Middle-energy electron anisotropies in the auroral region

Abstract. Field-aligned anisotropic electron distribution functions of T∥ > T⊥ type are observed on auroral field lines at both low and high altitudes. We show that typically the anisotropy is limited to a certain range of energies, often below 1keV, although sometimes extending to slightly higher energies as well. Almost always there is simultaneously an isotropic electron distribution at higher energies. Often the anisotropies are up/down symmetrical, although cases with net upward or downward electron flow also occur. For a statistical analysis of the anisotropies we divide the energy range into low (below 100eV), middle (100eV–1keV) and high (above 1keV) energies and develop a measure of anisotropy expressed in density units. The statistical magnetic local time and invariant latitude distribution of the middle-energy anisotropies obeys that of the average auroral oval, whereas the distributions of the low and high energy anisotropies are more irregular. This suggests that it is specifically the middle-energy anisotropies that have something to do with auroral processes. The anisotropy magnitude decreases monotonically with altitude, as one would expect, because electrons have high mobility along the magnetic field and thus, the anisotropy properties spread rapidly to different altitudes. Key words. Magnetospheric physics (auroral phenomena). Space plasma physics (wave-particle interactions; changed particle motion and acceleration)

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General dispersion properties of magnetized plasmas with drifting bi-Kappa distributions. DIS-K: Dispersion Solver for Kappa Plasmas

Journal of Plasma Physics ◽

10.1017/s0022377821000593 ◽

2021 ◽

Vol 87 (3) ◽

Author(s):

R.A. López ◽

S.M. Shaaban ◽

M. Lazar

Keyword(s):

Dominant Role ◽

High Energy ◽

Distribution Functions ◽

Magnetized Plasma ◽

Unstable Wave ◽

Space Plasmas ◽

Good Representation ◽

Particle Interactions ◽

Particle Collisions ◽

Dispersion Tensor

Space plasmas are known to be out of (local) thermodynamic equilibrium, as observations show direct or indirect evidences of non-thermal velocity distributions of plasma particles. Prominent are the anisotropies relative to the magnetic field, anisotropic temperatures, field-aligned beams or drifting populations, but also, the suprathermal populations enhancing the high-energy tails of the observed distributions. Drifting bi-Kappa distribution functions can provide a good representation of these features and enable for a kinetic fundamental description of the dispersion and stability of these collision-poor plasmas, where particle–particle collisions are rare but wave–particle interactions appear to play a dominant role in the dynamics. In the present paper we derive the full set of components of the dispersion tensor for magnetized plasma populations modelled by drifting bi-Kappa distributions. A new solver called DIS-K (DIspersion Solver for Kappa plasmas) is proposed to solve numerically the dispersion relations of high complexity. The solver is validated by comparing with the damped and unstable wave solutions obtained with other codes, operating in the limits of drifting Maxwellian and non-drifting Kappa models. These new theoretical tools enable more realistic characterizations, both analytical and numerical, of wave fluctuations and instabilities in complex kinetic configurations measured in-situ in space plasmas.

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POLARIZED STRUCTURE FUNCTIONS AND SPIN PHYSICS

International Journal of Modern Physics A ◽

10.1142/s0217751x02012703 ◽

2002 ◽

Vol 17 (23) ◽

pp. 3220-3238

Author(s):

UTA STÖSSLEIN

Keyword(s):

Parton Distribution ◽

Spin Structure ◽

High Energy ◽

Structure Functions ◽

Distribution Functions ◽

High Energy Particle ◽

Particle Interactions ◽

Parton Distribution Functions ◽

Spin Physics ◽

Further Development

Recent progress in the field of spin physics of high energy particle interactions is reviewed with particular emphasis on the spin structure functions as measured in polarized deep inelastic lepton-nucleon scattering (DIS). New measurements are presented to obtain more direct information on the composition of the nucleon angular momentum, with results from semi-inclusive DIS accessing flavour-separated parton distribution functions (PDF) and with first data from hard exclusive reactions which may be interpreted in terms of recently developed generalizations of parton distribution functions (GPD). Finally, experimental prospects are outlined which will lead to a further development of the virtues of QCD phenomenology of the spin structure of the nucleon.

