Ultralow Frequency Waves Research Articles

Dayside magnetospheric ULF wave frequency modulated by a solar wind dynamic pressure negative impulse

AbstractUltralow frequency (ULF) waves play an important role in the transport of the solar wind energy to the magnetosphere. In this paper, we present a ULF wave event in the dayside magnetosphere which shows a sudden decrease in frequency from 3.1 to 2.3 mHz around 0756 UT on 11 January 2010, when a solar wind dynamic pressure drop (from ∼5 to ∼2 nPa) was observed simultaneously. The wave exits globally. The phase differences between electric and magnetic fields indicate that the compressional mode wave is standing before and after the wave frequency decrease. This result suggests that the ULF wave should be associated with a cavity mode and the frequency decrease might be induced by the change of the cavity size. A theoretical calculation was made to estimate the cavity mode frequency. The calculated wave frequency before/after the negative impulse is 3.8/2.6 mHz, which is consistent with the observations.

Ultralow frequency wave characteristics extracted from particle data: Application of IGSO observations

Interaction between ultralow frequency (ULF) waves and charged particles plays an important role in the acceleration of particles in the Van Allen radiation belts. The strong wave-particle interaction predicts an energy-dependent observational signature of particle flux variations during different stages of the ULF wave evolution. In this paper, we find that the energetic particle data newly available from an IGSO spacecraft are quite consistent with theoretical predictions, which enables the application of a best-fit procedure to quantitatively extract key parameters of the ULF waves from the particle data. The general agreement between observations and the best-fit results validates the scenario of wave-particle drift resonance within the entire ULF life span, and provides a new technique to understand the ULF wave characteristics in the absence of electromagnetic field data. We also examine the minor differences between observations and the best-fit results, and propose that the differences may result from a longitudinal dependence of the ULF wave power to be considered in a future study.

On the predictive potential of Pc5 ULF waves to forecast relativistic electrons based on their relationships over two solar cycles

AbstractA statistical study of relativistic electron (>2 MeV) fluence derived from geosynchronous satellites and Pc5 ultralow frequency (ULF) wave power computed from a ground magnetic observatory data located in Canada's auroral zone has been carried out. The ground observations were made near the foot points of field lines passing through the GOESs from 1987 to 2009 (cycles 22 and 23). We determine statistical relationships between the two quantities for different phases of a solar cycle and validate these relationships in two different cycles. There is a positive linear relationship between log fluence and log Pc5 power for all solar phases; however, the power law indices vary for different phases of the cycle. High index values existed during the descending phase. The Pearson's cross correlation between electron fluence and Pc5 power indicates fluence enhancement 2–3 days after strong Pc5 wave activity for all solar phases. The lag between the two quantities is shorter for extremely high fluence (due to high Pc5 power), which tends to occur during the declining phases of both cycles. Most occurrences of extremely low fluence were observed during the extended solar minimum of cycle 23. The precursory attribute of Pc5 power with respect to fluence and the enhancement of fluence due to rising Pc5 power both support the notion of an electron acceleration mechanism by Pc5 ULF waves. This precursor behavior establishes the potential of using Pc5 power to predict relativistic electron fluence.

HEART RATE VARIABILITY, VENTRICULAR LATE POTENTIALS AND HEART RATE TURBULENCE AS INDICATORS OF CORONARY REPERFUSION IN ST SEGMENT ELEVATION MYOCARDIAL INFARCTION

Aim. To evaluate the dynamics of the parameters of autonomic balance and electrical instability of the myocardium depending on the effectiveness of the restoration of coronary blood flow in pharmacoinvasive revascularization in patients with acute ST segment elevation myocardial infarction. Material and methods . The study included 91 patients who underwent effective thrombolytic therapy (TLT) according to the ECG criteria, followed by (3-24 hour later) coronary angiography with percutaneous coronary intervention (PCI). Before and after PCI the telemetric ECG recording was conducted. The dynamics of the temporal and spectral characteristics of heart rate variability (HRV), presence of ventricular late potentials (VLP) and abnormal heart rate turbulence (HRT) were evaluated. Results. The episodes of ST-segment re-elevation by1 mm or more, lasting at least 1 min, and the dynamics of some HRV indices indicated the development of rethrombosis after TLT. The increase in the mean square deviation of normal intervals to 82.5 (64.5; 94) ms, the average value of the standard deviations of normal intervals calculated over 5-minute intervals throughout the entire recording to 37.5 (31.5; 47.5) ms, the total power of the spectrum and the power of high frequency waves, as well as the decrease in the power of ultra-low frequency waves were found after PCI in the group with a rethrombosis of the infarct-related coronary artery. The analysis of VLP in this group showed an increase in duration of the filtered QRS complex after TLT (to 128.7±34.5 ms), and the root mean square value of the last 40 ms of the QRS complex after PCI (to 49±50.3 μV). Pathological deviations of the HRT parameters (especially the onset of turbulence) independently on the absolute values were registered more often in patients with rethrombosis, and abnormal values of both HRT parameters were found only in patients with episodes of unstable coronary blood flow. Conclusion. The results are the indirect evidences of disruption of autonomic regulation of cardiac activity and increased arrhythmic readiness of myocardium in developing rethrombosis of coronary artery. The pronounced reperfusion injury of the myocardium evidently plays an important role in this process and is associated with embolization of the vessels of the microcirculatory bed, release of free radicals and alteration of cardiomyocytes, especially due to prolonged ischemia.

