PDF superior On a correlation between the ionospheric electric field and the time derivative of the magnetic field

On a correlation between the ionospheric electric field and the time derivative of the magnetic field

On a correlation between the ionospheric electric field and the time derivative of the magnetic field

equatorial F-region electric fields and the interplanetary magnetic field is the electric field of magnetospheric origin. If there is a substorm-related, magnetospherically induced electric field oriented from dusk to dawn across the nightside, the ring current will move closer to the Earth, causing an increase in the magnetic field at the surface that will be proportional to the distance to the ring current. Since distance is the integral of the velocity and the electric field, and if the magnetospheric field penetrates to the equator, as it must, E and ∂B/∂t will be correlated. During a substorm, magnetic energy stored in the distorted magnetosphere is released into the atmosphere as accelerated electrons and Joule heating. At such a time, the magnetic field relaxes to- wards dipole, which is the lowest energy state. This is called dipolarization, which is associated with the release of stored magnetic energy into the ionosphere-atmosphere system. Such an event was reported by [10] using the THEMIS instrumentation. Since the magnetic field lines can be considered to be frozen into the plasma, an eastward electric field must be associated with this dipolarization. They found that the equatorial magnetospheric electric field was in the range of 2–6 mV/m. Observations of penetrating electric fields (PPE) at the equator showed that the PPE is at least 0.5 times the equatorial field [11]. The magnetic field at the center of a current loop is inversely proportional to the radius a , that is, B = KI/a . Thus,
Mostrar más

5 Lee mas

Variations of low-latitude geomagnetic fields and Dst index caused by magnetospheric substorms

Variations of low-latitude geomagnetic fields and Dst index caused by magnetospheric substorms

Piura and Jicamarca magnetometers. The electric field measurements have a time resolution of 5 min and some data gaps. The sudden increase in the magnetometer H deviations at 0047 UT is related to the solar wind pressure impulse, and two other increases in the H deviations at 0306 and 0600 UT (2200 and 0100 MLT) are coincident with the substorm onsets. There are several important features in this case. (1) A westward electric field perturbation occurs after each substorm onset, which is consistent with the eastward electric field perturbation on the dayside. (2) There are three positive peaks in the electric field at 0440, 0650, and 0740 UT, and these peaks are related to the corresponding northward turnings of the IMF shown in Figure 5a but are not caused by the substorm onsets. Ionospheric electric field perturbations caused by northward IMF turnings are westward on the dayside and eastward on the nightside; such IMF-induced ionospheric electric field perturbations are also clear in Figure 3. (3) The magnetom- eter H deviations increase after each substorm onset and are not related to the substorm-induced westward electric field perturbation. The westward electric field perturbation would cause, if any, a decrease in the magnetometer H component. The IMF-induced eastward electric field perturbations at Figure 5. (a) Solar wind pressure and IMF B z measured by Wind on 18 April 2001. (b) Magnetospheric
Mostrar más

14 Lee mas

Cherenkov resonances in vortex dissipation in superconductors

Cherenkov resonances in vortex dissipation in superconductors

The LO effect is not a unique mechanism for producing a deviation of the I-V curve from linearity. If the vortex ve- locity exceeds the speed of sound in the crystal the dissipa- tion increases due to Cherenkov emission of sound waves. Each moving vortex creates an electric field acting on the crystal lattice and produces a shock wave 共 the Cherenkov cone 兲 . In a thin film with a magnetic field perpendicular to it the situation is two dimensional and the cone reduces to two lines. The velocity of a crystal lattice is localized on the shock wave but the force acting on the lattice is localized on the vortex positions. The Cherenkov contribution to the total dissipation is proportional to the product of the velocity and the force and hence the dissipation is enhanced when there is a match between vortex positions and the shock wave. If moving vortices are arranged into a vortex lattice then the matching condition can be easily reached when a direction of the shock wave coincides with some direction of the vortex lattice. Since the direction of the shock wave is determined by vortex velocity 共 electric field 兲 maxima of dissipation can be reached at some particular values of the electric field. According to this, the I-V curve should have a series of maxima as a function of voltage. This is the origin of the
Mostrar más

5 Lee mas

Gravitational wave emission from a magnetically deformed non barotropic neutron star

Gravitational wave emission from a magnetically deformed non barotropic neutron star

