Solar Wind Disturbances Research Articles

Cosmic ray fluctuations and MHD waves in the solar wind

During large-scale solar wind disturbances, variations in galactic cosmic rays with periods from several minutes to 2–3 hours, which are called cosmic ray fluctuations in the scientific literature, often occur. Such fluctuations are not observed in the absence of disturbances. Since cosmic rays are charged particles, their modulation in the heliosphere occurs mainly under the influence of the interplanetary magnetic field, or rather its turbulent part — MHD waves. In order to adequately describe the relationship between their fluctuation spectra, it is necessary to be able to isolate a certain type of MHD waves from direct measurements of the interplanetary medium parameters. In this paper, we consider some methods for determining the contribution of three solar wind MHD turbulence branches, namely, Alfvén, fast, and slow magnetosonic waves corresponding to the turbulence spectrum inertial region frequencies 10⁻⁴<ν<10⁻¹ Hz, at which cosmic ray fluctuations are observed, to the observed power spectra of interplanetary magnetic field modulus fluctuations. To do this, we apply the methods of spectral and polarization analysis. In the absence of measurement data on SW parameters, to identify the type of MHD turbulence we use the known wave polarization properties that Alfvén and magnetosonic waves are polarized in different planes relative to the plane containing the average IMF vector and wave vector.
 Our results show that with the correct determination of the spectra of three MHD wave types, their sum, within the limits of errors, agrees well with the observed spectra of the interplanetary magnetic field modulus, and a small difference can be attributed to static inhomogeneities and oscillations frozen into plasma, as well as to various discontinuities that are always inevitably present in the solar wind.

Флуктуации космических лучей и МГД-волны в солнечном ветре

During large-scale solar wind disturbances, variations in galactic cosmic rays with periods from several minutes to 2–3 hours, which are called cosmic ray fluctuations in the scientific literature, often occur. Such fluctuations are not observed in the absence of disturbances. Since cosmic rays are charged particles, their modulation in the heliosphere occurs mainly under the influence of the interplanetary magnetic field, or rather its turbulent part — MHD waves. In order to adequately describe the relationship between their fluctuation spectra, it is necessary to be able to isolate a certain type of MHD waves from direct measurements of the interplanetary medium parameters. In this paper, we consider some methods for determining the contribution of three solar wind MHD turbulence branches, namely, Alfvén, fast, and slow magnetosonic waves corresponding to the turbulence spectrum inertial region frequencies 10⁻⁴<ν<10⁻¹ Hz, at which cosmic ray fluctuations are observed, to the observed power spectra of interplanetary magnetic field modulus fluctuations. To do this, we apply the methods of spectral and polarization analysis. In the absence of measurement data on SW parameters, to identify the type of MHD turbulence we use the known wave polarization properties that Alfvén and magnetosonic waves are polarized in different planes relative to the plane containing the average IMF vector and wave vector. 
 Our results show that with the correct determination of the spectra of three MHD wave types, their sum, within the limits of errors, agrees well with the observed spectra of the interplanetary magnetic field modulus, and a small difference can be attributed to static inhomogeneities and oscillations frozen into plasma, as well as to various discontinuities that are always inevitably present in the solar wind.

Correction to: Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Correction to: Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Prompt responses of magnetospheric whistler-mode waves to solar wind dynamic pressure pulses

Whistler-mode waves play a critical role in shaping the Earth’s radiation belts, and their spatiotemporal distribution is vital for forecasting and modeling geospace weather. Previous works have extensively investigated the influences of geomagnetic activities, such as storms and substorms, on the modification of whistler-mode waves, but the direct impacts of solar wind disturbances have received relatively less attention. Recently, increasing research has highlighted the prompt impacts of solar wind dynamic pressure pulses on magnetospheric whistler-mode waves. This paper reviews the current progress in this field, specifically the prompt responses of chorus waves and plasmaspheric hiss to the solar wind dynamic pressure pulses. It will summarize the underlying mechanisms and pose some outstanding questions.

Unusual Martian Foreshock Waves Triggered by a Solar Wind Stream Interaction Region

Planetary bow shocks noncollisionally dissipate the incident bulk flow energy of solar wind into some other forms. To what extent and how solar wind disturbances affect the energy dissipation processes at the bow shocks on different planets remain unclear. With the Chinese Tianwen-1 and American Mars Atmosphere and Volatile EvolutioN missions, we present the first observation of significant modifications by a solar wind stream interaction region to the Martian foreshock waves, which are an important energy dissipation product of the bow shock. After the stream interface hitting Mars, an unusual band of foreshock waves emerged, with a central frequency of ∼0.4 Hz and frequency width of ∼0.2 Hz. These waves exhibited highly distorted waveforms, with peak-to-peak amplitudes of 10–25 nT in contrast to a background magnetic field of 6–9 nT. They were approximately elliptically polarized with respect to the wavevector and propagated highly obliquely to the background magnetic field. These waves reported here differed greatly from the commonly known Martian foreshock “30 s waves” and “1 Hz waves,” but resembled, to some extent, the less frequently occurring terrestrial foreshock “3 s waves.” Our present findings may imply an unexpected energy dissipation pattern of the Martian bow shock to the disturbed solar wind, which needs further observational, theoretical, and numerical investigations.

