performing three-dimensional magnetohydrodynamic simulations including Alfvén eigenmode perturbations most unstable to the ionospheric feedback effects, we examined the auroral vortex street that often appears just before substorm onset. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. We also found that there is a critical convection electric field for growth of the Alfvén eigenmodes. The vortex street is shown to be a consequence of coupling between the magnetospheric Alfvén waves carrying field-aligned currents and the ionospheric density waves driven by Pedersen/Hall currents.

Internal rotation of the Sun

International Nuclear Information System (INIS)

Duvall, T.L. Jr.; Goode, P.R.; Gouch, D.O.

1984-01-01

The frequency difference between prograde and retrograde sectoral solar oscillations is analysed to determine the rotation rate of the solar interior, assuming no latitudinal dependence. Much of the solar interior rotates slightly less rapidly than the surface, while the innermost part apparently rotates more rapidly. The resulting solar gravitational quadrupole moment is J 2 = (1.7 +- 0.4) x 10 -7 and provides a negligible contribution to current planetary tests of Einstein's theory of general relativity. (author)

Ultra high energy electrons powered by pulsar rotation.

Science.gov (United States)

Mahajan, Swadesh; Machabeli, George; Osmanov, Zaza; Chkheidze, Nino

2013-01-01

A new mechanism of particle acceleration, driven by the rotational slow down of the Crab pulsar, is explored. The rotation, through the time dependent centrifugal force, can efficiently excite unstable Langmuir waves in the electron-positron (hereafter e(±)) plasma of the star magnetosphere. These waves, then, Landau damp on electrons accelerating them in the process. The net transfer of energy is optimal when the wave growth and the Landau damping times are comparable and are both very short compared to the star rotation time. We show, by detailed calculations, that these are precisely the conditions for the parameters of the Crab pulsar. This highly efficient route for energy transfer allows the electrons in the primary beam to be catapulted to multiple TeV (~ 100 TeV) and even PeV energy domain. It is expected that the proposed mechanism may, unravel the puzzle of the origin of ultra high energy cosmic ray electrons.

The outer magnetosphere. [composition and comparison with earth

Science.gov (United States)

Schardt, A. W.; Behannon, K. W.; Lepping, R. P.; Carbary, J. F.; Eviatar, A.; Siscoe, G. L.

1984-01-01

Similarities between the Saturnian and terrestrial outer magnetosphere are examined. Saturn, like earth, has a fully developed magnetic tail, 80 to 100 RS in diameter. One major difference between the two outer magnetospheres is the hydrogen and nitrogen torus produced by Titan. This plasma is, in general, convected in the corotation direction at nearly the rigid corotation speed. Energies of magnetospheric particles extend to above 500 keV. In contrast, interplanetary protons and ions above 2 MeV have free access to the outer magnetosphere to distances well below the Stormer cutoff. This access presumably occurs through the magnetotail. In addition to the H+, H2+, and H3+ ions primarily of local origin, energetic He, C, N, and O ions are found with solar composition. Their flux can be substantially enhanced over that of interplanetary ions at energies of 0.2 to 0.4 MeV/nuc.

Vacuum Outer-Gap Structure in Pulsar Outer Magnetospheres

International Nuclear Information System (INIS)

Gui-Fang, Lin; Li, Zhang

2009-01-01

We study the vacuum outer-gap structure in the outer magnetosphere of rotation-powered pulsars by considering the limit of trans-field height through a pair production process. In this case, the trans-field height is limited by the photon-photon pair production process and the outer boundary of the outer gap can be extended outside the light cylinder. By solving self-consistently the Poisson equation for electrical potential and the Boltzmann equations of electrons/positrons and γ-rays in a vacuum outer gap for the parameters of Vela pulsar, we obtain an approximate geometry of the outer gap, i.e. the trans-field height is limited by the pair-production process and increases with the radial distance to the star and the width of the outer gap starts at the inner boundary (near the null charge surface) and ends at the outer boundary which locates inside or outside the light cylinder depending on the inclination angle. (geophysics, astronomy, and astrophysics)

The role of scientific ballooning for exploration of the magnetosphere

International Nuclear Information System (INIS)

Block, L.P.; Lazutin, L.L.; Riedler, W.

1984-11-01

The magnetosphere is explored in situ by satellites, but measurements near the low altitude magnetospheric boundary by rockets, balloons and groundbased instruments play a very significant role. The geomagnetic field provides a frame with anisotropic wave and particle propagation effects, enabling remote sensing of the distant magnetosphere by means of balloon-borne and groundbased instruments. Examples will be given of successful studies, with coordinated satellite and balloon observations, of substorm, pulsation and other phenomena propagating both along and across the geomagnetic field. Continued efforts with sophisticated balloon-borne instrumentations should contribute substantially to our understanding of magnetospheric physics. (Author)

Investigating stellar surface rotation using observations of starspots

DEFF Research Database (Denmark)

Korhonen, Heidi Helena

2011-01-01

Rapid rotation enhances the dynamo operating in stars, and thus also introduces significantly stronger magnetic activity than is seen in slower rotators. Many young cool stars still have the rapid, primordial rotation rates induced by the interstellar molecular cloud from which they were formed....... Also older stars in close binary systems are often rapid rotators. These types of stars can show strong magnetic activity and large starspots. In the case of large starspots which cause observable changes in the brightness of the star, and even in the shapes of the spectral line profiles, one can get...... information on the rotation of the star. At times even information on the spot rotation at different stellar latitudes can be obtained, similarly to the solar surface differential rotation measurements using magnetic features as tracers. Here, I will review investigations of stellar rotation based...

Comparative time-series analysis of MeV electron data by Ulysses and Pioneer 10/11 in the Jovian magnetosphere

International Nuclear Information System (INIS)

Dunzlaff, P.; Kiel Univ.; Heber, B.; Kopp, A.; North-West Univ., Potchefstroom; Potgieter, M.S.

2013-01-01

The dynamics of the Jovian magnetosphere is dominated by the planet's fast rotation with a period of ∝ 10 h.Within the magnetosphere, this periodicity can in particular be seen in the temporal variation of the spectral index of MeV electrons: every ∝ 10 h the counting rates show a maximum (minimum), while the spectral index shows a minimum (maximum) known as the Jovian ''clock'' mechanism. In this study we re-analyse Ulysses and Pioneer 10/11 data and show that another periodic modulation in the MeV electrons can be identified, manifested by local maxima of the spectral index and local minima of the counting rates. For Ulysses, this modulation can be observed throughout the magnetosphere near the magnetic equator, suggesting an azimuthal asymmetric distribution of MeV electrons near the current sheet. This modulation is found to trail the ''clock'' mechanism by ∝ 3.25 h. The Pioneer 10 data, however, only show occasional evidence of the presence of these local maxima while there is no evidence of this modulation in the Pioneer 11 data. A comparison of the times of observed minor peaks and Ulysses' distance from the current sheet using a simple rigid disc model as well as the model of Khurana and Schwarzl (2005) is performed.

Charged dust in saturn's magnetosphere

International Nuclear Information System (INIS)

Mendis, D.A.; Hill, J.R.; Houpis, H.L.F.

1983-01-01

Gravito-electrodynamic theory of charged dust grains is used to explain a variety of phenomena in those portions of the Saturnian ring system that are known to be dominated by fine (micron- and submicron-sized) dust, and in which collisional forces and Coulomb drag can be neglected. Among the phenomena discussed are the formation and evolution of the rotating near-radial spokes in the B-ring, the formation of waves in the F-ring, the cause of eccentricities of certain isolated ringlets, and the origin and morphology of the broad diffuse E-ring. Several novel processes predicted by the gravitoelectrodynamic theory, including 'magneto-gravitational capture' of exogenic dust by the magnetosphere, '1:1 magneto-gravitational orbital resonances' of charged dust with nearby satellites, and 'gyro-orbital resonances,' are used to explain individual observations. The effect of a ring current associated with this charged dust is also evaluated. Finally, the cosmogonic implications of the magneto-gravitational theory are briefly discussed. While several (although not all) of these processes have been discussed by one or more of the present authors elsewhere, the purpose of this paper is to synthesize all these processes within the framework of gravito-electrodynamics, and also to show its range of applicability within Saturn's ring system

Hydromagnetic Waves in the Magnetosphere and the Ionosphere

CERN Document Server

Alperovich, Leonid S

2007-01-01

The book deals with Ultra-Low-Frequency (ULF)-electromagnetic waves observed on Earth and in Space. These are so-called geomagnetic variations or pulsations. Alfvén's discovery related to the influence of the strong magnetic field on the conducting fluids (magnetohydrodynamics) led to development of the concept that the ULF-waves are magnetospheric magnetohydrodynamic (MHD)-waves. MHD-waves at their propagation gather information about the magnetosphere, ionosphere, and the ground. There are two applied aspects based on using the ULF electromagnetic oscillations. The first one is the ground-based diagnostics of the magnetosphere. This is an attempt to monitor in the real time the magnetosphere size, distance to the last closed field-lines, distribution of the cold plasma, etc. The second one is the deep electromagnetic sounding of the Earth. The basis for these studies is the capability of any electromagnetic wave to penetrate a conductor to a finite depth. The ULF-waves can reach the depth of a few hundred ...

Electric fields in the magnetosphere

International Nuclear Information System (INIS)

Falthammar, C.G.

1989-01-01

Electric field measurements on the satellites GEOS-1, GEOS-2, ISEE-1, and Viking have extended the empirical knowledge of electric fields in space so as to include the outer regions of the magnetosphere. While the measurements confirm some of the theoretically expected properties of the electric fields, they also reveal unexpected features and a high degree of complexity and variability. The existence of a magnetospheric dawn-to-dusk electric field, as expected on the basis of extrapolation from low altitude measurements, is confirmed in an average sense. However, the actual field exhibits large spatial and temporal variations, including strong fields of inductive origin. At the magnetopause, the average (dawn-to-dusk directed) tangential electric field component is typically obscured by irregular fluctuations of larger amplitude. The magnetic-field aligned component of the electric field, which is of particular importance for ionosphere-magnetosphere coupling and for auroral acceleration, is even now very difficult to measure directly. However, the data from electric field measurements provide further support for the conclusion, based on a variety of evidence, that a non-vanishing magnetic-field aligned electric field exists in the auroral acceleration region

Mission Concept to Connect Magnetospheric Physical Processes to Ionospheric Phenomena

Science.gov (United States)

Dors, E. E.; MacDonald, E.; Kepko, L.; Borovsky, J.; Reeves, G. D.; Delzanno, G. L.; Thomsen, M. F.; Sanchez, E. R.; Henderson, M. G.; Nguyen, D. C.; Vaith, H.; Gilchrist, B. E.; Spanswick, E.; Marshall, R. A.; Donovan, E.; Neilson, J.; Carlsten, B. E.

2017-12-01

On the Earth's nightside the magnetic connections between the ionosphere and the dynamic magnetosphere have a great deal of uncertainty: this uncertainty prevents us from scientifically understanding what physical processes in the magnetosphere are driving the various phenomena in the ionosphere. Since the 1990s, the space plasma physics group at Los Alamos National Laboratory has been working on a concept to connect magnetospheric physical processes to auroral phenomena in the ionosphere by firing an electron beam from a magnetospheric spacecraft and optically imaging the beam spot in the ionosphere. The magnetospheric spacecraft will carry a steerable electron accelerator, a power-storage system, a plasma contactor, and instruments to measure magnetic and electric fields, plasma, and energetic particles. The spacecraft orbit will be coordinated with a ground-based network of cameras to (a) locate the electron beam spot in the upper atmosphere and (b) monitor the aurora. An overview of the mission concept will be presented, including recent enabling advancements based on (1) a new understanding of the dynamic spacecraft charging of the accelerator and plasma-contactor system in the tenuous magnetosphere based on ion emission rather than electron collection, (2) a new understanding of the propagation properties of pulsed MeV-class beams in the magnetosphere, and (3) the design of a compact high-power 1-MeV electron accelerator and power-storage system. This strategy to (a) determine the magnetosphere-to-ionosphere connections and (b) reduce accelerator- platform charging responds to one of the six emerging-technology needs called out in the most-recent National Academies Decadal Survey for Solar and Space Physics. [LA-UR-17-23614

Anomalous Hydrodynamics and Normal Fluids in Rapidly Rotating Bose-Einstein Condensates

International Nuclear Information System (INIS)

Bourne, A.; Wilkin, N.K.; Gunn, J.M.F.

2006-01-01

In rapidly rotating condensed Bose systems we show that there is a regime of anomalous hydrodynamics which coincides with the mean field quantum Hall regime. A consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show that there are constraints which connect spatial variations of density and phase and that the vortex positions are not the simplest description of the dynamics. We demonstrate, inter alia, a simple relation between vortices and surface waves. We show that the surface waves can emulate a 'normal fluid', allowing dissipation by energy and angular momentum absorbtion from vortex motion in the trap. The time scale is sensitive to the initial configuration, which can lead to long-lived vortex patches--perhaps related to those observed at JILA

Anomalous Hydrodynamics and Normal Fluids in Rapidly Rotating Bose-Einstein Condensates

Science.gov (United States)

Bourne, A.; Wilkin, N. K.; Gunn, J. M. F.

2006-06-01

In rapidly rotating condensed Bose systems we show that there is a regime of anomalous hydrodynamics which coincides with the mean field quantum Hall regime. A consequence is the absence of a normal fluid in any conventional sense. However, even the superfluid hydrodynamics is not described by conventional Bernoulli and continuity equations. We show that there are constraints which connect spatial variations of density and phase and that the vortex positions are not the simplest description of the dynamics. We demonstrate, inter alia, a simple relation between vortices and surface waves. We show that the surface waves can emulate a “normal fluid,” allowing dissipation by energy and angular momentum absorbtion from vortex motion in the trap. The time scale is sensitive to the initial configuration, which can lead to long-lived vortex patches—perhaps related to those observed at JILA.

Multiple discrete-energy ion features in the inner magnetosphere: 9 February 1998, event

Directory of Open Access Journals (Sweden)

Y. Ebihara

2004-04-01

Full Text Available Multiple discrete-energy ion bands observed by the Polar satellite in the inner magnetosphere on 9 February 1998 were investigated by means of particle simulation with a realistic model of the convection electric field. The multiple bands appeared in the energy vs. L spectrum in the 1–100 keV range when Polar traveled in the heart of the ring current along the outbound and inbound paths. We performed particle tracing, and simulated the energy vs. L spectra of proton fluxes under the dipole magnetic field, the corotation electric field, and the realistic convection electric field model with its parameters depending on the solar wind data. Simulated spectra are shown to agree well with the observed ones. A better agreement is achieved when we rotate the convection electric potential eastward by 2h inMLT and we change the distribution function in time in the near-Earth magnetotail. It is concluded that the multiple bands are likely produced by two processes for this particular event, that is, changes in the convection electric field (for >3keV protons and changes in the distribution function in the near-Earth magnetotail (for <3keV protons. Key words. Magnetospheric physics (energetic particles, trapped; electric field – Space plasma physics (numerical simulation studies

Impulsive ion acceleration in earth's outer magnetosphere

International Nuclear Information System (INIS)

Baker, D.N.; Belian, R.D.

1985-01-01

Considerable observational evidence is found that ions are accelerated to high energies in the outer magnetosphere during geomagnetic disturbances. The acceleration often appears to be quite impulsive causing temporally brief (10's of seconds), very intense bursts of ions in the distant plasma sheet as well as in the near-tail region. These ion bursts extend in energy from 10's of keV to over 1 MeV and are closely associated with substorm expansive phase onsets. Although the very energetic ions are not of dominant importance for magnetotail plasma dynamics, they serve as an important tracer population. Their absolute intensity and brief temporal appearance bespeaks a strong and rapid acceleration process in the near-tail, very probably involving large induced electric fields substantially greater than those associated with cross-tail potential drops. Subsequent to their impulsive acceleration, these ions are injected into the outer trapping regions forming ion ''drift echo'' events, as well as streaming tailward away from their acceleration site in the near-earth plasma sheet. Most auroral ion acceleration processes occur (or are greatly enhanced) during the time that these global magnetospheric events are occurring in the magnetotail. A qualitative model relating energetic ion populations to near-tail magnetic reconnection at substorm onset followed by global redistribution is quite successful in explaining the primary observational features. Recent measurements of the elemental composition and charge-states have proven valuable for showing the source (solar wind or ionosphere) of the original plasma population from which the ions were accelerated

Wave--particle interactions in the magnetosphere and ionosphere

International Nuclear Information System (INIS)

Thorne, R.M.

1975-01-01

Two distinct aspects of the interaction between waves and particles in the earth's magnetosphere and ionosphere were discussed at the Yosemite Conference on Magnetosphere-Ionosphere Coupling; these will be briefly reviewed. Intense field-aligned currents flow between the ionosphere and magnetosphere at auroral latitudes. Under certain conditions these currents can become unstable, permitting potential drops to be established along the field lines. The present status of experimental evidence favoring such parallel electric fields is somewhat controversial. Theoretical models for their origin invoke regions of anomalous resistivity or electrostatic double layers. To date it is impossible to distinguish between these alternatives on the basis of experimental data. The nonadiabatic behavior of magnetospheric ring current particles during geomagnetic storms is largely controlled by wave-particle processes. During the storm main phase, intense fluctuating convection electric fields are responsible for injecting trapped particles into the outer radiation zone. The outer radiation zone also moves in closer to the earth following the storm time compression of the plasmapause. Simultaneous pitch angle scattering by higher-frequency plasma turbulence causes precipitation loss near the strong diffusion limit throughout the outer magnetosphere. During the storm recov []ry phase the plasmapause slowly moves out toward its prestorm location; energetic particle loss at such times appears to be dominated by cyclotron resonant scattering from electromagnetic turbulence. (auth)

The magnetosphere of the close accreting PMS binary V4046 Sgr

Directory of Open Access Journals (Sweden)

Gregory S. G.

2014-01-01

Full Text Available V4046 Sagittarii AB is a close short-period classical T Tauri binary. It is a circularised and synchronised system accreting from a circumbinary disk. In 2009 it was observed as part of a coordinated program involving near-simultaneous spectropolarimetric observations with ESPaDOnS at the Canada-France-Hawai’i Telescope and high-resolution X-ray observations with XMM-Newton. Magnetic maps of each star were derived from Zeeman-Doppler imaging. After briefly highlighting the most significant observational findings, we present a preliminary 3D model of the binary magnetosphere constructed from the magnetic maps using a newly developed binary magnetic field extrapolation code. The large-scale fields (the dipole components of both stars are highly tilted with respect to their rotation axes, and their magnetic fields are linked.

Inclined Pulsar Magnetospheres in General Relativity: Polar Caps for the Dipole, Quadrudipole, and Beyond

Science.gov (United States)

Gralla, Samuel E.; Lupsasca, Alexandru; Philippov, Alexander

2017-12-01

In the canonical model of a pulsar, rotational energy is transmitted through the surrounding plasma via two electrical circuits, each connecting to the star over a small region known as a “polar cap.” For a dipole-magnetized star, the polar caps coincide with the magnetic poles (hence the name), but in general, they can occur at any place and take any shape. In light of their crucial importance to most models of pulsar emission (from radio to X-ray to wind), we develop a general technique for determining polar cap properties. We consider a perfectly conducting star surrounded by a force-free magnetosphere and include the effects of general relativity. Using a combined numerical-analytical technique that leverages the rotation rate as a small parameter, we derive a general analytic formula for the polar cap shape and charge-current distribution as a function of the stellar mass, radius, rotation rate, moment of inertia, and magnetic field. We present results for dipole and quadrudipole fields (superposed dipole and quadrupole) inclined relative to the axis of rotation. The inclined dipole polar cap results are the first to include general relativity, and they confirm its essential role in the pulsar problem. The quadrudipole pulsar illustrates the phenomenon of thin annular polar caps. More generally, our method lays a foundation for detailed modeling of pulsar emission with realistic magnetic fields.

Investigating dynamical complexity in the magnetosphere using various entropy measures

Science.gov (United States)

Balasis, Georgios; Daglis, Ioannis A.; Papadimitriou, Constantinos; Kalimeri, Maria; Anastasiadis, Anastasios; Eftaxias, Konstantinos

2009-09-01

The complex system of the Earth's magnetosphere corresponds to an open spatially extended nonequilibrium (input-output) dynamical system. The nonextensive Tsallis entropy has been recently introduced as an appropriate information measure to investigate dynamical complexity in the magnetosphere. The method has been employed for analyzing Dst time series and gave promising results, detecting the complexity dissimilarity among different physiological and pathological magnetospheric states (i.e., prestorm activity and intense magnetic storms, respectively). This paper explores the applicability and effectiveness of a variety of computable entropy measures (e.g., block entropy, Kolmogorov entropy, T complexity, and approximate entropy) to the investigation of dynamical complexity in the magnetosphere. We show that as the magnetic storm approaches there is clear evidence of significant lower complexity in the magnetosphere. The observed higher degree of organization of the system agrees with that inferred previously, from an independent linear fractal spectral analysis based on wavelet transforms. This convergence between nonlinear and linear analyses provides a more reliable detection of the transition from the quiet time to the storm time magnetosphere, thus showing evidence that the occurrence of an intense magnetic storm is imminent. More precisely, we claim that our results suggest an important principle: significant complexity decrease and accession of persistency in Dst time series can be confirmed as the magnetic storm approaches, which can be used as diagnostic tools for the magnetospheric injury (global instability). Overall, approximate entropy and Tsallis entropy yield superior results for detecting dynamical complexity changes in the magnetosphere in comparison to the other entropy measures presented herein. Ultimately, the analysis tools developed in the course of this study for the treatment of Dst index can provide convenience for space weather

Nonlinear dynamical modeling and prediction of the terrestrial magnetospheric activity

International Nuclear Information System (INIS)

Vassiliadis, D.

1992-01-01

The irregular activity of the magnetosphere results from its complex internal dynamics as well as the external influence of the solar wind. The dominating self-organization of the magnetospheric plasma gives rise to repetitive, large-scale coherent behavior manifested in phenomena such as the magnetic substorm. Based on the nonlinearity of the global dynamics this dissertation examines the magnetosphere as a nonlinear dynamical system using time series analysis techniques. Initially the magnetospheric activity is modeled in terms of an autonomous system. A dimension study shows that its observed time series is self-similar, but the correlation dimension is high. The implication of a large number of degrees of freedom is confirmed by other state space techniques such as Poincare sections and search for unstable periodic orbits. At the same time a stability study of the time series in terms of Lyapunov exponents suggests that the series is not chaotic. The absence of deterministic chaos is supported by the low predictive capability of the autonomous model. Rather than chaos, it is an external input which is largely responsible for the irregularity of the magnetospheric activity. In fact, the external driving is so strong that the above state space techniques give results for magnetospheric and solar wind time series that are at least qualitatively similar. Therefore the solar wind input has to be included in a low-dimensional nonautonomous model. Indeed it is shown that such a model can reproduce the observed magnetospheric behavior up to 80-90 percent. The characteristic coefficients of the model show little variation depending on the external disturbance. The impulse response is consistent with earlier results of linear prediction filters. The model can be easily extended to contain nonlinear features of the magnetospheric activity and in particular the loading-unloading behavior of substorms

Echo 7: Magnetospheric properties determined by artificial electron beams

International Nuclear Information System (INIS)

Nemzek, R.J.

1990-01-01

The sounding rocket Echo 7 was launched from the Poker Flat Research Range. An on-board accelerator injected high-power electron beams into the magnetospheric tail near L = 6.5. After mirroring at the southern conjugate point, about 20 percent of the initial beam electrons returned to the North as Conjugate Echoes, where detectors (scintillators and spectrometers) on four subpayloads measured their energy and bounce time. The other 80 percent of the beam was pitch angle diffused by wave near the equatorial plane either into the conjugate atmosphere or up to mirror points above the payload. Comparison of measured values to calculations showed that the actual magnetosphere during the flight was well-described by the Tsyganenko-Usmanov model magnetosphere with a Kp value of 2- or 2+. Analysis of echo energies yielded values for the highly variable magnetospheric convection electric field

Rapidly rotating general relativistic stars. Pt. 2. Differentially rotating polytropes

Energy Technology Data Exchange (ETDEWEB)

Komatsu, Hidemi [Tokyo Univ. (Japan). Faculty of Science; Eriguchi, Yoshiharu [Tokyo Univ. (Japan). Dept. of Astronomy; Hachisu, Izumi [Kyoto Univ. (Japan). Dept. of Aeronautical Engineering

1989-07-01

We have applied the numerical method which was developed for Newtonian gravity to general relativistic, differentially rotating bodies including ring-like structures. A number of equilibrium structures are obtained for two different polytropic indices N=1/2 and N=3/2, because the various proposed equations of state for the nuclear density region fall into the range N=1/2 to 3/2 from the viewpoint of its softness. (author).

Modulation of cosmic microwave background polarization with a warm rapidly rotating half-wave plate on the Atacama B-Mode Search instrument.

Science.gov (United States)

Kusaka, A; Essinger-Hileman, T; Appel, J W; Gallardo, P; Irwin, K D; Jarosik, N; Nolta, M R; Page, L A; Parker, L P; Raghunathan, S; Sievers, J L; Simon, S M; Staggs, S T; Visnjic, K

2014-02-01

We evaluate the modulation of cosmic microwave background polarization using a rapidly rotating, half-wave plate (HWP) on the Atacama B-Mode Search. After demodulating the time-ordered-data (TOD), we find a significant reduction of atmospheric fluctuations. The demodulated TOD is stable on time scales of 500-1000 s, corresponding to frequencies of 1-2 mHz. This facilitates recovery of cosmological information at large angular scales, which are typically available only from balloon-borne or satellite experiments. This technique also achieves a sensitive measurement of celestial polarization without differencing the TOD of paired detectors sensitive to two orthogonal linear polarizations. This is the first demonstration of the ability to remove atmospheric contamination at these levels from a ground-based platform using a rapidly rotating HWP.

Current Sheets in Pulsar Magnetospheres and Winds: Particle Acceleration and Pulsed Gamma Ray Emission

Science.gov (United States)

Arons, Jonathan

The research proposed addresses understanding of the origin of non-thermal energy in the Universe, a subject beginning with the discovery of Cosmic Rays and continues, including the study of relativistic compact objects - neutron stars and black holes. Observed Rotation Powered Pulsars (RPPs) have rotational energy loss implying they have TeraGauss magnetic fields and electric potentials as large as 40 PetaVolts. The rotational energy lost is reprocessed into particles which manifest themselves in high energy gamma ray photon emission (GeV to TeV). Observations of pulsars from the FERMI Gamma Ray Observatory, launched into orbit in 2008, have revealed 130 of these stars (and still counting), thus demonstrating the presence of efficient cosmic accelerators within the strongly magnetized regions surrounding the rotating neutron stars. Understanding the physics of these and other Cosmic Accelerators is a major goal of astrophysical research. A new model for particle acceleration in the current sheets separating the closed and open field line regions of pulsars' magnetospheres, and separating regions of opposite magnetization in the relativistic winds emerging from those magnetopsheres, will be developed. The currents established in recent global models of the magnetosphere will be used as input to a magnetic field aligned acceleration model that takes account of the current carrying particles' inertia, generalizing models of the terrestrial aurora to the relativistic regime. The results will be applied to the spectacular new results from the FERMI gamma ray observatory on gamma ray pulsars, to probe the physics of the generation of the relativistic wind that carries rotational energy away from the compact stars, illuminating the whole problem of how compact objects can energize their surroundings. The work to be performed if this proposal is funded involves extending and developing concepts from plasma physics on dissipation of magnetic energy in thin sheets of

Energetic charged particles in the magnetosphere of Neptune

International Nuclear Information System (INIS)

Stone, E.C.; Cummings, A.C.; Looper, M.D.; Selesnick, R.S.; Lal, N.; McDonald, F.B.; Trainor, J.H.; Chenette, D.L.

1989-01-01

The Voyager 2 cosmic ray system (CRS) measured significant fluxes of energetic [approx-lt 1 megaelectron volt (MeV)] trapped electrons and protons in the magnetosphere of Neptune. The intensities at maximum near a magnetic L shell of 7, decreasing closer to the planet because of absorption by satellites and rings. In the region of the inner satellites of Neptune, the radiation belts have a complicated structure, which provides some constraints on the magnetic field geometry of the inner magnetosphere. Electron phase-space densities have a positive radial gradient, indicating that they diffuse inward from a source in the outer magnetosphere. Electron spectra from 1 to 5 MeV are generally well represented by power laws with indices near 6, which harden in the region of peak flux to power law indices of 4 to 5. Protons have significantly lower fluxes than electrons throughout the magnetosphere, with large anisotropies due to radial intensity gradients. The radiation belts resemble those of Uranus to the extent allowed by the different locations of the satellites, which limit the flux at each planet

Modeling magnetospheric plasma; Proceedings of the First Huntsville Workshop on Magnetosphere/Ionosphere Plasma Models, Guntersville, AL, Oct. 14-16, 1987

International Nuclear Information System (INIS)

Moore, T.E.; Waite, J.H. Jr.

1988-01-01

The conference presents papers on the global modeling of magnetospheric plasma processes, the modeling of the midlatitude ionosphere and plasmasphere, the modeling of the auroral zone and boundary layer, the modeling of the polar magnetosphere and ionosphere, and the modeling of the plasma sheet and ring current. Particular attention is given to the kinetic approach in magnetospheric plasma transport modeling, self-consistent neutral point current and fields from single particle dynamics, preliminary statistical survey of plasmaspheric ion properties from observations by DE 1/RIMS, and a model of auroral potential structures based on dynamics explorer plasma data. Other topics include internal shear layers in auroral dynamics, quantitative parameterization of energetic ionospheric ion outflow, and open flux merging in an expanding polarcap model

Plasma in Saturn's nightside magnetosphere and the implications for global circulation

Energy Technology Data Exchange (ETDEWEB)

Mcandrews, Hazel J [Los Alamos National Laboratory; Wilson, R J [Los Alamos National Laboratory; Henderson, M G [Los Alamos National Laboratory; Tokar, R L [Los Alamos National Laboratory; Jackman, C M [IMPERIAL COLLEGE; Khurana, K K [UNIV OF CAL; Sittler, E C [NASA/GSFC; Coates, A J [MSSL; Dougherty, M K [IMPERIAL COLLEGE

2009-01-01

We present a bulk ion flow map from the nightside equatorial region of Saturn's magnetosphere derived from the Cassini CAPS ion mass spectrometer data. The map clearly demonstrates the dominance of corotation flow over radial flow and suggests that the flux tubes sampled are still closed and attached to the planet up to distances of 50 R{sub s}. The plasma characteristics in the near-midnight region are described and indicate a transition between the region of the magnetosphere containing plasma on closed drift paths and that containing flux tubes which may not complete a full rotation around the planet. Data from the electron spectrometer reveal two plasma states of high and low density. These are attributed either to the sampling of mass-loaded and depleted flux tubes, respectively, or to the latitudinal structure of the plasma sheet Depleted, returning flux tubes are not, in general, directly observed in the ions, although the electron observations suggest that such a process must take place in order to produce the low density population. Flux tube content is conserved below a limIt defined by the mass-loading and magnetic field strength and indicates that the flux tubes sampled may survive their passage through the tail. The conditions for mass release are evaluated using measured densities, angular velocities and magnetic field strength, The results suggest that for the relatively dense ion populations detectable by IMS, the condition for flux-tube breakage has not yet been exceeded, However, the low-density regimes observed in the electron data suggest that loaded flux tubes at greater distances do exceed the threshold for mass loss and subsequently return to the inner magnetosphere significantly depleted of plasma.

Doppler-Zeeman Mapping of the Rapidly Rotating Magnetic CP Star HD37776

Science.gov (United States)

Khokhlova, V. L.; Vasilchenko, D. V.; Stepanov, V. V.; Romanyuk, I. I.

2000-03-01

We present the results of our analysis of magnetic-field configuration and abundance anomalies on the surface of the rapidly rotating, chemically peculiar helium-strong variable B2 V star HD37776 with unresolved Zeeman components of spectral lines. Simultaneous inversion of the observed Stokes I and V profiles, which realizes the method of Doppler-Zeeman mapping (Vasilchenko et al. 1996), has been applied for the first time. Spectroscopic observations were carried out with the Main stellar spectrograph of the 6-m Special Astrophysical Observatory telescope equipped with a Zeeman analyzer and a CCD array, which allowed spectra in right- and left-hand circularly polarized light to be taken simultaneously at a signal-to-noise ratio S/N > 200 (Romanyuk et al. 1999). The profile width of winged spectral lines (reaching 5 A) is determined by Zeeman line splitting; however, the observed Zeeman components are blurred and unresolved because of the rapid stellar rotation. When solving the inverse problem, we sought for the magnetic-field configuration in the form of a combination of arbitrarily oriented dipole, quadrupole, and octupole placed at the stellar center. The observed Stokes I and V profiles for eight spectral lines of He, OII, AlIII, SiIII, and FeIII averaged over the visible stellar surface were used as input data. We constructed a model of the magnetic field from the condition of coincidence of magnetic maps obtained from different lines of different chemical elements and from the condition of a minimum profile residual. This model is a combination of centered coaxial dipole and quadrupole with the dominant quadrupole component at 30 deg < i < 50 deg, beta = 40 deg, and a maximum surface field strength H_s = 60 kG. A comparison of our abundance maps with the field configuration shows that the He concentration is at a maximum in the regions of maximum radial field, while the maximum concentrations of O, Al, Si, and Fe coincide with the regions of maximum

Particle-in-Cell Simulations of the Twisted Magnetospheres of Magnetars. I.

Science.gov (United States)

Chen, Alexander Y.; Beloborodov, Andrei M.

2017-08-01

The magnetospheres of magnetars are believed to be filled with electron-positron plasma generated by electric discharge. We present a first numerical experiment demonstrating this process in an axisymmetric magnetosphere with a simple threshold prescription for pair creation, which is applicable to the inner magnetosphere with an ultrastrong field. The {e}+/- discharge occurs in response to the twisting of the closed magnetic field lines by a shear deformation of the magnetar surface, which launches electric currents into the magnetosphere. The simulation shows the formation of an electric “gap” with an unscreened electric field ({\\boldsymbol{E}}\\cdot {\\boldsymbol{B}}\

Massive-Star Magnetospheres: Now in 3-D!

Science.gov (United States)

Townsend, Richard

Magnetic fields are unexpected in massive stars, due to the absence of a dynamo convection zone beneath their surface layers. Nevertheless, kilogauss-strength, ordered fields were detected in a small subset of these stars over three decades ago, and the intervening years have witnessed the steady expansion of this subset. A distinctive feature of magnetic massive stars is that they harbor magnetospheres --- circumstellar environments where the magnetic field interacts strongly with the star's radiation-driven wind, confining it and channelling it into energetic shocks. A wide range of observational signatures are associated with these magnetospheres, in diagnostics ranging from X-rays all the way through to radio emission. Moreover, these magnetospheres can play an important role in massive-star evolution, by amplifying angular momentum loss in the wind. Recent progress in understanding massive-star magnetospheres has largely been driven by magnetohydrodynamical (MHD) simulations. However, these have been restricted to two- dimensional axisymmetric configurations, with three-dimensional configurations possible only in certain special cases. These restrictions are limiting further progress; we therefore propose to develop completely general three-dimensional models for the magnetospheres of massive stars, on the one hand to understand their observational properties and exploit them as plasma-physics laboratories, and on the other to gain a comprehensive understanding of how they influence the evolution of their host star. For weak- and intermediate-field stars, the models will be based on 3-D MHD simulations using a modified version of the ZEUS-MP code. For strong-field stars, we will extend our existing Rigid Field Hydrodynamics (RFHD) code to handle completely arbitrary field topologies. To explore a putative 'photoionization-moderated mass loss' mechanism for massive-star magnetospheres, we will also further develop a photoionization code we have recently

Corotation-driven magnetosphere-ionosphere coupling currents in Saturn’s magnetosphere and their relation to the auroras

Directory of Open Access Journals (Sweden)

S. W. H. Cowley

2003-08-01

Full Text Available We calculate the latitude profile of the equatorward-directed ionospheric Pedersen currents that are driven in Saturn’s ionosphere by partial corotation of the magnetospheric plasma. The calculation incorporates the flattened figure of the planet, a model of Saturn’s magnetic field derived from spacecraft flyby data, and angular velocity models derived from Voyager plasma data. We also employ an effective height-integrated ionospheric Pedersen conductivity of 1 mho, suggested by a related analysis of Voyager magnetic field data. The Voyager plasma data suggest that on the largest spatial scales, the plasma angular velocity declines from near-rigid corotation with the planet in the inner magnetosphere, to values of about half of rigid corotation at the outer boundary of the region considered. The latter extends to ~ 15–20 Saturn radii (RS in the equatorial plane, mapping along magnetic field lines to ~ 15° co-latitude in the ionosphere. We find in this case that the ionospheric Pedersen current peaks near the poleward (outer boundary of this region, and falls toward zero over ~ 5°–10° equator-ward of the boundary as the plasma approaches rigid corotation. The peak current near the poleward boundary, integrated in azimuth, is ~ 6 MA. The field-aligned current required for continuity is directed out of the ionosphere into the magnetosphere essentially throughout the region, with the current density peaking at ~ 10 nA m-2 at ~ 20° co-latitude. We estimate that such current densities are well below the limit requiring field-aligned acceleration of magnetospheric electrons in Saturn’s environment ( ~ 70 nAm-2, so that no significant auroral features associated with this ring of upward current is anticipated. The observed ultraviolet auroras at Saturn are also found to occur significantly closer to the pole (at ~ 10°–15° co-latitude, and show considerable temporal and local time variability, contrary to expectations for corotation

Surface conductivity of Mercury provides current closure and may affect magnetospheric symmetry

Directory of Open Access Journals (Sweden)

P. Janhunen

2004-04-01

Full Text Available We study what effect a possible surface conductivity of Mercury has on the closure of magnetospheric currents by making six runs with a quasi-neutral hybrid simulation. The runs are otherwise identical but use different synthetic conductivity models: run 1 has a fully conducting planet, run 2 has a poorly conducting planet ( m and runs 3-6 have one of the hemispheres either in the dawn-dusk or day-night directions, conducting well, the other one being conducting poorly. Although the surface conductivity is not known from observations, educated guesses easily give such conductivity values that magnetospheric currents may close partly within the planet, and as the conductivity depends heavily on the mineral composition of the surface, the possibility of significant horizontal variations cannot be easily excluded. The simulation results show that strong horizontal variations may produce modest magnetospheric asymmetries. Beyond the hybrid simulation, we also briefly discuss the possibility that in the nightside there may be a lack of surface electrons to carry downward current, which may act as a further source of surface-related magnetospheric asymmetry. Key words. Magnetospheric physics (planetary magnetospheres; current systems; solar wind-magnetosphere interactions.6

Breakdown of I-Love-Q Universality in Rapidly Rotating Relativistic Stars

Science.gov (United States)

Doneva, Daniela D.; Yazadjiev, Stoytcho S.; Stergioulas, Nikolaos; Kokkotas, Kostas D.

2014-01-01

It was shown recently that normalized relations between the moment of inertia (I), the quadrupole moment (Q), and the tidal deformability (Love number) exist and for slowly rotating neutron stars they are almost independent of the equation of state (EOS). We extend the computation of the I-Q relation to models rotating up to the mass-shedding limit and show that the universality of the relations is lost. With increasing rotation rate, the normalized I-Q relation departs significantly from its slow-rotation limit, deviating up to 40% for neutron stars and up to 75% for strange stars. The deviation is also EOS dependent and for a broad set of hadronic and strange matter EOSs the spread due to rotation is comparable to the spread due to the EOS, if one considers sequences with fixed rotational frequency. Still, for a restricted sample of modern realistic EOSs one can parameterize the deviations from universality as a function of rotation only. The previously proposed I-Love-Q relations should thus be used with care, because they lose their universality in astrophysical situations involving compact objects rotating faster than a few hundred Hz.

BREAKDOWN OF I-LOVE-Q UNIVERSALITY IN RAPIDLY ROTATING RELATIVISTIC STARS

International Nuclear Information System (INIS)

Doneva, Daniela D.; Yazadjiev, Stoytcho S.; Kokkotas, Kostas D.; Stergioulas, Nikolaos

2014-01-01

It was shown recently that normalized relations between the moment of inertia (I), the quadrupole moment (Q), and the tidal deformability (Love number) exist and for slowly rotating neutron stars they are almost independent of the equation of state (EOS). We extend the computation of the I-Q relation to models rotating up to the mass-shedding limit and show that the universality of the relations is lost. With increasing rotation rate, the normalized I-Q relation departs significantly from its slow-rotation limit, deviating up to 40% for neutron stars and up to 75% for strange stars. The deviation is also EOS dependent and for a broad set of hadronic and strange matter EOSs the spread due to rotation is comparable to the spread due to the EOS, if one considers sequences with fixed rotational frequency. Still, for a restricted sample of modern realistic EOSs one can parameterize the deviations from universality as a function of rotation only. The previously proposed I-Love-Q relations should thus be used with care, because they lose their universality in astrophysical situations involving compact objects rotating faster than a few hundred Hz

A New Approach to Modeling Jupiter's Magnetosphere

Science.gov (United States)

Fukazawa, K.; Katoh, Y.; Walker, R. J.; Kimura, T.; Tsuchiya, F.; Murakami, G.; Kita, H.; Tao, C.; Murata, K. T.

2017-12-01

The scales in planetary magnetospheres range from 10s of planetary radii to kilometers. For a number of years we have studied the magnetospheres of Jupiter and Saturn by using 3-dimensional magnetohydrodynamic (MHD) simulations. However, we have not been able to reach even the limits of the MHD approximation because of the large amount of computer resources required. Recently thanks to the progress in supercomputer systems, we have obtained the capability to simulate Jupiter's magnetosphere with 1000 times the number of grid points used in our previous simulations. This has allowed us to combine the high resolution global simulation with a micro-scale simulation of the Jovian magnetosphere. In particular we can combine a hybrid (kinetic ions and fluid electrons) simulation with the MHD simulation. In addition, the new capability enables us to run multi-parameter survey simulations of the Jupiter-solar wind system. In this study we performed a high-resolution simulation of Jovian magnetosphere to connect with the hybrid simulation, and lower resolution simulations under the various solar wind conditions to compare with Hisaki and Juno observations. In the high-resolution simulation we used a regular Cartesian gird with 0.15 RJ grid spacing and placed the inner boundary at 7 RJ. From these simulation settings, we provide the magnetic field out to around 20 RJ from Jupiter as a background field for the hybrid simulation. For the first time we have been able to resolve Kelvin Helmholtz waves on the magnetopause. We have investigated solar wind dynamic pressures between 0.01 and 0.09 nPa for a number of IMF values. These simulation data are open for the registered users to download the raw data. We have compared the results of these simulations with Hisaki auroral observations.

