Trapped particles around Jupiter detected by Advanced Stellar Compass

2020 ◽  
Author(s):  
Matija Herceg ◽  
John L. Jørgensen ◽  
Peter S. Jørgensen ◽  
Jose M. G. Merayo ◽  
Mathias Benn ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Magnetic Field Gradient ◽  
Rotation Period ◽  
High Energy ◽  
Radiation Shielding ◽  
Trapped Particles ◽  
Dipolar Fields ◽  
A Charge ◽  
The Magnetic Field

<p>The Advanced Stellar Compass (ASC), attitude reference for the MAG investigation onboard Juno, has continuously monitored high energy particles fluxes in Jupiter’s magnetosphere since Juno’s orbit insertion. The instrument performs this function by tracking the effects of radiation with sufficient energy to transit the instrument’s radiation shielding. Particles that Juno ASC observes have energy >15MeV for electrons, >80MeV for protons, and >~GeV for heavier elements.</p><p>Completing 24 highly elliptical orbits around Jupiter, results in a fairly detailed mapping of the trapped high energy flux at up to 20 Jupiter radius distances.</p><p>Traveling at velocities close to the speed of light, electrons measured by the ASC, maintain the motion governed by the three adiabatic invariants: gyrating motion around the magnetic field line, a north-south magnetic pole particle bounce, and a charge dependent drift around the planet.</p><p>The bounce period is much smaller than the Jovian rotation period, and a large east-west drift component is caused by the magnetic field gradient. For these reasons, the drift shell description traditionally used for dipolar fields, are far from adequate to describe the behavior of energetic particles travelling close to Jupiter.</p><p>In this work, we present the distribution of the trapped high energy electrons around Jupiter. Furthermore, we have constrained the spatial extent of the stable trapped regions and are presenting the distinctive pitch angle and its correlation with ”life” of a particle. At certain distances from Jupiter, pitch angle dependency is not as important to keep the particle trapped as is the injected energy. We also develop an adiabatic map which describes the radial bands for stable trapped particles as a function of the pitch angle and energy.</p><p> </p>

Earth inner drift shells as observed by the Advanced Stellar Compass on Swarm

2020 ◽  
Author(s):  
Jose M G Merayo ◽  
John L Joergensen ◽  
Peter S Joergensen ◽  
Matija Herceg ◽  
Mathias Benn ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Field Gradient ◽  
Minimum Energy ◽  
Rotation Period ◽  
High Energy ◽  
High Energy Particle ◽  
Flux Transport ◽  
The Earth ◽  
The Magnetic Field ◽  
East West

<p>Since launch in November 2013, the Swarm constellation of three satellites provides detailed measurements of the magnetic field of the Earth. To ensure the high accuracy of magnetic vector observation by Vector Field Magnetometer (VFM), the Swarm inertial attitude is determined by the micro Advanced Stellar Compass (μASC). Besides its primary function of attitude determination, the µASC is also capable of detecting particles with energies high enough to penetrate its camera shielding, where particles passing the focal plane CCD detector leave detectable ionization tracks. The typical shielding employed requires the minimum energy to penetrate >15MeV for electrons, > 80MeV for protons and >~GeV for heavier elements.</p><p>The signature of passing particle will only persist in one frame time, but the signature differs between electrons and protons. To ensure full attitude performance operations even during the most intense CMEs, the signatures are removed before star tracking. By counting the signatures, and using a model for the flux transport through the shielding, an accurate measure of the instantaneous high energy particle flux is achieved at each update cycle (250ms).</p><p>With this feature installed on all three Swarm spacecrafts, a hitherto unprecedented accurate mapping of the proton population around Earth is achieved at two distances, 450 and 530km.</p><p>The superrelativistic protons measured by the μASC (g>>1), travel at speeds very close to c, and bouncing between the North and South Earth sphere, encounters complex field structures for at least some of the time. The bounce period is much smaller than the Earth rotation period, and an east-west drift component is caused by the magnetic field gradient.</p><p>We will present observations of the trapped proton fluxes and show how the magnetic field affects their motion shells. Slightly deformed particle drift shells due to the magnetic field structure (for orbits with L>1.07) and the differential east-west drift as measured by the Swarm Alpha and Charlie satellites will be discussed.</p>

Electric fields parallel to the magnetic field in a laboratory plasma in a magnetic mirror field

1974 ◽  
Vol 12 (3) ◽  
pp. 467-486 ◽  
Author(s):  
R. Geller ◽  
N. Hopfgarten ◽  
B. Jacquot ◽  
C. Jacquot
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Electric Fields ◽  
Pitch Angle ◽  
Magnetic Field Gradient ◽  
Magnetic Mirror ◽  
Electron Velocity ◽  
Microwave Cavity ◽  
Resonance Zone ◽  
The Magnetic Field