The main novelty of this paper, compared to previous works on the subject (such as Colaiuda et al. 2008; Haskell et al. 2008; Lander & Jones 2009; Ciolfi et al. 2010), is that we do not require the star to be barotropic, i.e., we do not require it to have a one-to-one relation between pressure and density, p = p( ρ ). The reason for this is that neutron star matter is a multispecies fluid, in which different kinds of particles coexist, at the very least neutrons, protons and electrons. The relative abundances of these particles can be adjusted by weak interactions (such as beta decays; Urca processes in astrophysical jargon) and diffusive processes. However, the time-scales for these processes are much longer than the time for the fluid to reach a hydromagnetic equilibrium (force balance) state, which is likely to happen in a few Alfv´en times (of the order of seconds). In the process of settling to this hydromagnetic equilibrium, each fluid el- ement is free to move following the relevant forces, but it conserves its composition (relative abundances of species), which will thus not be exactly a function of pressure and density. Once the equi- librium is reached, the star will be radially stratified (Pethick 1992; Reisenegger & Goldreich 1992) to zeroth order, but the spherical symmetry (and with it the stratification) will be slightly perturbed by the presence of the magnetic field.
Mostrar más

12 Lee mas

Observability of an induced electric dipole moment of the neutron from nonlinear QED

Observability of an induced electric dipole moment of the neutron from nonlinear QED

on the angle between p IND and the neutron spin, suggest the definition of an asymmetry which could be detected in the scattering of polarized neutrons from heavy nuclei. We have introduced this asymmetry and discussed all possible sources of background asymmetries. We have also com- pared the new NLQED amplitude with ordinary electric scattering amplitudes, particularly the one due to the po- larization of the neutron in an electric field due to its quark substructure. The conclusion from this detailed analysis is that the asymmetry due to NLQED should be observable using epithermal neutrons, and even using thermalized neutrons from a hot moderator. This would be the first ever experimental confirmation of nonlinearity in electro- dynamics due to QED vacuum fluctuations. The numerical predictions for the asymmetry made in this paper were calculated using definite values for the parameters R and a. These were derived from the condition that the electric and magnetic fields should be below their critical values, beyond which the weak-field expansion of the effective Lagrangian breaks down. While the value of the asym- metry A for small q does not depend on R, it does depend on a as seen from Eq. (23) Hence, the numerical results given here should be correct up to a numerical factor of order one.
Mostrar más

12 Lee mas

Exact solutions for electromagnetic fields inside and outside a spherical surface with magneticelectric dipole distributed sources

Exact solutions for electromagnetic fields inside and outside a spherical surface with magneticelectric dipole distributed sources

show a discontinuity, which by Ampere’s law Eq. (38) re- produces the original meridian current distribution, Eq. (39). The electric intensity is evaluated as the rotational of the mag- netic induction via their Maxwell connection Eq. (40), with the explicit forms of Eqs. (41)-(42); exhibiting field lines in each meridian plane with a discontinuity in the radial di- rection at the spherical boundary connected with the surface charge distribution by Gauss’ law, Eq. (43), and consistent with the relationship between the charge and current ampli- tudes; the polar angle components are continuous, consistent with Faraday’s law; their field lines turn out to have the same shapes, Eqs. (44)-(45), as those of the magnetic induction for the magnetic dipole source Eqs. (15)-(16), allowing for the difference in their respective coefficients Eqs. (46)-(47) and Eqs. (17)-(18). Figures 5a, b, c illustrate their behaviour in the vicinity, inside and outside, of the source spherical sur- face, where the normal components are discontinuous, for increasing values of the frequency. Figures 6a, b, c illustrate the electric intensity field lines for the TM modes of the reso- nant cavities determined by the vanishing of the derivative of the product of the radial coordinate and the ordinary spheri- cal Bessel function, or the positions of the extremes of such a product, Fig. 4a, guaranteeing also the vanishing of the ex- ternal fields, Eqs. (37) and (42); notice that the field lines end radially at the source spherical surface where the charges are distributed.
Mostrar más