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The Nightside Auroral Oval

Convection and Substorms ◽

10.1093/oso/9780195085297.003.0014 ◽

1996 ◽

Author(s):

Charles F. Kennel

Keyword(s):

Local Time ◽

First Generation ◽

Basic Structure ◽

Auroral Oval ◽

Optical Wavelength ◽

Field Lines ◽

Auroral Phenomena ◽

Auroral Imaging ◽

Time Sector ◽

Local Time Sector

The basic structure of the auroral oval was pieced together from relatively local magnetometer measurements and all-sky photographs taken on the ground. The all-sky cameras picked out relatively intense features whose intensities exceeded roughly one kilorayleigh. Their fields of view had a 500-1000 km radius at auroral altitudes, and so extended over 5-10 degrees of latitude and about 90 minutes of local time. Had the aurora been stationary and time-independent, this would have been enough, and it was enough to spot the existence of substorms. It was not enough to solve the substorm problem. As the instruments to study auroral phenomena grew in sophistication and comprehensiveness, so also did our understanding of the concept of the auroral oval. This chapter is dedicated to communicating some of this modern understanding as a prelude to the discussion of substorms in the next chapter. Ground instruments can follow the time development of events within their fields of view but have difficulty separating changes in space and time on scales longer than an hour of universal time or local time, because the observing station rotates with the earth to a local time sector where the aurora may differ. This difficulty can be offset to some extent by airplane flights that remain at a constant local time. However, the real breakthrough came with auroral imaging from space. In the 1970s, optical wavelength imaging from low-altitude polar orbit provided snapshots of the aurora over several thousand kilometer scale portions of the oval on each polar pass of the spacecraft (Shepherd et al., 1973; Anger et al., 1973; Lui and Anger, 1973; Pike and Whalen, 1974; Snyder and Akasofu, 1974). And the spacecraft could detect the precipitating particles responsible for the auroral light emitted from the magnetic footprint of the field lines along its path. The results from the first generation of auroral imaging experiments have been summarized in excellent reviews (Akasofu, 1974, 1976; Hultquist, 1974; Burch, 1979). Ultraviolet imaging allows one to see the dayside aurora.

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Observations of auroral zone processes by the Viking satellite

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1989.0032 ◽

1989 ◽

Vol 328 (1598) ◽

pp. 209-220 ◽

Cited By ~ 3

Keyword(s):

Magnetic Field ◽

Auroral Oval ◽

Auroral Zone ◽

Double Layers ◽

Particle Interactions ◽

Imaging Experiment ◽

Auroral Electrons ◽

Field Lines ◽

Scientific Results ◽

The Magnetic Field

The scientific results of the Viking project obtained up to the spring of 1988 are reviewed. During solar minimum conditions, when Viking was operated, the dayside auroral oval has been found to be the most active part, except during strong substorms and storms. A number of new auroral morphological features have been seen with the imaging experiment onboard Viking. Large-amplitude slow fluctuations of the electric field heat the ionospheric plasma and pump up the magnetic moment of the ionospheric ions so that they may leave the ionosphere. These fluctuations also accelerate ionospheric electrons upwards along the magnetic field lines. The importance of the acceleration of auroral electrons into the atmosphere by magnetic field-aligned potential differences has been confirmed. The first satellite-borne plasma wave interferometer on Viking has made it possible to determine a number of characteristics of the ‘weak’ double layers, seen first by the S3-3 satellite. A large number of these along the magnetic field lines produce large electric potential differences. Many new results concerning wave-particle interactions have been obtained, of which a few are presented here.

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Upward high-energy field-aligned electron beams above the polar edge of auroral oval: observations from the SKA-3 instruments onboard the Auroral Probe (Interball-2)

Annales Geophysicae ◽

10.1007/s00585-998-1046-1 ◽

1998 ◽

Vol 16 (9) ◽

pp. 1046-1055 ◽

Cited By ~ 4

Author(s):

V. A. Stepanov ◽

Y. I. Galperin ◽

A. K. Kuzmin ◽

F. K. Shuiskaya ◽

L. S. Gorn ◽

...