2D full-wave simulation of waves in space and tokamak plasmas

Simulation results using a 2D full-wave code (FW2D) for space and NSTX fusion plasmas are presented. The FW2D code solves the cold plasma wave equations using the finite element method. The wave code has been successfully applied to describe low frequency waves in planetary magnetospheres (i.e., dipole geometry) and the results include generation and propagation of externally driven ultra-low frequency waves via mode conversion at Mercury and mode coupling, refraction and reflection of internally driven field-aligned propagating left-handed electromagnetic ion cyclotron (EMIC) waves at Earth. In this paper, global structure of linearly polarized EMIC waves is examined and the result shows such resonant wave modes can be localized near the equatorial plane. We also adopt the FW2D code to tokamak geometry and examine radio frequency (RF) waves in the scape-off layer (SOL) of tokamaks. By adopting the rectangular and limiter boundary, we compare the results with existing AORSA simulations. The FW2D code results for the high harmonic fast wave heating case on NSTX with a rectangular vessel boundary shows excellent agreement with the AORSA code.

Effects of ULF wave power on relativistic radiation belt electrons: 8–9 October 2012 geomagnetic storm

AbstractElectromagnetic ultralow‐frequency (ULF) waves are known to play a substantial role in radial transport, acceleration, and loss of relativistic particles trapped in the Earth's outer radiation belt. Using in situ observations by multiple spacecraft operating in the vicinity of outer radiation belts, we analyze the temporal and spatial behavior of ULF waves throughout the geomagnetic storm of 8–9 October 2012 and compare with the dynamics of relativistic electron fluxes on board the twin Van Allen Probes spacecraft. The analysis shows that the relativistic electron fluxes reduce from their prestorm levels during the first phase of the storm and rapidly increase during the second phase of the storm. We demonstrate that the behavior of ULF wave power changes throughout the storm, from ULF oscillations being a mixture of compressional and shear magnetic components during the first phase of the storm to ULF oscillations being dominated by transverse (shear) components during the second phase. We analyze the parameters of ULF‐driven radial diffusion throughout the storm and compare the observed diffusion coefficients with their statistical averages. We demonstrate that the observed diffusion coefficients are strong enough to impact the redistribution of relativistic electron fluxes from and to the outer boundary of radiation belts and the diffusion might influence the effects of any local electron acceleration by transporting fluxes inward or outward according to phase space density gradients.

Effects of ULF waves on local and global energetic particles: Particle energy and species dependences

AbstractAfter 06:13 UT on 24 August 2005, an interplanetary shock triggers large‐amplitude ultralow‐frequency (ULF) waves (|δB| ≥ 15 nT) in the Pc4–Pc5 wave band (1.6–9 mHz) near the noon geosynchronous orbit (6.6 RE). The local and global effects of ULF waves on energetic particles are observed by five Los Alamos National Laboratory satellites at different magnetic local times. The large‐amplitude ULF waves cause the synchronous oscillations of energetic electrons and protons (≥75 keV) at the noon geosynchronous orbit. When the energetic particles have a negative phase space density radial gradient, they undergo rapid outward radial diffusion and loss in the wave activity region. In the particle drift paths without strong ULF waves, only the rapidly drifting energetic electrons (≥225 keV) display energy‐dispersive oscillations and flux decays, whereas the slowly drifting electrons (<225 keV) and protons (75–400 keV) have no ULF oscillation and loss feature. When the dayside magnetopause is compressed to the geosynchronous orbit, most of energetic electrons and protons are rapidly lost because of open drift trajectories. The global and multicomposition particle measurements demonstrate that the effect of ULF waves on nonlocal particle flux depends on the particle energy and species, whereas magnetopause shadowing effect is independent of the energetic particle species. For the rapidly drifting outer radiation belt particles (≥225 keV), nonlocal particle loss/acceleration processes could also change their fluxes in the entire drift trajectory in the absence of “Dst effect” and substorm injection.

Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes

Abstract. Powerful high-frequency (HF) radio waves can be used to efficiently modify the upper-ionospheric plasmas of the F region. The pressure gradient induced by modulated electron heating at ultralow-frequency (ULF) drives a local oscillating diamagnetic ring current source perpendicular to the ambient magnetic field, which can act as an antenna radiating ULF waves. In this paper, utilizing the HF heating model and the model of ULF wave generation and propagation, we investigate the effects of both the background ionospheric profiles at different latitudes in the daytime and nighttime ionosphere and the modulation frequency on the process of the HF modulated heating and the subsequent generation and propagation of artificial ULF waves. Firstly, based on a relation among the radiation efficiency of the ring current source, the size of the spatial distribution of the modulated electron temperature and the wavelength of ULF waves, we discuss the possibility of the effects of the background ionospheric parameters and the modulation frequency. Then the numerical simulations with both models are performed to demonstrate the prediction. Six different background parameters are used in the simulation, and they are from the International Reference Ionosphere (IRI-2012) model and the neutral atmosphere model (NRLMSISE-00), including the High Frequency Active Auroral Research Program (HAARP; 62.39° N, 145.15° W), Wuhan (30.52° N, 114.32° E) and Jicamarca (11.95° S, 76.87° W) at 02:00 and 14:00 LT. A modulation frequency sweep is also used in the simulation. Finally, by analyzing the numerical results, we come to the following conclusions: in the nighttime ionosphere, the size of the spatial distribution of the modulated electron temperature and the ground magnitude of the magnetic field of ULF wave are larger, while the propagation loss due to Joule heating is smaller compared to the daytime ionosphere; the amplitude of the electron temperature oscillation decreases with latitude in the daytime ionosphere, while it increases with latitude in the nighttime ionosphere; both the electron temperature oscillation amplitude and the ground ULF wave magnitude decreases as the modulation frequency increases; when the electron temperature oscillation is fixed as input, the radiation efficiency of the ring current source is higher in the nighttime ionosphere than in the daytime ionosphere.

Observations of magnetospheric ULF waves in connection with the Kelvin‐Helmholtz instability at Mercury

AbstractThe magnetic field data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is investigated to establish the presence of magnetospheric ultralow frequency (ULF) waves in connection with 131 previously observed nonlinear Kelvin‐Helmholtz (KH) waves at Mercury. Distinct ULF wave signatures are detected in 44 out of the 131 magnetospheric traversals prior to or after observing the KH waves. Of these ULF events, 39 out of 44 are highly coherent at the frequency of maximum power spectral density and occur more often on the dayside magnetosphere than away from it. The waves observed at the dayside magnetosphere, which appear mainly at the duskside and naturally following the KH wave occurrence asymmetry, are significantly different from the eveningside or morningside events and have the following distinct wave characteristics: a polarization mainly in the perpendicular (azimuthal) direction to the mean magnetic field, a wave normal angle closer to the parallel than the perpendicular direction, an absolute ellipticity increasing away from noon, almost exclusively a right‐hand polarization, and frequencies in the narrow range of 0.02–0.04 Hz (well below the local Na+ gyrofrequency and in the same range as the KH waves). The results strongly suggest that the large majority of the ULF waves at the dayside observed in this study are driven by KH waves at the magnetopause and that they occur in the vicinity of a field line resonance, which in turn manifests the importance of the Kelvin‐Helmholtz instability in terms of energy and momentum transport throughout Mercury's magnetosphere.

Propagation of ULF waves from the upstream region to the midnight sector of the inner magnetosphere

AbstractUltralow frequency (ULF) waves generated in the ion foreshock are a well‐known source of Pc3‐Pc4 waves (7–100 mHz) observed in the dayside magnetosphere. We use data acquired on 10 April 2013 by multiple spacecraft to demonstrate that ULF waves of upstream origin can propagate to the midnight sector of the inner magnetosphere. At 1130–1730 UT on the selected day, the two Van Allen Probes spacecraft and the geostationary ETS‐VIII satellite detected compressional 20 to 40 mHz magnetic field oscillations between L ∼ 4 and L ∼ 7 in the midnight sector, along with other spacecraft located closer to noon. Upstream origin of the oscillations is concluded from the wave frequency that matches a theoretical model, globally coherent amplitude modulation, and duskward propagation that is consistent with expected entry of the upstream wave energy through the dawnside flank under the observed interplanetary magnetic field. The oscillations are attributed to magnetohydrodynamic fast‐mode waves based on their propagation velocity of ∼300 km/s and the relationship between the electric and magnetic field perturbations. The magnitude of the azimuthal wave number is estimated to be ∼30. There is no evidence that the oscillations propagated to the ground in the midnight sector.