10 Lee mas

Chapter 27 Sources of the Magnetic Field

Chapter 27 Sources of the Magnetic Field

Picture the Problem The field lines for the electric dipole are shown in the sketch to the left and the field lines for the magnetic dipole are shown in the sketch to the right. Note that, while the far fields (the fields far from the dipoles) are the same, the near fields (the fields between the two charges and inside the current loop/magnetic dipole) are not, and that, in the region between the two charges, the electric field is in the opposite direction to that of the magnetic field at the center of the magnetic dipole. It is especially important to note that while the electric field lines begin and terminate on electric charges, the magnetic field lines are continuous, i.e., they form closed loops.
Mostrar más

106 Lee mas

Angular dependence of hysteresis shift in oblique deposited ferromagnetic/antiferromagnetic coupled bilayers

Angular dependence of hysteresis shift in oblique deposited ferromagnetic/antiferromagnetic coupled bilayers

In the process of films deposition, the FM layer was always deposited first than the AF one. As a result, the uniax- ial anisotropy easy axis induced in FM layer is given by a combination of two mechanisms: (i) grain formation mecha- nism due to the oblique deposition and (ii) the application of the in-situ magnetic field during deposition. Both mecha- nisms have different microscopic contribution for the result- ant FM layer anisotropy and they compete against each other as a varies from 20 to 70 (see Fig. 1(a)). As the AF atoms are being deposited on the FM layer, they are submitted to combined effects that control the resultant direction of the AF lattice magnetizations: (i) microscopic textures built on the FM surface due to the elongated grains; (ii) the superpo- sition of the local field created by FM grains with the applied in-situ field; and (iii) the oblique deposition that itself might induces microstructrures characteristics of the IrMn. Therefore, we must to / u 6¼ / E consider in Eq. (2).
Mostrar más

6 Lee mas

Magnetic field determination of chromospheric spicules using the Weak Field Approximation

Magnetic field determination of chromospheric spicules using the Weak Field Approximation

Trujillo Bueno et al. (2005) ([42]) used a theoretical modelling of the Hanle and Zeeman effects together with spectropolarimetric observations in the He I 10830 line to infer the magnetic field vector in a field of quiet-sun spicules. They used observations carried out in 2001 with the Tenerife Infrared Polarimeter (TIP) mounted on the German Vacuum Tower Telescope (VTT) at the Ob- servatorio del Teide. The height above the solar limb of their observations was of 2000 km, similar to the heights of the analysis conducted in this study. Their data consist of several slit images, the equivalent of drawing a “straight line” over the data presented here at each time frame at a particular height above the visible limb. Furthermore, a temporal sum was applied to increase the Signal to Noise Ratio (SNR), resulting in an effective cadence of almost 5 min. Their inference provided the full magnetic vector, resulting in magnetic field strength values of the order of 10 G. They did not discard, however, the possibility of the presence of much stronger magnetic fields in future observations, as is reported here.
Mostrar más

43 Lee mas

On the integration of fields and quanta in time dependent backgrounds

On the integration of fields and quanta in time dependent backgrounds

The introduction of the Goldstone boson field π(x, t) to parametrize the breaking of time translation invariance has invigorated our understanding of cosmic inflation from the effective field theory (EFT) point of view [12, 13]. In particular, it has led to a reliable model independent description of the generation of primordial curvature perturbations, without the need of a detailed knowledge of the ultraviolet physics (UV) taking place at very short distances (or sub-horizon scales). In this scheme, curvature perturbations are intimately related to the Goldstone boson field, whose action appears highly constrained by the symmetries of the original ultraviolet UV-complete action. In particular, the unknown UV-physics is parametrized by self-interactions of the Goldstone boson that non-linearly relate field operators at different orders in perturbation theory. This framework has of- fered a powerful approach to analyze the large variety of infrared observables predicted by inflation, including the prediction of non-trivial signals in the primordial power spectrum and bispectrum [8, 14–25].
Mostrar más

39 Lee mas

Local electric field enhancement at the heterojunction region of SiGe/Si axially heterostructured nanowires

Local electric field enhancement at the heterojunction region of SiGe/Si axially heterostructured nanowires

Prior to the Raman measurements the NWs morphology and their environment are studied by scanning electron microscopy (SEM). If we want good and reliable Raman measurements it is crucial to find isolated NWs with a clean environment. Firstly, the absence of foreign particles ensures a “clean” Raman spectrum, with Raman radiation coming only from the NW. Secondly, the composition of the NW varies along its axis, then the measurement method will consist of a longitudinal series of Raman spectra, recorded every 100 nm along the NW axis. This permits to easily locate the NW ends, where the signal falls off, and the presence of the HJ when the spectrum changes dramatically. The presence of other NWs in the vicinity of the one being studied could interfere with the measurement if they are close enough.
Mostrar más