GALAXY ROTATION AND RAPID SUPERMASSIVE BINARY COALESCENCE

Energy Technology Data Exchange (ETDEWEB)

Holley-Bockelmann, Kelly [Vanderbilt University, Nashville, TN (United States); Khan, Fazeel Mahmood, E-mail: k.holley@vanderbilt.edu [Institute of Space Technology (IST), Islamabad (Pakistan)

2015-09-10

Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolution in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy.

GALAXY ROTATION AND RAPID SUPERMASSIVE BINARY COALESCENCE

International Nuclear Information System (INIS)

Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood

2015-01-01

Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolution in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy

Comparative time-series analysis of MeV electron data by Ulysses and Pioneer 10/11 in the Jovian magnetosphere

Energy Technology Data Exchange (ETDEWEB)

Dunzlaff, P. [North-West Univ., Potchefstroom (South Africa). Centre for Space Research; Kiel Univ. (Germany). Inst. fuer Experimentelle und Angewandte Physik; Heber, B. [Kiel Univ. (Germany). Inst. fuer Experimentelle und Angewandte Physik; Kopp, A. [Kiel Univ. (Germany). Inst. fuer Experimentelle und Angewandte Physik; North-West Univ., Potchefstroom (South Africa). Centre for Space Research; Potgieter, M.S. [North-West Univ., Potchefstroom (South Africa). Centre for Space Research

2013-11-01

The dynamics of the Jovian magnetosphere is dominated by the planet's fast rotation with a period of {proportional_to} 10 h.Within the magnetosphere, this periodicity can in particular be seen in the temporal variation of the spectral index of MeV electrons: every {proportional_to} 10 h the counting rates show a maximum (minimum), while the spectral index shows a minimum (maximum) known as the Jovian ''clock'' mechanism. In this study we re-analyse Ulysses and Pioneer 10/11 data and show that another periodic modulation in the MeV electrons can be identified, manifested by local maxima of the spectral index and local minima of the counting rates. For Ulysses, this modulation can be observed throughout the magnetosphere near the magnetic equator, suggesting an azimuthal asymmetric distribution of MeV electrons near the current sheet. This modulation is found to trail the ''clock'' mechanism by {proportional_to} 3.25 h. The Pioneer 10 data, however, only show occasional evidence of the presence of these local maxima while there is no evidence of this modulation in the Pioneer 11 data. A comparison of the times of observed minor peaks and Ulysses' distance from the current sheet using a simple rigid disc model as well as the model of Khurana and Schwarzl (2005) is performed.

Magnetosphere, exosphere, and surface of Mercury

International Nuclear Information System (INIS)

Cheng, A.F.; Krimigis, S.M.; Johnson, R.E.; Lanzerotti, L.J.

1987-01-01

It is presently suggested in light of the atomic Na exosphere discovered for Mercury that this planet, like the Jupiter moon Io, is capable of maintaining a heavy ion magnetosphere. Na(+) ions from the exosphere are in this scenario accelerated to keV energies en route to making substantial contributions to the mass and energy budgets of the magnetosphere. Since Mercury's Na supply to the exosphere is primarily internal, it would appear that Mercury is losing its semivolatiles and that this process will proceed by way of photosputtering, which maintains an adequate Na-ejection rate from the planet's surface. 39 references

Theory of imperfect magnetosphere-ionosphere coupling

International Nuclear Information System (INIS)

Kan, J.R.; Lee, L.C.

1980-01-01

Atheory of magnetosphere-ionosphere coupling in the presence of field-aligned potential drops is formulated within the framework of magnetohydrodynamic equations. Our formulation allows the magnetosphere as well as the ionosphere to respond self-consistently to the parallel potential drop along auroral field lines. Equipotential contours are distorted into a V-shaped structure near the convection reversal boundary and S-shaped on the equatorward side, each gives rise to an inverted V precipitation band. The loading effect of the imperfect coupling results in a valley in the electric field profile which occurs equatorward of the convection reversal boundary

Problems related to macroscopic electric fields in the magnetosphere

International Nuclear Information System (INIS)

Faelthammar, C.

1977-01-01

The macroscopic electric fields in the magnetosphere originate from internal as well as external sources. The fields are intimately coupled with the dynamics of magnetospheric plasma convection. They also depend on the complicated electrical properties of the hot collisionless plasma. Macroscopic electric fields are responsible for some important kinds of energization of charged particles that take place in the magnetosphere and affect not only particles of auroral energy but also, by multistep processes, trapped high-energy particles. A particularly interesting feature of magnetospheric electric fields is that they can have substantial components along the geomagnetic field, as has recently been confirmed by observations. Several physical mechanisms have been identified by which such electric fields can be supported even when collisions between particles are negligible. Comments are made on the magnetic mirror effect, anomalous resistivity, the collisionless thermoelectric effect, and electric double layers, emphasizing key features and differences and their significance in the light of recent observational data

Modelling Mercury's magnetosphere and plasma entry through the dayside magnetopause

Science.gov (United States)

Massetti, S.; Orsini, S.; Milillo, A.; Mura, A.

2007-09-01

Owing to the next space mission Messenger (NASA) and BepiColombo (ESA/JAXA), there is a renewed interest in modelling the Mercury's environment. The geometry of the Mercury's magnetosphere, as well as its response to the solar wind conditions, is one of the major issues. The weak magnetic field of the planet and the increasing weight of the IMF BX component at Mercury's orbit, introduce critical differences with respect to the Earth's case, such as a strong north-south asymmetry and a significant solar wind precipitation into the dayside magnetosphere even for non-negative IMF BZ. With the aim of analysing the interaction between the solar wind and Mercury's magnetosphere, we have developed an empirical-analytical magnetospheric model starting from the Toffoletto-Hill TH93 code. Our model has been tuned to reproduce the key features of the Mariner 10 magnetic data, and to mimic the magnetic field topology obtained by the self-consistent hybrid simulation developed by Kallio and Janhunen [Solar wind and magnetospheric ion impact on Mercury's magnetosphere. Geophys. Res. Lett. 30, 1877, doi: 10.1029/2003GL017842]. The new model has then been used to study the effect of the magnetic reconnection on the magnetosheath plasma entry through the open areas of the dayside magnetosphere (cusps), which are expected to be one of the main sources of charged particles circulating inside the magnetosphere. We show that, depending on the Alfvén speeds on both sides of the magnetopause discontinuity, the reconnection process would be able to accelerate solar wind protons up to few tens of keV: part of these ions can hit the surface and then trigger, via ion-sputtering, the refilling of the planetary exosphere. Finally, we show that non-adiabatic effects are expected to develop in the cusp regions as the energy gained by injected particles increases. The extent of these non-adiabatic regions is shown to be also modulated by upstream IMF condition.

Scaling laws for the rotational velocity of a J x B driven rotating plasma

International Nuclear Information System (INIS)

Igarashi, Yasuhito; Kataoka, Tomohiro; Ikehata, Takashi; Sato, Naoyuki; Tanabe, Toshio; Mase, Hiroshi

1994-01-01

Rapidly rotating plasmas of helium and argon have been extracted from a coaxial plasma gun operated in pulsed glow mode. The rotational velocity and its parametric dependence have been analyzed systematically by means of visible - emission spectroscopy. The plasma is observed to rotate rigidly inside the diameter of the gun anode while outside the velocity decreases rapidly ; furthermore, different ions are found to rotate at different angular frequencies as ω (Ar + ) = 0.5 x 10 6 rad/sec, ω (Ar 2+ ) = 1.1 x 10 6 rad/sec, ω (C 2+ ) = 1.8 x 10 6 rad/sec, ω (N + ) = 1.2 x 10 6 rad/sec. The plasma density and rotational velocity have been measured as a function of the discharge current and magnetic field to derive experimental scaling laws. They are summarized as : 1. Ion density is proportional to the square of discharge current. 2. Rotational and axial velocities are proportional to the driving force per ion. These results are confirmed to agree well with a theoretical prediction. (author)

Gamma-Ray Pulsar Light Curves as Probes of Magnetospheric Structure

Science.gov (United States)

Harding, A. K.

2016-01-01

The large number of gamma-ray pulsars discovered by the Fermi Gamma-Ray Space Telescope since its launch in 2008 dwarfs the handful that were previously known. The variety of observed light curves makes possible a tomography of both the ensemble-averaged field structure and the high-energy emission regions of a pulsar magnetosphere. Fitting the gamma-ray pulsar light curves with model magnetospheres and emission models has revealed that most of the high-energy emission, and the particles acceleration, takes place near or beyond the light cylinder, near the current sheet. As pulsar magnetosphere models become more sophisticated, it is possible to probe magnetic field structure and emission that are self-consistently determined. Light curve modeling will continue to be a powerful tool for constraining the pulsar magnetosphere physics.

The High-Energy Polarization-Limiting Radius of Neutron Star Magnetospheres 1, Slowly Rotating Neutron Stars

CERN Document Server

Heyl, J S; Lloyd, D; CERN. Geneva; Heyl, Jeremy S.; Shaviv, Nir J.; Lloyd, Don

2003-01-01

In the presence of strong magnetic fields, the vacuum becomes a birefringent medium. We show that this QED effect decouples the polarization modes of photons leaving the NS surface. Both the total intensity and the intensity in each of the two modes is preserved along a ray's path through the neutron-star magnetosphere. We analyze the consequences that this effect has on aligning the observed polarization vectors across the image of the stellar surface to generate large net polarizations. Counter to previous predictions, we show that the thermal radiation of NSs should be highly polarized even in the optical. When detected, this polarization will be the first demonstration of vacuum birefringence. It could be used as a tool to prove the high magnetic field nature of AXPs and it could also be used to constrain physical NS parameters, such as $R/M$, to which the net polarization is sensitive.

Evaluation of recent quantitative magnetospheric magnetic field models

International Nuclear Information System (INIS)

Walker, R.J.

1976-01-01

Recent quantitative magnetospheric field models contain many features not found in earlier models. Magnetopause models which include the effects of the dipole tilt were presented. More realistic models of the tail field include tail currents which close on the magnetopause, cross-tail currents of finite thickness, and cross-tail current models which model the position of the neutral sheet as a function of tilt. Finally, models have attempted to calculate the field of currents distributed in the inner magnetosphere. As the purpose of a magnetospheric model is to provide a mathematical description of the field that reasonably reproduces the observed magnetospheric field, several recent models were compared with the observed ΔB(B/sub observed/--B/sub main field/) contours. Models containing only contributions from magnetopause and tail current systems are able to reproduce the observed quiet time field only in an extremely qualitative way. The best quantitative agreement between models and observations occurs when currents distributed in the inner magnetosphere are added to the magnetopause and tail current systems. However, the distributed current models are valid only for zero tilt. Even the models which reproduce the average observed field reasonably well may not give physically reasonable field gradients. Three of the models evaluated contain regions in the near tail in which the field gradient reverses direction. One region in which all the models fall short is that around the polar cusp, though most can be used to calculate the position of the last closed field line reasonably well

The aurora and the magnetosphere - The Chapman Memorial Lecture. [dynamo theory development, 1600-present

Science.gov (United States)

Akasofu, S.-I.

1974-01-01

Review of recent progress in magnetospheric physics, in particular, in understanding the magnetospheric substorm. It is shown that a number of magnetospheric phenomena can now be understood by viewing the solar wind-magnetosphere interaction as an MHD dynamo; auroral phenomena are powered by the dynamo. Also, magnetospheric responses to variations of the north-south and east-west components of the interplanetary magnetic field have been identified. The magnetospheric substorm is entirely different from the responses of the magnetosphere to the southward component of the interplanetary magnetic field. It may be associated with the formation of a neutral line within the plasma sheet and with an enhanced reconnection along the line. A number of substorm-associated phenomena can be understood by noting that the new neutral line formation is caused by a short-circuiting of a part of the magnetotail current.

Possibility of detecting magnetospheric radio bursts from Uranus and Neptune

International Nuclear Information System (INIS)

Kennel, C.F.; Maggs, J.E.

1976-01-01

It is known that Earth, Jupiter and Saturn are sources of intense sporadic bursts of electromagnetic radiation, known as magnetospheric radio bursts. These bursts are here described. It is thought that the similarities in the power flux spectra, together with the burst occurrence patterns, suggest a common physical origin for these bursts in all three planets. The common mechanism may be noise amplification by field aligned currents, since it has been shown that the Earth's MRBs are associated with bright auroral arcs that involve intense field aligned currents. Such currents result from the interaction of the solar wind with the magnetosphere and should be a general feature of the interaction between the solar wind and planetary magnetospheres. If MRBs are produced by solar wind-magnetosphere interaction their total radiated power might scale with the solar wind input into the magnetosphere, and it has been suggested that the frequency of emission scales with the polar magnetic field strength of a planet. The intensity of MRBs is here scaled to the solar wind input and the frequency of emission to the polar field strength with a view to estimating the possibility of detecting MRBs from Uranus and Neptune. It is found that scaling of MRB power to the solar wind-magnetosphere dissipation power is probably a reasonable hypothesis. It is suggested that detection of MRB bursts from Uranus and Neptune might be a reasonable radioastronomy objective on future missions to the outer Solar System. (U.K.)

Factors associated with shift work disorder in nurses working with rapid-rotation schedules in Japan: the nurses' sleep health project.

Science.gov (United States)

Asaoka, Shoichi; Aritake, Sayaka; Komada, Yoko; Ozaki, Akiko; Odagiri, Yuko; Inoue, Shigeru; Shimomitsu, Teruichi; Inoue, Yuichi

2013-05-01

Workers who meet the criteria for shift work disorder (SWD) have elevated levels of risk for various health and behavioral problems. However, the impact of having SWD on shiftworkers engaged in rapid-rotation schedules is unknown. Moreover, the risk factors for the occurrence of SWD remain unclear. To clarify these issues, we conducted a questionnaire-based, cross-sectional survey on a sample of shiftworking nurses. Responses were obtained from 1202 nurses working at university hospitals in Tokyo, Japan, including 727 two-shift workers and 315 three-shift workers. The questionnaire included items relevant to age, gender, family structure, work environment, health-related quality of life (QOL), diurnal type, depressive symptoms, and SWD. Participants who reported insomnia and/or excessive sleepiness for at least 1 mo that was subjectively relevant to their shiftwork schedules were categorized as having SWD. The prevalence of SWD in the sampled shiftworking nurses was 24.4%; shiftworking nurses with SWD showed lower health-related QOL and more severe depressive symptoms, with greater rates of both actual accidents/errors and near misses, than those without SWD. The results of logistic regression analyses showed that more time spent working at night, frequent missing of nap opportunities during night work, and having an eveningness-oriented chronotype were significantly associated with SWD. The present study indicated that SWD might be associated with reduced health-related QOL and decreased work performance in shiftworking nurses on rapid-rotation schedules. The results also suggested that missing napping opportunities during night work, long nighttime working hours, and the delay of circadian rhythms are associated with the occurrence of SWD among shiftworking nurses on rapid-rotation schedules.

Magnetic reconnection in the terrestrial magnetosphere

International Nuclear Information System (INIS)

Feldman, W.C.

1984-01-01

An overview is given of quantitative comparisons between measured phenomena in the terrestrial magnetosphere thought to be associated with magnetic reconnection, and related theoretical predictions based on Petschek's simple model. Although such a comparison cannot be comprehensive because of the extended nature of the process and the relatively few in situ multipoint measurements made to date, the agreement is impressive where comparisons have been possible. This result leaves little doubt that magnetic reconnection does indeed occur in the terrestrial magnetosphere. The maximum reconnection rate, expressed in terms of the inflow Mach number, M/sub A/, is measured to be M/sub A/ = 0.2 +- 0.1

Magnetosphere as an Alfven maser

International Nuclear Information System (INIS)

Trakhtengerts, V.Yu.

1979-01-01

The Earth magnetosphere is considered as an Alfven maser. The operation mechanism of such a maser is duscussed. The main fact of this mechanism is ''overpopulation'' of the Earth radiation belt with particles moving with cross velocities. The cross velocity particles excess results in the excitation of cyclotron instability in the radiation belt and in the self-arbitrary increase of Alfven waves. At late the theory of cyclotron instability of radiation belts has been universally developed. On the basis of ideas on magnetosphere maser on cyclotron resonance it was possible to explain many geophysical phenomena such as periodical spillings out of particles from the radiation belts, pulsing polar lights, oscillations of magnetic force tubes etc. It is proposed to carry out active cosmic experiments to understand deeper the processes occuring in radiation belts

Recent investigation at INPE in magnetospheric physics and geomagnetism

International Nuclear Information System (INIS)

Gonzales, W.D.; Trivedi, N.B.

1984-01-01

During recent years the following research activities related to the earth's magnetosphere have been intensified: a) studies on electric field and energy transfer from the solar wind to the magnetosphere; b) studies on high latitude magnetospheric electric fields and on their penetration into the plasmasphere; c) measurements of atmospheric-large scale-electric fields, related to the low latitude magnetospheric-ionospheric coupling and to the local atmospheric electrodynamics, using detectors on board stratospheric balloons; and d) measurements of atmospheric X-rays, related to the process of energetic particle precipitation at the South Atlantic Magnetic Anomaly, using detectors also on board stratospheric balloons. Similarly, the following research activities related to geomagnetism are being pursued: a) studies on the variability of the geomagnetic field and on the dynamics of the equatorial electrojet from local geomagnetic field measurements; b) studies on terrestrial electromagnetic induction through local measurements of the geo-electromagnetic field; and c) studies on the influence of geomagnetic activity on particle precipitation at the South Atlantic Magnetic Anomaly. (Author) [pt

ON THE GLOBAL STRUCTURE OF PULSAR FORCE-FREE MAGNETOSPHERE

International Nuclear Information System (INIS)

Petrova, S. A.

2013-01-01

The dipolar magnetic field structure of a neutron star is modified by the plasma originating in the pulsar magnetosphere. In the simplest case of a stationary axisymmetric force-free magnetosphere, a self-consistent description of the fields and currents is given by the well-known pulsar equation. Here we revise the commonly used boundary conditions of the problem in order to incorporate the plasma-producing gaps and to provide a framework for a truly self-consistent treatment of the pulsar magnetosphere. A generalized multipolar solution of the pulsar equation is found, which, as compared to the customary split monopole solution, is suggested to better represent the character of the dipolar force-free field at large distances. In particular, the outer gap location entirely inside the light cylinder implies that beyond the light cylinder the null and critical lines should be aligned and become parallel to the equator at a certain altitude. Our scheme of the pulsar force-free magnetosphere, which will hopefully be followed by extensive analytic and numerical studies, may have numerous implications for different fields of pulsar research.

Laboratory simulation of energetic flows of magnetospheric planetary plasma

International Nuclear Information System (INIS)

Shaikhislamov, I F; Posukh, V G; Melekhov, A V; Boyarintsev, E L; Zakharov, Yu P; Prokopov, P A; Ponomarenko, A G

2017-01-01

Dynamic interaction of super-sonic counter-streaming plasmas moving in dipole magnetic dipole is studied in laboratory experiment. First, a quasi-stationary flow is produced by plasma gun which forms a magnetosphere around the magnetic dipole. Second, explosive plasma expanding from inner dipole region outward is launch by laser beams focused at the surface of the dipole cover. Laser plasma is energetic enough to disrupt magnetic field and to sweep through the background plasma for large distances. Probe measurements showed that far from the initially formed magnetosphere laser plasma carries within itself a magnetic field of the same direction but order of magnitude larger in value than the vacuum dipole field at considered distances. Because no compression of magnetic field at the front of laser plasma was observed, the realized interaction is different from previous experiments and theoretical models of laser plasma expansion into uniform magnetized background. It was deduced based on the obtained data that laser plasma while expanding through inner magnetosphere picks up a magnetized shell formed by background plasma and carries it for large distances beyond previously existing magnetosphere. (paper)

Magnetospheric Response Associated With Multiple Atmospheric Reflections of Precipitated Electrons in Aurora.

Science.gov (United States)

Khazanov, G. V.; Merkin, V. G.; Zesta, E.; Sibeck, D. G.; Grubbs, G. A., II; Chu, M.; Wiltberger, M. J.

2017-12-01

The magnetosphere and ionosphere are strongly coupled by precipitating electrons during storm times. Therefore, first principle simulations of precipitating electron fluxes are required to understand storm time variations of ionospheric conductances and related electric fields. As has been discussed by Khazanov et al. [2015 - 2017], the first step in such simulations is initiation of electron precipitation from the Earth's plasma sheet via wave particle interaction processes into both magnetically conjugate points, and the step 2 is the follow up of multiple atmospheric reflections of electron fluxes formed at the boundary between the ionosphere and magnetosphere of two magnetically conjugate points. To demonstrate this effect on the global magnetospheric response the Lyon-Fedder-Mobarry global magnetosphere model coupled with the Rice Convection Model of the inner magnetosphere has been used and run for the geomagnetic storm of 17 March 2013.

Penetration of magnetosonic waves into the magnetosphere: influence of a transition layer

Directory of Open Access Journals (Sweden)

A. S. Leonovich

Full Text Available We have constructed a theory for the penetration of magnetosonic waves from the solar wind into the magnetosphere through a transition layer in a plane-stratified model for the medium. In this model the boundary layer is treated as a region, inside of which the parameters of the medium vary from values characteristic for the magnetosphere, to values typical of the solar wind. It is shown that if such a layer has sufficiently sharp boundaries, then magnetosonic eigen-oscillations can be excited inside of it. The boundaries of such a layer are partially permeable for magnetosonic waves. Therefore, if the eigen-oscillations are not sustained by an external source, they will be attenuated, because some of the energy is carried away by the oscillations that penetrate the solar wind and the magnetosphere. It is shown that about 40% of the energy flux of the waves incident on the transition layer in the magnetotail region penetrate to the magnetosphere’s interior. This energy flux suffices to sustain the stationary convection of magnetospheric plasma. The total energy input to the magnetosphere during a time interval of the order of the substorm growth phase time is comparable with the energetics of an average substorm.

Key words. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions – Space plasma physics (kinetic and MHD theory

Penetration of magnetosonic waves into the magnetosphere: influence of a transition layer

Directory of Open Access Journals (Sweden)

A. S. Leonovich

2003-05-01

Full Text Available We have constructed a theory for the penetration of magnetosonic waves from the solar wind into the magnetosphere through a transition layer in a plane-stratified model for the medium. In this model the boundary layer is treated as a region, inside of which the parameters of the medium vary from values characteristic for the magnetosphere, to values typical of the solar wind. It is shown that if such a layer has sufficiently sharp boundaries, then magnetosonic eigen-oscillations can be excited inside of it. The boundaries of such a layer are partially permeable for magnetosonic waves. Therefore, if the eigen-oscillations are not sustained by an external source, they will be attenuated, because some of the energy is carried away by the oscillations that penetrate the solar wind and the magnetosphere. It is shown that about 40% of the energy flux of the waves incident on the transition layer in the magnetotail region penetrate to the magnetosphere’s interior. This energy flux suffices to sustain the stationary convection of magnetospheric plasma. The total energy input to the magnetosphere during a time interval of the order of the substorm growth phase time is comparable with the energetics of an average substorm.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions – Space plasma physics (kinetic and MHD theory

A STUDY OF VEGA: A RAPIDLY ROTATING POLE-ON STAR

International Nuclear Information System (INIS)

Hill, Graham; Gulliver, Austin F.; Adelman, Saul J.

2010-01-01

Ultra-high signal-to-noise, high dispersion spectroscopy over the wavelength range λλ4519-4535 shows Vega to be a rapidly rotating star with V eq of 211 km s -1 seen almost pole-on. The analysis of five independent series of spectroscopic data is combined with analyses of the hydrogen lines, Hγ, Hβ, and Hα, and the latest absolute continuum flux for Vega to yield the following results: Vsin i = 20.8 ± 0.2 km s -1 , polar T eff = 10, 000 ± 30 K, polar log g = 4.04 ± 0.01 dex, V eq = 211 ± 4 km s -1 , breakup fraction = 0.81 ± 0.02, microturbulence (ξ T ) = 1.0 ± 0.1 km s -1 , macroturbulence (ζ) = 7.4 ± 0.5 km s -1 , and an inclination i = 5. 0 7 ± 0. 0 1. The variations in T eff and log g over the photosphere total 1410 K and 0.26 dex, respectively, while the mean temperature is 9560 ± 30 K and log g is 3.95 ± 0.01 dex. Low level variations in the Ti II 4529 A profile are also illustrated.

Interplanetary Magnetic Field Control of the Entry of Solar Energetic Particles into the Magnetosphere

Science.gov (United States)

Richard, R. L.; El-Alaoui, M.; Ashour-Abdalla, M.; Walker, R. J.

2002-01-01

We have investigated the entry of energetic ions of solar origin into the magnetosphere as a function of the interplanetary magnetic field orientation. We have modeled this entry by following high energy particles (protons and 3 He ions) ranging from 0.1 to 50 MeV in electric and magnetic fields from a global magnetohydrodynamic (MHD) model of the magnetosphere and its interaction with the solar wind. For the most part these particles entered the magnetosphere on or near open field lines except for some above 10 MeV that could enter directly by crossing field lines due to their large gyroradii. The MHD simulation was driven by a series of idealized solar wind and interplanetary magnetic field (IMF) conditions. It was found that the flux of particles in the magnetosphere and transport into the inner magnetosphere varied widely according to the IMF orientation for a constant upstream particle source, with the most efficient entry occurring under southward IMF conditions. The flux inside the magnetosphere could approach that in the solar wind implying that SEPs can contribute significantly to the magnetospheric energetic particle population during typical SEP events depending on the state of the magnetosphere.

Rotational velocities of low-mass stars

International Nuclear Information System (INIS)

Stauffer, J.B.; Hartmann, L.W.; Harvard-Smithsonian Center for Astrophysics, Cambridge, MA)

1986-01-01

The rotational velocities of stars provide important clues to how stars form and evolve. Yet until recently, studies of stellar rotation were limited to stars more massive than the sun. This is beginning to change, and an observational outline of the rotational velocity evolution of stars less massive than the sun can now be provided. Low-mass stars rotate slowly during the early stages of premain-sequence evolution, and spin up as they contract to the main sequence. This spin-up culminates in a brief period of very rapid rotation at an age of order 50 million years. Physical interpretation of this increase in rotation and the subsequent main-sequence spin-down are complicated by the possibility of differential internal rotation. The observed rapidity of spin-down among G dwarfs suggests that initially only the outer convective envelopes of these stars are slowed. The data suggest an intrinsic spread in angular momentum among young stars of the same mass and age, a spread which is apparently minimized by the angular-momentum loss mechanism in old low-mass stars. 83 references

Ensemble downscaling in coupled solar wind-magnetosphere modeling for space weather forecasting.

Science.gov (United States)

Owens, M J; Horbury, T S; Wicks, R T; McGregor, S L; Savani, N P; Xiong, M

2014-06-01

Advanced forecasting of space weather requires simulation of the whole Sun-to-Earth system, which necessitates driving magnetospheric models with the outputs from solar wind models. This presents a fundamental difficulty, as the magnetosphere is sensitive to both large-scale solar wind structures, which can be captured by solar wind models, and small-scale solar wind "noise," which is far below typical solar wind model resolution and results primarily from stochastic processes. Following similar approaches in terrestrial climate modeling, we propose statistical "downscaling" of solar wind model results prior to their use as input to a magnetospheric model. As magnetospheric response can be highly nonlinear, this is preferable to downscaling the results of magnetospheric modeling. To demonstrate the benefit of this approach, we first approximate solar wind model output by smoothing solar wind observations with an 8 h filter, then add small-scale structure back in through the addition of random noise with the observed spectral characteristics. Here we use a very simple parameterization of noise based upon the observed probability distribution functions of solar wind parameters, but more sophisticated methods will be developed in the future. An ensemble of results from the simple downscaling scheme are tested using a model-independent method and shown to add value to the magnetospheric forecast, both improving the best estimate and quantifying the uncertainty. We suggest a number of features desirable in an operational solar wind downscaling scheme. Solar wind models must be downscaled in order to drive magnetospheric models Ensemble downscaling is more effective than deterministic downscaling The magnetosphere responds nonlinearly to small-scale solar wind fluctuations.

Electromagnetic field for an open magnetosphere

International Nuclear Information System (INIS)

Heikkila, W.J.

1984-01-01

The boundary-layer-dominated models of the earth EM field developed by Heikkila (1975, 1978, 1982, and 1983) and Heikkila et al. (1979) to account for deficiencies in the electric-field descriptions of quasi-steady-state magnetic-field-reconnection models (such as that of Cowley, 1980) are characterized, reviewing the arguments and indicating the most important implications. The mechanisms of boundary-layer formation and field direction reversal are explained and illustrated with diagrams, and it is inferred that boundary-layer phenomena rather than magnetic reconnection may be the cause of large-scale magnetospheric circulation, convection, plasma-sheet formation and sunward convection, and auroras, the boundary layer acting basically as a viscous process mediating solar-wind/magnetosphere interactions. 23 references

Magnetospheric radio sounding

International Nuclear Information System (INIS)

Ondoh, Tadanori; Nakamura, Yoshikatsu; Koseki, Teruo; Watanabe, Sigeaki; Murakami, Toshimitsu

1977-01-01

Radio sounding of the plasmapause from a geostationary satellite has been investigated to observe time variations of the plasmapause structure and effects of the plasma convection. In the equatorial plane, the plasmapause is located, on the average, at 4 R sub(E) (R sub(E); Earth radius), and the plasma density drops outwards from 10 2 -10 3 /cm 3 to 1-10/cm 3 in the plasmapause width of about 600 km. Plasmagrams showing a relation between the virtual range and sounding frequencies are computed by ray tracing of LF-VLF waves transmitted from a geostationary satellite, using model distributions of the electron density in the vicinity of the plasmapause. The general features of the plasmagrams are similar to the topside ionograms. The plasmagram has no penetration frequency such as f 0 F 2 , but the virtual range of the plasmagram increases rapidly with frequency above 100 kHz, since the distance between a satellite and wave reflection point increases rapidly with increasing the electron density inside the plasmapause. The plasmapause sounder on a geostationary satellite has been designed by taking account of an average propagation distance of 2 x 2.6 R sub(E) between a satellite (6.6 R sub(E)) and the plasmapause (4.0 R sub(E)), background noise, range resolution, power consumption, and receiver S/N of 10 dB. The 13-bit Barker coded pulses of baud length of 0.5 msec should be transmitted in direction parallel to the orbital plane at frequencies for 10 kHz-2MHz in a pulse interval of 0.5 sec. The transmitter peak power of 70 watts and 700 watts are required respectively in geomagnetically quiet and disturbed (strong nonthermal continuum emissions) conditions for a 400 meter cylindrical dipole of 1.2 cm diameter on the geostationary satellite. This technique will open new area of radio sounding in the magnetosphere. (auth.)

Magnetized Kelvin-Helmholtz instability: theory and simulations in the Earth's magnetosphere context

Science.gov (United States)

Faganello, Matteo; Califano, Francesco

2017-12-01

The Kelvin-Helmholtz instability, proposed a long time ago for its role in and impact on the transport properties at magnetospheric flanks, has been widely investigated in the Earth's magnetosphere context. This review covers more than fifty years of theoretical and numerical efforts in investigating the evolution of Kelvin-Helmholtz vortices and how the rich nonlinear dynamics they drive allow solar wind plasma bubbles to enter into the magnetosphere. Special care is devoted to pointing out the main advantages and weak points of the different plasma models that can be adopted for describing the collisionless magnetospheric medium and in underlying the important role of the three-dimensional geometry of the system.

Three-dimensional magnetospheric equilibrium with isotropic pressure

International Nuclear Information System (INIS)

Cheng, C.Z.

1995-05-01

In the absence of the toroidal flux, two coupled quasi two-dimensional elliptic equilibrium equations have been derived to describe self-consistent three-dimensional static magnetospheric equilibria with isotropic pressure in an optimal (Ψ,α,χ) flux coordinate system, where Ψ is the magnetic flux function, χ is a generalized poloidal angle, α is the toroidal angle, α = φ - δ(Ψ,φ,χ) is the toroidal angle, δ(Ψ,φ,χ) is periodic in φ, and the magnetic field is represented as rvec B = ∇Ψ x ∇α. A three-dimensional magnetospheric equilibrium code, the MAG-3D code, has been developed by employing an iterative metric method. The main difference between the three-dimensional and the two-dimensional axisymmetric solutions is that the field-aligned current and the toroidal magnetic field are finite for the three-dimensional case, but vanish for the two-dimensional axisymmetric case. With the same boundary flux surface shape, the two-dimensional axisymmetric results are similar to the three-dimensional magnetosphere at each local time cross section

Side-band mutual interactions in the magnetosphere

Science.gov (United States)

Chang, D. C. D.; Helliwell, R. A.; Bell, T. F.

1980-01-01

Sideband mutual interactions between VLF waves in the magnetosphere are investigated. Results of an experimental program involving the generation of sidebands by means of frequency shift keying are presented which indicate that the energetic electrons in the magnetosphere can interact only with sidebands generated by signals with short modulation periods. Using the value of the memory time during which electrons interact with the waves implied by the above result, it is estimated that the length of the electron interaction region in the magnetosphere is between 4000 and 2000 km. Sideband interactions are found to be similar to those between constant-frequency signals, exhibiting suppression and energy coupling. Results from a second sideband transmitting program show that for most cases the coherence bandwidth of sidebands is about 50 Hz. Sideband mutual interactions are then explained by the overlap of the ranges of the parallel velocity of the electrons which the sidebands organize, and the wave intensity in the interaction region is estimated to be 2.5-10 milli-gamma, in agreement with satellite measurements.

Geometric corrections due to inhomogeneous field in the magnetospheric double current layer

International Nuclear Information System (INIS)

Callebaut, D.K.; Van den Buys, A.M.

1985-01-01

The case of oblique incidence and of a slope in the magnetic field for plane parallel models of the magnetospheric double layer is considered. The two models are the Magnetospheric Double Layer (MDL) and the Magnetospheric Double Current Layer (MDCL). The latter is more appropriate but due to some approximations it gives sometimes incorrect results. An improved model uses a triple current layer. (R.P.)

Magnetospheric Plasma Physics : the Impact of Jim Dungey’s Research

CERN Document Server

Southwood, David; Mitton, Simon

2015-01-01

This book makes good background reading for much of modern magnetospheric physics. Its origin was a Festspiel for Professor Jim Dungey, former professor in the Physics Department at Imperial College on the occasion of his 90th birthday, 30 January 2013. Remarkably, although he retired 30 years ago, his pioneering and, often, maverick work in the 50’s through to the 70’s on solar terrestrial physics is probably more widely appreciated today than when he retired. Dungey was a theoretical plasma physicist. The book covers how his reconnection model of the magnetosphere evolved to become the standard model of solar-terrestrial coupling. Dungey’s open magnetosphere model now underpins a holistic picture explaining not only the magnetic and plasma structure of the magnetosphere, but also its dynamics which can be monitored in real time. The book also shows how modern day simulation of solar terrestrial coupling can reproduce the real time evolution of the solar terrestrial system in ways undreamt of in 1961 w...

Thick Escaping Magnetospheric Ion Layer in Magnetopause Reconnection with MMS Observations

Science.gov (United States)

Nagai, T.; Kitamura, N.; Hasagawa, H.; Shinohara, I.; Yokota, S.; Saito, Y.; Nakamura, R.; Giles, B. L.; Pollock, C.; Moore, T. E.;

Magnetospheric storm dynamics in terms of energy output rate

International Nuclear Information System (INIS)

Prigancova, A.; Feldstein, Ya.I.

1992-01-01

Using hourly values of both the global magnetospheric disturbance characteristic DR, and AE index of auroral ionospheric currents during magnetic storm intervals, the energy output rate dynamics is evaluated for a magnetic storm main/recovery phase and a whole storm interval. The magnetospheric response to the solar wind energy input rate under varying interplanetary and magnetospheric conditions is considered from the temporal variability point of view. The peculiarities of the response are traced separately. As far as quantitative characteristics of energy output rate are concerned, the time dependence pattern of the ring current decay parameter is emphasized to be fairly important. It is pointed out that more insight into the plasma processes, especially at L = 3 - 5, is needed for adequate evidence of the dependence. (Author)

Terrestrial VLF transmitter injection into the magnetosphere

Science.gov (United States)

Cohen, M. B.; Inan, U. S.

2012-08-01

Very Low Frequency (VLF, 3-30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly impact the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributing to the formation of the slot region. However, calculations of the global impacts of VLF waves are based on models of trans-ionospheric propagation to calculate the VLF energy reaching the magnetosphere. Limited comparisons of these models to individual satellite passes have found that the models may significantly (by >20 dB) overestimate amplitudes of ground based VLF transmitters in the magnetosphere. To form a much more complete empirical picture of VLF transmitter energy reaching the magnetosphere, we present observations of the radiation pattern from a number of ground-based VLF transmitters by averaging six years of data from the DEMETER satellite. We divide the slice at ˜700 km altitude above a transmitter into pixels and calculate the average field for all satellite passes through each pixel. There are enough data to see 25 km features in the radiation pattern, including the modal interference of the subionospheric signal mapped upwards. Using these data, we deduce the first empirical measure of the radiated power into the magnetosphere from these transmitters, for both daytime and nighttime, and at both the overhead and geomagnetically conjugate region. We find no detectable variation of signal intensity with geomagnetic conditions at low and mid latitudes (L ionospheric heating by one VLF transmitter which modifies the trans-ionospheric absorption of signals from other transmitters passing through the heated region.

Magnetic field in the magnetosphere. Numerical simulation of the magnetospheric magnetic field

International Nuclear Information System (INIS)

Mal'kov, M.V.

1993-01-01

The last version of the empirical model of the magnetospheric magnetic field (Tsyganenko, 1989) is considered. Total number of data used for construction of the model contains 36682 average vector values of the field. This number of data is obtained by satellite measurements at distances of r=4-66 R e (R e is the Earth radius). 5 figs., 2 tabs

General-relativistic pulsar magnetospheric emission

Science.gov (United States)

Pétri, J.

2018-06-01

Most current pulsar emission models assume photon production and emission within the magnetosphere. Low-frequency radiation is preferentially produced in the vicinity of the polar caps, whereas the high-energy tail is shifted to regions closer but still inside the light cylinder. We conducted a systematic study of the merit of several popular radiation sites like the polar cap, the outer gap, and the slot gap. We computed sky maps emanating from each emission site according to a prescribed distribution function for the emitting particles made of an electron/positron mixture. Calculations are performed using a three-dimensional integration of the plasma emissivity in the vacuum electromagnetic field of a rotating and centred general-relativistic dipole. We compare Newtonian electromagnetic fields to their general-relativistic counterpart. In the latter case, light bending is also taken into account. As a typical example, light curves and sky maps are plotted for several power-law indices of the particle distribution function. The detailed pulse profiles strongly depend on the underlying assumption about the fluid motion subject to strong electromagnetic fields. This electromagnetic topology enforces the photon propagation direction directly, or indirectly, from aberration effects. We also discuss the implication of a net stellar electric charge on to sky maps. Taking into account, the electric field strongly affects the light curves originating close to the light cylinder, where the electric field strength becomes comparable to the magnetic field strength.

Outstanding Issues and Future Directions of Inner Magnetospheric Research (Invited)

Science.gov (United States)

Brandt, P. C.

2009-12-01

Several research areas of the inner magnetosphere and ionosphere (MI) system have reached a state, where the coupling mechanisms can no longer be treated as boundary conditions or ad-hoc assumptions in our physical models. It is nothing new that our community has become increasingly aware of the necessity to use global measurements from multiple observation platforms and missions, in order to understand both the system as a whole as well as its individual subsystems. In this presentation we briefly review the current status and outstanding issues of inner MI research. We attempt to establish a working definition of the term "Systems Approach", then present observational tools and techniques that enable such an approach. Physical modeling plays a central role not only in understanding the mechanisms at work, but also in determining the key quantities to be measured. We conclude by discussing questions relevant to future directions. Are there new techniques that need more attention? Should multi-platform observations be included as a default component already at the mission-level in the future? Is solar minimum uninteresting from an MI perspective? Should we actively compare to magnetospheres of other planets? Examples of outstanding issues in inner MI research include the circulation of ionospheric plasma from low to high latitudes and its escape to the magnetosphere, where it is energized by magnetospheric processes and becomes a part of the plasma pressure that in turn affects the ionospheric and magnetospheric electric field. The electric field, in turn, plays a controlling role in the transport of both magnetospheric and ionospheric plasma, which is intimately linked with ionospheric conductance. The conductance, in turn, is controlled by thermospheric chemistry coupled with plasma flow and heating and magnetospheric precipitation and Joule heating. Several techniques have emerged as important tools: auroral imaging, inversions of ENA images to retrieve the

Coupled storm-time magnetosphere-ionosphere-thermosphere simulations including microscopic ionospheric turbulence

Science.gov (United States)

Merkin, V. G.; Wiltberger, M. J.; Zhang, B.; Liu, J.; Wang, W.; Dimant, Y. S.; Oppenheim, M. M.; Lyon, J.

