A Proton-Cyclotron Wave Storm Generated by Unstable Proton Distribution Functions in the Solar Wind

Wicks, Robert T.; Alexander, Robert; Stevens, Michael L.; Wilson, L. B.; Moya, P. S.; Viñas, A. F.; Jian, L. K.; Roberts, D. A.; O’Modhrain, Sile; Gilbert, Jason A.; Zurbuchen, T. H.

doi:10.3847/0004-637x/819/1/6

Cited by 70 publications

(66 citation statements)

References 39 publications

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“…Finally, we note that experimentally measured distribution functions can be used to predict the fastest growing wave mode and its properties (Gary et al 2016;Jian et al 2016;Wicks et al 2016). Simultaneously observing the predicted waves and their properties using the method presented in this Letter would provide strong evidence for in situ plasma wave generation in the solar wind.…”

Section: Discussionmentioning

confidence: 78%

Experimental Determination of Whistler Wave Dispersion Relation in the Solar Wind

Stansby¹,

Horbury²,

Chen³

et al. 2016

ApJL

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The origins and properties of large-amplitude whistler wavepackets in the solar wind are still unclear. In this Letter, we utilize single spacecraft electric and magnetic field waveform measurements from the ARTEMIS mission to calculate the plasma frame frequency and wavevector of individual wavepackets over multiple intervals. This allows direct comparison of experimental measurements with theoretical dispersion relations to identify the observed waves as whistler waves. The whistlers are right-hand circularly polarized, travel anti-sunward, and are aligned with the background magnetic field. Their dispersion is strongly affected by the local electron parallel beta in agreement with linear theory. The properties measured are consistent with the electron heat flux instability acting in the solar wind to generate these waves.

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Section: Discussionmentioning

confidence: 78%

Experimental Determination of Whistler Wave Dispersion Relation in the Solar Wind

Stansby¹,

Horbury²,

Chen³

et al. 2016

ApJL

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“…Analysis of the upper hybrid line via the technique of quasi-thermal noise spectroscopy (Meyer-Vernet & Perche 1989) yields an accurate measurement of n e unaffected by spacecraft potential. The unbiased value of n e measured by TNR is used to validate and refine the spacecraft potential correction, improving accuracy of the electron moments.The study is limited to data derived from velocity moments of the entire species over the observed energy ranges, e.g., we do not separate the electron data into the core, halo, or strahl components (e.g., Bale et al 2013;Pulupa et al 2014a;Horaites et al 2018) nor do we account for secondary proton beam contributions (e.g., Wicks et al 2016). We also do not separate the distributions by fast or slow solar wind speeds, as this will be addressed in detail in a future study that will also examine the subcomponents of each species (e.g., C. S. Salem et al 2018, in preparation).…”

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confidence: 99%

The Statistical Properties of Solar Wind Temperature Parameters Near 1 au

Wilson

Stevens

Kasper

et al. 2018

ApJS

118

103

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We present a long-duration (∼10 yr) statistical analysis of the temperatures, plasma betas, and temperature ratios for the electron, proton, and alpha-particle populations observed by the Wind spacecraft near 1 au. The mean (median) scalar temperatures are T e,tot = 12.2(11.9) eV, T p,tot = 12.7(8.6) eV, and T α,tot = 23.9(10.8) eV. The mean (median) total plasma betas are β e,tot = 2.31(1.09), β p,tot = 1.79(1.05), and β α,tot = 0.17(0.05). The mean(median) temperature ratios are (T e /T p ) tot = 1.64(1.27), (T e /T α ) tot = 1.24(0.82), and (T α /T p ) tot = 2.50(1.94). We also examined these parameters during time intervals that exclude interplanetary (IP) shocks, times within the magnetic obstacles (MOs) of interplanetary coronal mass ejections (ICMEs), and times that exclude MOs. The only times that show significant alterations to any of the parameters examined are those during MOs. In fact, the only parameter that does not show a significant change during MOs is the electron temperature. Although each parameter shows a broad range of values, the vast majority are near the median. We also compute particle-particle collision rates and compare to effective wave-particle collision rates. We find that, for reasonable assumptions of wave amplitude and occurrence rates, the effect of wave-particle interactions on the plasma is equal to or greater than the effect of Coulomb collisions. Thus, wave-particle interactions should not be neglected when modeling the solar wind.Key words: plasmas -shock waves -solar wind -Sun: coronal mass ejections (CMEs)Supporting material: tar.gz file Background and MotivationUnderstanding the relationship between various macroscopic parameters for the different species of a gas is critical for understanding the evolution and dynamics of said gas. A gas in thermodynamic equilibrium exhibits equal temperatures between all constituent species, i.e., (T s′ /T s ) tot = 1 for s′ ¹ s (see Appendix A for further details and parameter/symbol definitions) and does not allow for heat flow. The phase-space distributions for the constituents of a gas in thermodynamic equilibrium are isotropic, they exhibit no skewness (i.e., heat flux), and they are centered at the same bulk flow velocity. A subtle contrast exists for thermal equilibrium where one still maintains (T s′ /T s ) tot = 1 for s′ ¹ s but this does not require isotropic or uniformly flowing velocity distributions, e.g., one can have heat fluxes or counter-streaming populations (e.g., Hoover 1986; Evans & Morriss 1990). A non-equilibrium gas can exhibit (T s′ /T s ) tot ¹ 1, among other departures from a maximal entropy state. If the temperatures are mass-proportional, i.e., uniform thermal speeds, then the species can be said to have the same velocity distribution (e.g., Ogilvie & Wilkerson 1969).Generally, a gas requires some form of irreversible energy dissipation and transfer between species to reach thermodynamic equilibrium. In the Earth's atmosphere, the primary mechanism is binary particle collisions (e.g., Petschek 1958...

