The Common Spectrum for Accelerated Ions in the Quiet-Time Solar Wind

Fisk, L. A.; Gloeckler, G.

doi:10.1086/503293

Cited by 216 publications

(211 citation statements)

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“…Close to the Sun, where pickup ion intensities are low and contamination therefore minimized, SPP may be able to discover the energization mechanism for the suprathermal tails. Two competing acceleration possibilities are (a) resonant statistical acceleration by waves, including quasi-linear 2nd order Fermi acceleration and transit-time damping (Fisk et al 1974;Miller 1998), and (b) non-resonant stochastic acceleration by turbulent fluid compressions and rarefactions (Ptuskin 1988;Webb et al 2003;Le Roux et al 2002;Cho and Lazarian 2006;Fisk and Gloeckler 2006). Key measurements by SWEAP will include (i) suprathermal ion spectra; (ii) wave modes, density, and velocity vectors, amplitudes and polarization properties, and correlating with magnetic field observations; (iii) plasma turbulence, power spectra (up to the dissipation range of frequencies greater than the proton gyro-frequency, ∼ tens of Hz at ∼ 20R s ), the outer scale, wavevectors (slab/2D), cross-correlations between velocity and density, structure functions, helicity and cross-helicity (Roberts et al 1987;Bavassano et al 2000), and (iv) the radial evolution of turbulent power and relevant length scales (Zhou and Matthaeus 1990;Zank et al 1996) and identification of driving mechanisms (fast/slow stream interactions, shear, and compressions).…”

Section: (3) Determine If Stochastic In Situ Acceleration and Energetmentioning

confidence: 99%

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

et al. 2015

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The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on SolarProbe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.

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Section: (3) Determine If Stochastic In Situ Acceleration and Energetmentioning

confidence: 99%

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

et al. 2015

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“…On the basis of these observations, Fisk and Gloeckler [2006] argued that there is a universal k $ 1.5 suprathermal tail of hydrogen ions which persists throughout the solar wind above 2 to 3 times v sw ($1 keV). In practice the energy range and resolution has a significant influence on the functional fit.…”

Section: Introductionmentioning

confidence: 99%

Implications of solar wind suprathermal tails for IBEX ENA images of the heliosheath

et al. 2008

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[1] Decades of interplanetary measurements of the solar wind and other space plasmas have established that the suprathermal ion intensity distributions (j) are non-Maxwellian and are characterized by high-energy power law tails (j $ E Àk ). Recent analysis by Fisk and Gloeckler of suprathermal ion observations between 1-5 AU demonstrates that a particular differential intensity distribution function emerges universally between $2-10 times the solar wind speed with k $ 1.5. This power law tail is particularly apparent in downstream distributions beyond reverse shocks associated with corotating interaction regions. Similar power law tails have been observed in the downstream flow beyond the termination shock by the Low Energy Charged Particle instrument on both Voyager 1 and Voyager 2. Using kappa distributions with internal energy, density, and bulk flow derived from large-scale magnetohydrodynamic models, we calculate the simulated flux of energetic neutral atoms (ENAs) produced in the heliosheath by charge exchange between solar wind protons and interstellar hydrogen. We then produce simulated ENA maps of the heliosheath, such as will be measured by the Interstellar Boundary Explorer Mission (IBEX). We also estimate the expected signal to noise and background ratio for IBEX. The solar wind suprathermal tail significantly increases the ENA flux within the IBEX energy range, $0.01-6 keV, by more than an order of magnitude at the highest energies over the estimates using a Maxwellian. It is therefore essential to consider suprathermal tails in the interpretation of IBEX ENA images and theoretical modeling of the heliospheric termination shock.

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“…(39) except for the diffusion term, would deliver as a result of the transport equation the distribution f ∼ v −α . This distribution thus should evidently be much flatter than the obviously observed distribution f ∼ v −5 (Fisk & Gloeckler 2006) indicating that energy diffusion in fact plays an inferior role.…”

Section: The Relative Effectiveness Of Energy Diffusion and Convectivmentioning

confidence: 80%

“…First we discuss the argument given by Fisk & Gloeckler (2006, 2007 that PUIs under resonant interaction with ambient compressive turbulences enter a quasi-equilibrium state with saturated powerlaw distributions of a somehow sacrosanct spectral velocity index of γ v = −5. The related, well-known Kolmogorov formalism is based on a "dimensional" reasoning: The problem concerning the energy distribution in eddies of a typical wave number k is considered using two different dimensional quantities: namely the spectral energy density E k and the wave number k. The spectral energy flux is then defined by…”

Section: Can Power-law Ion Distributions Be In Equilibrium With Hydromentioning

confidence: 99%

“…To determine v ∞ we follow the idea presented by Fisk & Gloeckler (2006, 2007 assuming that PUI-power-law distributions result from a specific quasi-equilibrium state self-establishing such that the wave field transfers per unit of time as much energy to PUIs by energy diffusion, as energy is expended in the solar wind frame for the work done by the pressure gradient of comoving PUIs against the magnetosonic fluctuations. The important restriction to energy diffusion by nonlinear interaction with the compressive fluctuations is that the typical diffusion period τ diff 3L 2 m /vλ should be much larger than the convection period given by τ conv L m /U (see Chalov et al 2003).…”

Section: Determination Of the Inner And Outer Velocity Bordermentioning

confidence: 99%

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Injection to the pick-up ion regime from high energies and induced ion power-laws

Fahr

Чашей

Verscharen

2009

A&A

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Though pick-up ions (PUIs) are a well-known phenomenon in the inner heliosphere, their phase-space distribution nevertheless is a theoretically unsettled problem. Especially the question of how PUIs form their suprathermal tails, extending to far above their injection energies, still now is unsatisfactorily answered. Though Fermi-2 velocity diffusion theories have revealed that such tails are populated, they nevertheless show that resulting population densities are much less than seen in observations showing power-laws with a velocity index of "−5". We first investigate here, whether or not observationally suggested power-laws can be the result of a quasi-equilibrium state between suprathermal ions and magnetohydrodynamic turbulences in energy exchange with each other. We demonstrate that such an equilibrium cannot be established, since it would require too high PUI pressures enforcing a shock-free deceleration of the solar wind. We furthermore show that Fermi-2 type energy diffusion in the outer heliosphere is too inefficient to determine the shape of the distribution function there. As we can show, however, power-laws beyond the injection threshold can be established, if the injection takes place at higher energies of the order of 100 keV. As we demonstrate here, such an injection is connected with modulated anomalous cosmic ray (ACR) particles at the lower end of their spectrum when they again start being convected outwards with the solar wind. Therefore, we refer to these particles as ACR-PUIs. In our quantitative calculation of the PUI spectrum resulting under such conditions we in fact find again power-laws, however with a velocity-power index of "−4" and fairly distance-independent spectral intensities. As it seems these facts are observationally well supported by VOYAGER measurements in the lowest energy channels.

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The Common Spectrum for Accelerated Ions in the Quiet-Time Solar Wind

Cited by 216 publications

References 10 publications

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

Implications of solar wind suprathermal tails for IBEX ENA images of the heliosheath

Injection to the pick-up ion regime from high energies and induced ion power-laws

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