ULF Range Research Articles

Anomalous Geomagnetic Signal Emphasized before the Mw8.2 Coastal Alaska Earthquake, Occurred on 29 July 2021.

A very strong earthquake of magnitude Mw8.2 struck the coastal zone of Alaska (USA), on 29 July 2021. This earthquake was felt around the Gulf of Alaska, on a wide offshore area belonging to USA and Canada. In order to identify an anomalous geomagnetic signal before the onset of this earthquake, we retrospectively analyze the data collected on the interval 17 June–31 July 2021, via internet, at the two geomagnetic observatories, College (CMO)—Alaska and Newport (NEW)—USA, by using the polarization parameter (BPOL) and the strain effect related to geomagnetic signal identification. Thus, for both observation sites (CMO and NEW), the daily mean distribution of the BPOL and its standard deviation (STDEV) are carried out using an FFT band-pass filtering in the ULF range (0.001–0.0083 Hz). Further on, a statistical analysis based on a standardized random variable equation is applied to emphasize the following: (a) the anomalous signature related to Mw8.2 earthquake on the both time series BPOL*(CMO) and BPOL*(NEW); (b) the differentiation of the transient local anomalies associated with Mw8.2 earthquake from the internal and external parts of the geomagnetic field, taking the NEW observatory as reference. Finally, on the BPOL*(NEW-CMO) time series, carried out on the interval 7–31 July 2021, a very clear anomaly of maximum, greater than 1.2 STDEV, was detected on 22 July, with 7 days before the onset of the Mw8.2 earthquake.

ОБЗОР ЭЛЕКТРОМАГНИТНЫХ МОНИТОРИНГОВЫХ ИССЛЕДОВАНИЙ В ПРОГНОЗЕ ЗЕМЛЕТРЯСЕНИЙ: ПОСЛЕДНИЕ РЕЗУЛЬТАТЫ И НОВЫЕ ПЕРСПЕКТИВЫ

In order to make comparisons and find new perspectives in terms of electromagnetic phenomena in earthquake prediction, ULF range was chosen. For comparison, tables consisting of the results of studies from previous years and the last 10 years have been compiled. In order to find new perspectives, the graphs were drawn and comparative analysis was carried out on the basis of these results. It was concluded that the ULF precursors can be found before earthquakes reaching up to 30 km in depth, and it can be considered a promising effective range in detecting precursors of earthquakes. In addition, due to the connection between the epicenter distances and the depths of the earthquakes and their magnitudes, attempts to detect the precursors have been made so that the epicenter of the earthquakes is ±100km. The article also provides information about ULF networks and about researchers who had critical opinions on electromagnetic phenomena associated with earthquakes.

Effectiveness of electromagnetic monitoring in studying earthquakes

Numerous researches conducted in connection with the study of earthquakes have shown that electromagnetic monitoring studies have led to some important results. From the Loma Prieta earthquake to the Guam earthquake, electromagnetic monitoring studies led to significant results. Since then, there have been numerous reports of possible elect-romagnetic precursors to earthquakes, some of which have involved frequencies covered by ELF/VLF (10—32 kHz) monitoring system Fraser-Smith et al. [1990]. Sometime later, they retrieved and started processing their ULF data. They had less reason to expect electromagnetic precursors in this latter data, because previous reports of precursory signals at frequencies below the ELF/VLF range have, with few exceptions, involved frequencies either below or predominantly below their ULF range (0.01—10 Hz) of operation. They found out that ELF/VLF data do not appear to show precursory activity, whereas ULF data contain a number of anomalous features that may prove to be earthquake precursors. The lack of observation of precursory ELF/VLF noise so close to the epicenters of several mode-rate to moderately-large earthquakes showed that ELF/VLF noise need not be a strong or obvious feature of every earthquake, as Fraser-Smith et al. [1990] reported in their paper.
 At present, numerous studies have been conducted in this area and researches are being improved. From my experience as a young researcher, it became clear that electromagnetic monitoring research is necessary, and that more important and significant results can be achieved if continuous research is conducted in a certain area. Thus, these studies may play a significant role in the detection of earthquake precursors.