2017-12-01

During geomagnetic storms the magnetosphere-ionosphere-thermosphere system becomes activated in ways that are unique to disturbed conditions. This leads to emergence of physical feedback loops that provide tighter coupling between the system elements, often operating across disparate spatial and temporal scales. One such process that has recently received renewed interest is the generation of microscopic ionospheric turbulence in the electrojet regions (electrojet turbulence, ET) that results from strong convective electric fields imposed by the solar wind-magnetosphere interaction. ET leads to anomalous electron heating and generation of non-linear Pedersen current - both of which result in significant increases in effective ionospheric conductances. This, in turn, provides strong non-linear feedback on the magnetosphere. Recently, our group has published two studies aiming at a comprehensive analysis of the global effects of this microscopic process on the magnetosphere-ionosphere-thermosphere system. In one study, ET physics was incorporated in the TIEGCM model of the ionosphere-thermosphere. In the other study, ad hoc corrections to the ionospheric conductances based on ET theory were incorporated in the conductance module of the Lyon-Fedder-Mobarry (LFM) global magnetosphere model. In this presentation, we make the final step toward the full coupling of the microscopic ET physics within our global coupled model including LFM, the Rice Convection Model (RCM) and TIEGCM. To this end, ET effects are incorporated in the TIEGCM model and propagate throughout the system via thus modified TIEGCM conductances. The March 17, 2013 geomagnetic storm is used as a testbed for these fully coupled simulations, and the results of the model are compared with various ionospheric and magnetospheric observatories, including DMSP, AMPERE, and Van Allen Probes. Via these comparisons, we investigate, in particular, the ET effects on the global magnetosphere indicators such as the

LUNAR SURFACE AND DUST GRAIN POTENTIALS DURING THE EARTH’S MAGNETOSPHERE CROSSING

Energy Technology Data Exchange (ETDEWEB)

Vaverka, J.; Richterová, I.; Pavlu, J.; Šafránková, J.; Němeček, Z., E-mail: jana.safrankova@mff.cuni.cz [Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Prague (Czech Republic)

2016-07-10

Interaction between the lunar surface and the solar UV radiation and surrounding plasma environment leads to its charging by different processes like photoemission, collection of charged particles, or secondary electron emission (SEE). Whereas the photoemission depends only on the angle between the surface and direction to the Sun and varies only slowly, plasma parameters can change rapidly as the Moon orbits around the Earth. This paper presents numerical simulations of one Moon pass through the magnetospheric tail including the real plasma parameters measured by THEMIS as an input. The calculations are concentrated on different charges of the lunar surface itself and a dust grain lifted above this surface. Our estimations show that (1) the SEE leads to a positive charging of parts of the lunar surface even in the magnetosphere, where a high negative potential is expected; (2) the SEE is generally more important for isolated dust grains than for the lunar surface covered by these grains; and (3) the time constant of charging of dust grains depends on their diameter being of the order of hours for sub-micrometer grains. In view of these results, we discuss the conditions under which and the areas where a levitation of the lifted dust grains could be observed.

Comparing models of rapidly rotating relativistic stars constructed by two numerical methods

Science.gov (United States)

Stergioulas, Nikolaos; Friedman, John L.

1995-05-01

We present the first direct comparison of codes based on two different numerical methods for constructing rapidly rotating relativistic stars. A code based on the Komatsu-Eriguchi-Hachisu (KEH) method (Komatsu et al. 1989), written by Stergioulas, is compared to the Butterworth-Ipser code (BI), as modified by Friedman, Ipser, & Parker. We compare models obtained by each method and evaluate the accuracy and efficiency of the two codes. The agreement is surprisingly good, and error bars in the published numbers for maximum frequencies based on BI are dominated not by the code inaccuracy but by the number of models used to approximate a continuous sequence of stars. The BI code is faster per iteration, and it converges more rapidly at low density, while KEH converges more rapidly at high density; KEH also converges in regions where BI does not, allowing one to compute some models unstable against collapse that are inaccessible to the BI code. A relatively large discrepancy recently reported (Eriguchi et al. 1994) for models based on Friedman-Pandharipande equation of state is found to arise from the use of two different versions of the equation of state. For two representative equations of state, the two-dimensional space of equilibrium configurations is displayed as a surface in a three-dimensional space of angular momentum, mass, and central density. We find, for a given equation of state, that equilibrium models with maximum values of mass, baryon mass, and angular momentum are (generically) either all unstable to collapse or are all stable. In the first case, the stable model with maximum angular velocity is also the model with maximum mass, baryon mass, and angular momentum. In the second case, the stable models with maximum values of these quantities are all distinct. Our implementation of the KEH method will be available as a public domain program for interested users.

Ionosphere-Magnetosphere Energy Interplay in the Regions of Diffuse Aurora

Science.gov (United States)

Khazanov, G. V.; Glocer, A.; Sibeck, D. G.; Tripathi, A. K.; Detweiler, L.G.; Avanov, L. A.; Singhal, R. P.

2016-01-01

Both electron cyclotron harmonic (ECH) waves and whistler mode chorus waves resonate with electrons of the Earths plasma sheet in the energy range from tens of eV to several keV and produce the electron diffuse aurora at ionospheric altitudes. Interaction of these superthermal electrons with the neutral atmosphere leads to the production of secondary electrons (E500600 eV) and, as a result, leads to the activation of lower energy superthermal electron spectra that can escape back to the magnetosphere and contribute to the thermal electron energy deposition processes in the magnetospheric plasma. The ECH and whistler mode chorus waves, however, can also interact with the secondary electrons that are coming from both of the magnetically conjugated ionospheres after they have been produced by initially precipitated high-energy electrons that came from the plasma sheet. After their degradation and subsequent reflection in magnetically conjugate atmospheric regions, both the secondary electrons and the precipitating electrons with high (E600 eV) initial energies will travel back through the loss cone, become trapped in the magnetosphere, and redistribute the energy content of the magnetosphere-ionosphere system. Thus, scattering of the secondary electrons by ECH and whistler mode chorus waves leads to an increase of the fraction of superthermal electron energy deposited into the core magnetospheric plasma.

Crafoord Symposium on Magnetospheric Physics : Achievements and Prospects

CERN Document Server

Fälthammar, C-G

1990-01-01

This book contains the proceedings of the 1989 Crafoord Symposium organized by the Royal Swedish Academy of Sciences. The scientific field for the Crafoord Prize of 1989 was decided in 1988 by the Academy to be Magnetospheric Physics. On September 27,1989 the Academy awarded the 1989 Crafoord Prize to Professor J. A. Van Allen, Iowa City, USA "for his pioneer work in space research, in particular for the discovery of the high energy charged particles that are trapped in the Earth's magnetic field and form the radiation belts -often called the Van Allen belts - around the Earth". The subject for the Crafoord Symposium, which was held on September 28-29 at the Royal Swedish Academy of Sciences in Stockholm, was Magnetospheric Physics, Achievements and Prospects. Some seventy of the world's leading scientists in magnetospheric physics (see list of participants) were invited to the Symposium. The program contained only invited papers. After the ?resentation of the Crafoord Prize Laureate, Prof. J . A. Van Allen, ...

The AMPTE program's contribution to studies of the solar wind-magnetosphere-ionosphere interaction

International Nuclear Information System (INIS)

Sibeck, D.G.

1990-01-01

The Active Magnetospheric Particle Tracer Explorers (AMPTE) program provided important information on the behavior of clouds of plasma artificially injected into the solar wind and the earth's magnetosphere. Now that the releases are over, data from the satellites are being analyzed to investigate the processes by which the ambient solar wind mass, momentum, and energy are transferred to the magnetosphere. Work in progress at APL indicates that the solar wind is much more inhomogeneous than previously believed, that the solar wind constantly buffets the magnetosphere, and that ground observers may remotely sense these interactions as geomagnetic pulsations. 8 refs

Surface conductivity of Mercury provides current closure and may affect magnetospheric symmetry

Directory of Open Access Journals (Sweden)

P. Janhunen

2004-04-01

Full Text Available We study what effect a possible surface conductivity of Mercury has on the closure of magnetospheric currents by making six runs with a quasi-neutral hybrid simulation. The runs are otherwise identical but use different synthetic conductivity models: run 1 has a fully conducting planet, run 2 has a poorly conducting planet ( m and runs 3-6 have one of the hemispheres either in the dawn-dusk or day-night directions, conducting well, the other one being conducting poorly. Although the surface conductivity is not known from observations, educated guesses easily give such conductivity values that magnetospheric currents may close partly within the planet, and as the conductivity depends heavily on the mineral composition of the surface, the possibility of significant horizontal variations cannot be easily excluded. The simulation results show that strong horizontal variations may produce modest magnetospheric asymmetries. Beyond the hybrid simulation, we also briefly discuss the possibility that in the nightside there may be a lack of surface electrons to carry downward current, which may act as a further source of surface-related magnetospheric asymmetry.

Key words. Magnetospheric physics (planetary magnetospheres; current systems; solar wind-magnetosphere interactions.6

Terrestrial magnetospheric imaging: Numerical modeling of low energy neutral atoms

International Nuclear Information System (INIS)

Moore, K.R.; Funsten, H.O.; McComas, D.J.; Scime, E.E.; Thomsen, M.F.

1993-01-01

Imaging of the terrestrial magnetosphere can be performed by detection of low energy neutral atoms (LENAs) that are produced by charge exchange between magnetospheric plasma ions and cold neutral atoms of the Earth's geocorona. As a result of recent instrumentation advances it is now feasible to make energy-resolved measurements of LENAs from less than I key to greater than 30 key. To model expected LENA fluxes at a spacecraft, we initially used a simplistic, spherically symmetric magnetospheric plasma model. 6 We now present improved calculations of both hydrogen and oxygen line-of-sight LENA fluxes expected on orbit for various plasma regimes as predicted by the Rice University Magnetospheric Specification Model. We also estimate expected image count rates based on realistic instrument geometric factors, energy passbands, and image accumulation intervals. The results indicate that presently proposed LENA instruments are capable of imaging of storm time ring current and potentially even quiet time ring current fluxes, and that phenomena such as ion injections from the tail and subsequent drifts toward the dayside magnetopause may also be deduced

On the penetration of solar wind inhomogeneities into the magnetosphere

International Nuclear Information System (INIS)

Maksimov, V.P.; Senatorov, V.N.

1980-01-01

Laboratory experiments were used as a basis to study the process of interaction between solar wind inhomogeneities and the Earth's magnetosphere. The given inhomogeneity represents a lump of plasma characterized by an increased concentration of particles (nsub(e) approximately 20-30 cm -3 ), a discrete form (characteristic dimensions of the lump are inferior to the magnetosphere diameter) and the velocity v approximately 350 km/s. It is shown that there is the possibility of penetration of solar wind inhomogeneities inside the Earth's magnetosphere because of the appearance in the inhomogeneity of an electric field of transverse polarization. The said process is a possible mechanism of the formation of the magnetopshere entrance layer

Modeling Jovian Magnetospheres Beyond the Solar System

Science.gov (United States)

Williams, Peter K. G.

2018-06-01

Low-frequency radio observations are believed to represent one of the few means of directly probing the magnetic fields of extrasolar planets. However, a half-century of low-frequency planetary observations within the Solar System demonstrate that detailed, physically-motivated magnetospheric models are needed to properly interpret the radio data. I will present recent work in this area focusing on the current state of the art: relatively high-frequency observations of relatively massive objects, which are now understood to have magnetospheres that are largely planetary in nature. I will highlight the key challenges that will arise in future space-based observations of lower-mass objects at lower frequencies.

Electron–Positron Pair Flow and Current Composition in the Pulsar Magnetosphere

Science.gov (United States)

Brambilla, Gabriele; Kalapotharakos, Constantinos; Timokhin, Andrey N.; Harding, Alice K.; Kazanas, Demosthenes

2018-05-01

We perform ab initio particle-in-cell (PIC) simulations of a pulsar magnetosphere with electron–positron plasma produced only in the regions close to the neutron star surface. We study how the magnetosphere transitions from the vacuum to a nearly force-free configuration. We compare the resulting force-free-like configuration with those obtained in a PIC simulation where particles are injected everywhere as well as with macroscopic force-free simulations. We find that, although both PIC solutions have similar structure of electromagnetic fields and current density distributions, they have different particle density distributions. In fact, in the injection from the surface solution, electrons and positrons counterstream only along parts of the return current regions and most of the particles leave the magnetosphere without returning to the star. We also find that pair production in the outer magnetosphere is not critical for filling the whole magnetosphere with plasma. We study how the current density distribution supporting the global electromagnetic configuration is formed by analyzing particle trajectories. We find that electrons precipitate to the return current layer inside the light cylinder and positrons precipitate to the current sheet outside the light cylinder by crossing magnetic field lines, contributing to the charge density distribution required by the global electrodynamics. Moreover, there is a population of electrons trapped in the region close to the Y-point. On the other hand, the most energetic positrons are accelerated close to the Y-point. These processes can have observational signatures that, with further modeling effort, would help to distinguish this particular magnetosphere configuration from others.

Modelling of the ring current in Saturn's magnetosphere

Directory of Open Access Journals (Sweden)

G. Giampieri

2004-01-01

Full Text Available The existence of a ring current inside Saturn's magnetosphere was first suggested by Smith et al. (1980 and Ness et al. (1981, 1982, in order to explain various features in the magnetic field observations from the Pioneer 11 and Voyager 1 and 2 spacecraft. Connerney et al. (1983 formalized the equatorial current model, based on previous modelling work of Jupiter's current sheet and estimated its parameters from the two Voyager data sets. Here, we investigate the model further, by reconsidering the data from the two Voyager spacecraft, as well as including the Pioneer 11 flyby data set. First, we obtain, in closed form, an analytic expression for the magnetic field produced by the ring current. We then fit the model to the external field, that is the difference between the observed field and the internal magnetic field, considering all the available data. In general, through our global fit we obtain more accurate parameters, compared to previous models. We point out differences between the model's parameters for the three flybys, and also investigate possible deviations from the axial and planar symmetries assumed in the model. We conclude that an accurate modelling of the Saturnian disk current will require taking into account both of the temporal variations related to the condition of the magnetosphere, as well as non-axisymmetric contributions due to local time effects. Key words. Magnetospheric physics (current systems; planetary magnetospheres; plasma sheet

Energetic magnetospheric protons in the plasma depletion layer

International Nuclear Information System (INIS)

Fuselier, S.A.

1992-01-01

Interplanetary magnetic field draping against the Earth's dayside subsolar magnetopause creates a region of reduced plasma density and increased magnetic field called the plasma depletion layer. In this region, leakage of energetic ions from the Earth's magnetosphere onto magnetic field lines in the plasma depletion layer can be studied without interference from ions accelerated at the Earth's quasi-parallel bow shock. Active Magnetospheric Particle Tracer Experiment/Charge Composition Explorer (AMPTE/CCE) observations for 13 plasma depletion layer events are used to determine the characteristics of energetic protons between a few keV/e and ∼100keV/e leaked from the magnetosphere. Results indicate that the leaked proton distributions resemble those in the magnetosphere except that they have lower densities and temperatures and much higher velocities parallel (or antiparallel) and perpendicular to the magnetic field. Compared to the low-energy magnetosheath proton distributions present in the depletion layer, the leaked energetic proton distributions typically have substantially higher flow velocities along the magnetic field indicate that the leaked energetic proton distributions to contribute to the energetic proton population seen upstream and downstream from the quasi-parallel bow shock. However, their contribution is small compared to the contribution from acceleration of protons at the bow shock because the leaked proton densities are on the order of 10 times smaller than the energetic proton densities typically observed in the vicinity of the quasi-parallel bow shock

Outer Magnetospheric Boundaries Cluster Results

CERN Document Server

Paschmann, Goetz; Schwartz, S J

2006-01-01

When the stream of plasma emitted from the Sun (the solar wind) encounters Earth's magnetic field, it slows down and flows around it, leaving behind a cavity, the magnetosphere. The magnetopause is the surface that separates the solar wind on the outside from the Earth's magnetic field on the inside. Because the solar wind moves at supersonic speed, a bow shock must form ahead of the magnetopause that acts to slow the solar wind to subsonic speeds. Magnetopause, bow shock and their environs are rich in exciting processes in collisionless plasmas, such as shock formation, magnetic reconnection, particle acceleration and wave-particle interactions. They are interesting in their own right, as part of Earth's environment, but also because they are prototypes of similar structures and phenomena that are ubiquitous in the universe, having the unique advantage that they are accessible to in situ measurements. The boundaries of the magnetosphere have been the target of direct in-situ measurements since the beginning ...

Discontinuities and the magnetospheric phenomena

International Nuclear Information System (INIS)

Rajaram, R.; Kalra, G.L.; Tandon, J.N.

1978-01-01

Wave coupling at contact discontinuities has an important bearing on the transmission of waves from the solar wind into the magnetosphere across the cusp region of the solar wind-magnetosphere boundary and on the propagation of geomagnetic pulsations in the polar exosphere. Keeping this in view, the problems of wave coupling across a contact discontinuity in a collisionless plasma, described by a set of double adiabatic fluid equations, is examined. The magnetic field is taken normal to the interface and it is shown that total reflection is not possible for any angle of incidence. The Alfven and the magneto-acoustic waves are not coupled. The transmission is most efficient for small density discontinuities. Inhibition of the transmission of the Alfven wave by the sharp density gradients above the F2-peak in the polar exosphere appears to account for the decrease in the pulsation amplitude, on the ground, as the poles are approached from the auroral zone. (author)

Escape of charged particles from a neutron star

International Nuclear Information System (INIS)

Pelizzari, M.A.

1976-01-01

The theory of particle trajectories in an axisymmetric magnetic field, formulated by C. Stormer, can be extended to cover conservative force fields as well. As such, it is an ideal tool to study the escape of charged particles from a rapidly rotating neutron star, enabling one to determine the maximum range of their trajectories in space. With the aid of this theory, it is shown that a neutron star, rotating in a vacuum with rotation and magnetic axes aligned, will not evolve a perfectly conducting magnetosphere if the neutron star is the only source of charge. The sign of charge accelerated from the equatorial regions will be magnetically trapped to a toroidal region very near the star, and the opposite sign of charge, emerging from the polar regions, will escape from the magnetosphere until a critical stellar charge is reached, after which polar charges will be electrostatically bound to the magnetosphere. This selective magnetic trapping of one sign of charge, which prevents the formation of a stellar wind, is a consequence of the magnetic field's orientation relative to the internal charge density of the neutron star

Two-stream instability in pulsar magnetospheres

International Nuclear Information System (INIS)

Usov, V.V.

1987-01-01

If the electron-positron plasma flow from the pulsar environment is stationary, the two-stream instability does not have enough time to develop in the pulsar magnetosphere. In that case the outflowing electron-positron plasma gathers into separate clouds. The clouds move along magnetic field lines and disperse as they go farther from the pulsar. At a distance of about 10 to the 8th cm from the pulsar surface, the high-energy particles of a given cloud catch up with the low-energy particles that belong to the cloud going ahead of it. In this region of a pulsar magnetosphere, the energy distribution of plasma particles is two-humped, and a two-stream instability may develop. The growth rate of the instability is quite sufficient for its development. 17 references

Structure and stability of rapidly rotating fluid bodies in general relativity. II. The structure of uniformly rotating pseudopolytropes

International Nuclear Information System (INIS)

Butterworth, E.M.

1976-01-01

A method is described for obtaining numerical solutions to the exact Einstein field equations that represent uniformly rotating perfect fluid bodies which are stationary and obey equations of state of the form (pressure) proportional (energy density) 1+1 //subn/. Sequences parametrized by the rate of rotation are generated for polytropic indices n between 0.5 and 3 and for varying strengths of relativity. All are found to terminate at surface velocities which are approximately 10 percent or more of the velocity of light. The configurations considered here are probably at least as relativistic as any stable astrophysical object in uniform rotation now thought to exist, but the phenomenon of an ergoregion appears in none of them and probably is absent in actual stars if magnetic viscosity or some other mechanism can induce rigid rotation

Some recent results from European sounding rocket and satellite observations of the hot magnetospheric plasma

International Nuclear Information System (INIS)

Hultqvist, B.

1979-03-01

A brief summary of some recent results from European studies of the hot magnetospheric plasma is presented. The material is organized in four main sections: 1) Observations of keV auroral electrons. 2) Observation of the hot ion component of the magnetospheric plasma. 3) Sudden changes of the distribution of the hot plasma in the dayside magnetosphere. 4) Banded electron cyclotron harmonic instability in the magnetosphere - a first comparison of theory and experiment. (E.R.)

Magnetic fields of Jupiter and Saturn

International Nuclear Information System (INIS)

Ness, N.F.

1981-01-01

The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected

Introduction to the thematic series "Coupling of the magnetosphere-ionosphere system"

Science.gov (United States)

Yao, Z. H.; Murphy, K. R.; Rae, I. J.; Balan, N.

2017-12-01

This thematic series contains 4 papers mostly presented at the 2016 AOGS meeting in Beijing. The four papers investigate four key regions in the magnetosphere-ionosphere coupling process: mid-tail magnetosphere, near-Earth magnetosphere, inner magnetosphere, and the polar ground region. Guo et al. (Geosci Lett 4:18, 2017) study the current system in reconnection region using 2.5D particle-in-cell simulations. Yao et al. (Geosci Lett 4:8, 2017) use conjugate measurements from ground auroral imagers and in situ THEMIS spacecraft to reveal the mechanism for the wave-like auroral structures prior to substorm onset. Zhang et al. (Geosci Lett 4:20, 2017) investigate the profiles of resonance zone and resonant frequency in the Landau resonance between radiation belt electrons and magnetosonic waves and between protons and cyclotron waves. Rae et al. (Geosci Lett 4:23, 2017) determine the relative timing between sudden increases in amplitude, or onsets, of different ultra-low-frequency wave bands during substorms.

Towards the geophysical regime in numerical dynamo models: studies of rapidly-rotating convection driven dynamos with low Pm and constant heat flux boundary conditions

DEFF Research Database (Denmark)

Sheyko, A.A.; Finlay, Chris; Marti, P.

We present a set of numerical dynamo models with the convection strength varied by a factor of 30 and the ratio of magnetic to viscous diffusivities by a factor of 20 at rapid rotation rates (E =nu/(2 Omega d^2 ) = 10-6 and 10-7 ) using a heat flux outer BC. This regime has been little explored...... on the structure of the dynamos and how this changes in relation to the selection of control parameters, a comparison with the proposed rotating convection and dynamo scaling laws, energy spectra of steady solutions and inner core rotation rates. Magnetic field on the CMB. E=2.959*10-7, Ra=6591.0, Pm=0.05, Pr=1....

On the significance of magnetospheric research for progress in astrophysics

International Nuclear Information System (INIS)

Faelthammar, C-G.; Akasofu, S-I.; Alfen, H.

1978-04-01

Recent discoveries by means of in situ measurements have led to a substantial revision of our picture of the magnetosphere and parts of the heliosphere. This concerns such essential aspects as the character and distribution of electric fields and currents, the ways in which charged particles are energized, and the chemical composition of the magnetospheric plasma. This revision reflects the fact that even in fundamental respects, real cosmical plasmas behave in different ways than predicted by the idealized models that have traditionally been used in magnetospheric physics as well as in astrophysics. The new understanding of the general properties of cosmical plasma that has been, and continues to be, provided by in situ measurements gives us a much improved basis on which to interpret astrophysical observations

Theory of quasi-spherical accretion in X-ray pulsars

Science.gov (United States)

Shakura, N.; Postnov, K.; Kochetkova, A.; Hjalmarsdotter, L.

2012-02-01

A theoretical model for quasi-spherical subsonic accretion on to slowly rotating magnetized neutron stars is constructed. In this model, the accreting matter subsonically settles down on to the rotating magnetosphere forming an extended quasi-static shell. This shell mediates the angular momentum removal from the rotating neutron star magnetosphere during spin-down episodes by large-scale convective motions. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere. The settling regime of accretion can be realized for moderate accretion rates ? g s-1. At higher accretion rates, a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of the spin-up/spin-down rates (the angular rotation frequency derivative ?, and ? near the torque reversal) of X-ray pulsars with known orbital periods, it is possible to determine the main dimensionless parameters of the model, as well as to estimate the magnetic field of the neutron star. We illustrate the model by determining these parameters for three wind-fed X-ray pulsars GX 301-2, Vela X-1 and GX 1+4. The model explains both the spin-up/spin-down of the pulsar frequency on large time-scales and the irregular short-term frequency fluctuations, which can correlate or anticorrelate with the X-ray flux fluctuations in different systems. It is shown that in real pulsars an almost iso-angular-momentum rotation law with ω˜ 1/R2, due to strongly anisotropic radial turbulent motions sustained by large-scale convection, is preferred.

Results from Navigator GPS Flight Testing for the Magnetospheric MultiScale Mission

Science.gov (United States)

Lulich, Tyler D.; Bamford, William A.; Wintermitz, Luke M. B.; Price, Samuel R.

2012-01-01

The recent delivery of the first Goddard Space Flight Center (GSFC) Navigator Global Positioning System (GPS) receivers to the Magnetospheric MultiScale (MMS) mission spacecraft is a high water mark crowning a decade of research and development in high-altitude space-based GPS. Preceding MMS delivery, the engineering team had developed receivers to support multiple missions and mission studies, such as Low Earth Orbit (LEO) navigation for the Global Precipitation Mission (GPM), above the constellation navigation for the Geostationary Operational Environmental Satellite (GOES) proof-of-concept studies, cis-Lunar navigation with rapid re-acquisition during re-entry for the Orion Project and an orbital demonstration on the Space Shuttle during the Hubble Servicing Mission (HSM-4).

The dependence of magnetosphere-ionosphere system on the Earth's magnetic dipole moment

Science.gov (United States)

Ngwira, C. M.; Pulkkinen, A. A.; Sibeck, D. G.; Rastaetter, L.

2017-12-01

Space weather is increasingly recognized as an international problem affecting several different man-made technologies. The ability to understand, monitor and forecast Earth-directed space weather is of paramount importance for our highly technology-dependent society and for the current rapid developments in awareness and exploration within the heliosphere. It is well known that the strength of the Earth's magnetic field changes over long time scales. We use physics-based simulations with the University of Michigan Space Weather Modeling Framework (SWMF) to examine how the magnetosphere, ionosphere, and ground geomagnetic field perturbations respond as the geomagnetic dipole moment changes. We discuss the implication of these results for our community and the end-users of space weather information.

The magnetosphere under weak solar wind forcing

Directory of Open Access Journals (Sweden)

C. J. Farrugia

2007-02-01

Full Text Available The Earth's magnetosphere was very strongly disturbed during the passage of the strong shock and the following interacting ejecta on 21–25 October 2001. These disturbances included two intense storms (Dst*≈−250 and −180 nT, respectively. The cessation of this activity at the start of 24 October ushered in a peculiar state of the magnetosphere which lasted for about 28 h and which we discuss in this paper. The interplanetary field was dominated by the sunward component [B=(4.29±0.77, −0.30±0.71, 0.49±0.45 nT]. We analyze global indicators of geomagnetic disturbances, polar cap precipitation, ground magnetometer records, and ionospheric convection as obtained from SuperDARN radars. The state of the magnetosphere is characterized by the following features: (i generally weak and patchy (in time low-latitude dayside reconnection or reconnection poleward of the cusps; (ii absence of substorms; (iii a monotonic recovery from the previous storm activity (Dst corrected for magnetopause currents decreasing from ~−65 to ~−35 nT, giving an unforced decreased of ~1.1 nT/h; (iv the probable absence of viscous-type interaction originating from the Kelvin-Helmholtz (KH instability; (v a cross-polar cap potential of just 20–30 kV; (vi a persistent, polar cap region containing (vii very weak, and sometimes absent, electron precipitation and no systematic inter-hemisphere asymmetry. Whereas we therefore infer the presence of a moderate amount of open flux, the convection is generally weak and patchy, which we ascribe to the lack of solar wind driver. This magnetospheric state approaches that predicted by Cowley and Lockwood (1992 but has never yet been observed.

The effects of curvature on the flow field in rapidly rotating gas centrifuges

International Nuclear Information System (INIS)

Wood, H.G.; Jordan, J.A.

1984-01-01

The effects of curvature on the fluid dynamics of rapidly rotating gas centrifuges are studied. A governing system of a linear partial differential equation and boundary conditions is derived based on a linearization of the equations for viscous compressible flow. This system reduces to the Onsager pancake model if the effects of curvature are neglected. Approximations to the solutions of the governing equations with and without curvature terms are obtained via a finite-element method. Two examples are considered: first where the flow is driven by a thermal gradient at the wall of the centrifuge, and then for the flow being driven by the introduction and removal of mass through the ends of the centrifuge. Comparisons of the results obtained show that, especially for the second example, the inclusion of the terms due to curvature in the model can have an appreciable effect on the solution. (author)

Trajectory traces of charged particles in the magnetosphere

International Nuclear Information System (INIS)

Ejiri, M.

1978-01-01

The characteristic enhancements of ring current particles with energies of about 1--1000keV, associated with magnetospheric substorms, were observed by Explorer 45 (S 3 -A) around the plasmapause in the afternoon to midnight region and showed the characteristic structure called a 'noise' in the proton spectrograms. This paper examines the time developing characteristics of newly injected particles in the magnetosphere under a recently proposed convection electric field and a dipole magnetic field. Approximate equations of a bounce period, a second adiabatic invariant, and a bounce-averaged azimuthal velocity are given with an error of less than about 10 -3 for all pitch angles. The complete set of flow patterns of 90 0 pitch angles is also described by means of inflection lines through whicch radial and/or azimuthal drifts change their directions and where particle velocities show their local minima, i.e., the flow becomes sluggish. These particle tracings in the magnetosphere, from which time dependent particle fronts can be constructed, give the basic concept and mechanics to explain the complex and dynamical properties of the magnetic storm time particle enhancements

The influence of solar wind variability on magnetospheric ULF wave power

International Nuclear Information System (INIS)

Pokhotelov, D.; Rae, I.J.; Mann, I.R.

2015-01-01

Magnetospheric ultra-low frequency (ULF) oscillations in the Pc 4-5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF) orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind-IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996-2004) of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature), plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind-magnetosphere coupling.

Artificial Neural Network L* from different magnetospheric field models

Science.gov (United States)

Yu, Y.; Koller, J.; Zaharia, S. G.; Jordanova, V. K.

2011-12-01

The third adiabatic invariant L* plays an important role in modeling and understanding the radiation belt dynamics. The popular way to numerically obtain the L* value follows the recipe described by Roederer [1970], which is, however, slow and computational expensive. This work focuses on a new technique, which can compute the L* value in microseconds without losing much accuracy: artificial neural networks. Since L* is related to the magnetic flux enclosed by a particle drift shell, global magnetic field information needed to trace the drift shell is required. A series of currently popular empirical magnetic field models are applied to create the L* data pool using 1 million data samples which are randomly selected within a solar cycle and within the global magnetosphere. The networks, trained from the above L* data pool, can thereby be used for fairly efficient L* calculation given input parameters valid within the trained temporal and spatial range. Besides the empirical magnetospheric models, a physics-based self-consistent inner magnetosphere model (RAM-SCB) developed at LANL is also utilized to calculate L* values and then to train the L* neural network. This model better predicts the magnetospheric configuration and therefore can significantly improve the L*. The above neural network L* technique will enable, for the first time, comprehensive solar-cycle long studies of radiation belt processes. However, neural networks trained from different magnetic field models can result in different L* values, which could cause mis-interpretation of radiation belt dynamics, such as where the source of the radiation belt charged particle is and which mechanism is dominant in accelerating the particles. Such a fact calls for attention to cautiously choose a magnetospheric field model for the L* calculation.

The electromagnetic field for an open magnetosphere

Science.gov (United States)

Heikkila, W. J.

1984-01-01

The boundary-layer-dominated models of the earth EM field developed by Heikkila (1975, 1978, 1982, and 1983) and Heikkila et al. (1979) to account for deficiencies in the electric-field descriptions of quasi-steady-state magnetic-field-reconnection models (such as that of Cowley, 1980) are characterized, reviewing the arguments and indicating the most important implications. The mechanisms of boundary-layer formation and field direction reversal are explained and illustrated with diagrams, and it is inferred that boundary-layer phenomena rather than magnetic reconnection may be the cause of large-scale magnetospheric circulation, convection, plasma-sheet formation and sunward convection, and auroras, the boundary layer acting basically as a viscous process mediating solar-wind/magnetosphere interactions.

Effects of Energetic Ion Outflow on Magnetospheric Dynamics

Science.gov (United States)

Kistler, L. M.; Mouikis, C.; Lund, E. J.; Menz, A.; Nowrouzi, N.

2016-12-01

There are two dominant regions of energetic ion outflow: the nightside auroral region and the dayside cusp. Processes in these regions can accelerate ions up to keV energies. Outflow from the nightside has direct access to the plasma sheet, while outflow from the cusp is convected over the polar cap and into the lobes. The cusp population can enter the plasma sheet from the lobe, with higher energy ions entering further down the tail than lower energy ions. During storm times, the O+ enhanced plasma sheet population is convected into the inner magnetosphere. The plasma that does not get trapped in the inner magnetosphere convects to the magnetopause where reconnection is taking place. An enhanced O+ population can change the plasma mass density, which may have the effect of decreasing the reconnection rate. In addition O+ has a larger gyroradius than H+ at the same velocity or energy. Because of this, there are larger regions where the O+ is demagnetized, which can lead to larger acceleration because the O+ can move farther in the direction of the electric field. In this talk we will review results from Cluster, Van Allen Probes, and MMS, on how outflow from the two locations affects magnetospheric dynamics. We will discuss whether enhanced O+ from either population has an effect on the reconnection rate in the tail or at the magnetopause. We will discuss how the two populations impact the inner magnetosphere during storm times. And finally, we will discuss whether either population plays a role in triggering substorms, particularly during sawtooth events.

Energy coupling function and solar wind-magnetosphere dynamo

International Nuclear Information System (INIS)

Kan, J.R.; Lee, L.C.

1979-01-01

The power delivered by the solar wind dynamo to the open magnetosphere is calculated based on the concept of field line reconnection, independent of the MHD steady reconnection theories. By recognizing a previously overlooked geometrical relationship between the reconnection electric field and the magnetic field, the calculated power is shown to be approximately proportional to the Akasofu-Perreault energy coupling function for the magnetospheric substorm. In addition to the polar cap potential, field line reconnection also gives rise to parallel electric fields on open field lines in the high-latitude cusp and the polar cap reions

Modeling the Interaction of Europa with the Jovian Magnetosphere

Science.gov (United States)

Rubin, M.; Combi, M. R.; Daldorff, L.; Gombosi, T. I.; Hansen, K. C.; Jia, X.; Kivelson, M. G.; Tenishev, V.

2011-12-01

The interaction of Jupiter's corotating magnetosphere with Europa's subsurface water ocean is responsible for the observed induced dipolar magnetic field. Furthermore the pick-up process of newly ionized particles from Europa's neutral atmosphere alters the magnetic and electric field topology around the moon. We use the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) of the Space Weather Modeling Framework (SWMF) to model the interaction of Europa with the Jovian magnetosphere. The BATS-R-US code solves the governing equations of magnetohydrodynamics (MHD) in a fully 3D adaptive mesh. In our approach we solve the equations for one single ion species, starting from the work by Kabin et al. (J. Geophys. Res., 104, A9, 19983-19992, 1999) accounting for the exospheric mass loading, ion-neutral charge exchange, and ion-electron recombination. We continue by separately solving the electron pressure equation and furthermore extend the magnetic induction equation by the resistive and Hall terms. The resistive term accounts for the finite electron diffusivity and thus allows a more adequate description of the effect of magnetic diffusion due to collisions [Ledvina et al., Sp. Sci. Rev., 139:143-189, 2008]. For this purpose we use ion-electron and electron-neutral collision rates presented by Schunk and Nagy (Ionospheres, Cambridge University Press, 2000). The Hall term allows ions and electrons to move at different velocities while the magnetic field remains frozen to the electrons. The assumed charge neutrality of the ion-electron plasma is maintained everywhere at all times. The model is run at different phases of Jupiter's rotation reflecting the different locations of Europa with respect to the center of the plasma sheet and is compared to measurements obtained by the Galileo magnetometer [Kivelson et al., J. Geophys. Res., 104:4609-4626, 1999]. The resulting influence on the induced magnetic dipolar field is studied and compared to the results from the

Experimental aspects of ion acceleration and transport in the Earth's magnetosphere

International Nuclear Information System (INIS)

Young, D.T.

1985-01-01

Major particle population within the Earth's magnetosphere have been studied via ion acceleration processes. Experimental advances over the past ten to fifteen years have demonstrated the complexity of the processes. A review is given here for areas where composition experiments have expanded perception on magnetospheric phenomena. 64 refs., 6 figs., 1 tab

Magnetic pseudo-fields in a rotating electron-nuclear spin system

Science.gov (United States)

Wood, A. A.; Lilette, E.; Fein, Y. Y.; Perunicic, V. S.; Hollenberg, L. C. L.; Scholten, R. E.; Martin, A. M.

2017-11-01

Analogous to the precession of a Foucault pendulum observed on the rotating Earth, a precessing spin observed in a rotating frame of reference appears frequency-shifted. This can be understood as arising from a magnetic pseudo-field in the rotating frame that nevertheless has physically significant consequences, such as the Barnett effect. To detect these pseudo-fields, a rotating-frame sensor is required. Here we use quantum sensors, nitrogen-vacancy (NV) centres, in a rapidly rotating diamond to detect pseudo-fields in the rotating frame. Whereas conventional magnetic fields induce precession at a rate proportional to the gyromagnetic ratio, rotation shifts the precession of all spins equally, and thus primarily affect 13C nuclear spins in the sample. We are thus able to explore these effects via quantum sensing in a rapidly rotating frame, and define a new approach to quantum control using rotationally induced nuclear spin-selective magnetic fields. This work provides an integral step towards realizing precision rotation sensing and quantum spin gyroscopes.

Electromagnetic ion cyclotron waves stimulated by modest magnetospheric compressions

Science.gov (United States)

Anderson, B. J.; Hamilton, D. C.

1993-01-01

AMPTE/CCE magnetic field and particle data are used to test the suggestion that increased hot proton temperature anisotropy resulting from convection during magnetospheric compression is responsible for the enhancement in Pc 1 emission via generation of electromagnetic ion cyclotron (EMIC) waves in the dayside outer equatorial magnetosphere. The relative increase in magnetic field is used to gauge the strength of the compression, and an image dipole model is used to estimate the motion of the plasma during compression. Proton data are used to analyze the evolution of the proton distribution and the corresponding changes in EMIC wave activity expected during the compression. It is suggested that enhancements in dynamic pressure pump the energetic proton distributions in the outer magnetosphere, driving EMIC waves. Waves are expected to be generated most readily close to the magnetopause, and transient pressure pulses may be associated with bursts of EMIC waves, which would be observed on the ground in association with ionospheric transient signatures.

The influence of solar wind variability on magnetospheric ULF wave power

Directory of Open Access Journals (Sweden)

D. Pokhotelov

2015-06-01

Full Text Available Magnetospheric ultra-low frequency (ULF oscillations in the Pc 4–5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind–IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996–2004 of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature, plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind–magnetosphere coupling.

Evolution of Eigenmodes of the Mhd-Waveguide in the Outer Magnetosphere

Science.gov (United States)

Chuiko, Daniil

EVOLUTION OF EIGENMODES OF THE MHD-WAVEGUIDE IN THE OUTER MAGNETOSPHERE Mazur V.A., Chuiko D.A. Institute of Solar-Terrestrial Physics, Irkutsk, Russia. Geomagnetic field and plasma inhomogeneties in the outer equatorial part of the magnetosphere al-lows for existence of a channel with low Alfven speeds, which spans from the nose to the far flanks of the magnetosphere, in the morning as well as in the evening sectors. This channel plays a role of a waveguide for fast magnetosonic waves. When an eigenmode travels along the waveguide (i.e. in the azimuthal direction) it undergoes certain evolution. The parameters of the waveguide are changing along the way of wave’s propagation and the eigenmode “adapts” to these parameters. Conditions of the Kelvin-Helmholtz instability are changing due to the increment in the solar wind speed along the magnetopause. The conditions of the solar wind hydromagnetic waves penetration to the magnetosphere are changing due to the same increment. As such, the process of the penetration turns to overreflection regime, which abruptly increases the pump level of the magnetospheric waveguide. There is an Alfven resonance deep within the magnetosphere, which corresponds to the propagation of the fast mode along the waveguide. Oscillation energy dissipation takes place in the vicinity of the Alfven resonance. Alfven resonance is a standing Alfven wave along the magnetic field lines, so it reaches the ionosphere and the Earth surface, when the fast modes of the waveguide, localized in the low Alfven speed channel cannot be observed on Earth. The evolution of the waveguide oscillation propagating from the nose to the far tail is theoretically investigated in this work with consideration of all aforementioned effects. The spatial structure var-iation character, spectral composition and amplitude along the waveguide are found.

Generation mechanisms for magnetic-field-aligned electric fields in the magnetosphere

International Nuclear Information System (INIS)

Faelthammar, C.-G.

1977-09-01

Magnetic-field-aligned electric fields in the magnetosphere can be generated in several different ways, and in this review some possible mechanisms are presented. Observational data now available indicates that more than one of the mechanisms mentioned are operative in the magnetosphere but it is not yet possible to evaluate their relative importance. (author)

Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

Directory of Open Access Journals (Sweden)

J. D. Nichols

2005-03-01

Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

Auroral phenomenology and magnetospheric processes earth and other planets

CERN Document Server

Keiling, Andreas; Bagenal, Fran; Karlsson, Tomas

2013-01-01

Published by the American Geophysical Union as part of the Geophysical Monograph Series. Many of the most basic aspects of the aurora remain unexplained. While in the past terrestrial and planetary auroras have been largely treated in separate books, Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets takes a holistic approach, treating the aurora as a fundamental process and discussing the phenomenology, physics, and relationship with the respective planetary magnetospheres in one volume. While there are some behaviors common in auroras of the diffe

Neoclassical poloidal and toroidal rotation in tokamaks

International Nuclear Information System (INIS)

Kim, Y.B.; Diamond, P.H.; Groebner, R.J.

