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 Observations of diffusion in the electron halo and strahl

2016 ◽  
Vol 34 (12) ◽  
pp. 1175-1189 ◽  
Author(s):  
Chris Gurgiolo ◽  
Melvyn L. Goldstein
Keyword(s):  
Magnetic Field ◽  
Energy Range ◽  
Lower Energy ◽  
Three Dimensional ◽  
Distribution Functions ◽  
Electron Velocity ◽  
Electron Velocity Distribution ◽  
Velocity Distribution Functions ◽  
The Magnetic Field ◽  
Solar Wind Electron

Abstract. Observations of the three-dimensional solar wind electron velocity distribution functions (VDF) using ϕ–θ plots often show a tongue of electrons that begins at the strahl and stretches toward a new population of electrons, termed the proto-halo, that exists near the projection of the magnetic field opposite that associated with the strahl. The energy range in which the tongue and proto-halo are observed forms a “diffusion zone”. The tongue first appears in energy generally near the lower-energy range of the strahl and in the absence of any clear core/halo signature. While the ϕ–θ plots give the appearance that the tongue and proto-halo are derived from the strahl, a close examination of their density suggests that their source is probably the upper-energy core/halo electrons which have been scattered by one or more processes into these populations.

Recent Evidence Concerning the Sidereal Anisotropy in the Charged Primary Cosmic Radiation

1969 ◽  
Vol 1 (6) ◽  
pp. 278-280 ◽  
Author(s):  
K. G. Jacklyn ◽  
A. Vrana
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Cosmic Radiation ◽  
Particle Trajectory ◽  
Magnetic Moments ◽  
Charged Particles ◽  
Significant Evidence ◽  
Primary Cosmic Radiation ◽  
The Magnetic Field ◽  
Sidereal Anisotropy

Significant evidence for a bi-directional sidereal anisotropy has been obtained from observations with meson telescopes at depths in the vicinity of 40 metres water equivalent (m.w.e.) underground. The anisotropy is of the type which should occur when charged particles which were formerly isotropic stream equally in both directions along a magnetic field, if there is a tendency for pitch angles to become reduced (the pitch angle being the angle between the particle trajectory and the direction of the field). If the magnetic moments of the particles are adiabatically invariant, changes in the magnetic field, both with position and time, could be responsible for the anisotropy.

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>

Determination of Solar Energetic Particle anisotropies based on four-sector measurements - Study based on STEREO/SEPT in preperation of SolO/EPT

2020 ◽  
Author(s):  
Maximilian Bruedern ◽  
Nina Dresing ◽  
Bernd Heber ◽  
Lars Berger ◽  
Alexander Kollhoff ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Radial Distance ◽  
Solar Energetic Particle ◽  
The Sun ◽  
Angle Scattering ◽  
Bootstrap Approach ◽  
The Magnetic Field ◽  
The Imf

<p>With the launch of Solar Orbiter (SolO) Solar Energetic Particles (SEPs) can be observed at a radial distance of 0.284 to 0.9 AU and an inclination out of the ecliptic up to 34 degree. The properties of SEP observations carry information about their source at the Sun as well as their transport through the interplanetary medium. Their energy is mostly determined close to the Sun. As SEPs propagate outward along the Interplanetary Magnetic Field (IMF) the pitch-angle with respect to the local field is systematically focused due to the radially decreasing IMF. However, stochastic changes are induced by scattering at fluctuations of the IMF. Often the first order anisotropy of SEPs is calculated to disentangle imprints of source and transport. Strong anisotropies indicate periods of weak pitch-angle scattering. Although many modeling and observational studies are based on the anisotropy, its uncertainty is often neglected which could result in inaccurate conclusions. Therefore, we propose a new method based on a bootstrap approach where we consider (1) directional instrument responses, (2) the variation of the magnetic field, and (3) the stochastic nature of detection. Here, we present our procedure and final results for different SEP events using measured data of the IMF and particle fluxes by the Solar Electron and Proton Telescope (SEPT) on board of each STEREO spacecraft. The SEPT provides four viewing directions with a view cone of 0.66 sr each on a three axis stabilized spacecraft. In contrast the Electron and Proton Telescope (EPT) on board SolO also consists of four viewing directions but each telescope has a much smaller view cone of 0.21 sr. Due to the very similar instrument setup we can apply our method both to the SEPT and EPT.</p>

scholarly journals The expected imprint of flux rope geometry on suprathermal electrons in magnetic clouds

2009 ◽  
Vol 27 (10) ◽  
pp. 4057-4067 ◽  
Author(s):  
M. J. Owens ◽  
N. U. Crooker ◽  
T. S. Horbury
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Pitch Angle ◽  
Flux Rope ◽  
Magnetic Clouds ◽  
Magnetic Field Direction ◽  
Magnetic Flux Rope ◽  
Suprathermal Electron ◽  
Angle Scattering ◽  
The Magnetic Field