Ультранизкочастотные эмиссии диапазона 0.1–3 Гц в приполярных областях

We examine the characteristics of oscillations of two types in the high-frequency edge of the ULF range (0.1–3 Hz), serpentine emission (SE), and discrete frequency dispersed signals (DS). Oscillations of both the types are observed in the polar caps exclusively with induction magnetometers. Since these instruments are currently practically absent at high latitudes, the analysis has been carried out from records obtained at the stations Vostok and Thule close to the geomagnetic poles in 1968–1971. The DS occurrence rate is shown to have a sharp peak at local magnetic noon. This fact indicates that DS emergence is rigidly tied to the geomagnetic field line passing through the observation station. At the same time, the seasonal variation in the frequency of DS occurrence has a main peak in local summer and an additional peak in local winter. We have revealed before that at least a part of DS is excited in the foreshock region. Taking this into account, we can assume that the wave packets incident to the magnetopause fall on the external field lines mainly in the noon region and propagate along these lines in both directions, eventually reaching Earth’s surface in the polar regions. Unlike DS, the SE occurrence rate has neither a daily nor a seasonal variation. We have tested and confirmed indirectly the hypothesis put forward earlier about the excitation of SE by cyclotron instability of protons in the solar wind, simulating frequency variations in ion-cyclotron waves at different levels of interplanetary plasma perturbation and comparing the results with the SE frequency variations observed under similar conditions. We conclude that it is necessary to resume continuous observations of ULF emissions, using induction magnetometers installed in polar caps near the projections of cusps and near geomagnetic poles.

ULTRA LOW FREQUENCY EMISSIONS RANGING FROM 0.1 TO 3 Hz IN CIRCUMPOLAR AREAS

We examine the characteristics of oscillations of two types in the high-frequency edge of the ULF range (0.1–3 Hz), serpentine emission (SE), and discrete frequency dispersed signals (DS). Oscillations of both the types are observed in the polar caps exclusively with induction magnetometers. Since these instruments are currently practically absent at high latitudes, the analysis has been carried out from records obtained at the stations Vostok and Thule close to the geomagnetic poles in 1968–1971. The DS occurrence rate is shown to have a sharp peak at local magnetic noon. This fact indicates that DS emergence is rigidly tied to the geomagnetic field line passing through the observation station. At the same time, the seasonal variation in the frequency of DS occurrence has a main peak in local summer and an additional peak in local winter. We have revealed before that at least a part of DS is excited in the foreshock region. Taking this into account, we can assume that the wave packets incident to the magnetopause fall on the external field lines mainly in the noon region and propagate along these lines in both directions, eventually reaching Earth’s surface in the polar regions. Unlike DS, the SE occurrence rate has neither a daily nor a seasonal variation. We have tested and confirmed indirectly the hypothesis put forward earlier about the excitation of SE by cyclotron instability of protons in the solar wind, simulating frequency variations in ion-cyclotron waves at different levels of interplanetary plasma perturbation and comparing the results with the SE frequency variations observed under similar conditions. We conclude that it is necessary to resume continuous observations of ULF emissions, using induction magnetometers installed in polar caps near the projections of cusps and near geomagnetic poles.

Algorithm for modeling electromagnetic channel of seismo-ionospheric coupling (SIC) and the variations in the electron concentration

We present in detail the algorithm of the electrostatic–quasi-stationary–electromagnetic/MHD approximations and equivalent external sources (EQUEMES method) to develop the quasi-stationary–electromagnetic models of seismo-ionospheric coupling. The penetration of the electromagnetic field created by near-Earth alternative currents of ULF range was simulated by solving equations for the horizontal electric field components Ex, Ey of the second order with respect to the vertical coordinate z. This system of two second-order equations is derived from the system of Maxwell equations. The penetration of rather strong horizontal electric field [of order of (1–10) mV/m] to the ionospheric E and F layers has been modeled. The corresponding variations in the electron concentration in the E and lower F layers of the ionosphere reach a value of order of (1–10)%. Farther increase in these variations can be connected with the related synergetic processes. A possibility of the effective initiation of electron concentration perturbations in the unstable near-equatorial plasma in the F layer of the ionosphere by the packet of atmospheric gravity waves radiated by the near-ground source is illustrated. A good correspondence of the results obtained on the basis of this model to the data of satellite observations is shown.