With electrostatic probes, the electric field component E∥ along the magnetic field B was comprehensively investigated in a collisionless plasma, the density of which was of the order of 1010 cm-3. The plasma in the experiment has several properties in common with the plasma of the ionosphere/magnetosphere scaled to laboratory dimensions. It is produced by means of electron cyclotron resonance in a microwave cavity located in the magnetic field gradient in one half of a magnetic mirror field. The magnetic field strength is 3600G in the resonance zone and 1800G in the middle of the mirror field. The measurements show that a stationary E∥ exists everywhere in the plasma, where the magnetic field gradient grad11 B in the direction of the field is different from zero. The direction of E‖ is opposite to that of grad‖B. The total potential drop along B between the resonance zone and the midplane of the mirror field is of the order of kilovolts. E‖ accelerates ions along B to energies of the order of kilo electron volts. Experimental parameters of importance for the production of E‖ are the neutral gas pressure p (normally a few times 10− Torr), the microwave power (usually about 2kW), and the mirror ratio γ in the mirror region opposite to the cavity side, γ was normally <2. For γ>2·3, an instability develops and no stationary E‖ remains. As p is increased, E‖ decreases successively. In terms of the mean free path λ, it is found that λ>5−10L is a necessary condition for the existence of E‖. L is twice the distance between the cavity and the midplane of the mirror field. In the experiment, the ion and electron pitch angle distributions are forced to be different; the ion velocity is mainly parallel to B, and the electron velocity essentially perpendicular to JB, and as consequence E‖ is created. In this way an experimental demonstration is presented of the theoretically predicted relation between E‖ and the pitch angle distributions. When imposing sufficiently strong radial electric fields Er (fields perpendicular to B), the distribution of the potential along B is deformed, probably due to changes in the particle distributions caused by E‖. We think that our results strongly support the idea that Et is produced in the magnetosphere, and is at least sometimes an important mechanism for the acceleration and precipitation of auroral particles.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

scholarly journals Magnetic nulls in interacting dipolar fields

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Todd Elder ◽  
Allen H. Boozer
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Magnetic Flux Tube ◽  
Electron Inertia ◽  
Characteristic Spatial Scale ◽  
Field Lines ◽  
Dipolar Fields ◽  
Time Required ◽  
Magnetic Null ◽  
The Magnetic Field

The prominence of nulls in reconnection theory is due to the expected singular current density and the indeterminacy of field lines at a magnetic null. Electron inertia changes the implications of both features. Magnetic field lines are distinguishable only when their distance of closest approach exceeds a distance $\varDelta _d$ . Electron inertia ensures $\varDelta _d\gtrsim c/\omega _{pe}$ . The lines that lie within a magnetic flux tube of radius $\varDelta _d$ at the place where the field strength $B$ is strongest are fundamentally indistinguishable. If the tube, somewhere along its length, encloses a point where $B=0$ vanishes, then distinguishable lines come no closer to the null than $\approx (a^2c/\omega _{pe})^{1/3}$ , where $a$ is a characteristic spatial scale of the magnetic field. The behaviour of the magnetic field lines in the presence of nulls is studied for a dipole embedded in a spatially constant magnetic field. In addition to the implications of distinguishability, a constraint on the current density at a null is obtained, and the time required for thin current sheets to arise is derived.

Detection of a change in the North-South ratio of count rates of particles of high-energy cosmic rays during a change in the polarity of the magnetic field of the Sun

JETP Letters ◽  
2015 ◽  
Vol 101 (4) ◽  
pp. 228-231
Author(s):  
A. V. Karelin ◽  
O. Adriani ◽  
G. C. Barbarino ◽  
G. A. Bazilevskaya ◽  
R. Bellotti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
High Energy ◽  
The Sun ◽  
High Energy Cosmic Rays ◽  
The North ◽  
The Magnetic Field

scholarly journals Remote manipulation of magnetic nanoparticles using magnetic field gradient to promote cancer cell death

2018 ◽  
Author(s):  
Mahendran Subramanian ◽  
Arkadiusz Miaskowski ◽  
Stuart Iain Jenkins ◽  
Jenson Lim ◽  
Jon Dobson
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Field Gradient ◽  
Biomedical Applications ◽  
Magnetic Field Gradient ◽  
Field Source ◽  
Remote Manipulation ◽  
Cancer Cell Death ◽  
The Magnetic Field

