Magnetospheric electron‐velocity‐distribution function information from wave observations

Benson, Robert F.; Viñas, A. F.; Osherovich, V. A.; Fainberg, J.; Purser, Carola M.; Adrian, M. L.; Galkin, I. A.; Reinisch, B. W.

doi:10.1002/jgra.50459

Cited by 13 publications

(13 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We note that in a study that appeared after the submission of the present work, Benson et al 45 extended the approach of Ref. 20, setting up a general tool to use the Q n resonances of electron Bernstein waves as a diagnostic for the electron kappa values in space.…”

Section: Discussionmentioning

confidence: 92%

Ion Bernstein waves in a plasma with a kappa velocity distribution

2013

View full text Add to dashboard Cite

Using a Vlasov-Poisson model, a numerical investigation of the dispersion relation for ion Bernstein waves in a kappa-distributed plasma has been carried out. The dispersion relation is found to depend significantly on the spectral index of the ions, κi, the parameter whose smallness is a measure of the departure from thermal equilibrium of the distribution function. Over all cyclotron harmonics, the typical Bernstein wave curves are shifted to higher wavenumbers (k) if κi is reduced. For waves whose frequency lies above the lower hybrid frequency, ωLH, an increasing excess of superthermal particles (decreasing κi) reduces the frequency, ωpeak, of the characteristic peak at which the group velocity vanishes, while the associated kpeak is increased. As the ratio of ion plasma to cyclotron frequency (ωpi/ωci) is increased, the fall-off of ω at large k is smaller for lower κi and curves are shifted towards larger wavenumbers. In the lower hybrid frequency band and harmonic bands above it, the frequency in a low-κi plasma spans only a part of the intraharmonic space, unlike the Maxwellian case, thus exhibiting considerably less coupling between adjacent bands for low κi. It is suggested that the presence of the ensuing stopbands may be a useful diagnostic for the velocity distribution characteristics. The model is applied to the Earth's plasma sheet boundary layer in which waves propagating perpendicularly to the ambient magnetic field at frequencies between harmonics of the ion cyclotron frequency are frequently observed.

show abstract

Section: Discussionmentioning

confidence: 92%

Ion Bernstein waves in a plasma with a kappa velocity distribution

2013

View full text Add to dashboard Cite

show abstract

“…Indeed, the Tsallis formalism, which appeared as consequence of using nonadditive entropies, has the distribution function as the main element of the theory (Milovanov & Zelenyi, 2000;Tsallis, 1988Tsallis, , 2009. They have been successfully used, both observationally and theoretically (e.g., Navarro et al, 2015;Pierrard & Meyer-Vernet, 2017;Viñas et al, 2015;Yoon & Livadiotis, 2017), to describe particle distribution functions for velocity or energy (PEDF) 10.1029/2018GL078631 in a number of plasma environments, from the Earth's and other planets magnetospheres (Benson et al, 2013;Kirpichev et al, 2017;Viñas et al, 2005) to solar radio bursts (Cairns et al, 2017). They behave similar to the Maxwellian case for low and central energies but include a power law regime that operates toward higher energies, with a slope determined by the index.…”

Section: Introductionmentioning

confidence: 99%

“…This behavior was much clearer for the electrons, which exhibited ∼ 2 for X ∼ 8R E and seemed to converge to = 4 − 5 for X > 15R E . These results were consistent with Viñas et al (2005) and Benson et al (2013), who found ∼ 2 near the magnetic midnight, in the low-latitude magnetosphere (small Z) near the plasmasphere. In this work we use the GSM coordinate system for the variables X, Y, and Z.…”

Section: Introductionmentioning

confidence: 99%

Ion and Electron κ Distribution Functions Along the Plasma Sheet

Espinoza

Stepanova

Moya

et al. 2018

Geophysical Research Letters

View full text Add to dashboard Cite

We use kappa distributions to model thousands of ion and electron flux spectra along the plasma sheet and analyze the variation of the spectral index κ and the temperature T in this region. We find that κ distributions are ubiquitous and fit well ion and electron flux spectra during quiet times, and during the expansion and recovery phases of substorms. Near Earth, and up to ∼12 RE, the κ indices are different than the rest of the plasma sheet, both for ions (κi) and electrons (κe). There is a significant dawn‐dusk asymmetry in κi toward the tail, which is enhanced during substorms. The ions also exhibit a permanent temperature asymmetry, determined by a colder dawnside. The whole tail becomes hotter during substorms, but it appears that most of the energy is deposited near Earth.

show abstract

“…Higher‐order terms will impose an even more restrictive condition on the minimal value of the κ index, and this condition ties κ min to the harmonic number. This is an undesirable restriction on the allowable values of the κ index, since it has been measured to be as low as κ ≃2 both in the solar wind and in the magnetosphere [ Maksimovic et al , ; Štverák et al , ; Benson et al , ]. The result implies that

ℋ_{n, κ}^{((), α, β)} (z)

could always be represented by a power series, which is not true. As we shall see below, for certain values of the λ index the function has a logarithmic behavior. Even when

ℋ_{n, κ}^{((), α, β)} (z)

is expressible as a power series, the lowest‐order terms contain a contribution proportional to a power that is not an integer, in general; these terms will also be lacking from the simplifying approach described above.…”

Section: Special Functions For Kappa Plasmasmentioning

confidence: 99%

“…Higher-order terms will impose an even more restrictive condition on the minimal value of the index, and this condition ties min to the harmonic number. This is an undesirable restriction on the allowable values of the index, since it has been measured to be as low as ≃ 2 both in the solar wind and in the magnetosphere [Maksimovic et al, 1997;Štverák et al, 2009;Benson et al, 2013].…”

Section: The Kappa Gyroradius Functionmentioning

confidence: 99%

The dispersion relations of dispersive Alfvén waves in superthermal plasmas

Gaelzer

Ziebell

2014

JGR Space Physics

View full text Add to dashboard Cite

The effects of velocity distribution functions (VDFs) that exhibit a power law dependence on the high-energy tail have been the subject of intense research by the space plasma community. Such functions, known as superthermal or kappa distributions, have been found to provide a better fitting to the VDF measured by several spacecraft in the plasma environment of the solar wind. In the literature, the general treatment for waves excited by (bi-)Maxwellian plasmas is well established. However, for kappa distributions, either isotropic or anisotropic, the wave characteristics have been studied mostly for the limiting cases of purely parallel or perpendicular propagation. Contributions for the general case of obliquely propagating waves have been scarcely reported so far. In this work we introduce a mathematical formalism that provides expressions for the dielectric tensor components and subsequent dispersion relations for oblique propagating dispersive Alfvén waves (DAWs) resulting from a kappa VDF. We employ an isotropic distribution, but the methods used here can be easily applied to more general anisotropic distributions, such as the bi-kappa or product-bi-kappa. The effect of the kappa index and thermal corrections on the dispersion relations of DAW is discussed.

show abstract

Magnetospheric electron‐velocity‐distribution function information from wave observations

Cited by 13 publications

References 58 publications

Ion Bernstein waves in a plasma with a kappa velocity distribution

Ion Bernstein waves in a plasma with a kappa velocity distribution

Ion and Electron κ Distribution Functions Along the Plasma Sheet

The dispersion relations of dispersive Alfvén waves in superthermal plasmas

Contact Info

Product

Resources

About