1991-01-01

Explicit expressions for the neoclassical poloidal and toroidal rotation speeds of primary ion and impurity species are derived via the Hirshman and Sigmar moment approach. The rotation speeds of the primary ion can be significantly different from those of impurities in various interesting cases. The rapid increase of impurity poloidal rotation in the edge region of H-mode discharges in tokamaks can be explained by a rapid steepening of the primary ion pressure gradient. Depending on ion collisionality, the poloidal rotation speed of the primary ions at the edge can be quite small and the flow direction may be opposite to that of the impurities. This may cast considerable doubts on current L to H bifurcation models based on primary ion poloidal rotation only. Also, the difference between the toroidal rotation velocities of primary ions and impurities is not negligible in various cases. In Ohmic plasmas, the parallel electric field induces a large impurity toroidal rotation close to the magnetic axis, which seems to agree with experimental observations. In the ion banana and plateau regime, there can be non-negligible disparities between primary ion and impurity toroidal rotation velocities due to the ion density and temperature gradients. Detailed analytic expressions for the primary ion and impurity rotation speeds are presented, and the methodology for generalization to the case of several impurity species is also presented for future numerical evaluation

Multiwavelength Polarization of Rotation-powered Pulsars

Energy Technology Data Exchange (ETDEWEB)

Harding, Alice K.; Kalapotharakos, Constantinos [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2017-05-10

Polarization measurements provide strong constraints on models for emission from rotation-powered pulsars. We present multiwavelength polarization predictions showing that measurements over a range of frequencies can be particularly important for constraining the emission location, radiation mechanisms, and system geometry. The results assume a generic model for emission from the outer magnetosphere and current sheet in which optical to hard X-ray emission is produced by synchrotron radiation (SR) from electron–positron pairs and γ -ray emission is produced by curvature radiation (CR) or SR from accelerating primary electrons. The magnetic field structure of a force-free magnetosphere is assumed and the phase-resolved and phase-averaged polarization is calculated in the frame of an inertial observer. We find that large position angle (PA) swings and deep depolarization dips occur during the light-curve peaks in all energy bands. For synchrotron emission, the polarization characteristics are strongly dependent on photon emission radius with larger, nearly 180°, PA swings for emission outside the light cylinder (LC) as the line of sight crosses the current sheet. The phase-averaged polarization degree for SR is less that 10% and around 20% for emission starting inside and outside the LC, respectively, while the polarization degree for CR is much larger, up to 40%–60%. Observing a sharp increase in polarization degree and a change in PA at the transition between X-ray and γ -ray spectral components would indicate that CR is the γ -ray emission mechanism.

Efficiency of Synchrotron Radiation from Rotation-powered Pulsars

Energy Technology Data Exchange (ETDEWEB)

Kisaka, Shota [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa, 252-5258 (Japan); Tanaka, Shuta J., E-mail: kisaka@phys.aoyama.ac.jp, E-mail: sjtanaka@center.konan-u.ac.jp [Department of Physics, Konan University, Kobe, Hyogo, 658-8501 (Japan)

2017-03-01

Synchrotron radiation is widely considered to be the origin of the pulsed non-thermal emissions from rotation-powered pulsars in optical and X-ray bands. In this paper, we study the synchrotron radiation emitted by the created electron and positron pairs in the pulsar magnetosphere to constrain the energy conversion efficiency from the Poynting flux to the particle energy flux. We model two pair creation processes, two-photon collision, which efficiently works in young γ -ray pulsars (≲10{sup 6} year), and magnetic pair creation, which is the dominant process to supply pairs in old pulsars (≳10{sup 6} year). Using the analytical model, we derive the maximum synchrotron luminosity as a function of the energy conversion efficiency. From the comparison with observations, we find that the energy conversion efficiency to the accelerated particles should be an order of unity in the magnetosphere, even though we make a number of the optimistic assumptions to enlarge the synchrotron luminosity. In order to explain the luminosity of the non-thermal X-ray/optical emission from pulsars with low spin-down luminosity L {sub sd} ≲ 10{sup 34} erg s{sup −1}, non-dipole magnetic field components should be dominant at the emission region. For the γ -ray pulsars with L {sub sd} ≲ 10{sup 35} erg s{sup −1}, observed γ -ray to X-ray and optical flux ratios are much higher than the flux ratio between curvature and the synchrotron radiations. We discuss some possibilities such as the coexistence of multiple accelerators in the magnetosphere as suggested from the recent numerical simulation results. The obtained maximum luminosity would be useful to select observational targets in X-ray and optical bands.

Direct imaging rapidly-rotating non-Kerr black holes

Energy Technology Data Exchange (ETDEWEB)

Bambi, Cosimo, E-mail: Cosimo.Bambi@physik.uni-muenchen.de [Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universitaet Muenchen, 80333 Munich (Germany); Caravelli, Francesco, E-mail: fcaravelli@perimeterinstitute.ca [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, 14476 Golm (Germany); Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Modesto, Leonardo, E-mail: lmodesto@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada)

2012-05-01

Recently, two of us have argued that non-Kerr black holes in gravity theories different from General Relativity may have a topologically non-trivial event horizon. More precisely, the spatial topology of the horizon of non-rotating and slow-rotating objects would be a 2-sphere, like in Kerr space-time, while it would change above a critical value of the spin parameter. When the topology of the horizon changes, the black hole central singularity shows up. The accretion process from a thin disk can potentially overspin these black holes and induce the topology transition, violating the Weak Cosmic Censorship Conjecture. If the astrophysical black hole candidates are not the black holes predicted by General Relativity, we might have the quite unique opportunity to see their central region, where classical physics breaks down and quantum gravity effects should appear. Even if the quantum gravity region turned out to be extremely small, at the level of the Planck scale, the size of its apparent image would be finite and potentially observable with future facilities.

Understanding the Magnetosphere: The Counter-intuitive Simplicity of Cosmic Electrodynamics

Science.gov (United States)

Vasyliūnas, V. M.

2008-12-01

Planetary magnetospheres exhibit an amazing variety of phenomena, unlimited in complexity if followed into endlessly fine detail. The challenge of theory is to understand this variety and complexity, ultimately by seeing how the observed effects follow from the basic equations of physics (a point emphasized by Eugene Parker). The basic equations themselves are remarkably simple, only their consequences being exceedingly complex (a point emphasized by Fred Hoyle). In this lecture I trace the development of electrodynamics as an essential ingredient of magnetospheric physics, through the three stages it has undergone to date. Stage I is the initial application of MHD concepts and constraints (sometimes phrased in equivalent single-particle terms). Stage II is the classical formulation of self-consistent coupling between magnetosphere and ionosphere. Stage III is the more recent recognition that properly elucidating time sequence and cause-effect relations requires Maxwell's equations combined with the unique constraints of large-scale plasma. Problems and controversies underlie the transition from each stage to the following. For each stage, there are specific observed aspects of the magnetosphere that can be understood at its level; also, each stage implies a specific way to formulate unresolved questions (particularly important in this age of extensive multi-point observations and ever-more-detailed numerical simulations).

The rapid formation of a large rotating disk galaxy three billion years after the Big Bang.

Science.gov (United States)

Genzel, R; Tacconi, L J; Eisenhauer, F; Schreiber, N M Förster; Cimatti, A; Daddi, E; Bouché, N; Davies, R; Lehnert, M D; Lutz, D; Nesvadba, N; Verma, A; Abuter, R; Shapiro, K; Sternberg, A; Renzini, A; Kong, X; Arimoto, N; Mignoli, M

2006-08-17

Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks--the primary components of present-day galaxies--were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.

Rapid fluctuations in ionospheric Faraday rotation angle and 4GHz amplitude scintillation observed at Suva, Fiji

International Nuclear Information System (INIS)

Buonsanto, M.J.; Northcott, R.L.; Wright, R.W.H.

1987-01-01

Observations are reported of rapid fluctuations in Faraday rotation angle (FRA) recorded at 137MHz and amplitude scintillation at 4 GHz. The observations were made at Suva, Fiji Islands (average ionospheric coordinates 17 0 S, 178 0 E) and cover the period September, 1978 through March, 1983. Monthly occurrence of both the FRA fluctuations and the amplitude scintillation are positively correlated with sunspot number and negatively correlated with Ap and hmF2 at Tahiti. No events were seen in the summer months (November, December, and January) and it is suggested that the south to north neutral wind may be responsible for this. Maximum occurrence of both the 137 MHz FRA fluctuations and the 4 GHz scintillation is in April-May and August-September. The more rapid FRA fluctuations, termed here V-type, occur more often in months when the ambient electron density is larger. Most events occur in the pre-midnight sector, as observed elsewhere. Fewer 4 GHz events are observed at later times in the evening, as compared to the 137 MHz FRA fluctuations

Space weather: Why are magnetospheric physicists interested in solar explosive phenomena

Science.gov (United States)

Koskinen, H. E. J.; Pulkkinen, T. I.

That solar activity drives magnetospheric dynamics has for a long time been the basis of solar-terrestrial physics. Numerous statistical studies correlating sunspots, 10.7 cm radiation, solar flares, etc., with various magnetospheric and geomagnetic parameters have been performed. However, in studies of magnetospheric dynamics the role of the Sun has often remained in the background and only the actual solar wind impinging the magnetosphere has gained most of the attention. During the last few years a new applied field of solar-terrestrial physics, space weather, has emerged. The term refers to variable particle and field conditions in our space environment, which may be hazardous to space-borne or ground-based technological systems and can endanger human life and health. When the modern society is becoming increasingly dependent on space technology, the need for better modelling and also forecasting of space weather becomes urgent. While for post analysis of magnetospheric phenomena it is quite sufficient to include observations from the magnetospheric boundaries out to L1 where SOHO is located, these observations do not provide enough lead-time to run space weather forecasting models and to distribute the forecasts to potential customers. For such purposes we need improved physical understanding and models to predict which active processes on the Sun will impact the magnetosphere and what their expected consequences are. An important change of view on the role of the Sun as the origin of magnetospheric disturbances has taken place during last 10--20 years. For a long time, the solar flares were thought to be the most geoeffective solar phenomena. Now the attention has shifted much more towards coronal mass ejections and the SOHO coronal observations seem to have turned the epoch irreversibly. However, we are not yet ready to make reliable perdictions of the terrestrial environment based on CME observations. From the space weather viewpoint, the key questions are

Field line projections of 6300 AA auroral emissions into the outer magnetosphere

International Nuclear Information System (INIS)

Shepherd, M.M.

1979-07-01

An empirical magnetospheric model is employed to project auroral intensity boundaries into the magnetosphere. The auroral data are in the form of instantaneous maps of 6300AA emission, acquired with the ISIS-II spacecraft and correspond to fluxes of low energy electrons. These are specific to a particular universal time and date. The magnetospheric model used is a purely empirical one, designed by Mead and Fairfield (1975) from 44.76 x 10 6 magnetic measurements made by 4 IMP satellites. Their model includes the dipole tilt as a variable, and permits selection from four different disturbance levels, so is particularly suited to these data. In a general way, the auroral projections agree with what is expected, giving some confidence in this application of the model. But a number of features appear that were not predicted, and which should permit new insights into the relationship of specific auroral boundaries to the structure of the magnetosphere. (author)

PC index as a proxy of the solar wind energy that entered into the magnetosphere and energy accumulated in the magnetosphere

Science.gov (United States)

Troshichev, Oleg; Sormakov, Dmitry

The PC index has been approved by the International Association of Geomagnetism and Aeronomy (Merida, Mexico, 2013) as a new international index of magnetic activity. Application of the PC index as a proxy of a solar wind energy that entered into the magnetosphere determines a principal distinction of the PC index from AL and Dst indices, which are regarded as characteristics of the energy that realized in magnetosphere in form of substorms and magnetic storms. This conclusion is based on results of analysis of relationships between the polar cap magnetic activity (PC-index) and parameters of the solar wind, on the one hand, relationships between changes of PC and development of magnetospheric substorms (AL-index) and magnetic storms (Dst-index), on the other hand. In this study the relationships between the PC and Dst indices in course of more than 200 magnetic storms observed in epoch of solar maximum (1998-2004) have been examined for different classes of storms separated by their kind and intensity. Results of statistical analysis demonstrate that depression of geomagnetic field starts to develop as soon as PC index steadily excess the threshold level ~1.5 mV/m; the storm intensity (DstMIN) follows, with delay ~ 1 hour, the maximum of PC in course of the storm. Main features of magnetic storms are determined, irrespective of their class and intensity, by the accumulated-mean PC value (PCAM): storm is developed as long as PCAM increases, comes to maximal intensity when PCAM attains the maximum, and starts to decay as soon as PCAM value displays decline. The run of “anomalous” magnetic storm on January 21-22, 2005, lasting many hours (with intensity of ≈ -100 nT) under conditions of northward or close to zero BZ component, is perfectly governed by behavior of the accumulated-mean PCAM index and, therefore, this storm should be regarded as an ordinary phenomenon. The conclusion is made that the PC index provides the unique on-line information on solar wind

Global fully kinetic models of planetary magnetospheres with iPic3D

Science.gov (United States)

Gonzalez, D.; Sanna, L.; Amaya, J.; Zitz, A.; Lembege, B.; Markidis, S.; Schriver, D.; Walker, R. J.; Berchem, J.; Peng, I. B.; Travnicek, P. M.; Lapenta, G.

2016-12-01

We report on the latest developments of our approach to model planetary magnetospheres, mini magnetospheres and the Earth's magnetosphere with the fully kinetic, electromagnetic particle in cell code iPic3D. The code treats electrons and multiple species of ions as full kinetic particles. We review: 1) Why a fully kinetic model and in particular why kinetic electrons are needed for capturing some of the most important aspects of the physics processes of planetary magnetospheres. 2) Why the energy conserving implicit method (ECIM) in its newest implementation [1] is the right approach to reach this goal. We consider the different electron scales and study how the new IECIM can be tuned to resolve only the electron scales of interest while averaging over the unresolved scales preserving their contribution to the evolution. 3) How with modern computing planetary magnetospheres, mini magnetosphere and eventually Earth's magnetosphere can be modeled with fully kinetic electrons. The path from petascale to exascale for iPiC3D is outlined based on the DEEP-ER project [2], using dynamic allocation of different processor architectures (Xeon and Xeon Phi) and innovative I/O technologies.Specifically results from models of Mercury are presented and compared with MESSENGER observations and with previous hybrid (fluid electrons and kinetic ions) simulations. The plasma convection around the planets includes the development of hydrodynamic instabilities at the flanks, the presence of the collisionless shocks, the magnetosheath, the magnetopause, reconnection zones, the formation of the plasma sheet and the magnetotail, and the variation of ion/electron plasma flows when crossing these frontiers. Given the full kinetic nature of our approach we focus on detailed particle dynamics and distribution at locations that can be used for comparison with satellite data. [1] Lapenta, G. (2016). Exactly Energy Conserving Implicit Moment Particle in Cell Formulation. arXiv preprint ar

First results from the RAPID imaging energetic particle spectrometer on board Cluster

Directory of Open Access Journals (Sweden)

B. Wilken

2001-09-01

Full Text Available The advanced energetic particle spectrometer RAPID on board Cluster can provide a complete description of the relevant particle parameters velocity, V , and atomic mass, A, over an energy range from 30 keV up to 1.5 MeV. We present the first measurements taken by RAPID during the commissioning and the early operating phases. The orbit on 14 January 2001, when Cluster was travelling from a perigee near dawn northward across the pole towards an apogee in the solar wind, is used to demonstrate the capabilities of RAPID in investigating a wide variety of particle populations. RAPID, with its unique capability of measuring the complete angular distribution of energetic particles, allows for the simultaneous measurements of local density gradients, as reflected in the anisotropies of 90° particles and the remote sensing of changes in the distant field line topology, as manifested in the variations of loss cone properties. A detailed discussion of angle-angle plots shows considerable differences in the structure of the boundaries between the open and closed field lines on the nightside fraction of the pass and the magnetopause crossing. The 3 March 2001 encounter of Cluster with an FTE just outside the magnetosphere is used to show the first structural plasma investigations of an FTE by energetic multi-spacecraft observations.Key words. Magnetospheric physics (energetic particles, trapped; magnetopause, cusp and boundary layers; magnetosheath

Fast Flows in the Magnetotail and Energetic Particle Transport: Multiscale Coupling in the Magnetosphere

Science.gov (United States)

Lin, Y.; Wang, X.; Fok, M. C. H.; Buzulukova, N.; Perez, J. D.; Chen, L. J.

2017-12-01

The interaction between the Earth's inner and outer magnetospheric regions associated with the tail fast flows is calculated by coupling the Auburn 3-D global hybrid simulation code (ANGIE3D) to the Comprehensive Inner Magnetosphere/Ionosphere (CIMI) model. The global hybrid code solves fully kinetic equations governing the ions and a fluid model for electrons in the self-consistent electromagnetic field of the dayside and night side outer magnetosphere. In the integrated computation model, the hybrid simulation provides the CIMI model with field data in the CIMI 3-D domain and particle data at its boundary, and the transport in the inner magnetosphere is calculated by the CIMI model. By joining the two existing codes, effects of the solar wind on particle transport through the outer magnetosphere into the inner magnetosphere are investigated. Our simulation shows that fast flows and flux ropes are localized transients in the magnetotail plasma sheet and their overall structures have a dawn-dusk asymmetry. Strong perpendicular ion heating is found at the fast flow braking, which affects the earthward transport of entropy-depleted bubbles. We report on the impacts from the temperature anisotropy and non-Maxwellian ion distributions associated with the fast flows on the ring current and the convection electric field.

Recent successes and emerging challenges for coordinated satellite/ground-based magnetospheric exploration and modeling.

Science.gov (United States)

Angelopoulos, Vassilis

With the availability of a distributed constellation of spacecraft (THEMIS, Geotail, Cluster) and increased capability ground based arrays (SuperDARN, THEMIS/GBOs), it is now pos-sible to infer simply from timing significant information regarding mapping of magnetospheric phenomena. Optical, magnetometer and radar data can pinpoint the location and nature of onset signatures. On the other hand, magnetic field modeling constrained by physical bound-aries (such as the isotropy boundary) the measured magnetic field and total pressure values at a distibuted network of satellites has proven to do a much better job at correlating ionospheric precipitation and diffuse auroral boundaries to magnetospheric phenomena, such as the inward boundary of the dipolarization fronts. It is now possible to routinely compare in-situ measured phase space densities of ion and electron distributions during ionosphere -magnetosphere con-junctions, in the absense of potential drops. It is also possible to not only infer equivalent current systems from the ground, but use reconstruction of the ionospheric current system from space to determine the full electrodynamics evolution of the ionosphere and compare with radars. Assimilation of this emerging ground based and global magnetospheric panoply into a self consistent magnetospheric model will likely be one of the most fruitful endeavors in magnetospheric exploration during the next few years.

A compact rotating dilution refrigerator

Science.gov (United States)

Fear, M. J.; Walmsley, P. M.; Chorlton, D. A.; Zmeev, D. E.; Gillott, S. J.; Sellers, M. C.; Richardson, P. P.; Agrawal, H.; Batey, G.; Golov, A. I.

2013-10-01

We describe the design and performance of a new rotating dilution refrigerator that will primarily be used for investigating the dynamics of quantized vortices in superfluid 4He. All equipment required to operate the refrigerator and perform experimental measurements is mounted on two synchronously driven, but mechanically decoupled, rotating carousels. The design allows for relative simplicity of operation and maintenance and occupies a minimal amount of space in the laboratory. Only two connections between the laboratory and rotating frames are required for the transmission of electrical power and helium gas recovery. Measurements on the stability of rotation show that rotation is smooth to around 10-3 rad s-1 up to angular velocities in excess of 2.5 rad s-1. The behavior of a high-Q mechanical resonator during rapid changes in rotation has also been investigated.

Magnetosphere - Ionosphere - Thermosphere (MIT) Coupling at Jupiter

Science.gov (United States)

Yates, J. N.; Ray, L. C.; Achilleos, N.

2017-12-01

Jupiter's upper atmospheric temperature is considerably higher than that predicted by Solar Extreme Ultraviolet (EUV) heating alone. Simulations incorporating magnetosphere-ionosphere coupling effects into general circulation models have, to date, struggled to reproduce the observed atmospheric temperatures under simplifying assumptions such as azimuthal symmetry and a spin-aligned dipole magnetic field. Here we present the development of a full three-dimensional thermosphere model coupled in both hemispheres to an axisymmetric magnetosphere model. This new coupled model is based on the two-dimensional MIT model presented in Yates et al., 2014. This coupled model is a critical step towards to the development of a fully coupled 3D MIT model. We discuss and compare the resulting thermospheric flows, energy balance and MI coupling currents to those presented in previous 2D MIT models.

Identification of the different magnetic field contributions during a geomagnetic storm in magnetospheric and ground observations

Directory of Open Access Journals (Sweden)

T. Alberti

2016-11-01

Full Text Available We used the empirical mode decomposition (EMD to investigate the time variation of the magnetospheric and ground-based observations of the Earth's magnetic field during both quiet and disturbed periods. We found two timescale variations in magnetospheric data which are associated with different magnetospheric current systems and the characteristic diurnal orbital variation, respectively. On the ground we identified three timescale variations related to the solar-wind–magnetosphere high-frequency interactions, the ionospheric processes, and the internal dynamics of the magnetosphere. This approach is able to identify the different physical processes involved in solar-wind–magnetosphere–ionosphere coupling. In addition, the large-timescale contribution can be used as a local index for the identification of the intensity of a geomagnetic storm on the ground.

Hydromagnetic stability of rotating stratified compressible fluid flows

Energy Technology Data Exchange (ETDEWEB)

Srinivasan, V; Kandaswamy, P [Dept. of Mathematics, Bharathiar University, Coimbatore, Tamil Nadu, India; Debnath, L [Dept. of Mathematics, University of Central Florida, Orlando, USA

1984-09-01

The hydromagnetic stability of a radially stratified compressible fluid rotating between two coaxial cylinders is investigated. The stability with respect to axisymmetric disturbances is examined. The fluid system is found to be thoroughly stable to axisymmetric disturbances provided the fluid rotates very rapidly. The system is shown to be unstable to non-axisymmetric disturbances, and the slow amplifying hydromagnetic wave modes propagate against the basic rotation. The lower and upper bounds of the azimuthal phase speeds of the amplifying waves are determined. A quadrant theorem on the slow waves characteristic of a rapidly rotating fluid is derived. Special attention is given to the effects of compressibility of the fluid. Some results concerning the stability of an incompressible fluid system are obtained as special cases of the present analysis.

On the electric field model for an open magnetosphere

Science.gov (United States)

Wang, Zhi; Ashour-Abdalla, Maha; Walker, Raymond J.

1993-01-01

We have developed a new canonical separator line type magnetospheric magnetic field and electric field model for use in magnetospheric calculations, we determine the magnetic and electric field by controlling the reconnection rate at the subsolar magnetopause. The model is applicable only for purely southward interplanetary magnetic field (IMF). We have obtained a more realistic magnetotail configuration by applying a stretch transformation to an axially symmetric field solution. We also discuss the Stern singularity in which there is an electric field singlarity in the canonical separate line models for B(sub y) not = to 0 by using a new technique that solves for the electric field along a field line directly instead of determining it by a potential mapping. The singularity not only causes an infinite electric field on the polar cap, but also causes the boundary conditions at plus infinity and minus infinity in the solar wind to contradict each other. This means that the canonical separator line models do not represent the open magnetosphere well, except for the case of purely southward IMF.

Results of investigation of magnetohydrodynamic flow round the magnetosphere

International Nuclear Information System (INIS)

Erkaev, N.V.

1988-01-01

Review of the main results of the study on the Earth magnetosphere quasi-stationary magnetohydrodynamic flow-around by the solar wind is given. The principle attenuation is paid to the problem of magnetic and electric fields calculation in the transition layer and at the magnetosphere boundary. Analysis of kinematic approximation and linear diffusion model is conducted. Existence condition for the magnetic barrier region, where kinematic approximation is inapplicable, is determined. Main properties of the solution - gasokinetic pressure decrease and magnetic pressure increase up to maximum at the numerical integration results of magnetohydrodynamic equations within the magnetic barrier range. Calculation problem of reconnection field at the magnetic barrier background is considered as the next step. It is shown, that the introduction of Petchek reconnection model into the problem solution general diagram allows to obtain at the magnetosphere boundary the values of electric and magnetic fields, compatible with the experiment. Problems, linked with choice of reconnection line direction and Petchek condition generalization for the case of the crossed field reconnection, are considered

Calculation of the Initial Magnetic Field for Mercury's Magnetosphere Hybrid Model

Science.gov (United States)

Alexeev, Igor; Parunakian, David; Dyadechkin, Sergey; Belenkaya, Elena; Khodachenko, Maxim; Kallio, Esa; Alho, Markku

2018-03-01

Several types of numerical models are used to analyze the interactions of the solar wind flow with Mercury's magnetosphere, including kinetic models that determine magnetic and electric fields based on the spatial distribution of charges and currents, magnetohydrodynamic models that describe plasma as a conductive liquid, and hybrid models that describe ions kinetically in collisionless mode and represent electrons as a massless neutralizing liquid. The structure of resulting solutions is determined not only by the chosen set of equations that govern the behavior of plasma, but also by the initial and boundary conditions; i.e., their effects are not limited to the amount of computational work required to achieve a quasi-stationary solution. In this work, we have proposed using the magnetic field computed by the paraboloid model of Mercury's magnetosphere as the initial condition for subsequent hybrid modeling. The results of the model have been compared to measurements performed by the Messenger spacecraft during a single crossing of the magnetosheath and the magnetosphere. The selected orbit lies in the terminator plane, which allows us to observe two crossings of the bow shock and the magnetopause. In our calculations, we have defined the initial parameters of the global magnetospheric current systems in a way that allows us to minimize paraboloid magnetic field deviation along the trajectory of the Messenger from the experimental data. We have shown that the optimal initial field parameters include setting the penetration of a partial interplanetary magnetic field into the magnetosphere with a penetration coefficient of 0.2.

Magnetospheric pulsations: Models and observations of compressional waves

International Nuclear Information System (INIS)

Zhu, Xiaoming.

1989-01-01

The first part of the dissertation models ultralow frequency (ULF) waves in a simplified geometry in order to understand the physics of the mode coupling between the compressional and shear Alfven waves in an inhomogeneous magnetized plasma. Wave mode coupling occurs when a field line resonant frequency (defined by the shear Alfven mode) matches the global mode frequency (defined by the compressional mode). Large wave amplitudes occur near the resonant field line. Although the wave amplitude of the global mode is small away from resonant field lines, significant wave energy is stored in the wave mode due to its large scale nature. It serves as a reservoir to continuously feed energy to resonant field lines. This mechanism may explain why some field line resonances can last for times longer than that predicted from the ionospheric Joule dissipation. A nonmonotonic Alfven velocity divides the magnetosphere into two or more cavities by the local maxima of the Alfven velocity. The global mode is typically localized in one of the cavities except at some preferred frequencies, the global mode can extend through more than one cavity. This may explain ULF wave excitations in the low latitude magnetosphere. The second part of the dissertation is devoted to study compressional waves in the outer magnetosphere using magnetic field and plasma data. Statistical information on the distribution of compressional Pc 5 waves in the outer magnetosphere is obtained. Large amplitude, long period compressional Pc 5 pulsations are found very common near the magnetic equator. They are polarized mainly in a meridian plane with comparable compressional and transverse amplitudes. Close correlation between compressional wave amplitude and plasma β is also found. Several case studies show that compressional waves are quenched in the region where β < 1

Magnetospheric signature of some F layer positive storms

International Nuclear Information System (INIS)

Miller, N.J.; Mayr, H.G.; Grebowsky, J.M.; Harris, I.; Tulunay, Y.K.

1981-01-01

Calculations using a self-consistent model of the global thermosphere-ionosphere system perturbed by high-latitude thermospheric heating show that the resultant electron density disturbances within the mid-latitude F layer can propagate upward along magnetic field lines to the equator. The F layer disturbances described by the model calculations correspond to the evolution of enhancements or reductions in electron density that is called the positive or negative phase of an F layer storm. We deduce that the positive phase of dayside F layer storms is initiated when high-latitude thermospheric heating generates equatorward winds. These winds raise the mid-latitude F layer along the geomagnetic field B through momentum transfer from neutral atoms to F layer ons that pull electrons with them. For Lapprox.3 or less the upward movement of ionospheric plasma results in ionization increases at all altitudes along B from the F2 maximum to the equator. An increase in the average magnitude of the equatorial dawn-dusk magnetospheric electric field retards the dayside development of a positive storm phase by drifting plasma away from mid-latitude field lines along which the electron density is increasing. During an F layer storm in June 1972, instruments on Explorer 45 and Ariel 4 detected dayside electron density enhancements simultaneously at 550 km over mid-latitudes and near the equatorial plane in the magnetosphere. These in situ measurements support the model prediction that disturbances in the magnetospheric plasma near the equator can arise through interactions occuring at lower altitudes along a magnetic field line. Our study demonstrates that some storm time enhancements of dayside magnetospheric plasma near Lapprox.2--3 may be signatures of the positive phase of an F layer storm

On the detection of magnetospheric radio bursts from Uranus and Neptune

International Nuclear Information System (INIS)

Kennel, C.F.; Maggs, J.E.

1975-11-01

Earth, Jupiter, and Saturn are sources of intense but sporadic bursts of electromagnetic radiation or magnetospheric radio bursts (MRB). The similarity of the differential power flux spectra of the MRB from all three planets is examined. The intensity of the MRB is scaled for the solar wind power input into a planetary magnetosphere. The possibility of detecting MRB from Uranus and Neptune is considered

Multi-fluid simulations of the coupled solar wind-magnetosphere-ionsphere system

Science.gov (United States)

Lyon, J.

2011-12-01

This paper will review recent work done with the multi-fluid version of the Lyon-Fedder-Mobarry (MF-LFM) global MHD simulation code. We will concentrate on O+ outflow from the ionosphere and its importance for magnetosphere-ionosphere (MI) coupling and also the importance of ionospheric conditions in determining the outflow. While the predominant method of coupling between the magnetosphere and ionosphere is electrodynamic, it has become apparent the mass flows from the ionosphere into the magnetosphere can have profound effects on both systems. The earliest models to attempt to incorporate this effect used very crude clouds of plasma near the Earth. The earliest MF-LFM results showed that depending on the details of the outflow - where, how much, how fast - very different magnetospheric responses could be found. Two approaches to causally driven models for the outflow have been developed for use in global simulations, the Polar Wind Outflow Model (PWOM), started at the Univ. of Michigan, and the model used by Bill Lotko and co-workers at Dartmouth. We will give a quick review of this model which is based on the empirical relation between outflow fluence and Poynting flux discovered by Strangeway. An additional factor used in this model is the precipitating flux of electrons, which is presumed to correlate with the scale height of the upwelling ions. parameters such as outflow speed and density are constrained by the total fluence. The effects of the outflow depend on the speed. Slower outflow tends to land in the inner magnetosphere increasing the strength of the ring current. Higher speed flow out in the tail. Using this model, simulations have shown that solar wind dynamic pressure has a profound effect on the amount of fluence. The most striking result has been the simulation of magnetospheric sawtooth events. We will discuss future directions for this research, emphasizing the need for better physical models for the outflow process and its coupling to the

Statistical analyses in the study of solar wind-magnetosphere coupling

International Nuclear Information System (INIS)

Baker, D.N.

1985-01-01

Statistical analyses provide a valuable method for establishing initially the existence (or lack of existence) of a relationship between diverse data sets. Statistical methods also allow one to make quantitative assessments of the strengths of observed relationships. This paper reviews the essential techniques and underlying statistical bases for the use of correlative methods in solar wind-magnetosphere coupling studies. Techniques of visual correlation and time-lagged linear cross-correlation analysis are emphasized, but methods of multiple regression, superposed epoch analysis, and linear prediction filtering are also described briefly. The long history of correlation analysis in the area of solar wind-magnetosphere coupling is reviewed with the assessments organized according to data averaging time scales (minutes to years). It is concluded that these statistical methods can be very useful first steps, but that case studies and various advanced analysis methods should be employed to understand fully the average response of the magnetosphere to solar wind input. It is clear that many workers have not always recognized underlying assumptions of statistical methods and thus the significance of correlation results can be in doubt. Long-term averages (greater than or equal to 1 hour) can reveal gross relationships, but only when dealing with high-resolution data (1 to 10 min) can one reach conclusions pertinent to magnetospheric response time scales and substorm onset mechanisms

Rotational superradiance in fluid laboratories

CERN Document Server

Cardoso, Vitor; Richartz, Mauricio; Weinfurtner, Silke

2016-01-01

Rotational superradiance has been predicted theoretically decades ago, and is the chief responsible for a number of important effects and phenomenology in black hole physics. However, rotational superradiance has never been observed experimentally. Here, with the aim of probing superradiance in the lab, we investigate the behaviour of sound and surface waves in fluids resting in a circular basin at the center of which a rotating cylinder is placed. We show that with a suitable choice for the material of the cylinder, surface and sound waves are amplified. By confining the superradiant modes near the rotating cylinder, an instability sets in. Our findings are experimentally testable in existing fluid laboratories and hence offer experimental exploration and comparison of dynamical instabilities arising from rapidly rotating boundary layers in astrophysical as well as in fluid dynamical systems.

The Response of the Thermosphere and Ionosphere to Magnetospheric Forcing

Science.gov (United States)

Rees, D.; Fuller-Rowell, T. J.

1989-06-01

During the past six years, rapid advances in three observational techniques (ground-based radars, optical interferometers and satellite-borne instruments) have provided a means of observing a wide range of spectacular interactions between the coupled magnetosphere, ionosphere and thermosphere system. Perhaps the most fundamental gain has come from the combined data-sets from the NASA Dynamics Explorer (DE) Satellites. These have unambiguously described the global nature of thermospheric flows, and their response to magnetospheric forcing. The DE spacecraft have also described, at the same time, the magnetospheric particle precipitation and convective electric fields which force the polar thermosphere and ionosphere. The response of the thermosphere to magnetospheric forcing is far more complex than merely the rare excitation of 1 km s-1 wind speeds and strong heating; the heating causes large-scale convection and advection within the thermosphere. These large winds grossly change the compositional structure of the upper thermosphere at high and middle latitudes during major geomagnetic disturbances. Some of the major seasonal and geomagnetic storm-related anomalies of the ionosphere are directly attributable to the gross wind-induced changes of thermospheric composition; the mid-latitude ionospheric storm `negative phase', however, is yet to be fully understood. The combination of very strong polar wind velocities and rapid plasma convection forced by magnetospheric electric fields strongly and rapidly modify F-region plasma distributions generated by the combination of local solar and auroral ionization sources. Until recently, however, it has been difficult to interpret the observed complex spatial and time-dependent structures and motions of the thermosphere and ionosphere because of their strong and nonlinear coupling. It has recently been possible to complete a numerical and computational merging of the University College London (UCL) global thermospheric

Effects of construction and operation of a satellite power system upon the magnetosphere

International Nuclear Information System (INIS)

Chiu, Y.T.; Luhmann, J.G.; Schulz, M.; Cornwall, J.M.

1979-01-01

This is the final report of an initial assessment of magnetospheric effects of the construction and operation of a satellite power system. This assessment effort is based on application of present scientific knowledge rather than on original scientific research. As such, it appears that mass and energy injections of the system are sufficient to modify the magnetosphere substantially, to the extent of possibly requiring mitigation measures for space systems but not to the extent of causing major redirection of efforts and concepts. The scale of the SPS is so unprecedentedly large, however, that these impressions require verification (or rejection) by in-depth assessment based on scientific treatment of the principal issues. Indeed, it is perhaps appropriate to state that present ignorance far exceeds present knowledge in regard to SPS magnetospheric effects, even though we only seek to define the approximate limits of magnetospheric modifications here

Differential rotation in magnetic stars

International Nuclear Information System (INIS)

Moss, D.

1981-01-01

The possibility that large-scale magnetic fields in stars are the product of a contemporary dynamo situated in the convective stellar core, rather than being a fossil from an earlier stage in the history of the star, is investigated. It is demonstrated that then the envelope will almost inevitably be in a state of differential rotation. Some simple models are constructed to illustrate the magnitude of the effects on the structure of the envelope and magnetic field. It is found that, for models which are relatively rapidly rotating, a modest differential rotation at the surface of the core may increase considerably the ratio of internal to surface field, but only give rise to a small surface differential rotation. (author)

The aurora at quite magnetospheric conditions: Repeatability and dipole tilt angle dependence

International Nuclear Information System (INIS)

Oznovich, I.; Eastes, R.W.; Huffman, R.E.; Tur, M.; Glaser, I.

1993-01-01

Is there a magnetospheric ground state? Do the position and size of the auroral oval depend on the magnetic dipole tilt angle at quiet magnetospheric conditions? In order to address these questions, northern hemisphere images of the aurora at 1356 Angstrom, obtained by Polar BEAR at solar minimum (beginning of 1987), were related to high temporal resolution IPM 8 measurements of the interplanetary magnetic field, to solar wind velocity, and to the ground-based activity index Kp. The first problem was addressed by a two-dimensional correlation study of the repeatability of auroral emissions in corrected geomagnetic space at conditions of minimum energy transfer from the magnetosphere. The correlation measure of auroral images was 0.6-0.85. Error simulations indicate that given the uncertainties in pixel position and intensity, the maximum expected value of the correlation measure is 0.65-0.9. The notion of a ground state magnetosphere is therefore supported by this data. Repeatability was found at the same level regardless of time or reconfigurations of the magnetosphere between images and independent of magnetic time sector. The second problem was addressed by relating latitudinal shifts of the aurora with dipole tilt angle without resorting to auroral boundary specification. This data indicate that the latitude of the continuous aurora is related to the dipole tilt angle at quiet magnetospheric conditions. In the winter hemisphere a 10 degrees increase in the dipole tilt angle causes a 1 degree decrease (increase) in the latitude of auroral emissions at noon (midnight). The magnetic local time distribution of the latitudinal shifts with dipole tilt angle support a simple model in which the dipole tilt angle determines the position of the center of the auroral circle along the magnetic meridian 1320-0120 MLT (for IMF B y positive) and does not affect its radius. 22 refs., 8 figs

A Cumulant-based Analysis of Nonlinear Magnetospheric Dynamics

International Nuclear Information System (INIS)

Johnson, Jay R.; Wing, Simon

2004-01-01

Understanding magnetospheric dynamics and predicting future behavior of the magnetosphere is of great practical interest because it could potentially help to avert catastrophic loss of power and communications. In order to build good predictive models it is necessary to understand the most critical nonlinear dependencies among observed plasma and electromagnetic field variables in the coupled solar wind/magnetosphere system. In this work, we apply a cumulant-based information dynamical measure to characterize the nonlinear dynamics underlying the time evolution of the Dst and Kp geomagnetic indices, given solar wind magnetic field and plasma input. We examine the underlying dynamics of the system, the temporal statistical dependencies, the degree of nonlinearity, and the rate of information loss. We find a significant solar cycle dependence in the underlying dynamics of the system with greater nonlinearity for solar minimum. The cumulant-based approach also has the advantage that it is reliable even in the case of small data sets and therefore it is possible to avoid the assumption of stationarity, which allows for a measure of predictability even when the underlying system dynamics may change character. Evaluations of several leading Kp prediction models indicate that their performances are sub-optimal during active times. We discuss possible improvements of these models based on this nonparametric approach

Dynamics of electrons and heavy ions in Mercury's magnetosphere

International Nuclear Information System (INIS)

Ip, W.H.

1987-01-01

The present investigation of Mercury magnetosphere processes employs simple models for the adiabatic acceleration and convection of equatorially mirroring charged particles, as well as the current sheet acceleration effect and the acceleration of such exospheric ions as that of Na(+) by both electric and magnetic magnetospheric fields near Mercury's surface. The large gyroradii of such heavy ions as those of Na allow surface reimpact as well as magnetopause-interception losses to occur; gyromotion-derived kinetic energy could in the case of the latter process account for the loss of as many as half of the planet's exospheric ions. 27 references

Whistler instability in a magnetospheric duct

International Nuclear Information System (INIS)

Talukdar, I.; Tripathi, V.K.; Jain, V.K.

1989-01-01

A whistler wave propagating through a preformed magnetospheric duct is susceptible to growth/amplification by an electron beam. The interaction is non-local and could be of Cerenkov or slow-cyclotron type. First-order perturbation theory is employed to obtain the growth rate for flat and Gaussian beam densities. (author)

The Magnetospheric Boundary in Cataclysmic Variables

Directory of Open Access Journals (Sweden)

Hellier Coel

2014-01-01

During outbursts, when the accretion flow increases by orders of magnitude, the disk pushes the magnetosphere inwards, and appears to feed field lines over a much greater range of magnetic azimuth. The non-equilibrium outburst behaviour shows an even richer phenomenology than in quiescence, adding DNOs and QPOs into the mix.

Analysis of multidimensional measurements of electromagnetic waves in the Earth's magnetosphere

OpenAIRE

Pechal, Radim

2011-01-01

Title: Analysis of multidimensional measurements of electromagnetic waves in the Earth's magnetosphere Author: Radim Pechal Department: Department of Surface and Plasma Science Supervisor: doc. RNDr. Lubomír Přech, Dr. Supervisor's e-mail address: Abstract: The thesis introduces into basic knowledge of waves in plasma, especially waves in the Earth's magnetosphere. There are mentioned some space projects focused on chorus waves. The second part of this thesis is a la...

Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

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T. J. Stubbs

2001-01-01

Full Text Available Solar wind/magnetosheath plasma in the magnetosphere can be identified using a component that has a higher charge state, lower density and, at least soon after their entry into the magnetosphere, lower energy than plasma from a terrestrial source. We survey here observations taken over 3 years of He2+ ions made by the Magnetospheric Ion Composition Sensor (MICS of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE instrument aboard POLAR. The occurrence probability of these solar wind ions is then plotted as a function of Magnetic Local Time (MLT and invariant latitude (7 for various energy ranges. For all energies observed by MICS (1.8–21.4 keV and all solar wind conditions, the occurrence probabilities peaked around the cusp region and along the dawn flank. The solar wind conditions were filtered to see if this dawnward asymmetry is controlled by the Svalgaard-Mansurov effect (and so depends on the BY component of the interplanetary magnetic field, IMF or by Fermi acceleration of He2+ at the bow shock (and so depends on the IMF ratio BX /BY . It is shown that the asymmetry remained persistently on the dawn flank, suggesting it was not due to effects associated with direct entry into the magnetosphere. This asymmetry, with enhanced fluxes on the dawn flank, persisted for lower energy ions (below a "cross-over" energy of about 23 keV but reversed sense to give higher fluxes on the dusk flank at higher energies. This can be explained by the competing effects of gradient/curvature drifts and the convection electric field on ions that are convecting sunward on re-closed field lines. The lower-energy He2+ ions E × B drift dawnwards as they move earthward, whereas the higher energy ions curvature/ gradient drift towards dusk. The convection electric field in the tail is weaker for northward IMF. Ions then need less energy to drift to the dusk flank, so that the cross-over energy, at which the asymmetry changes sense, is reduced

Time-dependent Models of Magnetospheric Accretion onto Young Stars

Energy Technology Data Exchange (ETDEWEB)

Robinson, C. E.; Espaillat, C. C. [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Owen, J. E. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Adams, F. C., E-mail: connorr@bu.edu [Physics Department, University of Michigan, Ann Arbor, MI 48109 (United States)

2017-04-01

Accretion onto Classical T Tauri stars is thought to take place through the action of magnetospheric processes, with gas in the inner disk being channeled onto the star’s surface by the stellar magnetic field lines. Young stars are known to accrete material in a time-variable manner, and the source of this variability remains an open problem, particularly on the shortest (∼day) timescales. Using one-dimensional time-dependent numerical simulations that follow the field line geometry, we find that for plausibly realistic young stars, steady-state transonic accretion occurs naturally in the absence of any other source of variability. However, we show that if the density in the inner disk varies smoothly in time with ∼day-long timescales (e.g., due to turbulence), this complication can lead to the development of shocks in the accretion column. These shocks propagate along the accretion column and ultimately hit the star, leading to rapid, large amplitude changes in the accretion rate. We argue that when these shocks hit the star, the observed time dependence will be a rapid increase in accretion luminosity, followed by a slower decline, and could be an explanation for some of the short-period variability observed in accreting young stars. Our one-dimensional approach bridges previous analytic work to more complicated multi-dimensional simulations and observations.