AbstractThe manipulation of magnetic nanoparticles (MNPs) using an external magnetic field, has been demonstrated to be useful in various biomedical applications. Some techniques have evolved utilizing this non-invasive external stimulus but the scientific community widely adopts few, and there is an excellent potential for more novel methods. The primary focus of this study is on understanding the manipulation of MNPs by a time-varying static magnetic field and how this can be used, at different frequencies and displacement, to manipulate cellular function. Here we explore, using numerical modeling, the physical mechanism which underlies this kind of manipulation, and we discuss potential improvements which would enhance such manipulation with its use in biomedical applications, i.e., increasing the MNP response by improving the field parameters. From our observations and other related studies, we infer that such manipulation depends mostly on the magnetic field gradient, the magnetic susceptibility and size of the MNPs, the magnet array oscillating frequency, the viscosity of the medium surrounding MNPs, and the distance between the magnetic field source and the MNPs. Additionally, we demonstrate cytotoxicity in neuroblastoma (SH-SY5Y) and hepatocellular carcinoma (HepG2) cells in vitro. This was induced by incubation with MNPs, followed by exposure to a magnetic field gradient, physically oscillating at various frequencies and displacement amplitudes. Even though this technique reliably produces MNP endocytosis and/or cytotoxicity, a better biophysical understanding is required to develop the mechanism used for this precision manipulation of MNPs, in vitro.

scholarly journals Excitation And Ionization By Auroral Protons

1966 ◽  
Vol 19 (3) ◽  
pp. 309 ◽  
Keyword(s):  
Magnetic Field ◽  
Energy Range ◽  
Pitch Angle ◽  
Proton Energy ◽  
Ionization Rate ◽  
Energy Spectra ◽  
Proton Fluxes ◽  
Atmospheric Ionization ◽  
The Magnetic Field

Height distributions are presented for the atmospheric ionization rate and Balmer radiation resulting from precipitation of auroral protons. These results have been computed assuming proton fluxes with several different energy spectra and pitch-angle distributions about the magnetic field, the total proton energy range being restricted to 1-1000 keY.

scholarly journals Magnetorheological Fluids Behaviour in Oscillatory Compression Squeeze: Experimental Testing and Analysis

2019 ◽  
Vol 13 (4) ◽  
pp. 221-225
Author(s):  
Wojciech Horak ◽  
Marcin Szczęch ◽  
Bogdan Sapiński
Keyword(s):  
Magnetic Field ◽  
Volume Fraction ◽  
Experimental Testing ◽  
Magnetic Field Gradient ◽  
Particle Volume Fraction ◽  
Excitation Frequency ◽  
Magnetorheological Fluid ◽  
Density Level ◽  
Particle Volume ◽  
The Magnetic Field

Abstract This article deals with experimental testing of magnetorheological fluid (MRF) behaviour in the oscillatory squeeze mode. The authors investigate and analyse the influence of excitation frequency and magnetic field density level on axial force in MRFs that differ in particle volume fraction. The results show that, under certain conditions, the phenomenon of self-sealing can occur as a result of the magnetic field gradient and a vacuum in the working gap of the system.

Precisely mapping the magnetic field gradient in vacuum with an atom interferometer

2010 ◽  
Vol 82 (6) ◽  
Author(s):  
Min-Kang Zhou ◽  
Zhong-Kun Hu ◽  
Xiao-Chun Duan ◽  
Bu-Liang Sun ◽  
Jin-Bo Zhao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Magnetic Field Gradient ◽  
Atom Interferometer ◽  
The Magnetic Field

scholarly journals The magnetic field of β Cep and the Be phenomenon

2000 ◽  
Vol 175 ◽  
pp. 324-329 ◽  
Author(s):  
H.F. Henrichs ◽  
J.A. de Jong ◽  
J.-F. Donati ◽  
C. Catala ◽  
G.A. Wade ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Longitudinal Magnetic Field ◽  
Rotation Period ◽  
Spectral Lines ◽  
Be Stars ◽  
Full Paper ◽  
Rapid Rotation ◽  
Rotator Model ◽  
Maximum Field ◽  
The Magnetic Field

AbstractNew circular spectropolarimetric observations of the B1 IIIe star β Cep (υsini = 25 km s−1) show a sinusoidally varying weak longitudinal magnetic field (~ 200 G peak-to-peak). The period corresponds to the 12 day period in the stellar wind variations observed in ultraviolet spectral lines. Maximum field occurs at maximum emission in the UV wind lines. This gives compelling evidence for a magnetic-rotator model for this star, with an unambiguous rotation period of 12 days.The similarity between the Hα emission phases in β Cep and in Be stars suggests that the origin of the Be phenomenon does not have to be rapid rotation: we propose that in β Cep the velocity to bring material in (Keplerian) orbit is provided by the high corotation velocity at the Alfvén radius (~10 R*), whereas in Be stars this is done by the rapid rotation of the surface. In both cases the cause of the emission phases has still to be found. Weak temporary magnetic fields remain the strongest candidate.A full paper, with results including additional measurements in June and July 1999, will appear in A & A.

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