Data driven analysis of cosmic rays in the heliosphere: diffusion of cosmic protons

Understanding the time-dependent relationship between the Sun’s variability and cosmic rays (GCR) is essential for developing predictive models of energetic radiation in space. When traveling inside the heliosphere, GCRs are affected by magnetic turbulence and solar wind disturbances which result in the so-called solar modulation effect. To investigate this phenomenon, we have performed a data-driven analysis of the temporal dependence of the GCR flux over the solar cycle. With a global statistical inference of GCR data collected in space by AMS-02 and PAMELA on monthly basis, we have determined the rigidity and time dependence of the GCR diffusion mean free path. Here we present our results for GCR protons, we discuss their interpretation in terms of basic processes of particle transport and their relations with the dynamics of the heliospheric plasma.

A preliminary investigation of the empirical relationship between small-amplitude Forbush Decreases and solar wind disturbances

ABSTRACTHigh-magnitude (amplitude $\le -3{{\ \rm per\ cent}}$) Forbush decreases (FDs) are generally employed by researchers investigating the solar-terrestrial connection mechanisms. Although it has been observed that small-amplitude FDs are relatively important as they may be the outcome of the response of cosmic ray time-intensity variations to solar ejections that generate interplanetary and solar wind plasma disturbances, empirical relations between weak FDs and solar-terrestrial parameters are rarely tested. In an attempt to analyse the suggested strong connections between weak FDs and solar-terrestrial phenomena, we employed some comparatively more efficient, accurate, and highly sensitive versions of the recently developed computer FD event selection software. Large catalogues of low-amplitude (FD(per cent) ≥−3) Forbush events were selected from Apatity, Moscow, Newark, and Oulu NMs. These catalogues allow us to test, for the first time, the empirical relations between small-amplitude FDs and solar wind data. We find significant negative correlations between solar wind speed (SWS) and the small FDs at OULU, NWRK, and MOSC stations. While the relation at OULU is strong and statistically significant at 95 per cent confidence level, the weak correlation at NWRK and MOSC is only significant at a 90 per cent level. The negative correlation between the small events at OULU and the interplanetary magnetic field (IMF) is also significant at the a 95 per cent level. The relation between SWS and IMF and high-amplitude FDs were also tested, and the correlation coefficients were negative, strong, and statistically significant at a 99.9 per cent level of significance.

Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Interplanetary Scintillation Observations of Solar-Wind Disturbances During Cycles 23 and 24

Co-rotating Solar Wind Disturbances in Radio Sounding Data and Local Measurements

In this paper, we present the results of two series of experiments on radio sounding of near-solarplasma by the signals of the Mars Express and Venus Express spacecraft in 2006 and Mars Express in 2008.The radio sounding data are compared with measurements of the proton concentration near the Earth’s orbiton the Wind satellite. This analysis shows that the general nature of the temporal dynamics of disturbancesobserved in two series of measurements is qualitatively similar. The sequence of amplifications of fluctuationsin the frequency and density of protons indicates that the observed disturbances are associated with co-rotatingregions of interaction of solar wind flows of various velocities

Co-rotating Solar Wind Disturbances in Radio Sounding Data and Local Measurements

Co-rotating Solar Wind Disturbances in Radio Sounding Data and Local Measurements

Modeling of Solar Wind Disturbances Associated with Coronal Mass Ejections and Verification of the Forecast Results

Solar wind (SW) disturbances associated with coronal mass ejections (CMEs) cause significant geomagnetic storms, which may lead to the malfunction or damage of sensitive on-ground and space-based critical infrastructure. CMEs are formed in the solar corona, and then propagate to the Earth through the heliosphere as Interplanetary CME (ICME) structures. We describe the main principles in development with the online, semi-empirical system known as the Space Monitoring Data Center (SMDC) of the Moscow State University, which forecasts arrival of ICMEs to Earth. The initial parameters of CMEs (speeds, startup times, location of the source) are determined using data from publicly available catalogs based on solar images from space telescopes and coronagraphs. After selecting the events directed to Earth, the expected arrival time and speed of ICMEs at the L1 point are defined using the Drag-Based model (DBM), which describes propagation of CMEs through the heliosphere under interaction with the modeled quasi-stationary SW. We present the test results of the ICME forecast in the falling phase of Cycle 24 obtained with the basic version of SMDC in comparison with results of other models, its optimization and estimations of the confidence intervals, and probabilities of a successful forecast.