Time-dependent Models of Magnetospheric Accretion onto Young Stars

International Nuclear Information System (INIS)

Robinson, C. E.; Espaillat, C. C.; Owen, J. E.; Adams, F. C.

2017-01-01

Accretion onto Classical T Tauri stars is thought to take place through the action of magnetospheric processes, with gas in the inner disk being channeled onto the star’s surface by the stellar magnetic field lines. Young stars are known to accrete material in a time-variable manner, and the source of this variability remains an open problem, particularly on the shortest (∼day) timescales. Using one-dimensional time-dependent numerical simulations that follow the field line geometry, we find that for plausibly realistic young stars, steady-state transonic accretion occurs naturally in the absence of any other source of variability. However, we show that if the density in the inner disk varies smoothly in time with ∼day-long timescales (e.g., due to turbulence), this complication can lead to the development of shocks in the accretion column. These shocks propagate along the accretion column and ultimately hit the star, leading to rapid, large amplitude changes in the accretion rate. We argue that when these shocks hit the star, the observed time dependence will be a rapid increase in accretion luminosity, followed by a slower decline, and could be an explanation for some of the short-period variability observed in accreting young stars. Our one-dimensional approach bridges previous analytic work to more complicated multi-dimensional simulations and observations.

A case study testing the cavity mode model of the magnetosphere

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D. V. Sarafopoulos

2005-07-01

Full Text Available Based on a case study we test the cavity mode model of the magnetosphere, looking for eigenfrequencies via multi-satellite and multi-instrument measurements. Geotail and ACE provide information on the interplanetary medium that dictates the input parameters of the system; the four Cluster satellites monitor the magnetopause surface waves; the POLAR (L=9.4 and LANL 97A (L=6.6 satellites reveal two in-situ monochromatic field line resonances (FLRs with T=6 and 2.5 min, respectively; and the IMAGE ground magnetometers demonstrate latitude dependent delays in signature arrival times, as inferred by Sarafopoulos (2004b. Similar dispersive structures showing systematic delays are also extensively scrutinized by Sarafopoulos (2005 and interpreted as tightly associated with the so-called pseudo-FLRs, which show almost the same observational characteristics with an authentic FLR. In particular for this episode, successive solar wind pressure pulses produce recurring ionosphere twin vortex Hall currents which are identified on the ground as pseudo-FLRs. The BJN ground magnetometer records the pseudo-FLR (alike with the other IMAGE station responses associated with an intense power spectral density ranging from 8 to 12 min and, in addition, two discrete resonant lines with T=3.5 and 7 min. In this case study, even though the magnetosphere is evidently affected by a broad-band compressional wave originated upstream of the bow shock, nevertheless, we do not identify any cavity mode oscillation within the magnetosphere. We fail, also, to identify any of the cavity mode frequencies proposed by Samson (1992.

Keywords. Magnetospheric physics (Magnetosphereionosphere interactions; Solar wind-magnetosphere interactions; MHD waves and instabilities

Propagation of microwaves in pulsar magnetospheres

Energy Technology Data Exchange (ETDEWEB)

Bodo, G; Ferrari, A [Turin Univ. (Italy). Ist. di Fisica Generale; Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica); Massaglia, S [Turin Univ. (Italy). Ist. di Fisica Generale; Cambridge Univ. (UK). Inst. of Astronomy)

1981-12-01

We discuss the dispersion relation of linearly-polarized waves, propagating along a strong background magnetic field embedded in an electron-positron plasma. The results are then applied to the study of the propagation conditions of coherent curvature radio radiation inside neutron stars magnetospheres, as produced by electric discharges following current pulsar models.

Coupling of the Magnetosphere-Ionosphere/Thermosphere and Oxygen Outflow-- MIT Mission

Science.gov (United States)

Fu, S.

2017-12-01

The goal of the MIT mission is to understand the coupling of the magnetosphere and ionosphere from the prospective of particles. It will focus on the outflow of the ionosphere particles (mainly oxygen ions) from the Earth, including the acceleration mechanisms of oxygen ions and their relative importance in different regions, the importance of these ions while transferred into the magnetosphere and the roles they played in magnetosphere activities. A constellation of four satellites orbiting at three elliptical orbits will provide the unique opportunities to observed there ions at three different altitude with temporal changes of the flux of these particles and the magnetic field environments. The conceptual design of the spacecraft and a summary of the payload will be presented. The MIT mission was selected as one of the five candidates for the upcoming mission plan in China.

The use of electron beams as probes of the distant magnetosphere

International Nuclear Information System (INIS)

Winckler, J.R.

1982-01-01

This chapter reports on experiments in which electron beams have been injected into the magnetosphere in order to diagnose plasma processes at a great distance by measurements made in the ionosphere. Topics considered include the beam injecting rocket system in the ionosphere; beam detection and analysis; echo detection by particle counters; echo analysis; the structure of echoes; the atmosphere as a detector; radio and radar methods; perturbation of the distant magnetosphere by beam injection; changes in the injected beam in the near-rocket region; some observations of the distant magnetosphere by beams; the comparison of distant and local electric fields; electron diffusion; the distant magnetic field; and future possibilities. Conjugate locations, field line lengths, electric and magnetic drifts, field fluctuations, and electron scattering and diffusion are analyzed. Echo detection by particle counters on some of the ECHO rocket series is discussed in detail

MESSENGER observations of magnetic reconnection in Mercury's magnetosphere.

Science.gov (United States)

Slavin, James A; Acuña, Mario H; Anderson, Brian J; Baker, Daniel N; Benna, Mehdi; Boardsen, Scott A; Gloeckler, George; Gold, Robert E; Ho, George C; Korth, Haje; Krimigis, Stamatios M; McNutt, Ralph L; Raines, Jim M; Sarantos, Menelaos; Schriver, David; Solomon, Sean C; Trávnícek, Pavel; Zurbuchen, Thomas H

2009-05-01

Solar wind energy transfer to planetary magnetospheres and ionospheres is controlled by magnetic reconnection, a process that determines the degree of connectivity between the interplanetary magnetic field (IMF) and a planet's magnetic field. During MESSENGER's second flyby of Mercury, a steady southward IMF was observed and the magnetopause was threaded by a strong magnetic field, indicating a reconnection rate ~10 times that typical at Earth. Moreover, a large flux transfer event was observed in the magnetosheath, and a plasmoid and multiple traveling compression regions were observed in Mercury's magnetotail, all products of reconnection. These observations indicate that Mercury's magnetosphere is much more responsive to IMF direction and dominated by the effects of reconnection than that of Earth or the other magnetized planets.

Enhanced ionosphere-magnetosphere data from the DMSP satellites

International Nuclear Information System (INIS)

Rich, F.J.; Hardy, D.A.; Gussenhoven, M.S.

1985-01-01

The satellites of the Defense Meteorological Satellite Program (DMSP) represent a series of low-altitude (835 km) polar-orbiting satellites. Their primary objective is related to the observation of the tropospheric weather with a high-resolution white light and infrared imaging system. It is also possible to make images of auroras. On a daily basis, information about auroras is used to assist various communication systems which are affected by the ionospheric disturbances associated with auroras. In the past few years, there have been several improvements in the ionospheric monitoring instrumentation. Since the high-latitude ionosphere is connected to the magnetosphere, the DMSP data are used to monitor magnetospheric processes. The instrumentation of the DMSP satellites is discussed, taking into account the data provided by them. 7 references

IMF BY and the seasonal dependences of the electric field in the inner magnetosphere

Directory of Open Access Journals (Sweden)

H. Matsui

2005-10-01

Full Text Available It is known that the electric field pattern at high latitudes depends on the polarity of the Y component of the interplanetary magnetic field (IMF BY and season. In this study, we investigate the seasonal and BY dependences in the inner magnetosphere using the perigee (4magnetosphere. These data are sorted by the polarities of IMF BZ and BY, and by seasons or hemispheres. It is demonstrated from our statistics that the electric fields in the inner magnetosphere depend on these quantities. The following three points are inferred: 1 The electric fields exhibit some differences statistically between Cluster locations at the Northern and Southern Hemispheres with the same dipole L and magnetic local time (MLT values and during the same IMF conditions. These differences in the electric fields might result from hemispherical differences in magnetic field geometry and/or those in field-aligned potential difference. 2 The IMF BY and seasonal dependence of the dawnside and duskside electric fields at 4magnetosphere measured by Cluster is often similar to that in the magnetotail lobe. In the future, it will be necessary to incorporate these dependencies on IMF BY and season into a realistic model of the inner magnetospheric convection electric field. Keywords. Magnetospheric physics (Electric fields; Magnetosphere-ionosphere interactions; Solar windmagnetosphere interactions

The Structure of Martian Magnetosphere at the Dayside Terminator Region as Observed on MAVEN Spacecraft

Science.gov (United States)

Vaisberg, O. L.; Ermakov, V. N.; Shuvalov, S. D.; Zelenyi, L. M.; Halekas, J.; DiBraccio, G. A.; McFadden, J.; Dubinin, E. M.

2018-04-01

We analyzed 44 passes of the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) spacecraft through the magnetosphere, arranged by the angle between electric field vector and the projection of spacecraft position radius vector in the plane perpendicular to the Mars-Sun line (θE). All passes were divided into three angular sectors near 0°, 90°, and 180° θE angles in order to estimate the role of the interplanetary magnetic field direction in plasma and magnetic properties of dayside Martian magnetosphere. The time interval chosen was from 17 January to 4 February 2016 when MAVEN was crossing the dayside magnetosphere at solar zenith angle 70°. Magnetosphere as the region with prevailing energetic planetary ions is always found between the magnetosheath and the ionosphere. The analysis of dayside interaction region showed that for each angular sector with different orientation of the solar wind electric field vector E = -1/c V × B one can find specific profiles of the magnetosheath, the magnetic barrier (Michel, 1971, https://doi.org/10.1029/RG009i002p00427; Zhang et al., 1991, https://doi.org/10.1029/91JA00088), and the magnetosphere. Magnetic barrier forms in front of the magnetosphere, and relative magnetic field magnitudes in these two domains vary. The average height of the boundary with ionosphere is 530 km, and the average height of the magnetopause is 730 km. We discuss the implications of the observed magnetosphere structure to the planetary ions loss mechanism.

Coupling between the solar wind and the magnetosphere: CDAW 6

International Nuclear Information System (INIS)

Tsurutani, B.T.; Slavin, J.A.; Kamide, Y.; Zwickl, R.D.; King, J.H.; Russell, C.T.

1985-01-01

Interplanetary conditions (VB 3 , V 2 B 3 and epsilon-c) are derived from ISEE 3 and IMP 8 field and plasma data for the two Coordinated Data Analysis Workshop (CDAW 6) intervals of study and are compared with various aspects of geomagnetic activity (AE, U/sub T/, derived Joule heating, electric potential, westward eastward and total electrojet currents). The March 22 (day 81), 1979, interval contains two distinct periods of geomagnetic activity, both highly correlated with interplanetary features. The start of the first active interval is caused by a southward turning of the interplanetary magnetic field (IMF) associated with the passage of a heliospheric current sheet. The start of the second interval is related to a second IMF southward turning. The geomagnetic activity intensifies when the second crossing of the current sheet, and a ram pressure increase of 4 to 6, impinges on the magnetosphere. Because the interplanetary parameters VB 3 , V 2 B 3 and epsilon-c decrease across the discontinuity, it is concluded that either additional energy is injected into the magnetosphere from the conversion of ram energy into magnetospheric substorm energy or some feature associated with current sheet crossing ''triggers'' the release of previously stored magnetosphere/magnetotail energy. It is not possible at this time to distinguish between these two possibilities. For day 81, VB 3 , V 2 4 3 , and epsilon-c were highly correlated with AL, AE, westward and equivalent currents with coefficients ranging from approx.0.75 to 0.90

Rotating saddle trap as Foucault's pendulum

Science.gov (United States)

Kirillov, Oleg N.; Levi, Mark

2016-01-01

One of the many surprising results found in the mechanics of rotating systems is the stabilization of a particle in a rapidly rotating planar saddle potential. Besides the counterintuitive stabilization, an unexpected precessional motion is observed. In this note, we show that this precession is due to a Coriolis-like force caused by the rotation of the potential. To our knowledge, this is the first example where such a force arises in an inertial reference frame. We also propose a simple mechanical demonstration of this effect.

Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

Science.gov (United States)

Jasinski, Jamie M.; Slavin, James A.; Raines, Jim M.; DiBraccio, Gina A.

2017-12-01

We analyze 94 traversals of Mercury's southern magnetospheric plasma mantle using data from the MESSENGER spacecraft. The mean and median proton number densities in the mantle are 1.5 and 1.3 cm-3, respectively. For sodium number density these values are 0.004 and 0.002 cm-3. Moderately higher densities are observed on the magnetospheric dusk side. The mantle supplies up to 1.5 × 108 cm-2 s-1 and 0.8 × 108 cm-2 s-1 of proton and sodium flux to the plasma sheet, respectively. We estimate the cross-electric magnetospheric potential from each observation and find a mean of 19 kV (standard deviation of 16 kV) and a median of 13 kV. This is an important result as it is lower than previous estimations and shows that Mercury's magnetosphere is at times not as highly driven by the solar wind as previously thought. Our values are comparable to the estimations for the ice giant planets, Uranus and Neptune, but lower than Earth. The estimated potentials do have a very large range of values (1-74 kV), showing that Mercury's magnetosphere is highly dynamic. A correlation of the potential is found to the interplanetary magnetic field (IMF) magnitude, supporting evidence that dayside magnetic reconnection can occur at all shear angles at Mercury. But we also see that Mercury has an Earth-like magnetospheric response, favoring -BZ IMF orientation. We find evidence that -BX orientations in the IMF favor the southern cusp and southern mantle. This is in agreement with telescopic observations of exospheric emission, but in disagreement with modeling.

Thermosphere as a sink of magnetospheric energy - a review of recent observations of dynamics

International Nuclear Information System (INIS)

Killeen, T.L.

1985-01-01

It is pointed out that the past few years have seen an unprecedented influx of new experimental information on the dynamics of the neutral upper atmosphere of the earth. Vector wind measurements provide new information for studies of the thermospheric response to magnetospheric forcing. This response occurs through the medium of convecting ionospheric ions set into motion by electric fields of magnetospheric origin. The ultimate sink for much of the energy and momentum coming from the magnetosphere is the neutral thermosphere whose dynamics have, in the past, received far less attention than their ionospheric counterpart because of basic experimental limitations. In this paper, a review is provided of the progress made in the last few years on the basis of the Dynamics Explorer neutral wind observations, taking into account the coupling between the magnetosphere and the thermosphere via the ionosphere. 26 references

Solar Rotational Periodicities and the Semiannual Variation in the Solar Wind, Radiation Belt, and Aurora

Science.gov (United States)

Emery, Barbara A.; Richardson, Ian G.; Evans, David S.; Rich, Frederick J.; Wilson, Gordon R.

2011-01-01

The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from S to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005 -2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (approx.1980, approx.1990, and approx. 2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995-1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27 -day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the > 2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods

Solar wind dynamic pressure variations and transient magnetospheric signatures

International Nuclear Information System (INIS)

Sibeck, D.G.; Baumjohann, W.

1989-01-01

Contrary to the prevailing popular view, we find some transient ground events with bipolar north-south signatures are related to variations in solar wind dynamic pressure and not necessarily to magnetic merging. We present simultaneous solar wind plasma observations for two previously reported transient ground events observed at dayside auroral latitudes. During the first event, originally reported by Lanzerotti et al. [1987], conjugate ground magnetometers recorded north-south magetic field deflections in the east-west and vertical directions. The second event was reported by Todd et al. [1986], we noted ground rader observations indicating strong northward then southward ionospheric flows. The events were associated with the postulated signatures of patchy, sporadic, merging of magnetosheath and magnetospheric magnetic field lines at the dayside magnetospause, known as flux transfer events. Conversely, we demonstrate that the event reported by Lanzerotti et al. was accompanied by a sharp increase in solar wind dynamic pressure, a magnetospheric compression, and a consequent ringing of the magnetospheric magnetic field. The event reported by Todd et al. was associated with a brief but sharp increase in the solar wind dynamic pressure. copyright American Geophysical Union 1989

First results from the RAPID imaging energetic particle spectrometer on board Cluster

Directory of Open Access Journals (Sweden)

B. Wilken

Full Text Available The advanced energetic particle spectrometer RAPID on board Cluster can provide a complete description of the relevant particle parameters velocity, V , and atomic mass, A, over an energy range from 30 keV up to 1.5 MeV. We present the first measurements taken by RAPID during the commissioning and the early operating phases. The orbit on 14 January 2001, when Cluster was travelling from a perigee near dawn northward across the pole towards an apogee in the solar wind, is used to demonstrate the capabilities of RAPID in investigating a wide variety of particle populations. RAPID, with its unique capability of measuring the complete angular distribution of energetic particles, allows for the simultaneous measurements of local density gradients, as reflected in the anisotropies of 90° particles and the remote sensing of changes in the distant field line topology, as manifested in the variations of loss cone properties. A detailed discussion of angle-angle plots shows considerable differences in the structure of the boundaries between the open and closed field lines on the nightside fraction of the pass and the magnetopause crossing. The 3 March 2001 encounter of Cluster with an FTE just outside the magnetosphere is used to show the first structural plasma investigations of an FTE by energetic multi-spacecraft observations.

Key words. Magnetospheric physics (energetic particles, trapped; magnetopause, cusp and boundary layers; magnetosheath

Modeling of the propagation of low-frequency electromagnetic radiation in the Earth’s magnetosphere

International Nuclear Information System (INIS)

Lebedev, N. V.; Rudenko, V. V.

2015-01-01

A numerical algorithm for solving the set of differential equations describing the propagation of low-frequency electromagnetic radiation in the magnetospheric plasma, including in the presence of geomagnetic waveguides in the form of large-scale plasma density inhomogeneities stretched along the Earth’s magnetic field, has been developed. Calculations of three-dimensional ray trajectories in the magnetosphere and geomagnetic waveguide with allowance for radiation polarization have revealed characteristic tendencies in the behavior of electromagnetic parameters along the ray trajectory. The results of calculations can be used for magnetospheric plasma diagnostics

Actions of magnetospheres on planetary atmospheres

International Nuclear Information System (INIS)

Hultqvist, Bengt.

1989-12-01

Planet Earth is rather special in terms of transfer of magnetospheric energy to the atmosphere (apart from Jupiter, which is extreme in almost all respects). The auroral particle energy input rate to the atmosphere per unit area, and therefore the resulting auroral emission intensity, is second only to that of Jupiter. The contribution of the Joule heating to the heating of the upper atmosphere, measured in terms of the energetic particle precipitation power, is probably larger on Earth than on all the other planets, possibly with the exception of Uranus (and perhaps Neptune, which we know nothing of when this is written). For all those planets which have a corotating plasmasphere extending to the magnetopause, the Joule heating power is small compared with the precipitating particle power. The extremely successful Pioneer and Voyager missions have provided us with most impressive sets of data from the outer planets and Phobos has recently added unique new data from Mars. Still, the conclusion that the observational basis for our understanding of the physics of the magnetosphere-atmosphere interactions at all the planets other than Earth is very limited, is a self-evident one. Even at Earth many aspects of this interaction are frontline areas of research. The grand tour of the Voyagers has demonstrated very clearly how different the magnetospheres and atmospheres of the various planets are and the very high degree of complexity of the plasma systems around the planets. Most questions of physics are still unanswered; those related to source and sink processes of the plasma and energetic particles being one set of examples. The Galileo and Cassini-Huygens missions will certainly contribute in very important ways to the answering of many open questions. (147 refs.)

Identification of dominant flow structures in rapidly rotating convection of liquid metals using Dynamic Mode Decomposition

Science.gov (United States)

Horn, S.; Schmid, P. J.; Aurnou, J. M.

2016-12-01

The Earth's metal core acts as a dynamo whose efficiency in generating and maintaining the magnetic field is essentially determined by the rotation rate and the convective motions occurring in its outer liquid part. For the description of the primary physics in the outer core the idealized system of rotating Rayleigh-Bénard convection is often invoked, with the majority of studies considering only working fluids with Prandtl numbers of Pr ≳ 1. However, liquid metals are characterized by distinctly smaller Prandtl numbers which in turn result in an inherently different type of convection. Here, we will present results from direct numerical simulations of rapidly rotating convection in a fluid with Pr ≈ 0.025 in cylindrical containers and Ekman numbers as low as 5 × 10-6. In this system, the Coriolis force is the source of two types of inertial modes, the so-called wall modes, that also exist at moderate Prandtl numbers, and cylinder-filling oscillatory modes, that are a unique feature of small Prandtl number convection. The obtained flow fields were analyzed using the Dynamic Mode Decomposition (DMD). This technique allows to extract and identify the structures that govern the dynamics of the system as well as their corresponding frequencies. We have investigated both the regime where the flow is purely oscillatory and the regime where wall modes and oscillatory modes co-exist. In the purely oscillatory regime, high and low frequency oscillatory modes characterize the flow. When both types of modes are present, the DMD reveals that the wall-attached modes dominate the flow dynamics. They precess with a relatively low frequency in retrograde direction. Nonetheless, also in this case, high frequency oscillations have a significant contribution.

UK review of radio science, 1984-1986. Ionosphere and magnetosphere

International Nuclear Information System (INIS)

Rishbeth, H.; Jones, D.

1986-12-01

The paper contains the United Kingdom (U.K.) review of Radio Science, 1984-1986, covering ionospheric and magnetospheric science. This is the current UK contribution towards an international review published by the International Union of Radio Science (URSI). The UK review is divided into topics prescribed by URSI and covers work that is actually published within the period October 1983 - Sept. 1986, also as prescribed by URSI. The topics discussed in the review include: incoherent and coherent scatter, probing the magnetosphere, plasma instabilities, ionospheric modification, composition, ionization and chemistry and ionospheric dynamics. (U.K.)

Fast Plasma Investigation for Magnetospheric Multiscale

Science.gov (United States)

Pollock, C.; Moore, T.; Coffey, V.; Dorelli J.; Giles, B.; Adrian, M.; Chandler, M.; Duncan, C.; Figueroa-Vinas, A.; Garcia, K.;

A kinetic approach to magnetospheric modeling

International Nuclear Information System (INIS)

Whipple, E.C. Jr.

1979-01-01

The earth's magnetosphere is caused by the interaction between the flowing solar wind and the earth's magnetic dipole, with the distorted magnetic field in the outer parts of the magnetosphere due to the current systems resulting from this interaction. It is surprising that even the conceptually simple problem of the collisionless interaction of a flowing plasma with a dipole magnetic field has not been solved. A kinetic approach is essential if one is to take into account the dispersion of particles with different energies and pitch angles and the fact that particles on different trajectories have different histories and may come from different sources. Solving the interaction problem involves finding the various types of possible trajectories, populating them with particles appropriately, and then treating the electric and magnetic fields self-consistently with the resulting particle densities and currents. This approach is illustrated by formulating a procedure for solving the collisionless interaction problem on open field lines in the case of a slowly flowing magnetized plasma interacting with a magnetic dipole

A kinetic approach to magnetospheric modeling

Science.gov (United States)

Whipple, E. C., Jr.

1979-01-01

The earth's magnetosphere is caused by the interaction between the flowing solar wind and the earth's magnetic dipole, with the distorted magnetic field in the outer parts of the magnetosphere due to the current systems resulting from this interaction. It is surprising that even the conceptually simple problem of the collisionless interaction of a flowing plasma with a dipole magnetic field has not been solved. A kinetic approach is essential if one is to take into account the dispersion of particles with different energies and pitch angles and the fact that particles on different trajectories have different histories and may come from different sources. Solving the interaction problem involves finding the various types of possible trajectories, populating them with particles appropriately, and then treating the electric and magnetic fields self-consistently with the resulting particle densities and currents. This approach is illustrated by formulating a procedure for solving the collisionless interaction problem on open field lines in the case of a slowly flowing magnetized plasma interacting with a magnetic dipole.

Electron and ion Bernstein waves in Saturnian Magnetosphere

Science.gov (United States)

Bashir, M. F.; Waheed, A.; Ilie, R.; Naeem, I.; Maqsood, U.; Yoon, P. H.

2017-12-01

The study of Bernstein mode is presented in order to interpret the observed micro-structures (MIS) and banded emission (BEM) in the Saturnian magnetosphere. The general dispersion relation of Bernstein wave is derived using the Lerche-NewBerger sum rule for the kappa distribution function and further analyzed the both electron Bernstein (EB) and ion Bernstein (IB) waves. The observational data of particle measurements is obtained from the electron spectrometer (ELS) and the ion mass spectrometer (IMS), which are part of the Cassini Plasma Spectrometer (CAPS) instrument suite on board the Cassini spacecraft. For additional electron data, the measurements of Low Energy Magnetospheric Measurements System of the Magnetospheric Imaging Instrument (LEMMS /MIMI) are also utilized. The effect of kappa spectral index, density ratio (nohe/noce for EB and nohe/noi for IB) and the temperature ratio (The/Tce for EB and The/T(h,c)i for IB) on the dispersion properties are discussed employing the exact numerical analysis to explain the appearing of additional maxima/minima (points where the perpendicular group velocity vanishes, i.e., ∂w/∂k = 0) above/below the lower (for IB) and upper hybrid (EB) bands in the observation and their relation to the MIS and BED. The results of these waves may also be compared with the simulation results of Space Weather Modeling Framework (SWMF) .

An MHD simulation of the effects of the interplanetary magnetic field By component on the interaction of the solar wind with the earth's magnetosphere during southward interplanetary magnetic field

Science.gov (United States)

Ogino, T.; Walker, R. J.; Ashour-Abdalla, M.; Dawson, J. M.

1986-01-01

The interaction between the solar wind and the earth's magnetosphere has been studied by using a time-dependent three-dimensional MHD model in which the IMF pointed in several directions between dawnward and southward. When the IMF is dawnward, the dayside cusp and the tail lobes shift toward the morningside in the northern magnetosphere. The plasma sheet rotates toward the north on the dawnside of the tail and toward the south on the duskside. For an increasing southward IMF component, the plasma sheet becomes thinner and subsequently wavy because of patchy or localized tail reconnection. At the same time, the tail field-aligned currents have a filamentary layered structure. When projected onto the northern polar cap, the filamentary field-aligned currents are located in the same area as the region 1 currents, with a pattern similar to that associated with auroral surges. Magnetic reconnection also occurs on the dayside magnetopause for southward IMF.

Table-top rotating turbulence : an experimental insight through Particle Tracking

NARCIS (Netherlands)

Castello, Del L.

2010-01-01

The influence of the Earth background rotation on oceanic and atmospheric currents, as well as the effects of a rapid rotation on the flow inside industrial machineries like mixers, turbines, and compressors, are only the most typical examples of fluid flows affected by rotation. Despite the

Jupiter's magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits

DEFF Research Database (Denmark)

Connerney, J. E. P.; Adriani, Alberto; Allegrini, F.

2017-01-01

The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno's capture orbit spanned the jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context...

Alpha Channeling in a Rotating Plasma

International Nuclear Information System (INIS)

Abraham J. Fetterman; Nathaniel J. Fisch

2008-01-01

The wave-particle α-channeling effect is generalized to include rotating plasma. Specifically, radio frequency waves can resonate with α particles in a mirror machine with E x B rotation to diffuse the α particles along constrained paths in phase space. Of major interest is that the α-particle energy, in addition to amplifying the RF waves, can directly enhance the rotation energy which in turn provides additional plasma confinement in centrifugal fusion reactors. An ancillary benefit is the rapid removal of alpha particles, which increases the fusion reactivity

α Channeling in a Rotating Plasma

International Nuclear Information System (INIS)

Fetterman, Abraham J.; Fisch, Nathaniel J.

2008-01-01

The wave-particle α-channeling effect is generalized to include rotating plasma. Specifically, radio frequency waves can resonate with α particles in a mirror machine with ExB rotation to diffuse the α particles along constrained paths in phase space. Of major interest is that the α-particle energy, in addition to amplifying the rf waves, can directly enhance the rotation energy which in turn provides additional plasma confinement in centrifugal fusion reactors. An ancillary benefit is the rapid removal of alpha particles, which increases the fusion reactivity

Cluster observations of reconnection due to the Kelvin-Helmholtz instability at the dawnside magnetospheric flank

Directory of Open Access Journals (Sweden)

K. Nykyri

2006-10-01

Full Text Available On 3 July 2001, the four Cluster satellites traversed along the dawnside magnetospheric flank and observed large variations in all plasma parameters. The estimated magnetopause boundary normals were oscillating in the z-direction and the normal component of the magnetic field showed systematic  2–3 min bipolar variations for 1 h when the IMF had a small positive b_z-component and a Parker-spiral orientation in the x,y-plane. Brief  33 s intervals with excellent deHoffman Teller frames were observed satisfying the Walén relation. Detailed comparisons with 2-D MHD simulations indicate that Cluster encountered rotational discontinuities generated by Kelvin-Helmholtz instability. We estimate a wave length of  6 R_E and a wave vector with a significant z-component.

Flow past a rotating cylinder

Science.gov (United States)

Mittal, Sanjay; Kumar, Bhaskar

2003-02-01

Flow past a spinning circular cylinder placed in a uniform stream is investigated via two-dimensional computations. A stabilized finite element method is utilized to solve the incompressible Navier Stokes equations in the primitive variables formulation. The Reynolds number based on the cylinder diameter and free-stream speed of the flow is 200. The non-dimensional rotation rate, [alpha] (ratio of the surface speed and freestream speed), is varied between 0 and 5. The time integration of the flow equations is carried out for very large dimensionless time. Vortex shedding is observed for [alpha] cylinder. The results from the stability analysis for the rotating cylinder are in very good agreement with those from direct numerical simulations. For large rotation rates, very large lift coefficients can be obtained via the Magnus effect. However, the power requirement for rotating the cylinder increases rapidly with rotation rate.

Quasi-periodic 1-hour pulsations in the Saturn's outer magnetosphere

Science.gov (United States)

Rusaitis, L.; Khurana, K. K.; Walker, R. J.; Kivelson, M.

2017-12-01

Pulsations in the Saturn's magnetic field and particle fluxes of approximately 1-hour periodicity have been frequently detected in the outer Saturnian magnetosphere by the Cassini spacecraft since 2004. These particle and magnetic field enhancements have been typically observed more often in the dusk sector of the planet, and mid to high latitudes. We investigate nearly 200 of these events as detected by the magnetometer and the Cassini Low-Energy Magnetospheric Measurement System detector (LEMMS) data during the 2004-2015 time frame to characterize these pulsations and suggest their origin. The mechanism needed to produce these observed enhancements needs to permit the acceleration of the energetic electrons to a few MeV and a variable periodicity of enhancements from 40 to 90 minutes. We examine the relation of the oscillations to the periodic power modulations in Saturn kilometric radiation (SKR), using the SKR phase model of Kurth et al. [2007] and Provan et al. [2011]. Finally, we show that similar pulsations can also be observed at 2.5-D MHD simulations of Saturn's magnetosphere.

Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

Full Text Available Solar wind/magnetosheath plasma in the magnetosphere can be identified using a component that has a higher charge state, lower density and, at least soon after their entry into the magnetosphere, lower energy than plasma from a terrestrial source. We survey here observations taken over 3 years of He²⁺ ions made by the Magnetospheric Ion Composition Sensor (MICS of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE instrument aboard POLAR. The occurrence probability of these solar wind ions is then plotted as a function of Magnetic Local Time (MLT and invariant latitude (7 for various energy ranges. For all energies observed by MICS (1.8–21.4 keV and all solar wind conditions, the occurrence probabilities peaked around the cusp region and along the dawn flank. The solar wind conditions were filtered to see if this dawnward asymmetry is controlled by the Svalgaard-Mansurov effect (and so depends on the B_Y component of the interplanetary magnetic field, IMF or by Fermi acceleration of He²⁺ at the bow shock (and so depends on the IMF ratio B_X /B_Y . It is shown that the asymmetry remained persistently on the dawn flank, suggesting it was not due to effects associated with direct entry into the magnetosphere. This asymmetry, with enhanced fluxes on the dawn flank, persisted for lower energy ions (below a "cross-over" energy of about 23 keV but reversed sense to give higher fluxes on the dusk flank at higher energies. This can be explained by the competing effects of gradient/curvature drifts and the convection electric field on ions that are convecting sunward on re-closed field lines. The lower-energy He²⁺ ions E × B drift dawnwards as they move earthward, whereas the higher energy ions curvature/ gradient drift towards dusk. The convection electric field in the tail is weaker for

Rapid oscillations in cataclysmic variables. III. An oblique rotator in AE aquarii

International Nuclear Information System (INIS)

Patternson, J.

1979-01-01

A rapid, strictly periodic oscillation has been discovered in the light curve of the novalike variable AE Aquarii. The fundamental period is 33.076737 s, with comparable power at the first harmonic. The amplitude averages 0.2--0.3% but can exceed 1% in flares. Pulse timings around the binary orbit prove that the periodicity arises in the white dwarf, and lead to an accurate measurement of the projected orbital velocity. The velocity curve and other constraints lead to a mass determination for the component stars :0.74 +- 0.06 M/sub sun/ for the late-type star and 0.94 +- 0.10 M/sub sun/ for the white dwarf. Estimates are also given for the system dimensions, luminosity, distance, and mass transfer rate.Quasi-periodic oscillations are also detected in flares, and have periods near the coherent periods of 16.5 and 33 s. Their characteristics suggest an origin in gaseous blobs produced by instabilities near the inner edge of the accretion disk.A model is presented in which the strict periodicity arises from the rotation of an accreting, magnetized white dwarf, with a surface field of 10 6 --10 7 gauss. Future spectroscopic, polarimetric, and X-ray observations should provide critical tests for predictions of the model

Dispersion equations for field-aligned cyclotron waves in axisymmetric magnetospheric plasmas

Directory of Open Access Journals (Sweden)

N. I. Grishanov

2006-03-01

Full Text Available In this paper, we derive the dispersion equations for field-aligned cyclotron waves in two-dimensional (2-D magnetospheric plasmas with anisotropic temperature. Two magnetic field configurations are considered with dipole and circular magnetic field lines. The main contribution of the trapped particles to the transverse dielectric permittivity is estimated by solving the linearized Vlasov equation for their perturbed distribution functions, accounting for the cyclotron and bounce resonances, neglecting the drift effects, and assuming the weak connection of the left-hand and right-hand polarized waves. Both the bi-Maxwellian and bi-Lorentzian distribution functions are considered to model the ring current ions and electrons in the dipole magnetosphere. A numerical code has been developed to analyze the dispersion characteristics of electromagnetic ion-cyclotron waves in an electron-proton magnetospheric plasma with circular magnetic field lines, assuming that the steady-state distribution function of the energetic protons is bi-Maxwellian. As in the uniform magnetic field case, the growth rate of the proton-cyclotron instability (PCI in the 2-D magnetospheric plasmas is defined by the contribution of the energetic ions/protons to the imaginary part of the transverse permittivity elements. We demonstrate that the PCI growth rate in the 2-D axisymmetric plasmasphere can be significantly smaller than that for the straight magnetic field case with the same macroscopic bulk parameters.

The distribution of Enceladus water-group neutrals in Saturn’s Magnetosphere

Science.gov (United States)

Smith, Howard T.; Richardson, John D.

2017-10-01

Saturn’s magnetosphere is unique in that the plumes from the small icy moon, Enceladus, serve at the primary source for heavy particles in Saturn’s magnetosphere. The resulting co-orbiting neutral particles interact with ions, electrons, photons and other neutral particles to generate separate H2O, OH and O tori. Characterization of these toroidal distributions is essential for understanding Saturn magnetospheric sources, composition and dynamics. Unfortunately, limited direct observations of these features are available so modeling is required. A significant modeling challenge involves ensuring that either the plasma and neutral particle populations are not simply input conditions but can provide feedback to each population (i.e. are self-consistent). Jurac and Richardson (2005) executed such a self-consistent model however this research was performed prior to the return of Cassini data. In a similar fashion, we have coupled a 3-D neutral particle model (Smith et al. 2004, 2005, 2006, 2007, 2009, 2010) with a plasma transport model (Richardson 1998; Richardson & Jurac 2004) to develop a self-consistent model which is constrained by all available Cassini observations and current findings on Saturn’s magnetosphere and the Enceladus plume source resulting in much more accurate neutral particle distributions. Here a new self-consistent model of the distribution of the Enceladus-generated neutral tori that is validated by all available observations. We also discuss the implications for source rate and variability.

Discovery and characteristics of the rapidly rotating active asteroid (62412) 2000 SY178 in the main belt

International Nuclear Information System (INIS)

Sheppard, Scott S.; Trujillo, Chadwick

2015-01-01

We report a new active asteroid in the main belt of asteroids between Mars and Jupiter. Object (62412) 2000 SY178 exhibited a tail in images collected during our survey for objects beyond the Kuiper Belt using the Dark Energy Camera on the CTIO 4 m telescope. We obtained broadband colors of 62412 at the Magellan Telescope, which, along with 62412's low albedo, suggests it is a C-type asteroid. 62412's orbital dynamics and color strongly correlate with the Hygiea family in the outer main belt, making it the first active asteroid known in this heavily populated family. We also find 62412 to have a very short rotation period of 3.33 ± 0.01 hours from a double-peaked light curve with a maximum peak-to-peak amplitude of 0.45 ± 0.01 mag. We identify 62412 as the fastest known rotator of the Hygiea family and the nearby Themis family of similar composition, which contains several known main belt comets. The activity on 62412 was seen over one year after perihelion passage in its 5.6 year orbit. 62412 has the highest perihelion and one of the most circular orbits known for any active asteroid. The observed activity is probably linked to 62412's rapid rotation, which is near the critical period for break-up. The fast spin rate may also change the shape and shift material around 62412's surface, possibly exposing buried ice. Assuming 62412 is a strengthless rubble pile, we find the density of 62412 to be around 1500 kg m −3 .

Rapid emission angle selection for rotating-shield brachytherapy

International Nuclear Information System (INIS)

Liu, Yunlong; Flynn, Ryan T.; Kim, Yusung; Bhatia, Sudershan K.; Sun, Wenqing; Yang Wenjun; Wu Xiaodong

2013-01-01

Purpose: The authors present a rapid emission angle selection (REAS) method that enables the efficient selection of the azimuthal shield angle for rotating shield brachytherapy (RSBT). The REAS method produces a Pareto curve from which a potential RSBT user can select a treatment plan that balances the tradeoff between delivery time and tumor dose conformity. Methods: Two cervical cancer patients were considered as test cases for the REAS method. The RSBT source considered was a Xoft Axxent TM electronic brachytherapy source, partially shielded with 0.5 mm of tungsten, which traveled inside a tandem intrauterine applicator. Three anchor RSBT plans were generated for each case using dose-volume optimization, with azimuthal shield emission angles of 90°, 180°, and 270°. The REAS method converts the anchor plans to treatment plans for all possible emission angles by combining neighboring beamlets to form beamlets for larger emission angles. Treatment plans based on exhaustive dose-volume optimization (ERVO) and exhaustive surface optimization (ERSO) were also generated for both cases. Uniform dwell-time scaling was applied to all plans such that that high-risk clinical target volume D 90 was maximized without violating the D 2cc tolerances of the rectum, bladder, and sigmoid colon. Results: By choosing three azimuthal emission angles out of 32 potential angles, the REAS method performs about 10 times faster than the ERVO method. By setting D 90 to 85–100 Gy 10 , the delivery times used by REAS generated plans are 21.0% and 19.5% less than exhaustive surface optimized plans used by the two clinical cases. By setting the delivery time budget to 5–25 and 10–30 min/fx, respectively, for two the cases, the D 90 contributions for REAS are improved by 5.8% and 5.1% compared to the ERSO plans. The ranges used in this comparison were selected in order to keep both D 90 and the delivery time within acceptable limits. Conclusions: The REAS method enables efficient RSBT

Traveling magnetospheric convection twin vortices: Another case study, global characteristics, and a model

International Nuclear Information System (INIS)

Glassmeier, K.H.; Heppner, C.

1992-01-01

A case study of a transient geomagnetic field variation event associated with a traveling magnetospheric convection twin vortex is presented. The characteristics of this event are different from those of other presented cases, as the sense of rotation of the associated ionospheric current system is reversed, that is, it exhibits upward (downward) field-aligned currents in the tailward (dayside) part of the vortex structure. In particular, a clear tailward motion at high latitudes can be deduced from local as well as global magnetic field observations. At low dayside latitudes, magnetic field variations similar to sudden impulse (SI) variations are recorded. Almost simultaneous onset and no westward propagation are observed, too. As possible source mechanisms of such transient events, localized magnetic field reconnection as well as pressure pulses at the dayside magnetopause are discussed. If the switch-on of magnetic reconnection can be regarded as equivalent to an equivalent current flowing against the existing magnetopause current and if this countercurrent is spatially localized, an Alfven wave is generated with downward (upward) field-aligned current flow in the tailward (dayside) par of the wave, as observed for some of the reported transients. However, the SI-like behavior of the event studied in this paper, its reversed sense of rotation, and the vortex associated field-aligned current density excludes such localized magnetic reconnection as a possible source mechanism and argues in favor of the existence of pressure pulses at the magnetopause

ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

Science.gov (United States)

Bentley, S. N.; Watt, C. E. J.; Owens, M. J.; Rae, I. J.