The structure of equidistant-frequency groups in the oscillation spectra of the dayside magnetosphere

The structure of natural signals (geomagnetic field disturbances in the ULF range registered at Mondy and Borok observatories) is studied for the first time by means of the APCF (amplitude and phase correlation function) method, unrelated to spectral analysis but based on analysing a specially constructed correlation function of the amplitude and phase fluctuations in the recorded signal. This method can detect the presence of a group of equidistant frequencies in the spectrum of the original signal as well as measuring the difference, Δf, of two adjacent frequencies in the group. The end product of the APCF method is a histogram of multiple Δf values. In the traditional spectral method of signal analysis, the presence in the spectrum of a peak at a certain frequency means that, in the original signal, the oscillation amplitude has a local maximum at this frequency. In the APCF “spectrum” (histogram), each peak corresponds, not to one, but to a whole group of equidistant frequencies in the original signal. The position of the peak on the horizontal axis defines, not a specific frequency, but the difference of two adjacent frequencies which is typical of the entire group.Comparison of one of the histograms for ULF disturbance records with the traditional spectrum shows that the chaotic spectrum, which is generally assumed to be noise, in reality possesses a strictly ordered structure. Most spectral peaks have been found to belong to one of many (more than 10) equidistant frequency groups. In the full spectrum, the peaks of these groups overlap forming a complex chaotic sequence.The analysis of the peaks in all the hist ograms makes it possible to conclude that the equidistant frequency groups corresponding to peaks in each histogram, are eigenfrequencies of a 2D Alfvén resonator. The existence of such a resonator in the magnetosphere, in the vicinity of the plasmapause outer edge, was earlier predicted in theoretical studies [Guglielmi, Polyakov, 1983; Leonovich, Mazur, 1987]. The APCF processing method allows this prediction to be confirmed experimentally.

Scattering Transform of Heart Rate Variability for the Prediction of Ischemic Stroke in Patients with Atrial Fibrillation.

Atrial fibrillation (AF) is an identified risk factor for ischemic strokes (IS). AF causes a loss in atrial contractile function that favors the formation of thrombi, and thus increases the risk of stroke. Also, AF produces highly irregular and complex temporal dynamics in ventricular response RR intervals. Thus, it is hypothesized that the analysis of RR dynamics could provide predictors for IS. However, these complex and nonlinear dynamics call for the use of advanced multiscale nonlinear signal processing tools. The global aim is to investigate the performance of a recently-proposed multiscale and nonlinear signal processing tool, the scattering transform, in predicting IS for patients suffering from AF. The heart rate of a cohort of 173 patients from Fujita Health University Hospital in Japan was analyzed with the scattering transform. First, p-values of Wilcoxon rank sum tests were used to identify scattering coefficients achieving significant (univariate) discrimination between patients with and without IS. Second, a multivariate procedure for feature selection and classification, the Sparse Support Vector Machine (S-SVM), was applied to predict IS. Groups of scattering coefficients, located at several time-scales, were identified as significantly higher (p-value < 0.05) in patients who developed IS than in those who did not. Though the overall predictive power of these indices remained moderate (around 60 %), it was found to be much higher when analysis was restricted to patients not taking antithrombotic treatment (around 80 %). Further, S-SVM showed that multivariate classification improves IS prediction, and also indicated that coefficients involved in classification differ for patients with and without antithrombotic treatment. Scattering coefficients were found to play a significant role in predicting IS, notably for patients not receiving antithrombotic treatment. S-SVM improves IS detection performance and also provides insight on which features are important. Notably, it shows that AF patients not taking antithrombotic treatment are characterized by a slow modulation of RR dynamics in the ULF range and a faster modulation in the HF range. These modulations are significantly decreased in patients with IS, and hence have a good discriminant ability.

Wavelet decomposition analysis is a clinically relevant strategy to evaluate cerebrovascular buffering of blood pressure after spinal cord injury.

The capacity of the cerebrovasculature to buffer changes in blood pressure (BP) is crucial to prevent stroke, the incidence of which is three- to fourfold elevated after spinal cord injury (SCI). Disruption of descending sympathetic pathways within the spinal cord due to cervical SCI may result in impaired cerebrovascular buffering. Only linear analyses of cerebrovascular buffering of BP, such as transfer function, have been used in SCI research. This approach does not account for inherent nonlinearity and nonstationarity components of cerebrovascular regulation, often depends on perturbations of BP to increase the statistical power, and does not account for the influence of arterial CO2 tension. Here, we used a nonlinear and nonstationary analysis approach termed wavelet decomposition analysis (WDA), which recently identified novel sympathetic influences on cerebrovascular buffering of BP occurring in the ultra-low-frequency range (ULF; 0.02-0.03Hz). WDA does not require BP perturbations and can account for influences of CO2 tension. Supine resting beat-by-beat BP (Finometer), middle cerebral artery blood velocity (transcranial Doppler), and end-tidal CO2 tension were recorded in cervical SCI ( n = 14) and uninjured ( n = 16) individuals. WDA revealed that cerebral blood flow more closely follows changes in BP in the ULF range ( P = 0.0021, Cohen's d = 0.89), which may be interpreted as an impairment in cerebrovascular buffering of BP. This persisted after accounting for CO2. Transfer function metrics were not different in the ULF range, but phase was reduced at 0.07-0.2 Hz ( P = 0.03, Cohen's d = 0.31). Sympathetically mediated cerebrovascular buffering of BP is impaired after SCI, and WDA is a powerful strategy for evaluating cerebrovascular buffering in clinical populations.