53 Lee mas

Retrieval of the Lidar overlap function using Raman signals

Retrieval of the Lidar overlap function using Raman signals

The Raman lidar model LR331D400 is described  in  detail  by  [10,11].  A  Nd:YAG  laser  generates  laser  pulses  at  355,  532  and  1064  nm  with  a  repetition  rate  of  10  Hz.  The  laser  beam  is  vertically  transmitted  into  the  atmosphere.  The  backscattered  radiation  is  collected  by  a  Cassegrain  telescope  with  a  primary  mirror  of  400mm‐diameter  and  transmitted  to  the  signal  detection  unit.  The  backscattered  signals  are  detected  at  the  three  emitted  wavelengths,  and  also  at  387  and  607  nm  resulting  from  Raman 
Mostrar más

5 Lee mas

TítuloMagnetic field strength and reproducibility of neodymium magnets useful for transcranial static magnetic field stimulation of the human cortex

TítuloMagnetic field strength and reproducibility of neodymium magnets useful for transcranial static magnetic field stimulation of the human cortex

The magnetic field strength was measured using a magnetic field-to-voltage transducer with an integrated Hall probe. The sensor is a complementary metal-oxide semiconductor one-axis Hall probe (model I1A) integrated into a transducer (YM12-3-5-5T) (SENIS GmbH, Zurich, Switzerland). The Hall element in the probe occupies an area of 150 μm × 150 μm, providing a very high spatial resolution and angular precision. The Hall probe measures along a single axis perpendicular to its surface. All measurements represent the strength of the magnetic field vector (usually represented with the international symbol B) along the axis perpendicular to the base surface of the cylinder. An integrated temperature sensor on the probe provides temperature compensation for better accuracy. The sensor is also protected against inductive currents that could disturb the measurement. The decay of the static magnetic field with distance was measured by increasing the distance between the Hall probe and the magnet surface, keeping the base of the sensor parallel to the surface of the magnet. For M60qr we performed measurements both on the cylinder axis and parallel to the cylinder axis. Note that because the magnetic field is normal to surface of the magnet only along the cylinder axis, our measurements parallel to the cylinder axis represent a lower bound of the actual strength of the magnetic field. The magnetic permeability of human tissues is similar to air or vacuum [8], so any differences in magnetic field strength between air and human tissues are negligible for the purpose of tSMS.
Mostrar más

5 Lee mas

Change of pulses propagating in SOFAR Channel by moving front

Change of pulses propagating in SOFAR Channel by moving front

The ocean acoustic tomography [1] is a technique to measure a distribution of temperatures over large regions of the ocean by accurately measuring propagation time of sound waves that propagate through the ocean. A number of transducers consisting of a sound source and a receiver are installed around the sea area to be measured. Propagation times of sound waves that propagate between these transducers are measured accurately. Measured changes in propagation time are converted to changes in temperature distribution through inverse problem analysis. In these analyses, the propagation path of an eigenray is usually assumed to be unchanged, and the difference in propagation time for a pulse is converted to the difference in temperature. However, the ocean contains many inhomogeneous media such as sea current, oceanic front, eddy, and microstructure. Those inhomogeneities have strong effects on the paths of sound wave propagation, making it difficult to process signals for the ocean acoustic tomography, and particularly to identify eigenrays.
Mostrar más

6 Lee mas

ism chapter 28 pdf

ism chapter 28 pdf

Picture the Problem We can use the expression for the period of this spring-and-mass oscillator to find the spring constant κ . We can express the induced current in the loop by relating it to the induced emf and relating the induced emf to the velocity of the loop. Knowing that the loop is executing SHM, we can express its velocity as a sinusoidal function of time. We can use the expression for the magnetic force on a current-carrying wire in a magnetic field to express the damping force acting on the loop.
Mostrar más