2018-04-01

Ultralow frequency (ULF) waves in the magnetosphere are involved in the energization and transport of radiation belt particles and are strongly driven by the external solar wind. However, the interdependency of solar wind parameters and the variety of solar wind-magnetosphere coupling processes make it difficult to distinguish the effect of individual processes and to predict magnetospheric wave power using solar wind properties. We examine 15 years of dayside ground-based measurements at a single representative frequency (2.5 mHz) and a single magnetic latitude (corresponding to L ˜ 6.6RE). We determine the relative contribution to ULF wave power from instantaneous nonderived solar wind parameters, accounting for their interdependencies. The most influential parameters for ground-based ULF wave power are solar wind speed vsw, southward interplanetary magnetic field component Bzstill account for significant amounts of power. We suggest that these three parameters correspond to driving by the Kelvin-Helmholtz instability, formation, and/or propagation of flux transfer events and density perturbations from solar wind structures sweeping past the Earth. We anticipate that this new parameter reduction will aid comparisons of ULF generation mechanisms between magnetospheric sectors and will enable more sophisticated empirical models predicting magnetospheric ULF power using external solar wind driving parameters.

A Rapid Generation Method of Character Doll with Rotatable Limbs Oriented to 3D Printer

Institute of Scientific and Technical Information of China (English)

LI Lin; CHU Xiao-li; Nie Wen-chao

2014-01-01

Currently, 3D printing of the character dolls is a very practical application for the average person. But the model of doll which can be obtained is static so the posture of the doll is single. On the other hand, the modification of the model is very difficult to non-professions. This paper proposes an rapid generation method of character doll with rotatable limbs, which is through adding the sphere joint to the doll’s model automatically. After the model is segmented by drawing a line interactively, the sphere joint is created based on the segmentation boundary through entity modeling method. Lastly the two models of the doll and the joint are composited and printed. Some doll’s model are tested on the FDM(Fused Deposition Modeling) 3D printer using this process. The results are more interesting and the efficiency has been greatly improved compared with modifying the model manually.

Modelling of the ring current in Saturn's magnetosphere

Directory of Open Access Journals (Sweden)

G. Giampieri

2004-01-01

Full Text Available The existence of a ring current inside Saturn's magnetosphere was first suggested by Smith et al. (1980 and Ness et al. (1981, 1982, in order to explain various features in the magnetic field observations from the Pioneer 11 and Voyager 1 and 2 spacecraft. Connerney et al. (1983 formalized the equatorial current model, based on previous modelling work of Jupiter's current sheet and estimated its parameters from the two Voyager data sets. Here, we investigate the model further, by reconsidering the data from the two Voyager spacecraft, as well as including the Pioneer 11 flyby data set.

First, we obtain, in closed form, an analytic expression for the magnetic field produced by the ring current. We then fit the model to the external field, that is the difference between the observed field and the internal magnetic field, considering all the available data. In general, through our global fit we obtain more accurate parameters, compared to previous models. We point out differences between the model's parameters for the three flybys, and also investigate possible deviations from the axial and planar symmetries assumed in the model. We conclude that an accurate modelling of the Saturnian disk current will require taking into account both of the temporal variations related to the condition of the magnetosphere, as well as non-axisymmetric contributions due to local time effects.

Key words. Magnetospheric physics (current systems; planetary magnetospheres; plasma sheet

Study of the energy spectra of the major ion species in the ring-current region of the magnetosphere during geomagnetic storms

International Nuclear Information System (INIS)

Kistler, L.M.

1987-01-01

Using the University of Maryland/Max Planck Institute for Aeronomy Charge Energy Mass (CHEM) spectrometer on the AMPTE Charge Composition Explorer (CCE) spacecraft, the author examined the near-equatorial storm-time energy spectra of four major magnetospheric ions, H + , O + , He + , and He ++ over the energy range 1-300 keV/e in the L-range 3-6. The data were obtained during the main phase of all geomagnetic storms with minimum Dst less than -50 in the time period September 1984 to November 1985. During this period, the orbit of the CCE precessed such that the full range of local times was covered. When the spectra are organized by local time, certain features emerge. In particular, there is a dip in the spectra of all ions at 10-20 keV/e in the drawn-to-noon sector, while in the noon-to-dusk sector the proton distribution function drops off sharply below ∼5 keV. These spectra were compared with those predicted by a model of ion drift and loss in the magnetosphere. It was found that the spectra are most consistent with a Volland-Stern electric field with γ = 2 and with a rotation of the nominal dawn-to-dusk electric field eastward by two hours local time

A simulation study of impulsive penetration of solar wind irregularities into the magnetosphere at the dayside magnetopause

International Nuclear Information System (INIS)

Ma, Z.W.; Hawkins, J.G.; Lee, L.C.

1991-01-01

A two-dimensional magnetohydrodynamic code is used to study impulsive penetration processes that occur when a plasma irregularity in the magnetosheath, modeled as a field-aligned filament, impinges on the dayside magnetopause. If the magnetic fields in the magnetosheath and magnetosphere are parallel or antiparallel, then a filament in the magnetosheath can always penetrate into the magnetosphere. However, if the fields in the magnetosheath and magnetosphere are not aligned, then a filament can only penetrate into the magnetosphere when its initial kinetic energy density exceeds the magnetic energy density attributed to the transverse component of the magnetic field by a factor of 50. In this case, the magnetospheric field lines reconnect behind the filament, thereby trapping it within the magnetosphere. Otherwise, the increasing magnetic stress in front of the filament will eventually stop the filament from further penetration. For typical parameters found at the dayside magnetopause, the threshold condition obtained from this two-dimensional model predicts that penetration is possible only when the angle between the fields is within approximately 5 of parallel or antiparallel. During the penetration process, velocity vortices are observed both inside the filament and in the external plasma. Either increased β within the magnetosphere, or the larger plasma density at the magnetopause associated with antiparallel magnetic fields, will act to reduce the penetration velocity

Different magnetospheric modes: solar wind driving and coupling efficiency

Directory of Open Access Journals (Sweden)

N. Partamies

2009-11-01

Full Text Available This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential, particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY. Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations during geomagnetically active conditions.

Low-energy neutral atom emission from the Earth's magnetosphere

International Nuclear Information System (INIS)

Moore, K.R.; Scime, E.E.; Funsten, H.O.; McComas, D.J.; Thomsen, M.F.

1994-01-01

Imaging of the terrestrial magnetosphere is possible through the detection of low-energy neutral atoms (LENAs) produced by charge exchange between magnetospheric plasma ions and neutral atoms of the Earth's geocorona. The authors present calculations of both hydrogen and oxygen line-of-sight LENA fluxes expected on orbit for various plasma regimes as predicted by the Rice University Magnetospheric Specification Model. To decrease the required computation time, they are in the process of adapting their code for massively parallel computers. The speed gains achieved from parallel algorithms are substantial, and they present results from computational runs on the Connection Machine CM-2 data parallel supercomputer. They also estimate expected image count rates and image quality based on realistic instrument geometric factors, energy passbands, neutral atom scattering in the instrument, and image accumulation intervals. The results indicate that LENA imaging instruments will need a geometric factor (G) on the order of 0.1 cm 2 sr eV/eV to be capable of imaging storm time ring currents, and a G of 1.0 cm 2 sr eV/eV in order to image the quiet time ring current fluxes, ion injections from the tail, and subsequent ion drifts toward the dayside magnetopause

What Might We Learn About Magnetospheric Substorms at the Earth from the MESSENGER Measurements at Mercury?

Science.gov (United States)

Slavin, James A.

2008-01-01

Satellite observations at the Earth, supported by theory and modeling, have established a close connection between the episodes of intense magnetospheric convection termed substorms and the occurrence of magnetic reconnection. Magnetic reconnection at the dayside magnetopause results in strong energy input to the magnetosphere. This energy can either be stored or used immediately to power the magnetospheric convection that produces the phenomena that collectively define the 'substorm.' However, many aspects of magnetic reconnection and the dynamic response of the coupled solar wind - magnetosphere - ionosphere system at the Earth during substorms remain poorly understood. For example, the rate of magnetic reconnection is thought to be proportional to the local Alfven speed, but the limited range of changes in this solar wind parameter at 1 AU have made it difficult to detect its influence over energy input to the Earth's magnetosphere. In addition, the electrical conductance of the ionosphere and how it changes in response to auroral charged particle precipitation are hypothesized to play a critical role in the development of substorms, but the nature of this electrodynamic interaction remain difficult to deduce from Earth observations alone. The amount of energy the terrestrial magnetosphere can store in its tail, the duration of the storage, and the trigger(s) for its dissipation are all thought to be determined by not only the microphysics of the cross-tail current layer, but also the properties of the coupled magnetosphere - ionosphere system. Again, the separation of microphysics effects from system response has proved very difficult using measurements taken only at the Earth. If MESSENGER'S charged particle and magnetic field measurements confirm the occurrence of terrestrial-style substorms in Mercury's miniature magnetosphere, then it may be possible to determine how magnetospheric convection, field-aligned currents, charged particle acceleration

Rotation of the bulge components of barred galaxies

International Nuclear Information System (INIS)

Kormendy, J.

1982-01-01

Stellar rotation and velocity-dispersion measurements are presented for the bulge components of the SBO galaxies NGC 1023, 2859, 2950, 4340, 4371, and 7743. The kinematics of nine SB bulges with data available are compared with bulges of unbarred galaxies studied by Kormendy and Illingworth. All of the SB bulges are found to rotate at least as rapidly as oblate-spheroid dynamical models which are flattened by rotation. This result confirms the conclusion of Kormendy and Illingworth that bulges rotate very rapidly. Six SB bulges found by Kormendy and Koo to be triaxial rotate even more rapidly than the oblate models. In this respect, they resemble published n-body models of bars. That is, triaxial bulges are dynamically like bars and unlike elliptical galaxies, which are also believed to be triaxial, but which rotate slowly. Measured velocity anisotropies are found to be consistent with these conclusions. Two ordinary bulges whose rotation is well described by isotropic modes have a ratio of radial to azimuthal velocity dispersion of sigma/sub r//sigma/sub theta/ = 0.96 +- 0.03. In contrast, the triaxial bulge of NGC 3945, which rotates much faster than the isotropic models, has sigma/sub r//sigma/sub theta/ approx.1.31 +- 0.06. This is similar to the degree of anisotropy, sigma/sub r//sigma/sub theta/approx.1.21 +- 0.03, found in a recent n-body bar model by Hohl and Zang. Altogether the kinematic observations imply the triaxial bulges are more disklike than SA bulges. They appear to have been formed with more dissipation than ordinary bulges. These results are consistent with the hypothesis that part of the bulge in many SB galaxies consists of disk material (i.e., gas) which has been transported to the center by the bar. The resulting star formation may produce a very centrally concentrated light distribution which resembles a bulge but which has dislike dynamics

Mercury's Atmosphere and Magnetosphere: MESSENGER Third Flyby Observations

Science.gov (United States)

Slavin, James A.; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Johnson, Catherine L.; Gloeckler, George; Killen, Rosemary M.; Krimigis, Stamatios M.; McClintock, William; McNutt, Ralph L., Jr.;

Characteristics of the magnetohydrodynamic waves observed in the earth's magnetosphere and on the ground

International Nuclear Information System (INIS)

Kuwashima, M.; Fujita, S.

1989-01-01

Current research topics on MHD waves in the earth's magnetosphere and on the ground are summarized. Upstream waves in the earth's foreshock region and their transmission into and propagation through the magnetosphere are discussed in the context of relationships of Pc3 magnetic pulsations on the ground. The characteristics of ssc-associated magnetic pulsations are considered, and instabilities with the hot plasma in the ring current in the magnetosphere are addressed in the context of the relationships of compressional Pc 4-5 waves. The characteristics of Pi2 magnetic pulsations are examined, and the role of the ionosphere on the modifications of MHD waves is addressed

The Importance of Differing Types of Io Volcanic Activity for the Jupiter Magnetosphere

Science.gov (United States)

Howell, R. R.

2016-12-01

The Jupiter magnetosphere is populated largely by sulfur and oxygen ultimately derived from the volcanoes on Io and correlations have been detected between changes in volcanic activity and the magnetosphere. However different types of volcanic activity on Io vary widely in the amount and composition of the gasses they release. For example while Loki is often the brightest volcanic hotspot in the infrared (and therefore most easily monitored from earth) it appears to release a comparatively small amount of gas compared to Prometheus type plumes and the giant plumes such as Pele. The dominant volatile released at most sites is sulfur dioxide but giant plumes such as Pele appear to contain significantly fractions of S2 gas. The amounts and type of dust produced may also differ. Finally, the way material is buffered in Io's surface and atmosphere before escaping to the magnetosphere is also uncertain. A better understanding of the connection between volcanic activity and the magnetosphere will require studying not just correlations between broad measures of activity but rather specific indices of different types of activity. Observations of possible storage buffers such as the atmosphere, as are now becoming possible with ALMA, will also be essential.

Comparing Jupiter and Saturn: dimensionless input rates from plasma sources within the magnetosphere

Directory of Open Access Journals (Sweden)

V. M. Vasyliūnas

2008-06-01

Full Text Available The quantitative significance for a planetary magnetosphere of plasma sources associated with a moon of the planet can be assessed only by expressing the plasma mass input rate in dimensionless form, as the ratio of the actual mass input to some reference value. Traditionally, the solar wind mass flux through an area equal to the cross-section of the magnetosphere has been used. Here I identify another reference value of mass input, independent of the solar wind and constructed from planetary parameters alone, which can be shown to represent a mass input sufficiently large to prevent corotation already at the source location. The source rate from Enceladus at Saturn has been reported to be an order of magnitude smaller (in absolute numbers than that from Io at Jupiter. Both reference values, however, are also smaller at Saturn than at Jupiter, by factors ~40 to 60; expressed in dimensionless form, the estimated mass input from Enceladus may be larger than that from Io by factors ~4 to 6. The magnetosphere of Saturn may thus, despite a lower mass input in kg s⁻¹, intrinsically be more heavily mass-loaded than the magnetosphere of Jupiter.

Comparing Jupiter and Saturn: dimensionless input rates from plasma sources within the magnetosphere

Directory of Open Access Journals (Sweden)

V. M. Vasyliūnas

2008-06-01

Full Text Available The quantitative significance for a planetary magnetosphere of plasma sources associated with a moon of the planet can be assessed only by expressing the plasma mass input rate in dimensionless form, as the ratio of the actual mass input to some reference value. Traditionally, the solar wind mass flux through an area equal to the cross-section of the magnetosphere has been used. Here I identify another reference value of mass input, independent of the solar wind and constructed from planetary parameters alone, which can be shown to represent a mass input sufficiently large to prevent corotation already at the source location. The source rate from Enceladus at Saturn has been reported to be an order of magnitude smaller (in absolute numbers than that from Io at Jupiter. Both reference values, however, are also smaller at Saturn than at Jupiter, by factors ~40 to 60; expressed in dimensionless form, the estimated mass input from Enceladus may be larger than that from Io by factors ~4 to 6. The magnetosphere of Saturn may thus, despite a lower mass input in kg s−1, intrinsically be more heavily mass-loaded than the magnetosphere of Jupiter.

How to emit a high-power electron beam from a magnetospheric spacecraft?

Science.gov (United States)

Delzanno, G. L.; Lucco Castello, F.; Borovsky, J.; Miars, G.; Leon, O.; Gilchrist, B. E.

2017-12-01

The idea of using a high-power electron beam to actively probe magnetic-field-line connectivity in space has been discussed since the 1970's. It could solve longstanding questions in magnetospheric/ionospheric physics by establishing causality between phenomena occurring in the magnetosphere and their image in the ionosphere. However, this idea has never been realized onboard a magnetospheric spacecraft because the tenuous magnetospheric plasma cannot provide the return current necessary to keep the charging of the spacecraft under control. Recently, Delzanno et al. [1] have proposed a spacecraft-charging mitigation scheme to enable the emission of a high-power electron beam from a magnetospheric spacecraft. It is based on the plasma contactor, i.e. a high-density neutral plasma emitted prior to and with the electron beam. The contactor acts as an ion emitter (not as an electron collector, as previously thought): a high ion current can be emitted off the quasi-spherical contactor surface, without the strong space-charge limitations typical of planar ion beams, and the electron-beam current can be successfully compensated. In this work, we will discuss our theoretical/simulation effort to improve the understanding of contactor-based ion emission. First, we will present a simple mathematical model useful for the interpretation of the results of [1]. The model is in spherical geometry and the contactor dynamics is described by only two surfaces (its quasi-neutral surface and the front of the outermost ions). It captures the results of self-consistent Particle-In-Cell (PIC) simulations with good accuracy and highlights the physics behind the charge-mitigation scheme clearly. PIC simulations connecting the 1D model to the actual geometry of the problem will be presented to obtain the scaling of the spacecraft potential varying contactor emission area. Finally, results for conditions relevant to an actual mission will also be discussed. [1] G. L. Delzanno, J. E. Borovsky

Long-lived particulate or gaseous structure in Saturn's outer magnetosphere

Science.gov (United States)

Lazarus, A. J.; Hasegawa, T.; Bagenal, F.

1983-01-01

Voyager 1 and 2 and Pioneer 11 data on the variations in the number density of low-energy plasma ions in the outer Saturn magnetosphere are discussed. Low and high latitude observations are compared in reference to the position of the spacecraft crossing of the field line. Abrupt decreases in the number density interrupted the tendancy for the number density to increase with spacecraft approach to Saturn. All three spacecraft are concluded to have encountered the same magnetospheric structure in the field line, with absorbers being present in the equatorial plane. The absorbers are suggested to be either gas or debris, which may be detectable visibly or with occultation techniques.

Movement of a charged particle beam in the Earth magnetosphere

International Nuclear Information System (INIS)

Veselovskij, I.S.

1977-01-01

The motion of a charged particle beam injected into the Earth magnetosphere in a dipole magnetic field was investigated. Examined were the simplest stationary distributions of particles. The evolution of the distribution function after pulse injection of the beam into the magnetosphere was studied. It was shown that the pulse shape depends on its starting duration. A long pulse spreads on the base and narrows on the flat top with the distance away from the point of injection. A short pulse spreads both on the base and along the height. The flat top is not present. An analytical expression for the pulse shape as a time function is given

Expected Navigation Flight Performance for the Magnetospheric Multiscale (MMS) Mission

Science.gov (United States)

Olson, Corwin; Wright, Cinnamon; Long, Anne

2012-01-01

The Magnetospheric Multiscale (MMS) mission consists of four formation-flying spacecraft placed in highly eccentric elliptical orbits about the Earth. The primary scientific mission objective is to study magnetic reconnection within the Earth s magnetosphere. The baseline navigation concept is the independent estimation of each spacecraft state using GPS pseudorange measurements (referenced to an onboard Ultra Stable Oscillator) and accelerometer measurements during maneuvers. State estimation for the MMS spacecraft is performed onboard each vehicle using the Goddard Enhanced Onboard Navigation System, which is embedded in the Navigator GPS receiver. This paper describes the latest efforts to characterize expected navigation flight performance using upgraded simulation models derived from recent analyses.

Particle-in-cell simulations of Earth-like magnetosphere during a magnetic field reversal

Science.gov (United States)

Barbosa, M. V. G.; Alves, M. V.; Vieira, L. E. A.; Schmitz, R. G.

2017-12-01

The geologic record shows that hundreds of pole reversals have occurred throughout Earth's history. The mean interval between the poles reversals is roughly 200 to 300 thousand years and the last reversal occurred around 780 thousand years ago. Pole reversal is a slow process, during which the strength of the magnetic field decreases, become more complex, with the appearance of more than two poles for some time and then the field strength increases, changing polarity. Along the process, the magnetic field configuration changes, leaving the Earth-like planet vulnerable to the harmful effects of the Sun. Understanding what happens with the magnetosphere during these pole reversals is an open topic of investigation. Only recently PIC codes are used to modeling magnetospheres. Here we use the particle code iPIC3D [Markidis et al, Mathematics and Computers in Simulation, 2010] to simulate an Earth-like magnetosphere at three different times along the pole reversal process. The code was modified, so the Earth-like magnetic field is generated using an expansion in spherical harmonics with the Gauss coefficients given by a MHD simulation of the Earth's core [Glatzmaier et al, Nature, 1995; 1999; private communication to L.E.A.V.]. Simulations show the qualitative behavior of the magnetosphere, such as the current structures. Only the planet magnetic field was changed in the runs. The solar wind is the same for all runs. Preliminary results show the formation of the Chapman-Ferraro current in the front of the magnetosphere in all the cases. Run for the middle of the reversal process, the low intensity magnetic field and its asymmetrical configuration the current structure changes and the presence of multiple poles can be observed. In all simulations, a structure similar to the radiation belts was found. Simulations of more severe solar wind conditions are necessary to determine the real impact of the reversal in the magnetosphere.

Intense energetic electron flux enhancements in Mercury's magnetosphere: An integrated view with high-resolution observations from MESSENGER.

Science.gov (United States)

Baker, Daniel N; Dewey, Ryan M; Lawrence, David J; Goldsten, John O; Peplowski, Patrick N; Korth, Haje; Slavin, James A; Krimigis, Stamatios M; Anderson, Brian J; Ho, George C; McNutt, Ralph L; Raines, Jim M; Schriver, David; Solomon, Sean C

2016-03-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury has provided a wealth of new data about energetic particle phenomena. With observations from MESSENGER's Energetic Particle Spectrometer, as well as data arising from energetic electrons recorded by the X-Ray Spectrometer and Gamma-Ray and Neutron Spectrometer (GRNS) instruments, recent work greatly extends our record of the acceleration, transport, and loss of energetic electrons at Mercury. The combined data sets include measurements from a few keV up to several hundred keV in electron kinetic energy and have permitted relatively good spatial and temporal resolution for many events. We focus here on the detailed nature of energetic electron bursts measured by the GRNS system, and we place these events in the context of solar wind and magnetospheric forcing at Mercury. Our examination of data at high temporal resolution (10 ms) during the period March 2013 through October 2014 supports strongly the view that energetic electrons are accelerated in the near-tail region of Mercury's magnetosphere and are subsequently "injected" onto closed magnetic field lines on the planetary nightside. The electrons populate the plasma sheet and drift rapidly eastward toward the dawn and prenoon sectors, at times executing multiple complete drifts around the planet to form "quasi-trapped" populations.

Spin-Label CW Microwave Power Saturation and Rapid Passage with Triangular Non-Adiabatic Rapid Sweep (NARS) and Adiabatic Rapid Passage (ARP) EPR Spectroscopy

Science.gov (United States)

Kittell, Aaron W.; Hyde, James S.

2015-01-01

Non-adiabatic rapid passage (NARS) electron paramagnetic resonance (EPR) spectroscopy was introduced by Kittell, A.W., Camenisch, T.G., Ratke, J.J. Sidabras, J.W., Hyde, J.S., 2011 as a general purpose technique to collect the pure absorption response. The technique has been used to improve sensitivity relative to sinusoidal magnetic field modulation, increase the range of inter-spin distances that can be measured under near physiological conditions, and enhance spectral resolution in copper (II) spectra. In the present work, the method is extended to CW microwave power saturation of spin-labeled T4 Lysozyme (T4L). As in the cited papers, rapid triangular sweep of the polarizing magnetic field was superimposed on slow sweep across the spectrum. Adiabatic rapid passage (ARP) effects were encountered in samples undergoing very slow rotational diffusion as the triangular magnetic field sweep rate was increased. The paper reports results of variation of experimental parameters at the interface of adiabatic and non-adiabatic rapid sweep conditions. Comparison of the forward (up) and reverse (down) triangular sweeps is shown to be a good indicator of the presence of rapid passage effects. Spectral turning points can be distinguished from spectral regions between turning points in two ways: differential microwave power saturation and differential passage effects. Oxygen accessibility data are shown under NARS conditions that appear similar to conventional field modulation data. However, the sensitivity is much higher, permitting, in principle, experiments at substantially lower protein concentrations. Spectral displays were obtained that appear sensitive to rotational diffusion in the range of rotational correlation times of 10−3 to 10−7 s in a manner that is analogous to saturation transfer spectroscopy. PMID:25917132

Vortex core structure and global properties of rapidly rotating Bose-Einstein condensates

International Nuclear Information System (INIS)

Baym, Gordon; Pethick, C.J.

2004-01-01

We develop an approach for calculating stationary states of rotating Bose-Einstein condensates in harmonic traps which is applicable for arbitrary ratios of the rotation frequency to the transverse frequency of the trap ω perpendicular . Assuming the number of vortices to be large, we write the condensate wave function as the product of a function that describes the structure of individual vortices times an envelope function varying slowly on the scale of the vortex spacing. By minimizing the energy, we derive Gross-Pitaevskii equations that determine the properties of individual vortices and the global structure of the cloud. For low rotation rates, the structure of a vortex is that of an isolated vortex in a uniform medium, while for rotation rates approaching the frequency of the trap (the mean-field lowest-Landau-level regime), the structure is that of the lowest p-wave state of a particle in a harmonic trap with frequency ω perpendicular . The global structure of the cloud is determined by minimizing the energy with respect to variations of the envelope function; for conditions appropriate to most experimental investigations to date, we predict that the transverse density profile of the cloud will be of the Thomas-Fermi form, rather than the Gaussian structure predicted on the assumption that the wave function consists only of components in the lowest Landau level for a regular array of vortices

Acceleration processes in the magnetospheric plasma: a review

Energy Technology Data Exchange (ETDEWEB)

Nishida, A [Tokyo Univ. (Japan). Inst. of Space and Aeronautical Science

1975-01-01

Our present knowledge on the acceleration process in the magnetospheric plasma is reviewed and major problems are summarized. Acceleration processes can be classified into three categories. First, acceleration can be made by the reconnection process in the magnetotail. The occurrence of reconnection during substorm expansion phases has been confirmed, but details of the energy conversion mechanism need be clarified. Second, acceleration by the electric potential drop along magnetic field lines has been strongly suggested from observations of precipitating particles. The position and structure of the potential layer, however, have not been clarified, and theoretical understanding of the process is still in the early stage of development. Third, particles can be adiabatically heated as they are driven toward the earth in the course of their convective motion. Spatial structure and dynamical development of the auroral precipitation pattern represent both challenge and clue to the understanding of the magnetospheric acceleration process.

Magnetospheres of accreting compact objects in binary systems

International Nuclear Information System (INIS)

Aly, J.J.

1985-09-01

Bright pulsating X-ray sources (X-ray pulsars, AM Her stars,...) have been identified as strongly magnetized compact objects accreting matter from a binary companion. We give here a summary of some of the work which has been recently done to try to understand the interaction between the magnetic field of the compact object and the matter around. We examine in turn the models describing the interaction of the field with: i) a spherically symmetric accretion flow; ii) a thin keplerian accretion disk; iii) the companion itself. In all these cases, we pay particular attention to the following problems: i) how the external plasma interacting with the magnetosphere can get mixed with the field; ii) by which mechanism the magnetic field controls the mass-momentum-energy exchanges between the two stars. In conclusion, we compare the magnetosphere of an accreting compact object with that one of a planet [fr

Cosmogony as an extrapolation of magnetospheric research

International Nuclear Information System (INIS)

Alfven, H.

1984-03-01

A theory of the origin and evolution of the Solar System (Alfven and Arrhenius, 1975: 1976) which considered electromagnetic forces and plasma effects is revised in the light of new information supplied by space research. In situ measurements in the magnetospheres and solar wind have changed our views of basic properties of cosmic plasmas. These results can be extrapolated both outwards in space, to interstellar clouds, backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of some cloud properties which are essential for the early phases in the formation of stars and solar nebule. The latter extrapolation makes possible to approach the cosmogonic processes by extrapolation of (rather) well-known magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it seems possible to reconstruct certain events 4-5 billion years ago with an accuracy of a few percent. This will cause a change in our views of the evolution of the solar system.(author)

The magnetosphere in relativistic physics

International Nuclear Information System (INIS)

Zapffe, C.A.

1982-01-01

The present paper takes off from the author's earlier epistemological analysis and criticism of the Special Theory of Relativity, identifies the problem as lying in Einstein's choice of the inertial frame of Newtonian mechanics rather than the electromagnetic frame of the locally embedding Maxwellian field when discussing electrodynamics, then proposes this Maxwellian field of the magnetosphere as the specific rest frame proper to all experimentation of optical or electromagnetic sort conducted within its bounds. The result is shown to remove all paradoxes from relativistic physics. (author)

MAVEN Observations of Magnetic Reconnection on the Dayside Martian Magnetosphere

Science.gov (United States)

DiBraccio, Gina A.; Espley, Jared R.; Connerney, John E. P.; Brain, David A.; Halekas, Jasper S.; Mitchell, David L.; Harada, Yuki; Hara, Takuya

2015-04-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission offers a unique opportunity to investigate the complex solar wind-planetary interaction at Mars. The Martian magnetosphere is formed as the interplanetary magnetic field (IMF) drapes around the planet's ionosphere and localized crustal magnetic fields. As the solar wind interacts with this induced magnetosphere, magnetic reconnection can occur at any location where a magnetic shear is present. Reconnection between the IMF and the induced and crustal fields facilitates a direct plasma exchange between the solar wind and the Martian ionosphere. Here we address the occurrence of magnetic reconnection on the dayside magnetosphere of Mars using MAVEN magnetic field and plasma data. When reconnection occurs on the dayside, a non-zero magnetic field component normal to the obstacle, B_N, will result. Using minimum variance analysis, we measure BN by transforming Magnetometer data into boundary-normal coordinates. Selected events are then further examined to identify plasma heating and energization, in the form of Alfvénic outflow jets, using Solar Wind Ion Analyzer measurements. Additionally, the topology of the crustal fields is validated from electron pitch angle distributions provided by the Solar Wind Electron Analyzer. To understand which parameters are responsible for the onset of reconnection, we test the dependency of the dimensionless reconnection rate, calculated from BN measurements, on magnetic field shear angle and plasma beta (the ratio of plasma pressure to magnetic pressure). We assess the global impact of reconnection on Mars' induced magnetosphere by combining analytical models with MAVEN observations to predict the regions where reconnection may occur. Using this approach we examine how IMF orientation and magnetosheath parameters affect reconnection on a global scale. With the aid of analytical models we are able to assess the role of reconnection on a global scale to better understand which

The role of the ionosphere in coupling upstream ULF wave power into the dayside magnetosphere

International Nuclear Information System (INIS)

Engebretson, M.J.; Cahill, L.J. Jr.; Arnoldy, R.L.; Anderson, B.J.; Rosenberg, T.J.; Carpenter, D.L.; Inan, U.S.; Eather, R.H.

1991-01-01

A series of recent studies of Pc 3 magnetic pulsations in the dayside outer magnetosphere has given new insights into the possible mechanisms of entry of ULF wave power into the magnetosphere from a bow shock related upstream source. In this paper, the authors first review many of these new observational results by presenting a comparison of data from two 10-hour intervals on successive days in April 1986 and then present a possible model for transmission of pulsation signals from the magnetosheath into the dayside magnetosphere. Simultaneous multi-instrument observations at South Pole Station, located below the cusp/cleft ionosphere near local noon, magnetic field observations by the AMPTE CCE satellite in the dayside outer magnetosphere, and upstream magnetic field observations by the IMP 8 satellite show clear interplanetary magnetic field field magnitude control of dayside resonant harmonic pulsations and band-limited very high latitude pulsations, as well as pulsation-modulated precipitation of what appear to be magnetosheath/boundary layer electrons. They believe that this modulated precipitation may be responsible for the propagation of upstream wave power in the Pc 3 frequency band into the high-latitude ionosphere, from whence it may be transported throughout the dayside outer magnetosphere by means of an ionospheric transistor. In this model, modulations in ionospheric conductivity caused by cusp/cleft precipitation cause varying ionospheric currents with frequency spectra determined by the upstream waves; these modulations will be superimposed on the Birkeland currents, which close via these ionospheric currents. Modulated region 2 Birkeland currents will in turn provide a narrow-band source of wave energy to a wide range of dayside local times in the outer magnetosphere

Modular model for Mercury's magnetospheric magnetic field confined within the average observed magnetopause.

Science.gov (United States)

Korth, Haje; Tsyganenko, Nikolai A; Johnson, Catherine L; Philpott, Lydia C; Anderson, Brian J; Al Asad, Manar M; Solomon, Sean C; McNutt, Ralph L

2015-06-01

Accurate knowledge of Mercury's magnetospheric magnetic field is required to understand the sources of the planet's internal field. We present the first model of Mercury's magnetospheric magnetic field confined within a magnetopause shape derived from Magnetometer observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft. The field of internal origin is approximated by a dipole of magnitude 190 nT R M 3 , where R M is Mercury's radius, offset northward by 479 km along the spin axis. External field sources include currents flowing on the magnetopause boundary and in the cross-tail current sheet. The cross-tail current is described by a disk-shaped current near the planet and a sheet current at larger (≳ 5  R M ) antisunward distances. The tail currents are constrained by minimizing the root-mean-square (RMS) residual between the model and the magnetic field observed within the magnetosphere. The magnetopause current contributions are derived by shielding the field of each module external to the magnetopause by minimizing the RMS normal component of the magnetic field at the magnetopause. The new model yields improvements over the previously developed paraboloid model in regions that are close to the magnetopause and the nightside magnetic equatorial plane. Magnetic field residuals remain that are distributed systematically over large areas and vary monotonically with magnetic activity. Further advances in empirical descriptions of Mercury's magnetospheric external field will need to account for the dependence of the tail and magnetopause currents on magnetic activity and additional sources within the magnetosphere associated with Birkeland currents and plasma distributions near the dayside magnetopause.

Io's Magnetospheric Interaction: An MHD Model with Day-Night Asymmetry

Science.gov (United States)

Kabin, K.; Combi, M. R.; Gombosi, T. I.; DeZeeuw, D. L.; Hansen, K. C.; Powell, K. G.

2001-01-01

In this paper we present the results of all improved three-dimensional MHD model for Io's interaction with Jupiter's magnetosphere. We have included the day-night asymmetry into the spatial distribution of our mass-loading, which allowed us to reproduce several smaller features or the Galileo December 1995 data set. The calculation is performed using our newly modified description of the pick-up processes that accounts for the effects of the corotational electric field existing in the Jovian magnetosphere. This change in the formulation of the source terms for the MHD equations resulted in significant improvements in the comparison with the Galileo measurements. We briefly discuss the limitations of our model and possible future improvements.

Magnetospheric MultiScale (MMS) System Manager

Science.gov (United States)

Schiff, Conrad; Maher, Francis Alfred; Henely, Sean Philip; Rand, David

2014-01-01

The Magnetospheric MultiScale (MMS) mission is an ambitious NASA space science mission in which 4 spacecraft are flown in tight formation about a highly elliptical orbit. Each spacecraft has multiple instruments that measure particle and field compositions in the Earths magnetosphere. By controlling the members relative motion, MMS can distinguish temporal and spatial fluctuations in a way that a single spacecraft cannot.To achieve this control, 2 sets of four maneuvers, distributed evenly across the spacecraft must be performed approximately every 14 days. Performing a single maneuver on an individual spacecraft is usually labor intensive and the complexity becomes clearly increases with four. As a result, the MMS flight dynamics team turned to the System Manager to put the routine or error-prone under machine control freeing the analysts for activities that require human judgment.The System Manager is an expert system that is capable of handling operations activities associated with performing MMS maneuvers. As an expert system, it can work off a known schedule, launching jobs based on a one-time occurrence or on a set reoccurring schedule. It is also able to detect situational changes and use event-driven programming to change schedules, adapt activities, or call for help.

Ultrathin foils used for low-energy neutral atom imaging of the terrestrial magnetosphere

International Nuclear Information System (INIS)

Funsten, H.O.; McComas, D.J.; Barraclough, B.L.

1993-01-01

Magnetospheric imaging by remote detection of low-energy neutral atoms (LENAs) that are created by charge exchange between magnetospheric plasma ions and neutral geocoronal atoms has been proposed as a method to provide global information of magnetospheric dynamics. For LENA detecting, carbon foils can be implemented to (1) ionize the LENAs and electrostatically remove them from the large background of solar UV scattered by the geocorona to which LENA detectors (e.g., microchannel plates) are sensitive and (2) generate secondary electrons to provide coincidence and/or LENA trajectory information. Quantification of LENA-foil interactions are crucial in defining LENA imager performance. The authors present equilibrium charge state distributions due to foil contamination from exposure to air. Angular scattering that results from the projectile-foil interaction is quantified and is shown to be independent of the charge state distribution

Compression of Jupiter's magnetosphere by the solar wind: Reexamination via MHD simulation of evolving corotating interaction regions

International Nuclear Information System (INIS)

Smith, Z.K.; Dryer, M.; Fillius, R.W.; Smith, E.J.; Wolfe, J.H.

1981-01-01

We examine the major changes in the solar wind before, during, and after the Pioneer 10 and 11 encounters with the Jovian magnetosphere during 1973 and 1974, respectively. In an earlier study, Smith et al. (1978) concluded that the Jovian magnetosphere was subjected to large-scale compression during at least three or four intervals during which it appeared that the spacecraft had reentered the solar wind or magnetosheath near 50 R/sub J/ after having first entered the magnetosphere near 100 R/sub J/. They based this suggestion on the observations of the sister spacecraft, which indicated--on the basis of a kinematic translation of corotating interaction regions (CIR's)--that these structures would be expected to arrive at Jupiter at the appropriate beginning of these three intervals. Our reexamination of this suggestion involved the numerical simulation of the multiple CIR evolutions from one spacecraft to the sister spacecraft. This approach, considered to be a major improvement, confirms the suggestion by Smith et al. (1978) that Jupiter's magnetosphere was compressed by interplanetary CIR's during three or four of these events. Our MHD simulation also suggests that Jupiter's magnetosphere reacts to solar wind rarefactions in the opposite way--by expanding. A previously unexplained pair of magnetopause crossings on the Pioneer 11 outbound pass may simply be due to a delayed reexpansion of Jupiter's magnetosphere from a compression that occurred during the inbound pass

Physics of the diffusion region in the Magnetospheric Multiscale era

Science.gov (United States)

Chen, L. J.; Hesse, M.; Wang, S.; Ergun, R.; Bessho, N.; Burch, J. L.; Giles, B. L.; Torbert, R. B.; Gershman, D. J.; Wilson, L. B., III; Dorelli, J.; Pollock, C. J.; Moore, T. E.; Lavraud, B.; Strangeway, R. J.; Russell, C. T.; Khotyaintsev, Y. V.; Le Contel, O.; Avanov, L. A.

2016-12-01

Encounters of reconnection diffusion regions by the Magnetospheric Multiscale (MMS) mission during its first magnetopause scan are studied in combination with theories and simulations. The goal is to understand by first-principles how stored magnetic energy is converted into plasma thermal and bulk flow energies via particle energization, mixing and interaction with waves. The magnetosheath population having much higher density than the magnetospheric plasma is an outstanding narrator for and participant in the magnetospheric part of the diffusion region. For reconnection with negligible guide fields, the accelerated magnetosheath population (for both electrons and ions) is cyclotron turned by the reconnected magnetic field to form outflow jets, and then gyrotropized downstream. Wave fluctuations are reduced in the central electron diffusion region (EDR) and do not dominate the energy conversion there. For an event with a significant guide field to magnetize the electrons, wave fluctuations at the lower hybrid frequency dominate the energy conversion in the EDR, and the fastest electron outflow is established dominantly by a strong perpendicular electric field via the ExB flow in one exhaust and by time-of-flight effects along with parallel electric field acceleration in the other. Whether the above features are common threads to magnetopause reconnection diffusion regions is a question to be further examined.

The non-linear response of the magnetosphere: 30 October 1978

International Nuclear Information System (INIS)

Price, C.P.; Prichard, D.

1993-01-01

The authors address the question of whether the response of the earth magnetosphere to the solar wind can be viewed as a nonlinear phenomena, rather than a linear response. The difficulty in answering this question is that the driving function, namely the solar wind, is very aperiodic, and it is difficult to argue that the system has time to go to any sort of a steady state in response to the driving force, prior to its making another random change. The application of nonlinear analysis methods in the face of this type of system is very limited. The authors pick a particular day, namely October 30, 1978, when the solar wind was very uniform for an extended period of time, and there is the possibility the system could converge to some type of strange attractor state within this period. They look at the auroral electrojet as a measure of the potential nonlinear response of the magnetosphere, and apply both nonlinear and linear analysis procedures to the data to try to determine if the data would support a nonlinear response of the magnetosphere to the solar wind driver, taken as the product of the solar wind speed v, and the southward component of the interplanetary magnetic field B s

Pulsar magnetospheres in binary systems

Science.gov (United States)

Ershkovich, A. I.; Dolan, J. F.

1985-01-01

The criterion for stability of a tangential discontinuity interface in a magnetized, perfectly conducting inviscid plasma is investigated by deriving the dispersion equation including the effects of both gravitational and centrifugal acceleration. The results are applied to neutron star magnetospheres in X-ray binaries. The Kelvin-Helmholtz instability appears to be important in determining whether MHD waves of large amplitude generated by instability may intermix the plasma effectively, resulting in accretion onto the whole star as suggested by Arons and Lea and leading to no X-ray pulsar behavior.

Overview of Mercury Magnetospheric Orbiter (MMO) for BepiColombo

Science.gov (United States)

Murakami, G.; Hayakawa, H.; Fujimoto, M.; BepiColombo Project Team

2018-05-01

The next Mercury exploration mission BepiColombo will be launched in October 2018 and will arrive at Mercury in December 2025. We present the current status, science goals, and observation plans of JAXA's Mercury Magnetospheric Orbiter (MMO).