The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

Abstract. We examined the coast effect in Antarctica along the 80∘ S magnetic parallel. We used the geomagnetic field measurements at the two coastal stations of Mario Zucchelli Station and Scott Base, and, as a reference, at the inland temporary station Talos Dome, during 18 January–14 March 2008. Spectral analysis in the Pc5 frequency range (1–7 mHz) revealed large differences between coastal and inland stations, such as higher spectral power levels in the vertical component and higher coherence between horizontal and vertical components at coastal stations. Using the interstation method on selected active time intervals, with Talos Dome as a remote reference station, we found that remote reference induction arrows are directed almost perpendicularly with respect to their respective coastlines. Moreover, the single-station analysis shows that at Talos Dome the amplitude of the induction arrows is much smaller than at coastal stations. These results clearly indicate that coast effect at a few hundred kilometers from the coastline is relatively small. The coast effect on polarization parameters was examined, for a Pc5 event that occurred on 11 March 2008. The results evidenced that the azimuthal angle of polarized signals at one of the coastal stations is largely different with respect to the inland station (by ∼ 110∘), while the polarization ratio and ellipticity attain comparable values. We proposed a correction method of the polarization parameters, which operates directly in the frequency domain, obtaining comparable azimuthal angles at coastal and inland stations. Keywords. Ionosphere (wave propagation) – magnetospheric physics (polar cap phenomena; storms and substorms)

Pre-seismic geomagnetic and ionosphere signatures related to the Mw5.7 earthquake occurred in Vrancea zone on September 24, 2016

To emphasize the relationship between the pre-seismic geomagnetic signals and Vrancea seismicity, in this work it is hypothesized that before an earthquake initiation, the high stress reached into seismogenic volume generates dehydration of the rocks and fracturing processes followed by release of electric charges along the faulting systems, which lead to resistivity changes. These changes were explored on September 2016 by the normalized function Bzn obtained from the geomagnetic data recorded in ULF range (0.001–0.0083 Hz). A statistical analysis was also performed to discriminate on the new Bzn* time series a pre-seismic signature related to the Mw5.7 earthquake. Significant anomalous behavior of Bzn* was identified on September 21, with 3 days prior to the onset of the seismic event. Similar information is provided by registrations of the magnetic and electron concentration variations in the ionosphere over the Vrancea zone, by Swarm satellites, 4 days and 1 day before the earthquake.

Synchronization of geomagnetic and ionospheric disturbances over Kazan station

The phenomena which accompany synchronization of night-time ionospheric and geomagnetic disturbances in an ULF range with periods 35–50 min near the mid-latitude station Kazan during a global magnetically quiet period have been analyzed. The comparison between dynamic spectra and wavelet patterns of these disturbances has revealed that spectral features of simultaneous disturbances of the F2-layer critical frequency and H, D, Z geomagnetic field components are similar. By studying spectral features of the F2-layer critical frequency over Kazan and disturbances of the H and D geomagnetic field components at magnetic stations which differ from Kazan station in longitude and latitude, we have established that the disturbances considered belong to the class of fast magnetosonic waves. The analysis of solar wind parameters, inter-planetary magnetic field (IMF), and values of the auro-ral index AL in the period under study has shown that this event is associated with IMF Bz component disturb-ances and occurs during substorm development.