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“…The automatic detection is carried out through dividing the long time series of solar wind magnetic fields into consecutive and overlapping time segments. Following the study by Zhao, Chu et al (), the sliding time segment is chosen to be 100 s with an overlap of 80 s, providing a frequency resolution of 0.01 Hz and a time resolution of 20 s. During the detection process for each segment, the magnetic field is first converted into a field‐aligned coordinate system with the z direction along the ambient magnetic field (i.e., an average field over the period of the segment) and the x ( y ) direction perpendicular (Gao et al, ; Wicks et al, ). Each time segment is filtered by a Hamming window to reduce edge effects (Bortnik et al, ).…”

Section: Data and Analysis Methodsmentioning

confidence: 99%

“…In recent years, a series of works were devoted to studies of ECWs concerning their observation, generation, and propagation (Boardsen et al, ; Jian et al, , , ; Omidi, Isenberg et al, ; Omidi, Russell et al, ; Wicks et al, ). Some results imply that (1) ECWs occur extensively and discretely in the solar wind, and (2) some wave characteristics depend on the heliocentric radial distance.…”

Section: Introductionmentioning

confidence: 99%

Statistical Study of Low‐Frequency Electromagnetic Cyclotron Waves in the Solar Wind at 1 AU

Zhao

Feng

et al. 2018

JGR Space Physics

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Electromagnetic cyclotron waves (ECWs) near the proton cyclotron frequency are common wave activities in the solar wind and have attracted much attention in recent years. This paper investigates 82,809 ECWs based on magnetic field data from the Solar Terrestrial Relations Observatory‐A mission between 2007 and 2013. Results show that ECWs may last for just a few seconds or incessantly for several tens of minutes. The time fraction of ECW storms among all solar wind is about 0.9%; the storms are obtained with the duration threshold of 10 min, amplitude criterion of 0.032 nT, and time separation limit of 3 min for combination of intermittent ECWs. Most of ECWs have their amplitudes less than 1 nT, while some ECWs have large amplitudes comparable to the ambient magnetic field. The distributions of the durations and amplitudes of these ECWs are characterized by power law spectra, respectively, with spectrum indexes around 4. Statistically, there seems to be a tendency that ECWs with a longer duration will have a larger amplitude. Observed ECW properties are time dependent, and the median frequency of left‐hand ECWs can be lower than that of right‐hand ECWs in some months in the spacecraft frame. The percentage of left‐hand ECWs varies in a large range with respect to months; it is much low (26%) in a month, though it frequently exceeds 50% in other months. Characteristics of ECWs with concurrent polarizations are also researched. The present study should be of importance for a more complete picture of ECWs in the solar wind.

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A Proton-Cyclotron Wave Storm Generated by Unstable Proton Distribution Functions in the Solar Wind

Cited by 70 publications

References 39 publications

Experimental Determination of Whistler Wave Dispersion Relation in the Solar Wind

Experimental Determination of Whistler Wave Dispersion Relation in the Solar Wind

The Statistical Properties of Solar Wind Temperature Parameters Near 1 au

Statistical Study of Low‐Frequency Electromagnetic Cyclotron Waves in the Solar Wind at 1 AU

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