GPS Navigation for the Magnetospheric Multi-Scale Mission

Science.gov (United States)

Bamford, William; Mitchell, Jason; Southward, Michael; Baldwin, Philip; Winternitz, Luke; Heckler, Gregory; Kurichh, Rishi; Sirotzky, Steve

2009-01-01

In 2014. NASA is scheduled to launch the Magnetospheric Multiscale Mission (MMS), a four-satellite formation designed to monitor fluctuations in the Earth's magnetosphere. This mission has two planned phases with different orbits (1? x 12Re and 1.2 x 25Re) to allow for varying science regions of interest. To minimize ground resources and to mitigate the probability of collisions between formation members, an on-board orbit determination system consisting of a Global Positioning System (GPS) receiver and crosslink transceiver was desired. Candidate sensors would be required to acquire GPS signals both below and above the constellation while spinning at three revolutions-per-minute (RPM) and exchanging state and science information among the constellation. The Intersatellite Ranging and Alarm System (IRAS), developed by Goddard Space Flight Center (GSFC) was selected to meet this challenge. IRAS leverages the eight years of development GSFC has invested in the Navigator GPS receiver and its spacecraft communication expertise, culminating in a sensor capable of absolute and relative navigation as well as intersatellite communication. The Navigator is a state-of-the-art receiver designed to acquire and track weak GPS signals down to -147dBm. This innovation allows the receiver to track both the main lobe and the much weaker side lobe signals. The Navigator's four antenna inputs and 24 tracking channels, together with customized hardware and software, allow it to seamlessly maintain visibility while rotating. Additionally, an extended Kalman filter provides autonomous, near real-time, absolute state and time estimates. The Navigator made its maiden voyage on the Space Shuttle during the Hubble Servicing Mission, and is scheduled to fly on MMS as well as the Global Precipitation Measurement Mission (GPM). Additionally, Navigator's acquisition engine will be featured in the receiver being developed for the Orion vehicle. The crosslink transceiver is a 1/4 Watt transmitter

Dynamics of a plasma in laboratory models of magnetospheres of the Earth and Uranus

International Nuclear Information System (INIS)

Podgornyj, I.M.; Dubinin, Eh.M.; Izrajlevich, P.L.; Potanin, Yu.N.

1977-01-01

The plasma convection schema in the artificial magnetosphere of the Earth and Uranus has been studied, the magnetic convection schema being not connected with the readjustment of the magnetic field. The data on the modelling of the conditions of the Earth and the Uranus are presented. In modelling the magnetosphere of the Earth, various pictures of the convection of plasma in the equatorial and the meridional planes have been considered; the distributions of the intensities of fields are presented. In modelling the magnetosphere of the Uranus, several models are considered. The magnetosphere possessing the tubular tail is shown to be possible. A possibility has been checked that at the magnetic tail of the Uranus not cylindrical, but a flat current layer may exist, which has been built of the principle of readjustment of the magnetic field. The schemes illustrating the configuration of the magnetic tail, magnetic field, and plasma penetration areas are presented. Presented are the dependences of the component of the magnetic field intensity, which is parallel to the velocity vector, and at various inclination angles. An analysis of the results of laboratory tests and of the data of measurements in the cosmic space has been carried out

On the adiabatic walking of plasma waves in a pulsar magnetosphere

International Nuclear Information System (INIS)

Melikidze, George I.; Gil, Janusz; Mitra, Dipanjan

2014-01-01

The pulsar radio emission is generated in the near magnetosphere of the neutron star, and it must propagate through the rest of it to emerge into the interstellar medium. An important issue is whether this propagation affects the planes of polarization of the generated radiation. Observationally, there is sufficient evidence that the emerging radiation is polarized parallel or perpendicular to the magnetic field line planes that should be associated with the ordinary (O) and extraordinary (X) plasma modes, respectively, excited by some radiative process. This strongly suggests that the excited X and O modes are not affected by the so-called adiabatic walking that causes a slow rotation of polarization vectors. In this paper, we demonstrate that the conditions for adiabatic walking are not fulfilled within the soliton model of pulsar radio emission, in which the coherent curvature radiation occurs at frequencies much lower than the characteristic plasma frequency, The X mode propagates freely and observationally represents the primary polarization mode. The O mode has difficulty escaping from the pulsar plasma; however, it is sporadically observed as a weaker secondary polarization mode. We discuss a possible scenario under which the O mode can also escape from the plasma and reach an observer.

SUPER STRONG MAGNETIC FIELDS OF NEUTRON STARS IN BE X-RAY BINARIES ESTIMATED WITH NEW TORQUE AND MAGNETOSPHERE MODELS

Energy Technology Data Exchange (ETDEWEB)

Shi, Chang-Sheng; Zhang, Shuang-Nan [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Li, Xiang-Dong, E-mail: zhangsn@ihep.ac.cn [Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093 (China)

2015-11-10

We re-estimate the surface magnetic fields of neutron stars (NSs) in Be X-ray binaries (BeXBs) with different models of torque, improved beyond Klus et al. In particular, a new torque model is applied to three models of magnetosphere radius. Unlike the previous models, the new torque model does not lead to divergent results for any fastness parameter. The inferred surface magnetic fields of these NSs for the two compressed magnetosphere models are much higher than that for the uncompressed magnetosphere model. The new torque model using the compressed magnetosphere radius leads to unique solutions near spin equilibrium in all cases, unlike other models that usually give two branches of solutions. Although our conclusions are still affected by the simplistic assumptions about the magnetosphere radius calculations, we show several groups of possible surface magnetic field values with our new models when the interaction between the magnetosphere and the infalling accretion plasma is considered. The estimated surface magnetic fields for NSs BeXBs in the Large Magellanic Cloud, the Small Magellanic Cloud and the Milk Way are between the quantum critical field and the maximum “virial” value by the spin equilibrium condition.

Magnetospheric Truncation, Tidal Inspiral, and the Creation of Short-period and Ultra-short-period Planets

Energy Technology Data Exchange (ETDEWEB)

Lee, Eve J.; Chiang, Eugene, E-mail: evelee@berkeley.edu [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

2017-06-10

Sub-Neptunes around FGKM dwarfs are evenly distributed in log orbital period down to ∼10 days, but dwindle in number at shorter periods. Both the break at ∼10 days and the slope of the occurrence rate down to ∼1 day can be attributed to the truncation of protoplanetary disks by their host star magnetospheres at corotation. We demonstrate this by deriving planet occurrence rate profiles from empirical distributions of pre-main-sequence stellar rotation periods. Observed profiles are better reproduced when planets are distributed randomly in disks—as might be expected if planets formed in situ—rather than piled up near disk edges, as would be the case if they migrated in by disk torques. Planets can be brought from disk edges to ultra-short (<1 day) periods by asynchronous equilibrium tides raised on their stars. Tidal migration can account for how ultra-short-period planets are more widely spaced than their longer-period counterparts. Our picture provides a starting point for understanding why the sub-Neptune population drops at ∼10 days regardless of whether the host star is of type FGK or early M. We predict planet occurrence rates around A stars to also break at short periods, but at ∼1 day instead of ∼10 days because A stars rotate faster than stars with lower masses (this prediction presumes that the planetesimal building blocks of planets can drift inside the dust sublimation radius).

Magnetospheric Truncation, Tidal Inspiral, and the Creation of Short-period and Ultra-short-period Planets

International Nuclear Information System (INIS)

Lee, Eve J.; Chiang, Eugene

2017-01-01

Sub-Neptunes around FGKM dwarfs are evenly distributed in log orbital period down to ∼10 days, but dwindle in number at shorter periods. Both the break at ∼10 days and the slope of the occurrence rate down to ∼1 day can be attributed to the truncation of protoplanetary disks by their host star magnetospheres at corotation. We demonstrate this by deriving planet occurrence rate profiles from empirical distributions of pre-main-sequence stellar rotation periods. Observed profiles are better reproduced when planets are distributed randomly in disks—as might be expected if planets formed in situ—rather than piled up near disk edges, as would be the case if they migrated in by disk torques. Planets can be brought from disk edges to ultra-short (<1 day) periods by asynchronous equilibrium tides raised on their stars. Tidal migration can account for how ultra-short-period planets are more widely spaced than their longer-period counterparts. Our picture provides a starting point for understanding why the sub-Neptune population drops at ∼10 days regardless of whether the host star is of type FGK or early M. We predict planet occurrence rates around A stars to also break at short periods, but at ∼1 day instead of ∼10 days because A stars rotate faster than stars with lower masses (this prediction presumes that the planetesimal building blocks of planets can drift inside the dust sublimation radius).

Transient plasma injections in the dayside magnetosphere: one-to-one correlated observations by Cluster and SuperDARN

Directory of Open Access Journals (Sweden)

A. Marchaudon

2004-01-01

Full Text Available Conjunctions in the cusp between the four Cluster spacecraft and SuperDARN ground-based radars offer unique opportunities to compare the signatures of transient plasma injections simultaneously in the high-altitude dayside magnetosphere and in the ionosphere. We report here on such observations on 17 March 2001, when the IMF initially northward and duskward, turns southward and dawnward for a short period. The changes in the convection direction at Cluster are well correlated with the interplanetary magnetic field (IMF By variations. Moreover, the changes in the ionosphere follow those in the magnetosphere, with a 2–3min delay. When mapped into the ionosphere, the convection velocity at Cluster is about 1.5 times larger than measured by SuperDARN. In the high-altitude cusp, field and particle observations by Cluster display the characteristic signatures of plasma injections into the magnetosphere suggestive of Flux Transfer Events (FTEs. Simultaneous impulsive and localized convection plasma flows are observed in the ionospheric cusp by the HF radars. A clear one-to-one correlation is observed for three successive injections, with a 2–3min delay between the magnetospheric and ionospheric observations. For each event, the drift velocity of reconnected flux tubes (phase velocity has been compared in the magnetosphere and in the ionosphere. The drift velocity measured at Cluster is of the order of 400–600ms–1 when mapped into the ionosphere, in qualitative agreement with SuperDARN observations. Finally, the reconnected flux tubes are elongated in the north-south direction, with an east-west dimension of 30–60km in the ionosphere from mapped Cluster observations, which is consistent with SuperDARN observations, although slightly smaller. Key words. Ionosphere (plasma convection – Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetosphere-ionosphere interactions

Recent progress in understanding of the ion composition in the magnetosphere and some major question mark

International Nuclear Information System (INIS)

Hultqvist, B.

1981-06-01

The observations of the energetic ion composition in the magnetosphere are reviewed with the emphasis on the recent measurements by means of GEOS-1 and -2, ISEE-1 and 2, PROGNOZ-7 and SCATHA. The observations are compared with the predictions of the open magnetosphere model. One of the major conclusions is that there are processes in the magnetosphere which play a much larger part than the model, as hitherto presented, predicts. Direct ejection of ionospheric ions, in combination with acceleration, along closed as well as open field lines may even be the dominating source process for the ring current/inner plasma sheet in magnetic storms. In very disturbed conditions this ejection mechanism must work over most of the hemispheres poleward of say 50degrees. Circulation of the ionospheric ions through the tail of the magnetosphere is not likely to be of primary importance for the energization of these ions in very disturbed conditions. (author)

Visualization and spectral synthesis of rotationally distorted stars

International Nuclear Information System (INIS)

Dall, T H; Sbordone, L

2011-01-01

Simple spherical, non-rotating stellar models are inadequate when describing real stars in the limit of very fast rotation: Both the observable spectrum and the geometrical shape of the star deviate strongly from simple models. We attempt to approach the problem of modeling geometrically distorted, rapidly rotating stars from a new angle: By constructing distorted geometrical models and integrating standard stellar models with varying temperature, gravity, and abundances, over the entire surface, we attempt a semi-empirical approach to modeling. Here we present our methodology, and present simple examples of applications.

Chorus source region localization in the Earth's outer magnetosphere using THEMIS measurements

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O. Agapitov

2010-06-01

Full Text Available Discrete ELF/VLF chorus emissions, the most intense electromagnetic plasma waves observed in the Earth's radiation belts and outer magnetosphere, are thought to propagate roughly along magnetic field lines from a localized source region near the magnetic equator towards the magnetic poles. THEMIS project Electric Field Instrument (EFI and Search Coil Magnetometer (SCM measurements were used to determine the spatial scale of the chorus source localization region on the day side of the Earth's outer magnetosphere. We present simultaneous observations of the same chorus elements registered onboard several THEMIS spacecraft in 2007 when all the spacecraft were in the same orbit. Discrete chorus elements were observed at 0.15–0.25 of the local electron gyrofrequency, which is typical for the outer magnetosphere. We evaluated the Poynting flux and wave vector distribution and obtained chorus wave packet quasi-parallel propagation to the local magnetic field. Amplitude and phase correlation data analysis allowed us to estimate the characteristic spatial correlation scale transverse to the local magnetic field to be in the 2800–3200 km range.

Spontaneous generation of auroral arcs in a three dimensionally coupled magnetosphere-ionosphere system

International Nuclear Information System (INIS)

Watanabe, Kunihiko; Sato, Tetsuya.

1988-01-01

This paper presents the first full three-dimensional dynamic simulation of auroral arc formation. The magnetospheric and ionospheric dynamics are represented by one-fluid magnetohydrodynamic equations and two-fluid weakly ionized plasma equations, respectively. The feedback coupling between magnetospheric Alfven waves and ionospheric density waves are self-consistently and three-dimensionally solved. Obtained is a spontaneous generation of longitudinally elongated striations of field-aligned currents and ionospheric electron densities, which compare very well with many features of quiet auroral arcs. (author)

Near-Earth Magnetic Field Effects of Large-Scale Magnetospheric Currents

Science.gov (United States)

Luehr, Hermann; Xiong, Chao; Olsen, Nils; Le, Guan

2016-01-01

Magnetospheric currents play an important role in the electrodynamics of near- Earth space. This has been the topic of many space science studies. Here we focus on the magnetic fields they cause close to Earth. Their contribution to the geomagnetic field is the second largest after the core field. Significant progress in interpreting the magnetic fields from the different sources has been achieved thanks to magnetic satellite missions like Ørsted, CHAMP and now Swarm. Of particular interest for this article is a proper representation of the magnetospheric ring current effect. Uncertainties in modelling its effect still produce the largest residuals between observations and present-day geomagnetic field models. A lot of progress has been achieved so far, but there are still open issues like the characteristics of the partial ring current. Other currents discussed are those flowing in the magnetospheric tail. Also their magnetic contribution at LEO orbits is non-negligible. Treating them as an independent source is a more recent development, which has cured some of the problems in geomagnetic field modelling. Unfortunately there is no index available for characterizing the tail current intensity. Here we propose an approach that may help to properly quantify the magnetic contribution from the tail current for geomagnetic field modelling. Some open questions that require further investigation are mentioned at the end.

Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System: Modeling Ion Outflow

Science.gov (United States)

Schunk, R. W.; Barakat, A. R.; Eccles, V.; Karimabadi, H.; Omelchenko, Y.; Khazanov, G. V.; Glocer, A.; Kistler, L. M.

2014-12-01

A Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System is being developed in order to provide a rigorous approach to modeling the interaction of hot and cold particle interactions. The framework will include ion and electron kinetic species in the ionosphere, plasmasphere and polar wind, and kinetic ion, super-thermal electron and fluid electron species in the magnetosphere. The framework is ideally suited to modeling ion outflow from the ionosphere and plasmasphere, where a wide range for fluid and kinetic processes are important. These include escaping ion interactions with (1) photoelectrons, (2) cusp/auroral waves, double layers, and field-aligned currents, (3) double layers in the polar cap due to the interaction of cold ionospheric and hot magnetospheric electrons, (4) counter-streaming ions, and (5) electromagnetic wave turbulence. The kinetic ion interactions are particularly strong during geomagnetic storms and substorms. The presentation will provide a brief description of the models involved and discuss the effect that kinetic processes have on the ion outflow.

Oblique propagating electromagnetic ion - Cyclotron instability with A.C. field in outer magnetosphere

Science.gov (United States)

Pandey, R. S.; Singh, Vikrant; Rani, Anju; Varughese, George; Singh, K. M.

2018-05-01

In the present paper Oblique propagating electromagnetic ion-cyclotron wave has been analyzed for anisotropic multi ion plasma (H+, He+, O+ ions) in earth magnetosphere for the Dione shell of L=7 i.e., the outer radiation belt of the magnetosphere for Loss-cone distribution function with a spectral index j in the presence of A.C. electric field. Detail for particle trajectories and dispersion relation has been derived by using the method of characteristic solution on the basis of wave particle interaction and transformation of energy. Results for the growth rate have been calculated numerically for various parameters and have been compared for different ions present in magnetosphere. It has been found that for studying the wave over wider spectrum, anisotropy for different values of j should be taken. The effect of frequency of A.C. electric field and angle which propagation vector make with magnetic field, on growth rate has been explained.

Solar rotation measurements at Mount Wilson. Pt. 2

International Nuclear Information System (INIS)

Labonte, B.J.; Howard, R.; Carnegie Institution of Washington, Pasadena

1981-01-01

Possible sources of systematic error in solar Doppler rotational velocities are examined. Scattered light is shown to affect the Mount Wilson solar rotation results, but this effect is not enough to bring the spectroscopic results in coincidence with the sunspot rotation. Interference fringes at the spectrograph focus at Mount Wilson have in two intervals affected the rotation results. It has been possible to correlate this error with temperature and thus correct for it. A misalignment between the entrance and exit slits is a possible source of error, but for the Mount Wilson slit configuration the amplitude of this effect is negligibly small. Rapid scanning of the solar image also produces no measurable effect. (orig.)

Principle and analysis of a rotational motion Fourier transform infrared spectrometer

Science.gov (United States)

Cai, Qisheng; Min, Huang; Han, Wei; Liu, Yixuan; Qian, Lulu; Lu, Xiangning

2017-09-01

Fourier transform infrared spectroscopy is an important technique in studying molecular energy levels, analyzing material compositions, and environmental pollutants detection. A novel rotational motion Fourier transform infrared spectrometer with high stability and ultra-rapid scanning characteristics is proposed in this paper. The basic principle, the optical path difference (OPD) calculations, and some tolerance analysis are elaborated. The OPD of this spectrometer is obtained by the continuously rotational motion of a pair of parallel mirrors instead of the translational motion in traditional Michelson interferometer. Because of the rotational motion, it avoids the tilt problems occurred in the translational motion Michelson interferometer. There is a cosine function relationship between the OPD and the rotating angle of the parallel mirrors. An optical model is setup in non-sequential mode of the ZEMAX software, and the interferogram of a monochromatic light is simulated using ray tracing method. The simulated interferogram is consistent with the theoretically calculated interferogram. As the rotating mirrors are the only moving elements in this spectrometer, the parallelism of the rotating mirrors and the vibration during the scan are analyzed. The vibration of the parallel mirrors is the main error during the rotation. This high stability and ultra-rapid scanning Fourier transform infrared spectrometer is a suitable candidate for airborne and space-borne remote sensing spectrometer.

Precision grip responses to unexpected rotational perturbations scale with axis of rotation.

Science.gov (United States)

De Gregorio, Michael; Santos, Veronica J

2013-04-05

It has been established that rapid, pulse-like increases in precision grip forces ("catch-up responses") are elicited by unexpected translational perturbations and that response latency and strength scale according to the direction of linear slip relative to the hand as well as gravity. To determine if catch-up responses are elicited by unexpected rotational perturbations and are strength-, axis-, and/or direction-dependent, we imposed step torque loads about each of two axes which were defined relative to the subject's hand: the distal-proximal axis away from and towards the subject's palm, and the grip axis which connects the two fingertips. Precision grip responses were dominated initially by passive mechanics and then by active, unimodal catch-up responses. First dorsal interosseous activity, marking the start of the catch-up response, began 71-89 ms after the onset of perturbation. The onset latency, shape, and duration (217-231 ms) of the catch-up response were not affected by the axis, direction, or magnitude of the rotational perturbation, while strength was scaled by axis of rotation and slip conditions. Rotations about the grip axis that tilted the object away from the palm and induced rotational slip elicited stronger catch-up responses than rotations about the distal-proximal axis that twisted the object between the digits. To our knowledge, this study is the first to investigate grip responses to unexpected torque loads and to show characteristic, yet axis-dependent, catch-up responses for conditions other than pure linear slip. Copyright © 2013 Elsevier Ltd. All rights reserved.

Magnetospheric conditions near the equatorial footpoints of proton isotropy boundaries

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V. A. Sergeev

2015-12-01

Full Text Available Data from a cluster of three THEMIS (Time History of Events and Macroscale Interactions during Substorms spacecraft during February–March 2009 frequently provide an opportunity to construct local data-adaptive magnetospheric models, which are suitable for the accurate mapping along the magnetic field lines at distances of 6–9 Re in the nightside magnetosphere. This allows us to map the isotropy boundaries (IBs of 30 and 80 keV protons observed by low-altitude NOAA POES (Polar Orbiting Environmental Satellites to the equatorial magnetosphere (to find the projected isotropy boundary, PIB and study the magnetospheric conditions, particularly to evaluate the ratio KIB (Rc/rc; the magnetic field curvature radius to the particle gyroradius in the neutral sheet at that point. Special care is taken to control the factors which influence the accuracy of the adaptive models and mapping. Data indicate that better accuracy of an adaptive model is achieved when the PIB distance from the closest spacecraft is as small as 1–2 Re. For this group of most accurate predictions, the spread of KIB values is still large (from 4 to 32, with the median value KIB ~13 being larger than the critical value Kcr ~ 8 expected at the inner boundary of nonadiabatic angular scattering in the current sheet. It appears that two different mechanisms may contribute to form the isotropy boundary. The group with K ~ [4,12] is most likely formed by current sheet scattering, whereas the group having KIB ~ [12,32] could be formed by the resonant scattering of low-energy protons by the electromagnetic ion-cyclotron (EMIC waves. The energy dependence of the upper K limit and close proximity of the latter event to the plasmapause locations support this conclusion. We also discuss other reasons why the K ~ 8 criterion for isotropization may fail to work, as well as a possible relationship between the two scattering mechanisms.

Modeling the entry and trapping of solar energetic particles in the magnetosphere during the November 24-25, 2001 storm

Science.gov (United States)

Richard, R. L.; El-Alaoui, M.; Ashour-Abdalla, M.; Walker, R. J.

2009-04-01

We have modeled the entry of solar energetic particles (SEPs) into the magnetosphere during the November 24-25, 2001 magnetic storm and the trapping of particles in the inner magnetosphere. The study used the technique of following many test particles, protons with energies greater than about 100 keV, in the electric and magnetic fields from a global magnetohydrodynamic (MHD) simulation of the magnetosphere during this storm. SEP protons formed a quasi-trapped and trapped population near and within geosynchronous orbit. Preliminary data comparisons show that the simulation does a reasonably good job of predicting the differential flux measured by geosynchronous spacecraft. Particle trapping took place mainly as a result of particles becoming non-adiabatic and crossing onto closed field lines. Particle flux in the inner magnetosphere increased dramatically as an interplanetary shock impacted and compressed the magnetosphere near 0600 UT, but long term trapping (hours) did not become widespread until about an hour later, during a further compression of the magnetosphere. Trapped and quasi-trapped particles were lost during the simulation by motion through the magnetopause and by precipitation, primarily the former. This caused the particle population near and within geosynchronous orbit to gradually decrease later on during the latter part of the interval.

NGC 1866: First Spectroscopic Detection of Fast-rotating Stars in a Young LMC Cluster

Energy Technology Data Exchange (ETDEWEB)

Dupree, A. K.; Dotter, A.; Johnson, C. I. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Marino, A. F.; Milone, A. P. [Australian National University, The Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Weston Creek, ACT 2611 (Australia); Bailey, J. I. III [Leiden Observatory, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Crane, J. D. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Mateo, M. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Olszewski, E. W. [The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)

2017-09-01

High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (∼200 Myr) Large Magellanic Cloud (LMC) cluster, NGC 1866, using the Michigan/ Magellan Fiber System and MSpec spectrograph on the Magellan -Clay 6.5 m telescope. These spectra reveal the first direct detection of rapidly rotating stars whose presence has only been inferred from photometric studies. The eMSTO stars exhibit H α emission (indicative of Be-star decretion disks), others have shallow broad H α absorption (consistent with rotation ≳150 km s{sup −1}), or deep H α core absorption signaling lower rotation velocities (≲150 km s{sup −1}). The spectra appear consistent with two populations of stars—one rapidly rotating, and the other, younger and slowly rotating.

Parabolic heavy ion flow in the polar magnetosphere

International Nuclear Information System (INIS)

Horwitz, J.L.

1987-01-01

Recent observations by the Dynamics Explorer 1 satellite over the dayside polar cap magnetosphere have indicated downward flows of heavy ions (O + , O ++ , N + , N ++ ) with flow velocities of the order 1 km/s (Lockwood et al., 1985b). These downward flows were interpreted as the result of parabolic flow of these heavy ionospheric ions from a source region associated with the polar cleft topside ionosphere. Here the author utilizes a two-dimensional kinetic model to elicit features of the transport of very low energy O + ions from the cleft ionosphere. Bulk parameter (density, flux, thermal energies, etc.) distributions in the noon-midnight meridian plane illustrate the effects of varying convection electric fields and source energies. The results illustrate that particularly under conditions of weak convection electric fields and weak ion heating in the cleft region, much of the intermediate altitude polar cap magnetosphere may be populated by downward flowing heavy ions. It is further shown how two-dimensional transport effects may alter the characteristic vertical profiles of densities and fluxes from ordinary profiles computed in one-dimensional steady state models

Electric fields in the outer magnetosphere - Recent progress and outstanding problems

International Nuclear Information System (INIS)

Faelthammar, C.-G.

1979-03-01

The electric field is a crucial parameter in theories of solar wind interaction with the magnetosphere. During the IMS this parameter has, for the first time, been directly measured in the interacting regions: outer magnetosphere, magnetopause, magnetosheath, bow shock and the adjacent solar wind. Among the first results are the verification of a large-scale dawn-to-dusk tangential electric field component at the magnetopause of typically 1 - 2 mV/m and a corresponding power dissipation of 50 Wkm -2 . The normal component of the electric field is typically of the same order of magnitude as the tangential component. Fine-structure features, possibly related to the entry of plasma, remain to be analyzed. (author)

A statistical approach for identifying the ionospheric footprint of magnetospheric boundaries from SuperDARN observations

Directory of Open Access Journals (Sweden)

G. Lointier

2008-02-01

Full Text Available Identifying and tracking the projection of magnetospheric regions on the high-latitude ionosphere is of primary importance for studying the Solar Wind-Magnetosphere-Ionosphere system and for space weather applications. By its unique spatial coverage and temporal resolution, the Super Dual Auroral Radar Network (SuperDARN provides key parameters, such as the Doppler spectral width, which allows the monitoring of the ionospheric footprint of some magnetospheric boundaries in near real-time. In this study, we present the first results of a statistical approach for monitoring these magnetospheric boundaries. The singular value decomposition is used as a data reduction tool to describe the backscattered echoes with a small set of parameters. One of these is strongly correlated with the Doppler spectral width, and can thus be used as a proxy for it. Based on this, we propose a Bayesian classifier for identifying the spectral width boundary, which is classically associated with the Polar Cap boundary. The results are in good agreement with previous studies. Two advantages of the method are: the possibility to apply it in near real-time, and its capacity to select the appropriate threshold level for the boundary detection.

Using the tools of the trade to understand plasma interactions at Jupiter and Saturn

Science.gov (United States)

Kivelson, Margaret G.

2017-10-01

For more than half a century, we have been learning how magnetospheres work. Fluid motions and electromagnetic interactions combine to produce the plasma and field environment of a planet. Kinetic responses often control the dynamics. Initial descriptions of the terrestrial magnetosphere were often theoretical (e.g., Chapman and Ferraro, Dungey) before an explosion of spacecraft data provided an atlas of the system and its temporal variations. The basic structure and dynamics of the terrestrial magnetosphere are now largely understood. A different situation exists for the magnetospheres of Jupiter, Saturn, and their moons. Data acquired from spacecraft flybys or from orbit have characterized many aspects of these systems, but measurements are far more limited than at Earth both in space and in time. Even after Cassini’s mission to Saturn and Juno’s prime mission at Jupiter have ended, large regions in the plasma environments of these planets will remain unexplored. No monitors are available to characterize the upstream solar wind. Theory is challenged by the complexity introduced by dynamical effects of the planets’ rapid rotation and the unfamiliar parameter regimes governing interactions with their large moons. Simulation has come to the rescue, providing computational models designed to incorporate the effects of rotation or to describe moon-magnetosphere interactions. Yet simulations must be viewed with appropriate skepticism as they invariably require some compromise with reality. This talk will describe a symbiotic approach to understanding the dynamics of giant planet magnetospheres and the plasma interactions between magnetospheric plasma and large moons. Data acquired along a spacecraft trajectory are compared with values extracted from a virtual spacecraft moving through the same path in the simulation. If results are similar, we use the simulation to identify the processes responsible for puzzling aspects of the signatures. If results differ

Variational symplectic algorithm for guiding center dynamics in the inner magnetosphere

International Nuclear Information System (INIS)

Li Jinxing; Pu Zuyin; Xie Lun; Fu Suiyan; Qin Hong

2011-01-01

Charged particle dynamics in magnetosphere has temporal and spatial multiscale; therefore, numerical accuracy over a long integration time is required. A variational symplectic integrator (VSI) [H. Qin and X. Guan, Phys. Rev. Lett. 100, 035006 (2008) and H. Qin, X. Guan, and W. M. Tang, Phys. Plasmas 16, 042510 (2009)] for the guiding-center motion of charged particles in general magnetic field is applied to study the dynamics of charged particles in magnetosphere. Instead of discretizing the differential equations of the guiding-center motion, the action of the guiding-center motion is discretized and minimized to obtain the iteration rules for advancing the dynamics. The VSI conserves exactly a discrete Lagrangian symplectic structure and has better numerical properties over a long integration time, compared with standard integrators, such as the standard and adaptive fourth order Runge-Kutta (RK4) methods. Applying the VSI method to guiding-center dynamics in the inner magnetosphere, we can accurately calculate the particles'orbits for an arbitrary long simulating time with good conservation property. When a time-independent convection and corotation electric field is considered, the VSI method can give the accurate single particle orbit, while the RK4 method gives an incorrect orbit due to its intrinsic error accumulation over a long integrating time.

The Extended Pulsar Magnetosphere

Science.gov (United States)

Constantinos, Kalapotharakos; Demosthenes, Kazanas; Ioannis, Contopoulos

2012-01-01

We present the structure of the 3D ideal MHD pulsar magnetosphere to a radius ten times that of the light cylinder, a distance about an order of magnitude larger than any previous such numerical treatment. Its overall structure exhibits a stable, smooth, well-defined undulating current sheet which approaches the kinematic split monopole solution of Bogovalov 1999 only after a careful introduction of diffusivity even in the highest resolution simulations. It also exhibits an intriguing spiral region at the crossing of two zero charge surfaces on the current sheet, which shows a destabilizing behavior more prominent in higher resolution simulations. We discuss the possibility that this region is physically (and not numerically) unstable. Finally, we present the spiral pulsar antenna radiation pattern.

The contribution of inductive electric fields to particle energization in the inner magnetosphere

Science.gov (United States)

Ilie, R.; Toth, G.; Liemohn, M. W.; Chan, A. A.

2017-12-01

Assessing the relative contribution of potential versus inductive electric fields at the energization of the hot ion population in the inner magnetosphere is only possible by thorough examination of the time varying magnetic field and current systems using global modeling of the entire system. We present here a method to calculate the inductive and potential components of electric field in the entire magnetosphere region. This method is based on the Helmholtz vector decomposition of the motional electric field as calculated by the BATS-R-US model, and is subject to boundary conditions. This approach removes the need to trace independent field lines and lifts the assumption that the magnetic field lines can be treated as frozen in a stationary ionosphere. In order to quantify the relative contributions of potential and inductive electric fields at driving plasma sheet ions into the inner magnetosphere, we apply this method for the March 17th, 2013 geomagnetic storm. We present here the consequences of slow continuous changes in the geomagnetic field as well as the strong tail dipolarizations on the distortion of the near-Earth magnetic field and current systems. Our findings indicate that the inductive component of the electric field is comparable, and even higher at times than the potential component, suggesting that the electric field induced by the time varying magnetic field plays a crucial role in the overall particle energization in the inner magnetosphere.

Experimental shift work studies of permanent night, and rapidly rotating, shift systems. Pt. 1. Behaviour of various characteristics of sleep

Energy Technology Data Exchange (ETDEWEB)

Knauth, P.; Rutenfranz, J.; Romberg, H.P.; Decoster, F.; Kiesswetter, E. (Dortmund Univ. (Germany, F.R.). Inst. fuer Arbeitsphysiologie); Schulz, H. (Max-Planck-Institut fuer Psychiatrie, Muenchen (Germany, F.R.). Klinisches Inst.)

1980-06-01

In connection with experimental shift work 20 volunteers were examined while working on different rapidly or slowly rotating shift systems. Sleep was analyzed over a total of 112 days. Sleep was disturbed by children's noise or traffic noise. Sleep duration and sleep quality were particularly badly affected by noise with a high information value (children's noise). The ultradian rhythmicity of sleep did not appear to be disrupted by the change from day to night work. There were no significant differences between morning sleep and afternoon sleep after night work. In the laboratory experiments with fixed sleep durations, no separate effects on sleep quality could be established for different shift systems.

On the interpretation of different flow vectors of different ion species in the magnetospheric boundary layer

International Nuclear Information System (INIS)

Lundin, R.; Stasiewicz, K.; Hultqvist, B.

1986-05-01

Recent measurements of the ion composition in the magnetospheric boundary layer indicate that the boundary layer may contain clouds of magnetosheath plasma which are gradually becoming mixed with the magnetospheric plasma. A significant difference between flow vectors of different ion species (ca50-100 km/s) implies that an ideal MHD equation E+VxB=0, does not describe the macroscopic plasma flow inside such inhomogeneities. An analysis based on the first order drift theory indicates that gradients of the partial ion pressure and of the magnetic field could induce differential ion drifts comparable in magnitude to the electric drift velocity. We discuss some implications of these results on the physics of solar wind-magnetosphere interactions. (authors)

Conductance Effects on Inner Magnetospheric Plasma Morphology: Model Comparisons with IMAGE EUV, MENA, and HENA Data

Science.gov (United States)

Liemohn, M.; Ridley, A. J.; Kozyra, J. U.; Gallagher, D. L.; Brandt, P. C.; Henderson, M. G.; Denton, M. H.; Jahn, J. M.; Roelof, E. C.; DeMajistre, R. M.

2004-01-01

Modeling results of the inner magnetosphere showing the influence of the ionospheric conductance on the inner magnetospheric electric fields during the April 17, 2002 magnetic storm are presented. Kinetic plasma transport code results are analyzed in combination with observations of the inner magnetospheric plasma populations, in particular those from the IMAGE satellite. Qualitative and quantitative comparisons are made with the observations from EW, MENA, and HENA, covering the entire energy range simulated by the model (0 to 300 keV). The electric field description, and in particular the ionospheric conductance, is the only variable between the simulations. Results from the data-model comparisons are discussed, detailing the strengths and weaknesses of each conductance choice for each energy channel.

Self-Consistent Model of Magnetospheric Electric Field, Ring Current, Plasmasphere, and Electromagnetic Ion Cyclotron Waves: Initial Results

Science.gov (United States)

Gamayunov, K. V.; Khazanov, G. V.; Liemohn, M. W.; Fok, M.-C.; Ridley, A. J.

2009-01-01

Further development of our self-consistent model of interacting ring current (RC) ions and electromagnetic ion cyclotron (EMIC) waves is presented. This model incorporates large scale magnetosphere-ionosphere coupling and treats self-consistently not only EMIC waves and RC ions, but also the magnetospheric electric field, RC, and plasmasphere. Initial simulations indicate that the region beyond geostationary orbit should be included in the simulation of the magnetosphere-ionosphere coupling. Additionally, a self-consistent description, based on first principles, of the ionospheric conductance is required. These initial simulations further show that in order to model the EMIC wave distribution and wave spectral properties accurately, the plasmasphere should also be simulated self-consistently, since its fine structure requires as much care as that of the RC. Finally, an effect of the finite time needed to reestablish a new potential pattern throughout the ionosphere and to communicate between the ionosphere and the equatorial magnetosphere cannot be ignored.

Young gamma-ray pulsar: from modeling the gamma-ray emission to the particle-in-cell simulations of the global magnetosphere

Science.gov (United States)

Brambilla, Gabriele; Kalapotharakos, Constantions; Timokhin, Andrey; Kust Harding, Alice; Kazanas, Demosthenes

2016-04-01

Accelerated charged particles flowing in the magnetosphere produce pulsar gamma-ray emission. Pair creation processes produce an electron-positron plasma that populates the magnetosphere, in which the plasma is very close to force-free. However, it is unknown how and where the plasma departs from the ideal force-free condition, which consequently inhibits the understanding of the emission generation. We found that a dissipative magnetosphere outside the light cylinder effectively reproduces many aspects of the young gamma-ray pulsar emission as seen by the Fermi Gamma-ray Space Telescope, and through particle-in-cell simulations (PIC), we started explaining this configuration self-consistently. These findings show that, together, a magnetic field structure close to force-free and the assumption of gamma-ray curvature radiation as the emission mechanism are strongly compatible with the observations. Two main issues from the previously used models that our work addresses are the inability to explain luminosity, spectra, and light curve features at the same time and the inconsistency of the electrodynamics. Moreover, using the PIC simulations, we explore the effects of different pair multiplicities on the magnetosphere configurations and the locations of the accelerating regions. Our work aims for a self-consistent modeling of the magnetosphere, connecting the microphysics of the pair-plasma to the global magnetosphere macroscopic quantities. This direction will lead to a greater understanding of pulsar emission at all wavelengths, as well as to concrete insights into the physics of the magnetosphere.

Solar energetic particles in the Earth magnetosphere: kinematic modeling of the 'non-shock' penetration

International Nuclear Information System (INIS)

Pavlov, N N

2013-01-01

Penetration of solar energetic particles into the Earth's magnetosphere is quantitatively studied with a simple kinematic model. The goal is to assess, for the first time, how does effectiveness of the penetration depend on such geometry factors as: distance of the magneto-pause (MP) from the Earth; shape of MP; angle at which solar energetic particle crosses MP; location of the crossing point; type of the particle motion in the magnetosphere. To get off excessive details, the model deliberately operates with just equatorial section of the static dipolar magnetic field confined with asymmetric boundary – MP. Several rather obvious facts are illustrated: finite orbits of longitudinal drift reside only inside the circle of the Störmer-unit-length radius; deepest penetration of a particle occurs if the particle crosses MP at the point closest to the Earth and with velocity-vector oriented along the particle's longitudinal drift inside MP (westward for protons); etc. The model's software allows the inquirer to vary geometry of MP, the type, energy and direction of flight of the energetic particle(s), the location(s), aperture and orientation(s) of a virtual sensor, then to run the model and obtain the reference particle distributions either global (for entire magnetosphere) or for specified locations, all along the time, energy and flux-orientation axes. Static and animated plots can be easily produced. The model provides a toolkit allowing one to evaluate and illustrate the process of particle penetration into the magnetosphere under various conditions in space. It may be used for the configuring of the satellite particle sensors; its results may be compared with the observations for to assess how strongly the real magnetosphere differs from its simplified form; it may be used in education.

Plasma Transport at the Magnetospheric Flank Boundary. Final report

International Nuclear Information System (INIS)

Otto, Antonius

2012-01-01

Progress is highlighted in these areas: 1. Model of magnetic reconnection induced by three-dimensional Kelvin Helmholtz (KH) modes at the magnetospheric flank boundary; 2. Quantitative evaluation of mass transport from the magnetosheath onto closed geomagnetic field for northward IMF; 3. Comparison of mass transfer by cusp reconnection and Flank Kelvin Helmholtz modes; 4. Entropy constraint and plasma transport in the magnetotail - a new mechanism for current sheet thinning; 5. Test particle model for mass transport onto closed geomagnetic field for northward IMF; 6. Influence of density asymmetry and magnetic shear on (a) the linear and nonlinear growth of 3D Kelvin Helmholtz (KH) modes, and (b) three-dimensional KH mediated mass transport; 7. Examination of entropy and plasma transport in the magnetotail; 8. Entropy change and plasma transport by KH mediated reconnection - mixing and heating of plasma; 9. Entropy and plasma transport in the magnetotail - tail reconnection; and, 10. Wave coupling at the magnetospheric boundary and generation of kinetic Alfven waves

Excitation of the Magnetospheric Cavity by Space-Based ELF/VLF Transmitters

National Research Council Canada - National Science Library

Bell, Timothy F; Inan, Umran; Kulkarni, P

2004-01-01

During the period of performance Stanford University: 1. Developed an analytical model describing the distribution of current along a dipole antenna radiating ELF/VLF waves in the magnetospheric cavity...

Field-aligned currents near the magnetosphere boundary

International Nuclear Information System (INIS)

Hones, E.W. Jr.

1984-01-01

This paper describes present thinking about the structure of magnetospheric boundary layers and their roles in the generation of the field-aligned currents that are observed in the polar regions. A principal effect of the momentum loss by magnetosheath plasma to the magnetosphere boundary regions just within the magnetopause, whether it be by a diffusive process or by magnetic reconnection, is the tailward pulling of the surface flux tubes relative to those deeper below the surface. The dayside region 1 currents at low altitudes flow along field lines in the resulting regions of magnetic shear. The direction of the shear and its magnitude, actually measured in the boundary region, confirm that the polarities and intensities of the dayside region 1 currents can be accounted for by this process. The low latitude boundary layer, formerly thought to be threaded entirely by closed field lines, now appears to contain at least some open field lines, newly reconnected, that are in the process of being swept into the high latitude tail to form the plasma mantle. The open flux tubes of the flux transfer events, thought to be the product of patchy reconnection have a spiral magnetic structure whose helicity is such as to suggest currents having the polarities of the region 1 currents. 13 references

Field-aligned currents near the magnetosphere boundary

International Nuclear Information System (INIS)

Hones, E.W. Jr.