Событие синхронных возмущений в ионосфере и геомагнитном поле над станцией Казань

We have analyzed the phenomena which accompany synchronization of night-time ionospheric and geomagnetic disturbances in an ULF range with periods 35–50 min near the mid-latitude station Kazan during a global magnetically quiet period. The comparison between dynamic spectra and wavelet patterns of these disturbances has revealed that spectral features of simultaneous disturbances of the F2-layer critical frequency and H, D, Z geomagnetic field components are similar. By studying spectral features of the F2-layer critical frequency over Kazan and disturbances of the H and D geomagnetic field components at magnetic stations which differ from Kazan in longitude and latitude, we have established that the disturbances considered belong to the class of fast magnetosonic waves. The analysis of solar wind parameters, interplanetary magnetic field (IMF), and values of the auroral index AL in the period under study has shown that this event is associated with IMF Bz component disturbances and occurs during substorm development.

Study of interaction of ELF–ULF range (0.1–200 Hz) electromagnetic waves with the earth’s crust and the ionosphere in the field of industrial power transmission lines (FENICS experiment)

This article is devoted to describing the theory, technique, and first experimental results of a control source electromagnetic (CSEM) study of the Earth’s crust and ionosphere with the use of two mutually orthogonal industrial transmission lines 109 and 120 km in length in the frame of FENICS (Fennoscandian Electrical Conductivity from Natural and Induction Control Source Soundings) experiment. The main part of the measurements is executed on the territory of the Fennoscandian shield at distances from the first hundreds kilometers up to 856 km from the source with the purpose of the deep electromagnetic sounding of the Earth’s crust and upper mantle. According to the results of these studies clarifying the parameters of “normal” (standard) geoelectric section of the lithosphere to a depth of 60–70 km, the anisotropy parameters are evaluated and a geothermal and rheological interpretation in conjunction with the analysis of the seismic data is executed. Furthermore, to study the propagation of ELF–LLF waves (0.1–200 Hz) in an “Earth–Ionosphere” waveguide, the measurements are carried out apart from Fennoscandian shield at distances up to 5600 km from the source (in Ukraine, Spitsbergen, Poland, Kamchatka, and other areas). According to the results of these studies, the experimental estimates of the influence of the ionosphere and of the displacement currents on the propagation of ELF–ULF waves in the upper half-space at the different azimuths generation of the primary field are obtained.

Geomagnetic field disturbances produced by Sychuan earthquake on April 20th 2013 (Ms=7,0)

Results of observations on location of wave disturbances registered during the preparation and development of the earthquake in the territory of China in Sychuan proovince on April 20th 2013 are analyzed. Experimental data have been obtained at the North Caucasian geophysical observatory, a part of Laboratory of Applied geophysics and volcanology of the IEPh RAS, situated in the area of the Elbrus volcanic center (North Caucasis) [Sobisevich, Gridnev et al., 2008] and the scientific stationary IZMIRAN (Karpogory, subauroral area) as well as magnetic observatories «Odessa» and «Kiev» in the territory of Ukraine. In the structure of observed abnormal magnetic disturbances in variations of the earth’s magnetic field, precursors of the earthquake, specific magnetic pseudo-wave forms of ULF range have been distinguished and partly analyzed, which reflect the processes of preparation and development of the crustal earthquake under examination. Materials on mac-roseismic and seismologic manifestations of the processes of preparation of the earthquake source as well as brief information on its tectonic location have been presented.

A method to predict electric field spectra from empirically modeled geomagnetic ULF activity

[1] A model for prediction of the Earth background electromagnetic field spectra in the ULF range (1 mHz to 10 Hz) is developed. The possibility to model the hourly integrated magnetic wave power spectra with two different mathematical models, a power law or a fourth‒order polynomial, is investigated. Spectral properties of 3 months of ground magnetic data show that the temporal evolution of the power law parameters can be modeled based on the hourly planetary magnetic activity, the Kp index. Furthermore, the parameters of the polynomial model are related to the magnetic wave power in two spectral bands within the Pc3 and Pc1 pulsation bands. Empirical models of the magnetic wave power in these bands are developed based on the diurnal variation and the correlation with solar wind velocity of geomagnetic pulsations. Comparison with observations shows that the power law model represents the spectra well for low frequencies. However, the polynomial model based on solar wind velocity provides a better representation for the bulk of the ULF domain with mean errors between 2 and 7 dB, increasing with decreasing frequency. The modeled magnetic wave spectrum and knowledge of the underlying electrical conductivity profile can be used to predict the induced ground electric field spectra. An apparent electric conductivity profile was found via model‒based inversion, and the predicted electric wave power is compared to observations from an electrode systems offshore of the test site. The mean error between the observed and predicted electric field amplitudes is 2–7 dB and is consistently lower than the 95% central range of the data set.