A statistical survey of ultralow-frequency wave power and polarization in the Hermean magnetosphere.

We present a statistical survey of ultralow‐frequency wave activity within the Hermean magnetosphere using the entire MErcury Surface, Space ENvironment, GEochemistry, and Ranging magnetometer data set. This study is focused upon wave activity with frequencies <0.5 Hz, typically below local ion gyrofrequencies, in order to determine if field line resonances similar to those observed in the terrestrial magnetosphere may be present. Wave activity is mapped to the magnetic equatorial plane of the magnetosphere and to magnetic latitude and local times on Mercury using the KT14 magnetic field model. Wave power mapped to the planetary surface indicates the average location of the polar cap boundary. Compressional wave power is dominant throughout most of the magnetosphere, while azimuthal wave power close to the dayside magnetopause provides evidence that interactions between the magnetosheath and the magnetopause such as the Kelvin‐Helmholtz instability may be driving wave activity. Further evidence of this is found in the average wave polarization: left‐handed polarized waves dominate the dawnside magnetosphere, while right‐handed polarized waves dominate the duskside. A possible field line resonance event is also presented, where a time‐of‐flight calculation is used to provide an estimated local plasma mass density of ∼240 amu cm−3.

Accurately characterizing the importance of wave-particle interactions in radiation belt dynamics: The pitfalls of statistical wave representations.

Wave‐particle interactions play a crucial role in energetic particle dynamics in the Earth's radiation belts. However, the relative importance of different wave modes in these dynamics is poorly understood. Typically, this is assessed during geomagnetic storms using statistically averaged empirical wave models as a function of geomagnetic activity in advanced radiation belt simulations. However, statistical averages poorly characterize extreme events such as geomagnetic storms in that storm‐time ultralow frequency wave power is typically larger than that derived over a solar cycle and Kp is a poor proxy for storm‐time wave power.

Explaining the dynamics of the ultra-relativistic third Van Allen radiation belt

Since the discovery of the Van Allen radiation belts over 50 years ago, an explanation for their complete dynamics has remained elusive. Especially challenging is understanding the recently discovered ultra-relativistic third electron radiation belt. Current theory asserts that loss in the heart of the outer belt, essential to the formation of the third belt, must be controlled by high-frequency plasma wave–particle scattering into the atmosphere, via whistler mode chorus, plasmaspheric hiss, or electromagnetic ion cyclotron waves. However, this has failed to accurately reproduce the third belt. Using a data-driven, time-dependent specification of ultra-low-frequency (ULF) waves we show for the first time how the third radiation belt is established as a simple, elegant consequence of storm-time extremely fast outward ULF wave transport. High-frequency wave–particle scattering loss into the atmosphere is not needed in this case. When rapid ULF wave transport coupled to a dynamic boundary is accurately specified, the sensitive dynamics controlling the enigmatic ultra-relativistic third radiation belt are naturally explained. The appearance of a third radiation belt in the Earth’s Van Allen belts is difficult to explain using existing models for two belts. However, a model based on ultra-low-frequency waves agrees quantitatively with measurements of the third belt.

Calculating ultra-low-frequency wave power of the compressional magnetic field vs. &amp;lt;i&amp;gt;L&amp;lt;/i&amp;gt; and time: multi-spacecraft analysis using the Van Allen probes, THEMIS and GOES

Abstract. Ultra-low-frequency (ULF) pulsations are critical in radial diffusion processes of energetic particles, and the power spectral density (PSD) of these fluctuations is an integral part of the radial diffusion coefficients and of assimilative models of the radiation belts. Using simultaneous measurements from two Geostationary Operational Environmental Satellites (GOES) geosynchronous satellites, three satellites of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft constellation and the two Van Allen probes during a 10-day period of intense geomagnetic activity and ULF pulsations of October 2012, we calculate the PSDs of ULF pulsations at different L shells. By following the time history of measurements at different L it is shown that, during this time, ULF wave power is not enhanced uniformly throughout the magnetosphere but instead is mostly enhanced in the outer L shells, close to the magnetopause, and to a lesser extent in the inner magnetosphere, closer to the plasmapause. Furthermore, by using phase differences between two GOES geosynchronous satellite pairs, we estimate the daily-averaged distribution of power at different azimuthal wave numbers. These results can have significant implications in better defining the effect of radial diffusion in the phase space density of energetic particles for different wave numbers or L shell distributions of ULF power.

Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

Abstract. Hydromagnetic waves, especially those of frequencies in the range of a few millihertz to a few hertz observed in the Earth's magnetosphere, are categorized as ultra low-frequency (ULF) waves or pulsations. They have been extensively studied due to their importance in the interaction with radiation belt particles and in probing the structures of the magnetosphere. We developed an approach to examining the toroidal standing Aflvén waves in a background magnetic field by recasting the wave equation into a Klein–Gordon (KG) form along individual field lines. The eigenvalue solutions to the system are characteristic of a propagation type when the corresponding eigenfrequency is greater than a critical frequency and a decaying type otherwise. We apply the approach to a compressed-dipole magnetic field model of the inner magnetosphere and obtain the spatial profiles of relevant parameters and the spatial wave forms of harmonic oscillations. We further extend the approach to poloidal-mode standing Alfvén waves along field lines. In particular, we present a quantitative comparison with a recent spacecraft observation of a poloidal standing Alfvén wave in the Earth's magnetosphere. Our analysis based on the KG equation yields consistent results which agree with the spacecraft measurements of the wave period and the amplitude ratio between the magnetic field and electric field perturbations.

High spatial resolution radar observations of ultralow frequency waves in the southern polar cap

AbstractWe present an analysis of ultralow frequency (ULF) waves detected in the southern polar cap using the Super Dual Auroral Radar Network (SuperDARN). These waves manifest as quasi‐sinusoidal oscillations in the Doppler velocity, which arise due to the oscillating ULF wave electric field in the F region ionosphere. The event reported in this study occurred during the southern polar winter under quiet geomagnetic conditions. The 1.1–1.3 mHz oscillations were observed throughout the polar cap by the McMurdo, Dome C East, and South Pole Station SuperDARN radars and also by the Dome Concordia and Scott Base magnetometers at corrected geomagnetic latitudes of ∼89°S and ∼80°S, respectively. In contrast to large‐scale toroidal field line resonances observed at auroral latitudes, we find that the magnetic perturbation vector of the polar cap oscillations did not undergo a 90° rotation upon transmission from the ionosphere to the ground and was instead rotated by about 30°. The polar cap oscillations were also accompanied by simultaneous field line resonance (FLR) activity in the dayside auroral zone, in the field of view of the Zhongshan SuperDARN radar. This FLR occurred at the same frequency and exhibited a similar azimuthal phase velocity to the polar cap oscillations, indicating that they may have been driven by the same source mechanism.

Observations of ULF waves on the ground and ionospheric Doppler shifts during storm sudden commencement

AbstractUsing data from ground‐based magnetometers and HF Doppler sounder, we study ultralow frequency (ULF) waves excited during the storm sudden commencement (SSC) on 8 March 2012 and find possible evidence on the link between ULF waves and ionospheric Doppler shifts. Pc1–Pc2 ULF waves are observed from 11:04 to 11:27 UT after the SSC by ground stations of L shell ranging from 1.06 to 2.31, mapping to the topside ionosphere. There are weak responses in this frequency range in the power spectra of ionospheric Doppler shift. From 11:19 to 11:23 UT, oscillations of magnetic field in a lower frequency range of Pc3–Pc4 are observed and are well correlated with the trace of Doppler shift. It is thus suggested that ionospheric Doppler shift can response to ULF oscillations in magnetic field in various frequency ranges, especially in the frequency range of Pc3–Pc4 and below. This paper demonstrates a new mechanism of magnetosphere‐ionosphere coupling.

Charged particle behavior in the growth and damping stages of ultralow frequency waves: Theory and Van Allen Probes observations

AbstractUltralow frequency (ULF) electromagnetic waves in Earth's magnetosphere can accelerate charged particles via a process called drift resonance. In the conventional drift resonance theory, a default assumption is that the wave growth rate is time independent, positive, and extremely small. However, this is not the case for ULF waves in the real magnetosphere. The ULF waves must have experienced an earlier growth stage when their energy was taken from external and/or internal sources, and as time proceeds the waves have to be damped with a negative growth rate. Therefore, a more generalized theory on particle behavior during different stages of ULF wave evolution is required. In this paper, we introduce a time‐dependent imaginary wave frequency to accommodate the growth and damping of the waves in the drift resonance theory, so that the wave‐particle interactions during the entire wave lifespan can be studied. We then predict from the generalized theory particle signatures during different stages of the wave evolution, which are consistent with observations from Van Allen Probes. The more generalized theory, therefore, provides new insights into ULF wave evolution and wave‐particle interactions in the magnetosphere.