1983-01-01

This paper reviews present thinking about the structure of magnetospheric boundary layers and their roles in the generation of the field-aligned currents that are observed in the polar regions. A principal effect of the momentum loss by magnetosheath plasma to the magnetosphere boundary regions just within the magnetopause, whether it be by a diffusive process or by magnetic reconnection, is the tailward pulling of surface flux tubes relative to those deeper below the surface. The dayside region 1 currents at low altitudes flow along field lines in the resulting regions of magnetic shear. The direction of the shear and its magnitude, measured in the boundary region, confirm tht the polarities and intensities of the dayside region 1 currents can be accounted for by this process. The low latitude boundary layer, formerly thought to be threaded entirely by closed field lines, now appears to contain at least some open field lines, newly reconnected, that are in the process of being swept into the high latitude tail to form the plasma mantle. The open flux tubes of the flux transfer events, thought to be the product of patchy reconnection have a spiral magnetic structure whose helicity is such as to suggest currents having the polarities of the region 1 currents

Spatial distribution of upstream magnetospheric ≥50 keV ions

Directory of Open Access Journals (Sweden)

G. C. Anagnostopoulos

2000-01-01

Full Text Available We present for the first time a statistical study of \\geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1 a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT of the bow shock, (2 highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF configuration, and (3 a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1 preferential leakage of ~50 keV magnetospheric ions from the dusk magnetopause, (2 nearly scatter free motion of ~50 keV ions within the magnetosheath, and (3 final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between ~16%-~34% in the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks

Spatial distribution of upstream magnetospheric ≥50 keV ions

Directory of Open Access Journals (Sweden)

G. Kaliabetsos

Full Text Available We present for the first time a statistical study of geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1 a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT of the bow shock, (2 highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF configuration, and (3 a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1 preferential leakage of ~50 keV magnetospheric ions from the dusk magnetopause, (2 nearly scatter free motion of ~50 keV ions within the magnetosheath, and (3 final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between ~16%-~34% in the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks

Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

Directory of Open Access Journals (Sweden)

L. Z. Biktash

2004-09-01

Full Text Available The equatorial ionosphere parameters, K_p, D_st, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the D_st index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

Yosemite conference on ionospheric plasma in the magnetosphere: sources, mechanisms and consequences, meeting report

International Nuclear Information System (INIS)

Gallagher, D.L.; Burch, J.L.; Klumpar, D.M.; Moore, T.E.; Waite, J.H. Jr.

1987-02-01

The sixth biennial Yosemite topical conference and the first as a Chapman Conference was held on February 3 to 6, 1986. Although the solar wind was once thought to dominate the supply of plasma in the Earth's magnetosphere, it is now thought that the Earth's ionosphere is a significant contributor. Polar wind and other large volume outflows of plasma have been seen at relatively high altitudes over the polar cap and are now being correlated with outflows found in the magnetotail. The auroral ion fountain and cleft ion fountain are examples of ionospheric sources of plasma in the magnetosphere, observed by the Dynamics Explorer 1 (DE 1) spacecraft. The conference was organized into six sessions: four consisting of prepared oral presentations, one poster session, and one session for open forum discussion. The first three oral sessions dealt separately with the three major topics of the conference, i.e., the sources, mechanisms, and consequences of ionospheric plasma in the magnetosphere. A special session of invited oral presentations was held to discuss extraterrestrial ionospheric/magnetospheric plasma processes. The poster session was extended over two evenings during which presenters discussed their papers on a one-on-one basis. The last session of the conferences was reserved for open discussions of those topics or ideas considered most interesting or controversial

Laboratory simulation of the magnetosphere, magnetotail reconnection and the study of field-aligned currents

International Nuclear Information System (INIS)

Yur, G.

1990-01-01

Laboratory simulation of the Earth's magnetosphere is performed. A wide plasma beam with plasma density ∼ 10 13 cm -3 , velocity ∼ 10 7 cm/s, temperature ∼ 10 eV and pulse duration ∼ 100μs simulates the solar wind plasma. An externally applied magnetic field throughout the interaction chamber is varied between -300 to +300 G to simulate the interplanetary magnet field (IMF). Detailed characterization of the flow of this plasma across the IMF shows various degrees of diamagnetism and rvec E x rvec B propagation. This magnetized plasma beam interacts with a spherical dipole magnetic field that simulates the planetary field to form a planetary type plasma sphere. Cusp structures and particle precipitations are studied with optical time exposure photographs of the simulated magnetosphere. The structure is strongly controlled by the polarity of the IMF. The global structure of the magnetosphere is measured in detail for different values of the IMF at various locations in the magnetosphere. Particularly, the magnetic field measurements in the tail reveal interesting reconnection processes and above the polar region, the structure of field aligned currents that are similar to the ones obtained from the satellites above the polar region of the Earth. The main experimental parameters are selected in such a way that, at least, MHD scaling is satisfied

Near-Earth Magnetic Field Effects of Large-Scale Magnetospheric Currents

DEFF Research Database (Denmark)

Lühr, Hermann; Xiong, Chao; Olsen, Nils

2017-01-01

. Significant progress in interpreting the magnetic fields from the different sources has been achieved thanks to magnetic satellite missions like Ørsted, CHAMP and now Swarm. Of particular interest for this article is a proper representation of the magnetospheric ring current effect. Uncertainties in modelling...... its effect still produce the largest residuals between observations and present-day geomagnetic field models. A lot of progress has been achieved so far, but there are still open issues like the characteristics of the partial ring current. Other currents discussed are those flowing......Magnetospheric currents play an important role in the electrodynamics of near-Earth space. This has been the topic of many space science studies. Here we focus on the magnetic fields they cause close to Earth. Their contribution to the geomagnetic field is the second largest after the core field...

Slowly braked, rotating neutron stars

Science.gov (United States)

Sato, H.

1975-01-01

A slowly braked, rotating neutron star is believed to be a star which rapidly rotates, has no nebula, is nonpulsing, and has a long initial braking time of ten thousand to a million years because of a low magnetic field. Such an object might be observable as an extended weak source of infrared or radio wave radiation due to the scattering of low-frequency strong-wave photons by accelerated electrons. If these objects exist abundantly in the Galaxy, they would act as sources of relatively low-energy cosmic rays. Pulsars (rapidly braked neutron stars) are shown to have difficulties in providing an adequate amount of cosmic-ray matter, making these new sources seem necessary. The possibility that the acceleration mechanism around a slowly braked star may be not a direct acceleration by the strong wave but an acceleration due to plasma turbulence excited by the strong wave is briefly explored. It is shown that white dwarfs may also be slowly braked stars with braking times longer than 3.15 million years.

Magnetospheric Effects as a New Aspect of the Asteroid Impact Problem: Necessity and Possibilities of Laboratory Simulation Experiments

Science.gov (United States)

Zakharov, Yuri P.; Nikitin, Sergei A.; Ponomarenko, Arnold G.; Minami, Shigeyuki

1997-05-01

This paper discusses the possible consequences to the Earth's magnetosphere, when due to too short an advanced warning, attempts at mitigation of a near-Earth object (NEO) must be made in close proximity to the Earth. The energy Eo, and explosive plasma release during impact may be compared with the kinetic energy Ek of the NEO and with the energy, Ee (Ee approximately Ek), needed for NEO deflection by a strong (protective force) explosive, at distances close to the scale of the magnetosphere. If the energy, Em, of the Earth's dipole field latter is relatively small (Em is less than Eo for a NEO size approximately 1 km), global or even catastrophic disturbances could occur. These ecologically important magnetospheric aspects of the NEO impact problem have been discussed recently; particularly in the context of the comet SL-9/Jupiter impact. In the latter case, the effect on Jupiter's magnetosphere of the 'NEO' explosions was very small (x equals Eo/Em approximately 0.001, where Em is the 'outer' magnetic energy of the planetary dipole field) and the corresponding model of its 'fireball' development could be simulated numerically in 'zero' approximation, with the assumption of an undisturbed magnetospheric media as a whole. However, in general, and, in the rather probable case of NEO impacts with values x approximately 1, the development of such 3D, nonstationary MHD or PIC-models at this time. Such information can be obtained from new kinds of simulation experiments with the laboratory magnetosphere, the so-called 'terrella'.

Globally Imaging the Magnetosphere

Science.gov (United States)

Sibeck, D. G.

2017-12-01

Over the past two decades, a host of missions have provided the multipoint in situ measurementsneeded to understand the meso- and micro-scale physics governing the solar wind-magnetosphereinteraction. Observations by the ISTP missions, Cluster, THEMIS, Double Star, and most recentlyMMS, have enabled us to identify the occurrence of some of the many proposed models for magneticreconnection and particle acceleration in a wide range of accessible magnetospheric contexts. However, todetermine which of these processes are most important to the overall interaction, we need globalobservations, from both ground-based instrumentation and imaging spacecraft. This talk outlinessome of the the global puzzles that remain to be solved and some of the very novel means that are availableto address them, including soft X-ray, energetic neutral atom, far and extreme ultraviolet imaging andenhanced arrays of ground observatories.

The Magnetospheric Multiscale Mission

Science.gov (United States)

Burch, James

Magnetospheric Multiscale (MMS), a NASA four-spacecraft mission scheduled for launch in November 2014, will investigate magnetic reconnection in the boundary regions of the Earth’s magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. Among the important questions about reconnection that will be addressed are the following: Under what conditions can magnetic-field energy be converted to plasma energy by the annihilation of magnetic field through reconnection? How does reconnection vary with time, and what factors influence its temporal behavior? What microscale processes are responsible for reconnection? What determines the rate of reconnection? In order to accomplish its goals the MMS spacecraft must probe both those regions in which the magnetic fields are very nearly antiparallel and regions where a significant guide field exists. From previous missions we know the approximate speeds with which reconnection layers move through space to be from tens to hundreds of km/s. For electron skin depths of 5 to 10 km, the full 3D electron population (10 eV to above 20 keV) has to be sampled at rates greater than 10/s. The MMS Fast-Plasma Instrument (FPI) will sample electrons at greater than 30/s. Because the ion skin depth is larger, FPI will make full ion measurements at rates of greater than 6/s. 3D E-field measurements will be made by MMS once every ms. MMS will use an Active Spacecraft Potential Control device (ASPOC), which emits indium ions to neutralize the photoelectron current and keep the spacecraft from charging to more than +4 V. Because ion dynamics in Hall reconnection depend sensitively on ion mass, MMS includes a new-generation Hot Plasma Composition Analyzer (HPCA) that corrects problems with high proton fluxes that have prevented accurate ion-composition measurements near the dayside magnetospheric boundary. Finally, Energetic Particle Detector (EPD) measurements of electrons and

Absorption of gamma-ray photons in a vacuum neutron star magnetosphere: II. The formation of "lightnings"

Science.gov (United States)

Istomin, Ya. N.; Sob'yanin, D. N.

2011-10-01

The absorption of a high-energy photon from the external cosmic gamma-ray background in the inner neutron star magnetosphere triggers the generation of a secondary electron-positron plasma and gives rise to a lightning—a lengthening and simultaneously expanding plasma tube. It propagates along magnetic fields lines with a velocity close to the speed of light. The high electron-positron plasma generation rate leads to dynamical screening of the longitudinal electric field that is provided not by charge separation but by electric current growth in the lightning. The lightning radius is comparable to the polar cap radius of a radio pulsar. The number of electron-positron pairs produced in the lightning in its lifetime reaches 1028. The density of the forming plasma is comparable to or even higher than that in the polar cap regions of ordinary pulsars. This suggests that the radio emission from individual lightnings can be observed. Since the formation time of the radio emission is limited by the lightning lifetime, the possible single short radio bursts may be associated with rotating radio transients (RRATs).

Electrodynamics of the magnetosphere-ionosphere coupling in the nightside subauroral zone

International Nuclear Information System (INIS)

Streltsov, A.V.; Foster, J.C.

2004-01-01

Results from a numerical study of the oscillations of the electric field measured by the Millstone Hill incoherent scatter radar in the E-layer of the nightside subauroral ionosphere during the geomagnetic storm of May 25, 2000 are presented. The frequencies of these oscillations correspond to the discrete frequencies of geomagnetic pulsations usually attributed to the field line resonances or global cavity modes at a high-latitude auroral zone, but they are well below the fundamental eigenfrequency of the subauroral magnetosphere. It is shown that these oscillations can be interpreted as an ionospheric footprint of the surface Alfven waves generated at the equatorial magnetosphere on a steep transverse gradient in the background plasma density associated with the inner edge of the plasmapause developed during strong geomagnetic storms/substorms. This density gradient together with the ionospheric Pedersen conductivity defines the location and amplitude of the electric field in the E-layer: the amplitude of the field is proportional to the amplitude of the density inhomogeneity and inversely proportional to its scale-size and the ionospheric conductivity. Interaction of the large amplitude perpendicular electric field with the low-conducting ionosphere can cause the ionospheric feedback instability, which leads to the formation of small-scale, intense structures in the electric field and the parallel current density in the subauroral magnetosphere

Relationship between PC index and magnetospheric field-aligned currents measured by Swarm satellites

DEFF Research Database (Denmark)

Troshichev, О.; Sormakov, D.; Behlke, R.

2018-01-01

Abstract The relationship between the magnetospheric field-aligned currents (FAC) monitored by the Swarm satellites and the magnetic activity PC index (which is a proxy of the solar wind energy incoming into the magnetosphere) is examined. It is shown that current intensities measured in the R1...... between the PC index and the intensity of field-aligned currents in the R1 dawn and dusk layers: increase of FAC intensity in the course of substorm development is accompanied by increasing the PC index values. Correlation between PC and FAC intensities in the R2 dawn and dusk layers is also observed...

The concept of Magnetically Driven Magnetosphere: storm/substorm dynamics and organization of the magnetotail

Science.gov (United States)

Pavlov, Nikolai

A set of novel ideas and approaches have been found in the long-lasting attempts to better understand how the magnetosphere operates. It is proposed a certain vision of the substorm/storm scenario, of the tail structure with moderate magnetic By-component, and with intrinsic turbulence. Particle acceleration and the place of the tail's current sheet(s) in the proposed vision are discussed as well. For the reasoning of the proposal, several key ideas on the purely magnetospheric topics are included in the presentation.

Additional measurements of pre-main-sequence stellar rotation

International Nuclear Information System (INIS)

Hartmann, L.; Stauffer, J.R.

1989-01-01

New rotational-velocity measurements for pre-main-sequence stars in the Taurus-Auriga molecular cloud are reported. Rotational velocities or upper limits of 10 km/s are now available for 90 percent of the T Tauri stars with V less than 14.7 in the catalog of Cohen and Kuhi. Measurements of 'continuum emission' stars, thought to be accreting high-angular-momentum material from a circumstellar disk, show that these objects are not especially rapid rotators. The results confirm earlier findings that angular-momentum loss proceeds very efficiently in the earliest stages of star formation, and suggest that stars older than about one million yr contract to the main sequence at nearly constant angular momentum. The slow rotation of T Tauri stars probably requires substantial angular-momentum loss via a magnetically coupled wind. 35 references

Formation of field-twisting flux tubes on the magnetopause and solar wind particle entry into the magnetosphere

International Nuclear Information System (INIS)

Sato, T.; Shimada, T.; Tanaka, M.; Hayashi, T.; Watanabe, K.

1986-01-01

A global interaction between the solar wind with a southward interplanetary magnetic field (IMF) and the magnetosphere is studied using a semi-global simulation model. A magnetic flux tube in which field lines are twisted is created as a result of repeated reconnection between the IMF and the outermost earth-rooted magnetic field near the equatorial plane and propagates to higher latitudes. When crossing the polar cusp, the flux tube penetrates into the magnetosphere reiterating reconnection with the earth-rooted higher latitude magnetic field, whereby solar wind particles are freely brought inside the magnetosphere. The flux tube structure has similarities in many aspects to the flux transfer events (FTEs) observed near the dayside magnetopause

Drift-resonant, relativistic electron acceleration at the outer planets: Insights from the response of Saturn's radiation belts to magnetospheric storms

Science.gov (United States)

Roussos, E.; Kollmann, P.; Krupp, N.; Paranicas, C.; Dialynas, K.; Sergis, N.; Mitchell, D. G.; Hamilton, D. C.; Krimigis, S. M.

2018-05-01

The short, 7.2-day orbital period of Cassini's Ring Grazing Orbits (RGO) provided an opportunity to monitor how fast the effects of an intense magnetospheric storm-time period (days 336-343/2016) propagated into Saturn's electron radiation belts. Following the storms, Cassini's MIMI/LEMMS instrument detected a transient extension of the electron radiation belts that in subsequent orbits moved towards the inner belts, intensifying them in the process. This intensification was followed by an equally fast decay, possibly due to the rapid absorption of MeV electrons by the planet's main rings. Surprisingly, all this cycle was completed within four RGOs, effectively in less than a month. That is considerably faster than the year-long time scales of Saturn's proton radiation belt evolution. In order to explain this difference, we propose that electron radial transport is partly controlled by the variability of global scale electric fields which have a fixed local time pointing. Such electric fields may distort significantly the orbits of a particular class of energetic electrons that cancel out magnetospheric corotation due to their westward gradient and curvature drifts (termed "corotation-resonant" or "local-time stationary" electrons) and transport them radially between the ring current and the radiation belts within several days and few weeks. The significance of the proposed process is highlighted by the fact that corotation resonance at Saturn occurs for electrons of few hundred keV to several MeV. These are the characteristic energies of seed electrons from the ring current that sustain the radiation belts of the planet. Our model's feasibility is demonstrated through the use of a simple test-particle simulation, where we estimate that uniform but variable electric fields with magnitudes lower that 1.0 mV/m can lead to a very efficient transport of corotation resonant electrons. Such electric fields have been consistently measured in the magnetosphere, and here we

Fine structure of striations observed in barium plasma injections in the magnetospheric cleft

International Nuclear Information System (INIS)

Simons, D.J.; Eastman, T.E.; Pongratz, M.B.

1976-01-01

In January and November of 1975, the Los Alamos Scientific Laboratory sponsored four high altitude shaped charge barium plasma injections in the magnetospheric cleft region. These experiments were TORDO UNO (January 6), TORDO DOS (January 11), PERIQUITO UNO (November 25), and PERIQUITO DOS (November 28). All four injections took place near 500 km altitude, and optical data were taken from two aircraft and a ground station. The TORDO DOS and the PERIQUITO experiments showed rapid formation of striations (within one minute after injection), and fast horizontal spreading in contrast with TORDO UNO. In PERIQUITO DOS, the debris cloud spread magnetically east-west with a small net northerly motion. TORDO UNO shows very rapid poleward motion, and the remaining two events resulted in magnetically east-west horizontal spreading, with no noticeable poleward motion. Striations observed in the PERIQUITO DOS experiment separate in opposite directions with relative velocities of up to 3 km/sec. These field-aligned structures appear to form in sheets of approximately constant magnetic latitude. Significant spatial variations occur on a scale of less than 200 meters. Spatial frequency power spectra across these striations have been determined at various times. Observations of the debris cloud and the fast barium streak show strong field-aligned coherency of striation fine structure, indicating a field line mapping of transverse electric fields and gradients

Investigation of the radiation properties of magnetospheric ELF waves induced by modulated ionospheric heating

Science.gov (United States)

Wang, Feng; Ni, Binbin; Zhao, Zhengyu; Zhao, Shufan; Zhao, Guangxin; Wang, Min

2017-05-01

Electromagnetic extremely low frequency (ELF) waves play an important role in modulating the Earth's radiation belt electron dynamics. High-frequency (HF) modulated heating of the ionosphere acts as a viable means to generate artificial ELF waves. The artificial ELF waves can reside in two different plasma regions in geo-space by propagating in the ionosphere and penetrating into the magnetosphere. As a consequence, the entire trajectory of ELF wave propagation should be considered to carefully analyze the wave radiation properties resulting from modulated ionospheric heating. We adopt a model of full wave solution to evaluate the Poynting vector of the ELF radiation field in the ionosphere, which can reflect the propagation characteristics of the radiated ELF waves along the background magnetic field and provide the initial condition of waves for ray tracing in the magnetosphere. The results indicate that the induced ELF wave energy forms a collimated beam and the center of the ELF radiation shifts obviously with respect to the ambient magnetic field with the radiation power inversely proportional to the wave frequency. The intensity of ELF wave radiation also shows a weak correlation with the size of the radiation source or its geographical location. Furthermore, the combination of ELF propagation in the ionosphere and magnetosphere is proposed on basis of the characteristics of the ELF radiation field from the upper ionospheric boundary and ray tracing simulations are implemented to reasonably calculate magnetospheric ray paths of ELF waves induced by modulated ionospheric heating.

Magnetic effects of magnetospheric currents at ground and in low orbit

DEFF Research Database (Denmark)

Stolle, Claudia; Naemi Willer, Anna; Finlay, Chris

to diminish with reducing solar activity (as was previously noted by Lühr & Maus, 2010), while the slope is hardly affected. There have been several suggestions for the origin of this systematic difference between ground and space based observations of magnetospheric fields. We compare magnetic residuals...... of selected observatories with those of CHAMP satellite observations at times of conjunctions, separating the data pairs by criteria including local time and longitude, season, solar and magnetic activity. Obtaining rough estimates of the ionospheric conductivity in this way, we are able to discuss possible...... field model from Magsat vector data. Geophys. Res. Lett. 7:793-96 Lühr H, Maus S. 2010. Solar cycle dependence of quiet-time magnetospheric currents and a model of their near-Earth magnetic fields. Earth Planets Space 62:843-48...

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

2004-03-01

Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the tail influence

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

Directory of Open Access Journals (Sweden)

T. J. Stubbs

2004-03-01

Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He²⁺ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the

Mathematical geophysics an introduction to rotating fluids and the Navier-Stokes equations

CERN Document Server

Chemin, Jean-Yves; Gallagher, Isabelle; Grenier, Emmanuel

2006-01-01

Aimed at graduate students and researchers in mathematics, engineering, oceanography, meteorology and mechanics, this text provides a detailed introduction to the physical theory of rotating fluids, a significant part of geophysical fluid dynamics. The Navier-Stokes equations are examined in both incompressible and rapidly rotating forms.

The UAH Spinning Terrella Experiment: A Laboratory Analog for the Earth's Magnetosphere

Science.gov (United States)

Sheldon, R. B.; Gallagher, D. L.; Craven, P. D.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

The UAH Spinning Terrella Experiment has been modified to include the effect of a second magnet. This is a simple laboratory demonstration of the well-known double-dipole approximation to the Earth's magnetosphere. In addition, the magnet has been biassed $\\sim$-400V which generates a DC glow discharge and traps it in a ring current around the magnet. This ring current is easily imaged with a digital camera and illustrates several significant topological properties of a dipole field. In particular, when the two dipoles are aligned, and therefore repel, they emulate a northward IMF Bz magnetosphere. Such a geometry traps plasma in the high latitude cusps as can be clearly seen in the movies. Likewise, when the two magnets are anti-aligned, they emulate a southward IMF Bz magnetosphere with direct feeding of plasma through the x-line. We present evidence for trapping and heating of the plasma, comparing the dipole-trapped ring current to the cusp-trapped population. We also present a peculiar asymmetric ring current produced in by the plasma at low plasma densities. We discuss the similarities and dissimilarities of the laboratory analog to the collisionless Earth plasma, and implications for the interpretation of IMAGE data.

Hot plasma and energetic particles in the earth's outer magnetosphere: new understandings during the IMS

International Nuclear Information System (INIS)

Baker, D.N.; Fritz, T.A.

1984-01-01

In this paper we review the major accomplishments made during the IMS period in clarifying magnetospheric particle variations in the region from roughly geostationary orbit altitudes into the deep magnetotail. We divide our review into three topic areas: (1) acceleration processes; (2) transport processes; and (3) loss processes. Many of the changes in hot plasmas and energetic particle populations are often found to be related intimately to geomagnetic storm and magnetospheric substorm effects and, therefore, substantial emphasis is given to these aspects of particle variations in this review. The IMS data, taken as a body, allow a reasonably unified view as one traces magnetospheric particles from their acceleration source through the plasma sheet and outer trapping regions and, finally, to their loss via ionospheric precipitation and ring current formation processes. It is this underlying, unifying theme which is pursued here. 52 references, 19 figures

Electrostatic noise bands associated with the electron gyrofrequency and plasma frequency in the outer magnetosphere

International Nuclear Information System (INIS)

Shaw, R.R.

1975-01-01

Naturally occurring noise bands near the electron plasma frequency are frequently detected by the University of Iowa plasma wave experiment on the IMP 6 satellite in the region from just inside the plasmapause to radial distances of about 10 earth radii in the outer magnetosphere. The electric field strength of these noise bands is usually small with electric field spectral densities near 10 -15 volts 2 meter -2 Hz -1 . A wave magnetic field has been detected only in a few unusually intense cases, and in these cases the magnetic field energy density is several orders of magnitude smaller than the electric field energy density. The bands are observed at all magnetic latitudes covered by the IMP 6 orbit (parallelγ/sub m/parallel less than or equal to 45 0 ) and appear to be a permanent feature of the outer magnetosphere. They are found at all local times and occur least frequently in the quadrant from 18 to 24 hours. The bands appear to consist of two distinct spectral types, diffuse and narrow. In both types the center frequency of the noise band is bounded by consecutive harmonics of the electron gyrofrequency, and the bands occur most often between harmonics that are near the local electron plasma frequency. These bands appear to merge continuously into two types of plasma wave emissions that are found in dissimilar regions of the magnetosphere (upper hybrid resonance noise, also called Region 3 noise, inside the plasmasphere and (n + 1/2)f/sub g/ harmonics in the outer magnetosphere). It is suggested that this smooth merging is caused by changes in the plasma wave dispersion relation that occur as the spacecraft moves from the cold plasma within the plasmasphere into the warm non-Maxwellian plasma found in the outer magnetosphere

Quantitative magnetotail characteristics of different magnetospheric states

Directory of Open Access Journals (Sweden)

M. A. Shukhtina

2004-03-01

Full Text Available Quantitative relationships allowing one to compute the lobe magnetic field, flaring angle and tail radius, and to evaluate magnetic flux based on solar wind/IMF parameters and spacecraft position are obtained for the middle magnetotail, X=(–15,–35RE, using 3.5 years of simultaneous Geotail and Wind spacecraft observations. For the first time it was done separately for different states of magnetotail including the substorm onset (SO epoch, the steady magnetospheric convection (SMC and quiet periods (Q. In the explored distance range the magnetotail parameters appeared to be similar (within the error bar for Q and SMC states, whereas at SO their values are considerably larger. In particular, the tail radius is larger by 1–3 RE at substorm onset than during Q and SMC states, for which the radius value is close to previous magnetopause model values. The calculated lobe magnetic flux value at substorm onset is ~1GWb, exceeding that at Q (SMC states by ~50%. The model magnetic flux values at substorm onset and SMC show little dependence on the solar wind dynamic pressure and distance in the tail, so the magnetic flux value can serve as an important discriminator of the state of the middle magnetotail. Key words. Magnetospheric physics (solar windmagnetosphere- interactions, magnetotail, storms and substorms

The Comprehensive Inner Magnetosphere-Ionosphere Model

Science.gov (United States)

Fok, M.-C.; Buzulukova, N. Y.; Chen, S.-H.; Glocer, A.; Nagai, T.; Valek, P.; Perez, J. D.

2014-01-01

Simulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5-9 April 2010 and then compared our results with data from the Two Wide-angle Imaging Neutral-atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self-consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.

Sodium Ion Dynamics in the Magnetospheric Flanks of Mercury

Science.gov (United States)

Aizawa, Sae; Delcourt, Dominique; Terada, Naoki

2018-01-01

We investigate the transport of planetary ions in the magnetospheric flanks of Mercury. In situ measurements from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft show evidences of Kelvin-Helmholtz instability development in this region of space, due to the velocity shear between the downtail streaming flow of solar wind originating protons in the magnetosheath and the magnetospheric populations. Ions that originate from the planet exosphere and that gain access to this region of space may be transported across the magnetopause along meandering orbits. We examine this transport using single-particle trajectory calculations in model Magnetohydrodynamics simulations of the Kelvin-Helmholtz instability. We show that heavy ions of planetary origin such as Na+ may experience prominent nonadiabatic energization as they E × B drift across large-scale rolled up vortices. This energization is controlled by the characteristics of the electric field burst encountered along the particle path, the net energy change realized corresponding to the maximum E × B drift energy. This nonadiabatic energization also is responsible for prominent scattering of the particles toward the direction perpendicular to the magnetic field.

Auroral electrojet dynamics during magnetic storms, connection with plasma precipitation and large-scale structure of the magnetospheric magnetic field

Directory of Open Access Journals (Sweden)

Y. I. Feldstein

1999-04-01

Full Text Available Effect of the equatorward shift of the eastward and westward electrojets during magnetic storms main phase is analyzed based on the meridional chains of magnetic observatories EISCAT and IMAGE and several Russian observatories (geomagnetic longitude ~110°, corrected geomagnetic latitudes 74°F 51°. Magnetic storms of various Dst index intensity where the main phase falls on 1000 UT - 2400 UT interval were selected so that one of the observatory chains was located in the afternoon - near midnight sector of MLT. The eastward electrojet center shifts equatorward with Dst intensity increase: when Dst ~ - 50 nT the electrojet center is located at F ~ 62°, when Dst ~ -300 nT it is placed at F ~54°. The westward electrojet center during magnetic storms main phase for intervals between substorms shifts equatorward with Dst increase: at F~ 62° when Dst ~ -100 nT and at F ~ 55° when Dst ~ -300 nT. During substorms within the magnetic storms intervals the westward electrojet widens poleward covering latitudes F~ 64°- 65°. DMSP (F08, F10 and F11 satellite observations of auroral energy plasma precipitations at upper atmosphere altitudes were used to determine precipitation region structure and location of boundaries of various plasma domains during magnetic storms on May 10-11, 1992, February 5-7 and February 21-22, 1994. Interrelationships between center location, poleward and equatorward boundaries of electrojets and characteristic plasma regions are discussed. The electrojet center, poleward and equatorward boundaries along the magnetic observatories meridional chain were mapped to the magnetosphere using the geomagnetic field paraboloid model. The location of auroral energy oxygen ion regions in the night and evening magnetosphere is determined. Considerations are presented on the mechanism causing the appearance in the inner magnetosphere during active intervals of magnetic storms of ions with energy of tens KeV. In the framework of the

THE ROTATION RATES OF MASSIVE STARS: THE ROLE OF BINARY INTERACTION THROUGH TIDES, MASS TRANSFER, AND MERGERS

Energy Technology Data Exchange (ETDEWEB)

De Mink, S. E. [Space Telescope Science Institute, Baltimore, MD (United States); Langer, N.; Izzard, R. G. [Argelander-Institut fuer Astronomie der Universitaet Bonn, D-53121 Bonn (Germany); Sana, H.; De Koter, A. [Astronomical Institute Anton Pannekoek, University of Amsterdam, 1098 XH Amsterdam (Netherlands)

2013-02-20

Rotation is thought to be a major factor in the evolution of massive stars-especially at low metallicity-with consequences for their chemical yields, ionizing flux, and final fate. Deriving the birth spin distribution is of high priority given its importance as a constraint on theories of massive star formation and as input for models of stellar populations in the local universe and at high redshift. Recently, it has become clear that the majority of massive stars interact with a binary companion before they die. We investigate how this affects the distribution of rotation rates, through stellar winds, expansion, tides, mass transfer, and mergers. For this purpose, we simulate a massive binary-star population typical for our Galaxy assuming continuous star formation. We find that, because of binary interaction, 20{sup +5} {sub -10}% of all massive main-sequence stars have projected rotational velocities in excess of 200 km s{sup -1}. We evaluate the effect of uncertain input distributions and physical processes and conclude that the main uncertainties are the mass transfer efficiency and the possible effect of magnetic braking, especially if magnetic fields are generated or amplified during mass accretion and stellar mergers. The fraction of rapid rotators we derive is similar to that observed. If indeed mass transfer and mergers are the main cause for rapid rotation in massive stars, little room remains for rapidly rotating stars that are born single. This implies that spin-down during star formation is even more efficient than previously thought. In addition, this raises questions about the interpretation of the surface abundances of rapidly rotating stars as evidence for rotational mixing. Furthermore, our results allow for the possibility that all early-type Be stars result from binary interactions and suggest that evidence for rotation in explosions, such as long gamma-ray bursts, points to a binary origin.

The kappa Distribution as Tool in Investigating Hot Plasmas in the Magnetospheres of Outer Planets

Science.gov (United States)

Krimigis, S. M.; Carbary, J. F.

2014-12-01

The first use of a Maxwellian distribution with a high-energy tail (a κ-function) was made by Olbert (1968) and applied by Vasyliunas (1968) in analyzing electron data. The k-function combines aspects of both Maxwellian and power law forms to provide a reasonably complete description of particle density, temperature, pressure and convection velocity, all of which are key parameters of magnetospheric physics. Krimigis et al (1979) used it to describe flowing plasma ions in Jupiter's magnetosphere measured by Voyager 1, and obtained temperatures in the range of 20 to 35 keV. Sarris et al (1981) used the κ-function to describe plasmas in Earth's distant plasma sheet. The κ-function, in various formulations and names (e. g., γ-thermal distribution, Krimigis and Roelof, 1983) has been used routinely to parametrize hot, flowing plasmas in the magnetospheres of the outer planets, with typical kT ~ 10 to 50 keV. Using angular measurements, it has been possible to obtain pitch angle distributions and convective flow directions in sufficient detail for computations of temperatures and densities of hot particle pressures. These 'hot' pressures typically dominate the cold plasma pressures in the high beta (β > 1) magnetospheres of Jupiter and Saturn, but are of less importance in the relatively empty (β Cambridge University Press, New York, 1983

Angular momentum transfer in primordial discs and the rotation of the first stars

Science.gov (United States)

Hirano, Shingo; Bromm, Volker

2018-05-01

We investigate the rotation velocity of the first stars by modelling the angular momentum transfer in the primordial accretion disc. Assessing the impact of magnetic braking, we consider the transition in angular momentum transport mode at the Alfvén radius, from the dynamically dominated free-fall accretion to the magnetically dominated solid-body one. The accreting protostar at the centre of the primordial star-forming cloud rotates with close to breakup speed in the case without magnetic fields. Considering a physically motivated model for small-scale turbulent dynamo amplification, we find that stellar rotation speed quickly declines if a large fraction of the initial turbulent energy is converted to magnetic energy (≳ 0.14). Alternatively, if the dynamo process were inefficient, for amplification due to flux freezing, stars would become slow rotators if the pre-galactic magnetic field strength is above a critical value, ≃10-8.2 G, evaluated at a scale of nH = 1 cm-3, which is significantly higher than plausible cosmological seed values (˜10-15 G). Because of the rapid decline of the stellar rotational speed over a narrow range in model parameters, the first stars encounter a bimodal fate: rapid rotation at almost the breakup level, or the near absence of any rotation.

THE SHORT ROTATION PERIOD OF HI’IAKA, HAUMEA’S LARGEST SATELLITE

Energy Technology Data Exchange (ETDEWEB)

Hastings, Danielle M.; Margot, Jean-Luc [University of California, Los Angeles, Department of Earth, Planetary, and Space Sciences, 595 Charles Young Drive East, Los Angeles, CA 90095 (United States); Ragozzine, Darin [Florida Institute of Technology, Department of Physics and Space Sciences, 150 West University Boulevard, Melbourne, FL 32901 (United States); Fabrycky, Daniel C. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Burkhart, Luke D.; Holman, Matthew [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Fuentes, Cesar [Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Santiago (Chile); Brown, Michael E., E-mail: dhastings@g.ucla.edu [California Institute of Technology, Division of Geological and Planetary Sciences, MC 150-21, Pasadena, CA 91125 (United States)

2016-12-01

Hi’iaka is the larger outer satellite of the dwarf planet Haumea. Using relative photometry from the Hubble Space Telescope and Magellan and a phase dispersion minimization analysis, we have identified the rotation period of Hi’iaka to be ∼9.8 hr (double peaked). This is ∼120 times faster than its orbital period, creating new questions about the formation of this system and possible tidal evolution. The rapid rotation suggests that Hi’iaka could have a significant obliquity and spin precession that could be visible in light curves within a few years. We then turn to an investigation of what we learn about the (currently unclear) formation of the Haumea system and family based on this unexpectedly rapid rotation rate. We explore the importance of the initial semimajor axis and rotation period in tidal evolution theory and find that they strongly influence the time required to despin to synchronous rotation, relevant to understanding a wide variety of satellite and binary systems. We find that despinning tides do not necessarily lead to synchronous spin periods for Hi’iaka, even if it formed near the Roche limit. Therefore, the short rotation period of Hi’iaka does not rule out significant tidal evolution. Hi’iaka’s spin period is also consistent with formation near its current location and spin-up due to Haumea-centric impactors.

Magnetospheric Multiscale Mission Observations of Magnetic Flux Ropes in the Earth's Plasma Sheet

Science.gov (United States)

Slavin, J. A.; Akhavan-Tafti, M.; Poh, G.; Le, G.; Russell, C. T.; Nakamura, R.; Baumjohann, W.; Torbert, R. B.; Gershman, D. J.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Burch, J. L.

2017-12-01

A major discovery by the Cluster mission and the previous generation of science missions is the presence of earthward and tailward moving magnetic flux ropes in the Earth's plasma sheet. However, the lack of high-time resolution plasma measurements severely limited progress concerning the formation and evolution of these reconnection generated structures. We use high-time resolution magnetic and electric field and plasma measurements from the Magnetospheric Multiscale mission's first tail season to investigate: 1) the distribution of flux rope diameters relative to the local ion and electron inertial lengths; 2) the internal force balance sustaining these structures; and 3) the magnetic connectivity of the flux ropes to the Earth and/or the interplanetary medium; 4) the specific entropy of earthward moving flux ropes and the possible effect of "buoyancy" on how deep they penetrate into the inner magnetosphere; and 5) evidence for coalescence of adjacent flux ropes and/or the division of existing flux ropes through the formation of secondary X-lines. The results of these initial analyses will be discussed in terms of their implications for reconnection-driven magnetospheric dynamics and substorms.

A PROPELLER MODEL FOR THE SUB-LUMINOUS STATE OF THE TRANSITIONAL MILLISECOND PULSAR PSR J1023+0038

Energy Technology Data Exchange (ETDEWEB)

Papitto, A.; Torres, D. F. [Institute of Space Sciences (CSIC-IEEC), Campus UAB, Carrer de Can Magrans, S/N, E-08193, Cerdanyola del Vallés, Barcelona (Spain)

2015-07-01

The discovery of millisecond pulsars switching between states powered either by the rotation of their magnetic field or by the accretion of matter has recently proved the tight link shared by millisecond radio pulsars and neutron stars in low-mass X-ray binaries. Transitional millisecond pulsars also show an enigmatic intermediate state in which the neutron star is surrounded by an accretion disk and emits coherent X-ray pulsations, but is sub-luminous in X-rays with respect to accreting neutron stars, and is brighter in gamma-rays than millisecond pulsars in the rotation-powered state. Here, we model the X-ray and gamma-ray emission observed from PSR J1023+0038 in such a state based on the assumptions that most of the disk in-flow is propelled away by the rapidly rotating neutron star magnetosphere, and that electrons can be accelerated to energies of a few GeV at the turbulent disk–magnetosphere boundary. We show that the synchrotron and self-synchrotron Compton emission coming from such a region, together with the hard disk emission typical of low states of accreting compact objects, is able to explain the radiation observed in the X-ray and gamma-ray bands. The average emission observed from PSR J1023+0038 is modeled by a disk in-flow with a rate of 1–3 × 10{sup −11} M{sub ⊙} yr{sup −1}, truncated at a radius ranging between 30 and 45 km, compatible with the hypothesis of a propelling magnetosphere. We compare the results we obtained with models that assume that a rotation-powered pulsar is turned on, showing how the spin-down power released in similar scenarios is hardly able to account for the magnitude of the observed emission.

Observations of magnetospheric ionization enhancements using upper-hybrid resonance noise band data from the RAE-1 satellite

Science.gov (United States)

Mosier, S. R.

1975-01-01

Noise bands associated with the upper-hybrid resonance were used to provide direct evidence for the existence of regions of enhanced density in the equatorial magnetosphere near L = 2. Density enhancements ranging from several percent to as high as 45 percent are observed with radial dimensions of several hundred kilometers. The enhancement characteristics strongly suggest their identification as magnetospheric whistler ducts.

Magnetospheric and atmospheric physics at the University of Natal

International Nuclear Information System (INIS)

Walker, A.D.M.

1982-01-01

A historical outline of geophysical work done at the University of Natal from 1938-1982 is given. Mention is also made of experimental work concerning whistlers and VLF, low-light level TV and geomagnetic pulsations. Current work on the magnetosphere, namely plasma convection in plasmasphere, auroral features, geomagnetic pulsations and the measuring of plasma properties is discussed

3-D Hybrid Simulation of Quasi-Parallel Bow Shock and Its Effects on the Magnetosphere

International Nuclear Information System (INIS)

Lin, Y.; Wang, X.Y.

2005-01-01

A three-dimensional (3-D) global-scale hybrid simulation is carried out for the structure of the quasi-parallel bow shock, in particular the foreshock waves and pressure pulses. The wave evolution and interaction with the dayside magnetosphere are discussed. It is shown that diamagnetic cavities are generated in the turbulent foreshock due to the ion beam plasma interaction, and these compressional pulses lead to strong surface perturbations at the magnetopause and Alfven waves/field line resonance in the magnetosphere

Analysis of collective excitations of rapidly rotating nuclei in an oscillator potential

International Nuclear Information System (INIS)

Akbarov, A.; Ignatyuk, A.V.; Mikhailov, I.N.; Molina, K.L.; Nazmitdinov, R.G.; Janssen, D.

1981-01-01

The spectrum of positive-parity collective excitations is analyzed in the random phase approximation for a wide range of angular momenta. The Hamiltonian of the model is taken in the form of a spherical harmonic-oscillator potential and isoscalar quadrupole forces. This model permits a description of the known data on the position of a giant quadrupole resonance for small spins and allows the variation of the resonance characteristics to be followed as the spin increases. It is shown that as the rotation velocity increases the energy of one of the branches of the resonance decreases to zero while the state remains strongly collectivized. The model also reproduces the low energy vibration mode which is related to the precession mode. The excitation energy and the B(E2) factor corresponding to this mode differ considerably from the estimates obtained in the rigid rotator model

Flute instability in the plasma shell of the earth's magnetosphere

International Nuclear Information System (INIS)

Ivanov, V.N.; Pokhotelov, O.A.

1987-01-01

In the plasma shell of the earth's magnetosphere, the surfaces of constant pressure may not coincide with surfaces of constant specific volume. This circumstance forces a reexamination of the theory for the flute instability, in which the pressure has been assumed to remain constant on surfaces of constant specific volume. The MHD equations for flute waves in a curvilinear magnetic field are used to show that an instability of a new type, with a pressure which does not remain constant on surfaces of constant specific volume, can occur in the plasma shell of the magnetosphere. An expression is derived for the growth rate of this instability. Analysis of the equation also shows that perturbations with wavelengths shorter than the ion Larmor radius are stable by virtue of magnetodrift effects. The growth rates of the flute instabilities are calculated for both a dipole magnetic field and an arbitrary magnetic-field configuration. Growth rates calculated for typical values of the characteristics of the earth's plasma shell are reported