Scaling characteristics of SEGMA magnetic field data around the Mw 6.3 Aquila earthquake

We apply detrended fluctuation analysis (DFA) on fluxgate and search-coil data in ULF range (scales 10–90 s or 0.1–0.011 Hz) for the months January–April 2009 available from the South European GeoMagnetic Array stations: Castello Tesino (CST), Ranchio (RNC), and L’Aquila (AQU) in Italy; Nagycenk (NCK) in Hungary; and Panagyuriste (PAG) in Bulgaria. DFA is a data processing method that allows for the detection of scaling behaviors in observational time series even in the presence of non-stationarities. The H and Z magnetic field components at night hours (00-03 UT, 01–04 LT) and their variations at the stations CST, AQU, NCK, and PAG have been examined and their scaling characteristics are analyzed depending on geomagnetic and local conditions. As expected, the scaling exponents are found to increase when the Kp index increases, indicating a good correlation with geomagnetic activity. The scaling exponent reveals also local changes (at L’Aquila), which include an increase for the Z (vertical) component, followed by a considerable decrease for the X (horizontal) component in the midst of February 2009. Attempts are made to explain this unique feature with artificial and/or natural sources including the enhanced earthquake activity in the months January–April 2009 at the L’Aquila district.

ELF/VLF recordings during the 11 March 2011 Japanese Tohoku earthquake

Broadband ELF/VLF radio recordings (0.2–40 kHz) were made at a site in Onagawa, Japan located ∼102 km from the epicenter of the M9.0 11 March 2011 earthquake, the fifth most powerful earthquake in recorded history. The receiver operated for about two minutes after the start of the earthquake, after which the receiver lost power. Examination of the VLF data shows no radio emissions preceding or coincident with the onset of the earthquake. However, once the secondary seismic waves reached the receiver, a number of impulses and diffuse noise bands arose which may result from the entire power grid shaking or from radio emissions from compressing rocks. Examination of the ELF data (0.2–1 kHz) show no precursor effect in the hours preceding the earthquake. Examination of VLF data from narrowband transmitters shows no anomalous activity in the days or weeks preceding the earthquake. Our instrument low‐frequency cut‐off is ∼200 Hz, and thus we cannot comment on emissions in the ULF range (&lt;10 Hz).

Coupling at the Atmosphere-Ionosphere-Magnetosphere Interface and Resonant Phenomena in the ULF Range

We discuss the electromagnetic processes in the ULF range which are important for the coupling between the atmosphere, ionosphere, and magnetosphere (AIM). The main attention is given to the Pc1–2 frequency ranges (f≈0.1–10 Hz) where some natural resonances in the AIM system are located. In particular, we consider the resonant structures in the spectra of the magnetic background noise related to the Alfven resonances in the ionosphere as a possible diagnostic tool for studies of the ionospheric parameters. We also discuss the self-excitation of Alfven waves in the ionosphere due to the AIM coupling and the role of such waves in the acceleration of electrons in the upper ionosphere and magnetosphere. Precipitation of magnetospheric ions due to their interaction with the ion-cyclotron waves is analyzed in relation to the ionospheric current systems, formation of partial ring current, and the influence of the ionosphere-magnetosphere feedback on the generation of such waves.

Low-altitude acceleration of ionospheric ions at Mars

[1] The objective of this study is to understand the acceleration processes that lead to outflow and escape of ionospheric ions from Mars. Observations show that accelerated dayside and flank ionospheric ions move slowly antisunward along the direction of the external/magnetosheath flow. At high altitudes, in the central tail, ions are further accelerated, up to keV energies. However, the primary acceleration process gives velocities in the 5–15 km/s range. Two acceleration processes, capable of generating a tailward stream of low-energy ions are feasible: Mass-loaded ion pickup, and wave acceleration. We demonstrate that wave acceleration is quite adequate to generate the ion outflow characterized by density modulations in the ULF range (3–20 mHz). The waves, of magnetosheath origin, penetrate into the Martian magnetosphere, down to low (pericenter) altitudes. A close relationship is found between solar wind dynamic pressure, ULF wave activity, and mass-loaded wave acceleration of ionospheric ions. Species-dependent differences in outflow velocity are consistent with an altitude dependent mass-loaded ion acceleration process.