Van Allen Probes, THEMIS, GOES, and Cluster observations of EMIC waves, ULF pulsations, and an electron flux dropout

AbstractWe examined an electron flux dropout during the 12–14 November 2012 geomagnetic storm using observations from seven spacecraft: the two Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS)‐A (P5), Cluster 2, and Geostationary Operational Environmental Satellites (GOES) 13, 14, and 15. The electron fluxes for energies greater than 2.0 MeV observed by GOES 13, 14, and 15 at geosynchronous orbit and by the Van Allen Probes remained at or near instrumental background levels for more than 24 h from 12 to 14 November. For energies of 0.8 MeV, the GOES satellites observed two shorter intervals of reduced electron fluxes. The first interval of reduced 0.8 MeV electron fluxes on 12–13 November was associated with an interplanetary shock and a sudden impulse. Cluster, THEMIS, and GOES observed intense He+ electromagnetic ion cyclotron (EMIC) waves from just inside geosynchronous orbit out to the magnetopause across the dayside to the dusk flank. The second interval of reduced 0.8 MeV electron fluxes on 13–14 November was associated with a solar sector boundary crossing and development of a geomagnetic storm with Dst &lt; −100 nT. At the start of the recovery phase, both the 0.8 and 2.0 MeV electron fluxes finally returned to near prestorm values, possibly in response to strong ultralow frequency (ULF) waves observed by the Van Allen Probes near dawn. A combination of adiabatic effects, losses to the magnetopause, scattering by EMIC waves, and acceleration by ULF waves can explain the observed electron behavior.

Interplanetary shocks and foreshocks observed by STEREO during 2007–2010

AbstractInterplanetary shocks in the heliosphere modify the solar wind through which they pass. In particular, shocks play an important role in particle acceleration. During the extended solar minimum (2007–2010) STEREO observed 65 forward shocks driven by stream interactions (SI), with magnetosonic Mach numbers Mms ≈ 1.1–4.0 and shock normal angles ~ 20–87°. We analyze the waves associated with these shocks and find that the region upstream can be permeated by whistler waves (f ~ 1 Hz) and/or ultra low frequency (ULF) waves (f ~ 10−2–10−1 Hz). While whistlers appear to be generated at the shock, the origin of ULF waves is most probably associated with local kinetic ion instabilities. We find that when the Mach number (Mms) is low and the shock is quasi‐perpendicular ( &gt; 45°) whistler waves remain close to the shock. As Mms increases, the shock profile changes and can develop a foot and overshoot associated with ion reflection and gyration. Whistler precursors can be superposed on the foot region, so that some quasi‐perpendicular shocks have characteristics of both subcritical and supercritical shocks. When the shock is quasi‐parallel ( &lt; 45°) a large foreshock with suprathermal ions and waves can form. Upstream, there are whistler trains at higher frequencies whose characteristics can be slightly modified probably by reflected and/or leaked ions and by almost circularly polarized waves at lower frequencies that may be locally generated by ion instabilities. In contrast with planetary bow shocks, most of the upstream waves studied here are mainly transverse and no steepening occurs. Some quasi‐perpendicular shocks (45° &lt; &lt; 60°) are preceded by ULF waves and ion foreshocks. Fluctuations downstream of quasi‐parallel shocks tend to have larger amplitudes than waves in the sheath of quasi‐perpendicular shocks. We compare SI‐driven shock properties with those of shocks generated by interplanetary coronal mass ejections (ICMEs). During the same years, STEREO observed 20 ICME‐driven shocks with Mms ≈ 1.2–4.0 and ~ 38–85°. We find that shocks driven by ICMEs tend to have larger proton foreshocks (dr ~ 0.1 AU) than shocks driven by stream interactions (dr ≤ 0.05 AU). This difference of ion foreshock size should be linked to shock age: ICME‐driven shocks form at shorter distances to the Sun and therefore can energize particles for longer times as they propagate to 1 AU, while stream interaction shocks form closer to Earth's orbit and have been accelerating ions for a shorter interval of time.