Wind/SWE observations of firehose constraint on solar wind proton temperature anisotropy

Kasper, J. C.; Lazarus, A. J.; Gary, S. Peter

doi:10.1029/2002gl015128

Cited by 289 publications

(357 citation statements)

References 14 publications

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“…In a poor-collisional plasma, these instabilities provide a plausible mechanism to prevent the development of excessive anisotropies and ensure a more fluid-like behavior Stverak et al 2008). Moreover, the electromagnetic wave turbulence leads to acceleration and pitch-angle scattering and diffusion, and must therefore play an important role in the evolution of plasma particles in the solar wind and the magnetosphere (Dröge 2003;Schlickeiser et al 2010;Pierrard et al 2011) Measurements of the plasma parameters at high altitudes in the solar wind ( < ∼ 1 AU) closely agree with theoretical and numerical predictions (Gary et al 1976;Quest & Shapiro 1996;Gary et al 1998;Hellinger & Matsumoto 2000;Matteini et al 2006) showing that any increase in the parallel proton temperature is constrained by the proton firehose instability (PFHI) (Kasper et al 2002;Hellinger et al 2006;Bale et al 2009). This instability is driven by an excess of the parallel kinetic energy, i.e.…”

Section: Introductionsupporting

confidence: 61%

Proton firehose instability in bi-Kappa distributed plasmas

Lazar

Poedts

Schlickeiser

2011

A&A

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Context. Protons or heavier ions with anisotropic velocity distributions and non-thermal departure from Maxwellian, are frequently reported in the magnetosphere and at different altitudes in the solar wind. These observations are sustained by an extended number of mechanisms of acceleration in any direction with respect to the interplanetary magnetic field. However, the observed anisotropy is not large and most probably constrained by the kinetic instabilities.Aims. An excess of parallel kinetic energy, T /T ⊥ > 1 (where and ⊥ denote directions relative to the background magnetic field) drives a proton firehose mode to grow, limiting any further increase in the anisotropy according to the observations. The effects of suprathermal populations on the principal characteristics of the proton firehose instability are investigated. Methods. For low-collisional plasmas, the dispersion approach is based on the fundamental kinetic Vlasov-Maxwell equations. The anisotropy of plasma distributions including suprathermal populations is modeled by bi-Kappa functions, and the new dispersion relations are derived in terms of the modified plasma dispersion function (for Kappa distributions), and analytical approximations of this function. Results. Growth rates of the proton firehose solutions and threshold conditions are provided in analytical forms for different plasma regimes. The proton firehose instability needs a larger anisotropy and a larger parameter β to occur in a Kappa-distributed plasma. A precise numerical evaluation shows that the growth rates are, in general, lower and the wave frequency is only slightly affected, but the influence of suprathermal populations is essentially dependent on both the proton and electron anisotropies. Departures from the standard dispersion of a Maxwellian plasma can eventually be used to evaluate the presence of suprathermal populations in solar flares and the magnetosphere.

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Section: Introductionsupporting

confidence: 61%

Proton firehose instability in bi-Kappa distributed plasmas

Lazar

Poedts

Schlickeiser

2011

A&A

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“…First, there may be a sufficient level of power in Alfvénic fluctuations in the solar wind to sustain this mode of heating [23,24]. Second, ion-cyclotron resonance could explain the large temperature anisotropies [2,8,25] and growing magnetic moments seen with distance from the Sun [26]. Finally, we propose that of the theories listed, only the ion-cyclotron mechanism is consistent with the precise relations between ion heating and plasma conditions reported herein.…”

supporting

confidence: 65%

“…3, which shows the H + temperature anisotropy factor, T ⊥p /T p , as a function of δv αp and β p . On average, in the solar wind at 1 AU, T ⊥p /T p ≈ 0.8, and it is generally less than unity [25]. Fig.…”

Section: Figmentioning

confidence: 99%

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

et al. 2013

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Plasma carrying a spectrum of counter-propagating field-aligned ion-cyclotron waves can strongly and preferentially heat ions through a stochastic Fermi mechanism. Such a process has been proposed to explain the extreme temperatures, temperature anisotropies, and speeds of ions in the solar corona and solar wind. We quantify how differential flow between ion species results in a Doppler shift in the wave spectrum that can prevent this strong heating. Two critical values of differential flow are derived for strong heating of the core and tail of a given ion distribution function. Our comparison of these predictions to observations from the Wind spacecraft reveals excellent agreement. Solar wind helium that meets the condition for strong core heating is nearly seven times hotter than hydrogen on average. Ion-cyclotron resonance contributes to heating in the solar wind, and there is a close link between heating, differential flow, and temperature anisotropy. Introduction.-The solar corona and solar wind are so tenuous that wave-particle interactions can dominate over fluid or collisional processes, resulting in highly nonthermal plasma as seen by spacecraft in interplanetary space. Heavier ions escape from the Sun at higher speeds than the ionized hydrogen (H + ) that dominates the solar wind. Within a given solar wind stream, different species flow through one another at speeds of up to several hundred km s −1 [1,2]. This differential flow appears to be stable as long as it is aligned with the local magnetic field B and below the Alfvén wave speed C A [3,4]. Heavier ions are also often much hotter than H + , with temperatures reaching and often exceeding mass proportionality [5][6][7][8]. These non-thermal properties can be used to identify the role wave-particle interactions play in heating the corona and solar wind [9][10][11]. If we can understand the underlying physics, we will be able to predict the relative heating of ions and electrons in the solar wind, the corona and other magnetized plasmas.

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“…The panel on the left shows the observed distribution at 1 AU of three million measurements as a function of proton temperature anisotropy R p and proton parallel plasma beta β ||p . The range in R p accessible to the solar wind is limited by the onset of the mirror, cyclotron, and firehose instabilities, which grow increasingly sharp as β ||p increases (Kasper et al 2002(Kasper et al , 2003. The image on the right shows the average value of T p , indicating that the plasma is heated anisotropically to bring it near the instability thresholds (Maruca et al 2011).…”

Section: Heating the Corona And Solar Windmentioning

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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Wind/SWE observations of firehose constraint on solar wind proton temperature anisotropy

Cited by 289 publications

References 14 publications

Proton firehose instability in bi-Kappa distributed plasmas

Proton firehose instability in bi-Kappa distributed plasmas

Sensitive Test for Ion-Cyclotron Resonant Heating in the Solar Wind

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

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