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We describe results from the first statistical study of waveform capture data during 67 interplanetary (IP) shocks with Mach numbers ranging from approximately 1-6. Most of the waveform captures and nearly 100% of the large amplitude waves were in the ramp region. Although solitary waves, Langmuir waves, and ion acoustic waves (IAWs) are all observed in the ramp region of the IP shocks, large amplitude IAWs dominate. The wave amplitude is correlated with the fast mode Mach number and with the shock strength. The observed waves produced anomalous resistivities from approximately 1-856 Omega.m (approximately 10(7) times greater than classical estimates.) The results are consistent with theory suggesting IAWs provide the primary dissipation for low Mach number shocks.

[1] We present observations of low-frequency waves (0.25 Hz < f < 10 Hz) at five quasi-perpendicular interplanetary (IP) shocks observed by the Wind spacecraft. Four of the five IP shocks had oblique precursor whistler waves propagating at angles with respect to the magnetic field of 20°-50°and large propagation angles with respect to the shock normal; thus they do not appear to be phase standing. One event, the strongest in our study and likely supercritical, had low-frequency waves consistent with steepened magnetosonic waves called shocklets. The shocklets are seen in association with diffuse ion distributions. Both the shocklets and precursor whistlers are often seen simultaneously with anisotropic electron distributions unstable to the whistler heat flux instability. The IP shock with upstream shocklets showed much stronger electron heating across the shock ramp than the four events without upstream shocklets. These results may offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

[1] We present observations of electromagnetic precursor waves, identified as whistler mode waves, at supercritical interplanetary shocks using the Wind search coil magnetometer. The precursors propagate obliquely with respect to the local magnetic field, shock normal vector, solar wind velocity, and they are not phase standing structures. All are right-hand polarized with respect to the magnetic field (spacecraft frame), and all but one are right-hand polarized with respect to the shock normal vector in the normal incidence frame. They have rest frame frequencies f ci < f ≪ f ce and wave numbers 0.02 ≲ kr ce ≲ 5.0. Particle distributions show signatures of specularly reflected gyrating ions, which may be a source of free energy for the observed modes. In one event, we simultaneously observe perpendicular ion heating and parallel electron acceleration, consistent with wave heating/acceleration due to these waves. Although the precursors can have dB/B o as large as 2, fluxgate magnetometer measurements show relatively laminar shock transitions in three of the four events.

Key Points:• Microscopic wave-particle interactions can regulate macroscopic shock structure • High-frequency large-amplitude waves are ubiquitous in collisionless shocks • Wave-particle interactions are the end result of nearly all dissipation pathways AbstractWe present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collisionless bow shock using data from the Time History of Events and Macroscale Interactions during Substorms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collisionless shocks. In every bow shock crossing examined, we observed both low-frequency (<10 Hz) and high-frequency (≳10 Hz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding B ∼ 10 nT and E ∼ 300 mV/m, though more typical values were B ∼ 0.1-1.0 nT and E ∼ 10-50 mV/m; (2) Poynting fluxes in excess of 2000 μW m −2 (typical values were ∼ 1-10 μW m −2 ); (3) resistivities > 9000 Ω m; and (4) associated energy dissipation rates > 10 μW m −3 . The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for ∼90% of the wave burst durations. For ∼22% of these times, the wave-particle interactions needed to only be ≤ 0.1% efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave-particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collisionless shocks.

[1] We present the first observations at an interplanetary shock of large-amplitude (> 100 mV/m pk-pk) solitary waves and large-amplitude (∼30 mV/m pk-pk) waves exhibiting characteristics consistent with electron Bernstein waves. The Bernstein-like waves show enhanced power at integer and half-integer harmonics of the cyclotron frequency with a broadened power spectrum at higher frequencies, consistent with the electron cyclotron drift instability. The Bernstein-like waves are obliquely polarized with respect to the magnetic field but parallel to the shock normal direction. Strong particle heating is observed in both the electrons and ions. The observed heating and waveforms are likely due to instabilities driven by the free energy provided by reflected ions at this supercritical interplanetary shock. These results offer new insights into collisionless shock dissipation and wave-particle interactions in the solar wind.

[1] We present results of a study of the characteristics of very large amplitude whistler mode waves inside the terrestrial magnetosphere at radial distances of less than 15 R E using waveform capture data from the Wind spacecraft. We observed 247 whistler mode waves with at least one electric field component (105/247 had ≥80 mV/m peak-to-peak amplitudes) and 66 whistler mode waves with at least one search coil magnetic field component (38/66 had ≥0.8 nT peak-to-peak amplitudes). Wave vectors determined from events with three magnetic field components indicate that 30/46 propagate within 20°of the ambient magnetic field, though some are more oblique (up to ∼50°). No relationship was observed between wave normal angle and GSM latitude. 162/247 of the large amplitude whistler mode waves were observed during magnetically active periods (AE > 200 nT). 217 out of 247 total whistler mode waves examined were observed inside the radiation belts. We present a waveform capture with the largest whistler wave magnetic field amplitude (^8 nT peak-to-peak) ever reported in the radiation belts. The estimated Poynting flux magnitude associated with this wave is^300 mW/m 2 , roughly four orders of magnitude above estimates from previous satellite measurements. Such large Poynting flux values are consistent with rapid energization of electrons. Citation: Wilson, L. B., III,

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...