Abstract. Magnetic clouds are a subset of interplanetary coronal mass ejections characterized by a smooth rotation in the magnetic field direction, which is interpreted as a signature of a magnetic flux rope. Suprathermal electron observations indicate that one or both ends of a magnetic cloud typically remain connected to the Sun as it moves out through the heliosphere. With distance from the axis of the flux rope, out toward its edge, the magnetic field winds more tightly about the axis and electrons must traverse longer magnetic field lines to reach the same heliocentric distance. This increased time of flight allows greater pitch-angle scattering to occur, meaning suprathermal electron pitch-angle distributions should be systematically broader at the edges of the flux rope than at the axis. We model this effect with an analytical magnetic flux rope model and a numerical scheme for suprathermal electron pitch-angle scattering and find that the signature of a magnetic flux rope should be observable with the typical pitch-angle resolution of suprathermal electron data provided ACE's SWEPAM instrument. Evidence of this signature in the observations, however, is weak, possibly because reconnection of magnetic fields within the flux rope acts to intermix flux tubes.

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.

Superbanana and superbanana plateau transport in finite aspect ratio tokamaks with broken symmetry

2014 ◽  
Vol 81 (2) ◽  
Author(s):  
K. C. Shaing
Keyword(s):  
Magnetic Field ◽  
Aspect Ratio ◽  
Pitch Angle ◽  
Plasma Pressure ◽  
Transport Processes ◽  
Broken Symmetry ◽  
Plasma Confinement ◽  
Main Effects ◽  
The Magnetic Field ◽  
Angle Parameter

Superbanana and superbanana plateau transport processes are critical to plasma confinement in tokamaks with broken symmetry. The transport is caused by the superbanana resonance, which occurs at a pitch angle that makes the toroidal drift speed vanish, i.e. the tips of the superbananas. The physics consequences of the resonance on the symmetry breaking induced toroidal momentum damping and on the energetic alpha particle transport have been demonstrated using large aspect ratio expansion. Here, the existing theory for the superbanana and superbanana plateau transport is extended for finite aspect ratio tokamaks with broken symmetry. The effects of finite plasma β, and magnetic field shear are naturally included. Here, β is the ratio of the thermal plasma pressure to the magnetic field pressure. The explicit expressions for the transport fluxes in these regimes in terms of the equilibrium quantities are presented. It is shown that the main effects are to modify the resonance function G(k) and the expression for the pitch angle parameter k in the existing theory.

scholarly journals Protons associated with centres of solar activity and their propagation in interplanetary magnetic-field regions co-rotating with the Sun

1968 ◽  
Vol 35 ◽  
pp. 403-403
Author(s):  
C. Y. Fan ◽  
M. Pick ◽  
R. Ryle ◽  
J. A. Simpson ◽  
D. R. Smith
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Interplanetary Magnetic Field ◽  
Active Regions ◽  
Alpha Particles ◽  
Western Hemisphere ◽  
Energy Spectra ◽  
The Sun ◽  
Long Term Storage ◽  
Proton Fluxes

The Pioneer-6 and Pioneer-7 space probes carried charged-particle telescopes which measure, for the first time, both the direction of arrival and differential energy spectra of protons and alpha particles. The intensity changes, directional distributions and energy spectra of proton fluxes associated with solar activity are investigated. The data were obtained in the beginning of the new solar cycle (no. 20), when it is possible to unambiguously associate proton-flux increases with specific solar active regions. The origin, possibly long-term storage, and propagation of these proton fluxes are investigated. It was observed that enhanced 0·6–13 MeV proton fluxes associated with specific active regions were present over heliographic longitude ranges as great as ~ 180°. These enhanced fluxes exhibit definite onsets and cut-offs which appear to be associated with the magnetic-sector boundaries observed by Ness on Pioneer-6. Discrete flare-produced intensity increases extending in energy to more than 50 MeV are observed, superposed on the enhanced flux. These increases displayed short transit times and short rise times. Both the enhanced and flare-produced fluxes propagate along the spiral interplanetary magnetic field from the Western hemisphere of the Sun. From these observations we are led to a model in which the magnetic fields from the active region are spread out over a longitude range of 100–180° in the solar corona. The existence of strong unidirectional anisotropies in the initial phases of flare-proton events implies that little scattering occurs between the Sun and spacecraft. However, the gradual approach to an isotropic flux at late times indicates that the decay phase is controlled by the interplanetary magnetic field.

Sign in / Sign up

Export Citation Format

Share Document