80 Lee mas

Majorana physics in hybrid nanowires, topological phases and transport

Majorana physics in hybrid nanowires, topological phases and transport

where ↑ and ↓ indicate the spin up and down degrees of freedom. The rest of the symbols have the same meaning of the Hamiltonian in Eq. (1.7). In this ap- proximation the two-body interaction is reduced to a single body self-interaction, like an external field. Eq. (1.8) Hamiltonian is given referred to a ground state of Cooper pairs presented below. The propagating bands of this Hamiltonian are shown in Fig. 1.1. They can be interpreted physically as the excitation energies of the quasiparticles not bounded to a Cooper pair (where ∆ is the Cooper pair breaking energy). These quasiparticles have simultaneous nonzero components of the particle and hole degrees of freedom. An electron-like quasiparticle has a greater electronic component while in a hole-like one is the other way around. No propa- gating states are found inside the gap because in non-topological superconductors no quasiparticle excitations can be found for energies lower than the Cooper pair binding energy. Superconductivity in combination with the Rashba and Zeeman effects will make the superconductor topological allowing a perfect mixture of both degrees of freedom at zero energy. In this manner, the Majorana neutral quasi- particle can be obtained. The kind of Hamiltonian presented in Eq. (1.8) is called Bogoliubov-deGennes Hamiltonian. Here, it is written using second quantization notation although it is equivalent up to a basis change to the more familiar version shown below in Eq. (1.12).
Mostrar más

135 Lee mas

The Nador dipole: one of the main magnetic anomalies of the NE Rif

The Nador dipole: one of the main magnetic anomalies of the NE Rif

In order to study on land the features of the main aeromagnetic anomalies, new total field magnetic intensity measurements have been acquired with a proton precision GSM9 magnetometer with 1 nT precision. The position at each station was given by a GPS Garmin e-Trex with 5 m accuracy. The altitude is obtained using a barometric altimeter with 0.5 m precision. The distance between measurement sta- tions is around 500 m. The magnetic anomalies have been determined after the correction of diurnal varia- tions, taking into account the ROA (San Fernando,
Mostrar más

6 Lee mas

A Field Study on Social Loafing: Implications of Expectations on Co-Workers, Task Meaningfulness, Relationship Meaningfulness and Indivual s Orientation-Edición Única

A Field Study on Social Loafing: Implications of Expectations on Co-Workers, Task Meaningfulness, Relationship Meaningfulness and Indivual s Orientation-Edición Única

Previous hypotheses are consistent with theoretical frameworks such as the Expectancy theory (Vroom, 1964) and the Collective effort model (CEM; Karau & Williams, 1993). Expectancy theory and the Collective effort model (Expectancy theory in a collectivistic setting) state that individuals will be willing to exert effort on a collective task, if they believe their effort will result in performance that is instrumental in obtaining valued outcomes. If the individual believes performance on a task and a good relationship with co-members depends on his or her individual effort and sees this task and / or the relationship as an instrument in obtaining an ultimate valued outcome (e.g. better pay, job satisfaction, recognition, acceptance from co-workers or a sense of belonging in the group) it would be expected that this individual be motivated to work harder. As a result, Social loafing will be less contingent on expectations on co-workers and the relationship between ECW and SL will be weaker with high Task and Relationship meaningfulness and stronger with low Task and Relationship meaningfulness.
Mostrar más

265 Lee mas

Multi-fluid Eulerian model of an electrospray in a host gas.

Multi-fluid Eulerian model of an electrospray in a host gas.

As the flux is increased toward its critical value, the electric field induced by the charge of the droplets partially balances the field due to the applied voltage in the vicinity of [r]

24 Lee mas

Hypersonic plasma plume expansion in space

Hypersonic plasma plume expansion in space

continue into the ambient plasma. The currents required to deflect the beam are proportional to its kinetic energy, and inversely proportional to the curvature radius of the deflected trajectories and the intensity of the field. Provided that the background density is much lower than the beam density (typically several orders of magnitude), fulfillment of current continuity ∇ · j = 0 demands very large velocities outside of the plume. Therefore, electron inertial effects and collisions will strongly limit the value of the cross-beam j that can develop, and hence the magnitude of the magnetic force j × B that deflects the plume. The effect is difficult to assess from our simple axisymmetric model, requiring a more detailed analysis. Ideally, in the case of zero ambient density, a clean plasma edge, and α = 90 deg, when the magnetic field tries to deflect ions and electrons in opposite directions a strong electric field E ' −u i × B would appear to avoid charge
Mostrar más

14 Lee mas

Show all 10000 documents...