The role pickup ions play in the termination shock

Ariad, Daniel; Gedalin, M.

doi:10.1002/jgra.50170

Cited by 11 publications

(14 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They were shown theoretically to be efficiently accelerated at a plane high-Mach number shock by surfing or multiple reflections [see, e.g., 27,50,51]. This acceleration is consistent with the observations of energetic particles at the termination shock where the pickup ions are one of the major channels of the energy re-distribition [1,13,16,41] due to their high density. The density of superthermal pickup ions in the inner heliosphere is low so that they do not affect the shock profile.…”

Section: Pickup Ionssupporting

confidence: 73%

“…In the present paper we restrict ourselves to the ion dynamics in the one-dimension and stationary shock structure, leaving the analysis of the effects of the rippling and/or non-stationarity for elsewhere [21,44,49]. Despite these limitations, the ion dynamics is rich, and the macroscopic fields were shown to be responsible for a number of phenomena: ion reflection at the shock front [10,19,46], production of backstreaming ions [22,33], acceleration of pickup ions [1,11,27,50], and formation of the downstream gyrating distributions and magnetic oscillations [5,38,39,43].…”

Section: Introductionmentioning

confidence: 99%

“…Unless there is a substantial superthermal population of ions upstream of the shock [1], the field structure in the shock front (at least at the scales between the electron inertial scale and ion inertial scale) is intimately related to the ion distributions which are formed when the thermal solar wind protons cross the shock. Analyzing only the integral characteristics of these distributions, it is possible, in principle, to find the shock parameters which are not directly measured (like the cross-shock potential).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ion dynamics in quasi-perpendicular collisionless interplanetary shocks: a case study

Gedalin

Droege

2013

Front. Physics

View full text Add to dashboard Cite

Interplanetary shocks are believed to play an important role in the acceleration of charged particles in the heliosphere. While the acceleration to high energies proceeds via the diffusive mechanism at the scales exceeding by far the shock width, the initial stage (injection) should occur at the shock itself. Numerical tracing of ions is done in a model quasi-perpendicular shock front with a typical interplanetary shock parameters (Mach number, upstream ion temperature). The analysis of the distribution of the transmitted solar wind is used to adjust the cross-shock potential which is not directly measured. It is found that, for typical upstream ion temperatures, acceleration of the ions from the tail of the solar wind distribution is unlikely. Pickup ions with a shell distribution are found to be effectively energized and may be injected into further diffusive acceleration regime. Pre-accelerated ions are efficiently upscaled in energies. A part of these ions is returned to the upstream region where they can further be diffusively accelerated.

show abstract

Section: Pickup Ionssupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ion dynamics in quasi-perpendicular collisionless interplanetary shocks: a case study

Gedalin

Droege

2013

Front. Physics

View full text Add to dashboard Cite

show abstract

“…considerations by Ariad and Gedalin [2013] showing that the pickup ion density should be comparable to the thermal ion density at the termination shock if the high-energy tail of the pickup ion distribution is neglected. The upstream pickup ion temperature of 8.6 ± 0.7 MK agrees with the prediction (~9 MK at 90 AU) of the latest three-fluid solar wind model [Usmanov et al, 2014] that includes eddy viscosity and turbulent resistivity but does not include the termination shock.…”

Section: 1002/2015ja021437mentioning

confidence: 99%

“…Recent kinetic simulations [Ariad and Gedalin, 2013] use Liouville mapping of pickup ion test particles in a stationary termination shock structure to find the downstream pickup ion distribution. They came to the conclusion that the contribution of the high-energy tail of pickup ions is negligible at the shock transition, although this population does contribute to decelerating the solar wind upstream of the shock [Florinski et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

Constraining the pickup ion abundance and temperature through the multifluid reconstruction of the Voyager 2 termination shock crossing

et al. 2015

View full text Add to dashboard Cite

Voyager 2 observations revealed that the hot solar wind ions (the so‐called pickup ions) play a dominant role in the thermodynamics of the termination shock and the heliosheath. The number density and temperature of this hot population, however, have remained unknown, since the plasma instrument on board Voyager 2 can only detect the colder thermal ion component. Here we show that due to the multifluid nature of the plasma, the fast magnetosonic mode splits into a low‐frequency fast mode and a high‐frequency fast mode. The coupling between the two fast modes results in a quasi‐stationary nonlinear wave mode, the “oscilliton,” which creates a large‐amplitude trailing wave train downstream of the thermal ion shock. By fitting multifluid shock wave solutions to the shock structure observed by Voyager 2, we are able to constrain both the abundance and the temperature of the undetected pickup ions. In our three‐fluid model, we take into account the nonnegligible partial pressure of suprathermal energetic electrons (0.022–1.5 MeV) observed by the Low‐Energy Charged Particle Experiment instrument on board Voyager 2. The best fitting simulation suggests a pickup ion abundance of 20 ± 3%, an upstream pickup ion temperature of 13.4 ± 2 MK, and a hot electron population with an apparent temperature of ~0.83 MK. We conclude that the actual shock transition is a subcritical dispersive shock wave with low Mach number and high plasma β.

show abstract

In Situ Observations of Interstellar Pickup Ions from 1 au to the Outer Heliosphere

et al. 2022

View full text Add to dashboard Cite

Interstellar pickup ions are an ubiquitous and thermodynamically important component of the solar wind plasma in the heliosphere. These PUIs are born from the ionization of the interstellar neutral gas, consisting of hydrogen, helium, and trace amounts of heavier elements, in the solar wind as the heliosphere moves through the local interstellar medium. As cold interstellar neutral atoms become ionized, they form an energetic ring beam distribution comoving with the solar wind. Subsequent scattering in pitch angle by intrinsic and self-generated turbulence and their advection with the radially expanding solar wind leads to the formation of a filled-shell PUI distribution, whose density and pressure relative to the thermal solar wind ions grows with distance from the Sun.This paper reviews the history of in situ measurements of interstellar PUIs in the heliosphere. Starting with the first detection in the 1980s, interstellar PUIs were identified by their highly nonthermal distribution with a cutoff at twice the solar wind speed. Measurements of the PUI distribution shell cutoff and the He focusing cone, a downwind region of increased density formed by the solar gravity, have helped characterize the properties of the interstellar gas from near-Earth vantage points. The preferential heating of interstellar PUIs compared to the core solar wind has become evident in the existence of suprathermal PUI tails, the nonadiabatic cooling index of the PUI distribution, and PUIs’ mediation of interplanetary shocks. Unlike the Voyager and Pioneer spacecraft, New Horizon’s Solar Wind Around Pluto (SWAP) instrument is taking the only direct measurements of interstellar PUIs in the outer heliosphere, currently out to $\sim47~\text{au}$ ∼ 47 au from the Sun or halfway to the heliospheric termination shock.

show abstract

The role pickup ions play in the termination shock

Cited by 11 publications

References 41 publications

Ion dynamics in quasi-perpendicular collisionless interplanetary shocks: a case study

Ion dynamics in quasi-perpendicular collisionless interplanetary shocks: a case study

Constraining the pickup ion abundance and temperature through the multifluid reconstruction of the Voyager 2 termination shock crossing

In Situ Observations of Interstellar Pickup Ions from 1 au to the Outer Heliosphere

Contact Info

Product

Resources

About