Keyword(s):

Particle Acceleration ◽

Electric Field ◽

Energy Range ◽

Electron Beams ◽

High Energy ◽

Auroral Oval ◽

Particle Interactions ◽

Acceleration Wave ◽

Energy Field ◽

Long Time

Abstract. A new phenomenon was found at the polar edge of the auroral oval in the postmidnight-morning sectors: field-aligned (FA) high-energy upward electron beams in the energy range 20–40 keV at altitudes about 3RE, accompanied by bidirectional electron FA beams of keV energy. The beam intensity often reaches more than 0.5·103 electrons/s·sr·keV·cm2, and the beams are observed for a relatively long time (~3·102–103s), when the satellite at the apogee moves slowly in the ILAT-MLT frame. A qualitative scenario of the acceleration mechanism is proposed, according to which the satellite is within a region of bidirectional acceleration where a stochastic FA acceleration is accomplished by waves with fluctuating FA electric field components in both directions.Key words. Ionosphere (particle acceleration; wave-particle interactions) · Magnetospheric physics (magnetosphere-ionosphere interactions)

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Juno observations of spot structures and a split tail in Io-induced aurorae on Jupiter

Science ◽

10.1126/science.aat1450 ◽

2018 ◽

Vol 361 (6404) ◽

pp. 774-777 ◽

Cited By ~ 18

Author(s):

A. Mura ◽

A. Adriani ◽

J. E. P. Connerney ◽

S. Bolton ◽

F. Altieri ◽

...

Keyword(s):

Magnetic Field ◽

High Energy ◽

Auroral Oval ◽

Upper Atmosphere ◽

Vortex Street ◽

Infrared Observations ◽

High Energy Electrons ◽

Galilean Moons ◽

Field Lines ◽

Magnetohydrodynamic Interaction

Jupiter’s aurorae are produced in its upper atmosphere when incoming high-energy electrons precipitate along the planet’s magnetic field lines. A northern and a southern main auroral oval are visible, surrounded by small emission features associated with the Galilean moons. We present infrared observations, obtained with the Juno spacecraft, showing that in the case of Io, this emission exhibits a swirling pattern that is similar in appearance to a von Kármán vortex street. Well downstream of the main auroral spots, the extended tail is split in two. Both of Ganymede’s footprints also appear as a pair of emission features, which may provide a remote measure of Ganymede’s magnetosphere. These features suggest that the magnetohydrodynamic interaction between Jupiter and its moon is more complex than previously anticipated.

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Calculation of spatially inhomogeneous electron distribution functions

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:1998703 ◽

1998 ◽

Vol 08 (PR7) ◽

pp. Pr7-33-Pr7-42

Author(s):

L. L. Alves ◽

G. Gousset ◽

C. M. Ferreira

Keyword(s):

Electron Distribution ◽

Distribution Functions ◽

Spatially Inhomogeneous

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Penetration of MeV electrons into the mesosphere accompanying pulsating aurorae

Scientific Reports ◽

10.1038/s41598-021-92611-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Y. Miyoshi ◽

K. Hosokawa ◽

S. Kurita ◽

S.-I. Oyama ◽

Y. Ogawa ◽

...

Keyword(s):

High Energy ◽

Daily Basis ◽

Maximum Energy ◽

Energy Electron ◽

High Energy Electron ◽

Whistler Mode ◽

Chorus Waves ◽

Mesospheric Ozone ◽

Field Lines ◽

Eiscat Radar

AbstractPulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a few MeV during a PsA associated with a weak geomagnetic storm. Simultaneously, the Arase spacecraft has observed intense whistler-mode chorus waves at the conjugate location along magnetic field lines. A computer simulation based on the EISCAT observations shows immediate catalytic ozone depletion at the mesospheric altitudes. Since PsA occurs frequently, often in daily basis, and extends its impact over large MLT areas, we anticipate that the PsA possesses a significant forcing to the mesospheric ozone chemistry in high latitudes through high energy electron precipitations. Therefore, the generation of PsA results in the depletion of mesospheric ozone through high-energy electron precipitations caused by whistler-mode chorus waves, which are similar to the well-known effect due to solar energetic protons triggered by solar flares.

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High-energy operator product expansion at sub-eikonal level

Journal of High Energy Physics ◽

10.1007/jhep06(2021)096 ◽

2021 ◽

Vol 2021 (6) ◽

Author(s):

Giovanni Antonio Chirilli

Keyword(s):

Operator Product Expansion ◽

Evolution Equations ◽

Energy Operator ◽

High Energy ◽

Structure Functions ◽

Distribution Functions ◽

Impact Factors ◽

Operator Product ◽

The Impact ◽

New Distribution

Abstract The high energy Operator Product Expansion for the product of two electromagnetic currents is extended to the sub-eikonal level in a rigorous way. I calculate the impact factors for polarized and unpolarized structure functions, define new distribution functions, and derive the evolution equations for unpolarized and polarized structure functions in the flavor singlet and non-singlet case.

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