Magnetohydrodynamic Simulation of Multiple Coronal Mass Ejections: An Effect of “Pre-events”

Coronal mass ejections (CMEs) are a major source of solar wind disturbances that affect the space plasma and magnetic field environment along their propagation path. Accurate prediction of the arrival of a CME at Earth or any point in the heliosphere is still a daunting task. In this study we explore an often overlooked factor—the effects of “pre-events” that can alter the propagation of a CME due to a preceding CME. A data-driven magnetohydrodynamic numerical model is used to simulate the propagation of multiple CMEs and their driven shocks that occurred in 2012 July. The simulation results are validated with in situ solar wind plasma and magnetic field measurements at 1 au, testing the appropriateness of our simulation results for interpreting the CME/shock evolution. By comparing the simulation results with and without preceding CMEs, we find that the trailing CME can be accelerated by the “wake” of a preceding CME. A detailed analysis suggests that the acceleration is caused partially by an increase in the background solar wind and partially by the so-called “snowplow” effect, with the latter being the major contributor for the 2012 July event.

Forbush decreases associated with coronal mass ejections from active and non-active regions: statistical comparison

ABSTRACT In this paper, Forbush decreases (FDs) from 1997 to 2020 associated with coronal mass ejections from active and non-active regions are compared between themselves and to FDs caused by high-speed streams from coronal holes. The two types of sporadic FDs are also compared when corresponding solar wind (SW) disturbances contain, or do not contain, magnetic clouds (MCs) near Earth. Cosmic ray density and anisotropy variations, SW speed, interplanetary magnetic field (IMF) strength, and geomagnetic indices have been examined using statistical methods. The results reveal that these parameters are larger for FDs associated with active region (AR) ejections and have highly skewed distributions for both types of sporadic events. In the same ranges of SW parameters, FD magnitude is larger for flare-associated events; more efficient modulation occurs in FDs associated with AR ejections. Differences between FDs associated with AR and non-AR ejections are more pronounced when an MC is registered. For IMF strength and geomagnetic indices, differences between the distributions depend more upon MC presence or absence than on the type of solar source. Correlation of IMF strength and SW speed differs slightly between FDs caused by AR and non-AR ejections regardless of the presence or absence of an MC, akin to the partial correlation between FD magnitude and IMF strength. Difference between the speeds of disturbed and background SW is larger for FDs associated with AR ejections especially when an MC is registered; the interaction region of different-speed SW streams occurs more frequently in interplanetary disturbances induced by AR ejections.

Formation of Coronal Mass Ejection and Posteruption Flow of Solar Wind on 2010 August 18 Event

The state of the space environment plays a significant role in the forecasting of geomagnetic storms produced by disturbances of the solar wind (SW). Coronal mass ejections (CMEs) passing through the heliosphere often have a prolonged (up to several days) trail with declining speed, which affects propagation of the subsequent SW streams. We studied the CME and posteruption plasma flows behind the CME rear in the event on 2010 August 18 that was observed in quadrature by several space-based instruments. Observations of the eruption in the corona with EUV telescopes and coronagraphs revealed several discrete outflows followed by a continuous structureless posteruption stream. The interplanetary coronal mass ejection (ICME) associated with this CME was registered by the Plasma and Suprathermal Ion Composition instrument aboard the Solar Terrestrial Relations Observatory between August 20, 16:14 UT and August 21, 13:14 UT, after which the SW disturbance was present over 3 days. Kinematic consideration with the use of the gravitational and drag-based models has shown that the discrete plasma flows can be associated with the ICME, whereas the posteruption outflow arrived in the declining part of the SW transient. We simulated the Fe ion charge distributions of the ICME and post-CME parts of the SW using the plasma temperature and density in the ejection region derived from the differential emission measure analysis. The results demonstrate that in the studied event, the post-ICME trailing region was associated with the posteruption flow from the corona rather than with the ambient SW entrained by the CME.

Forbush decreases caused by paired interacting solar wind disturbances

ABSTRACTThe paper discusses changes in various characteristics of the solar wind, interplanetary magnetic field, geomagnetic activity, and cosmic rays during the registration of paired interacting solar wind disturbances on the Earth using the data base of Forbush effects and interplanetary disturbances – FEID. The cases of pair interaction are considered for 1995–2020: (i) successive coronal mass ejections; (ii) coronal mass ejections and high-speed streams from coronal holes; (iii) successive high-speed streams from coronal holes. It is shown that for the first events from a pair, the times for reaching the maximum values of the interplanetary magnetic field and solar wind velocity are significantly reduced, and the amplitudes of the recorded Forbush decreases decline. It is also found that the presence of interaction enriches the second event at the expense of the resources of the first, increasing geomagnetic efficiency and the degree of cosmic ray modulation for the second event in comparison with isolated events, which is especially pronounced for a pair of interacting coronal mass ejections. The existence of the described effects can be explained by the observed increase in the interplanetary magnetic field magnitude in the second events due to the presence of interaction.

A Preliminary Investigation of the Empirical Relationship between Small Amplitude Forbush Decreases and Solar Wind Disturbances

A Preliminary Investigation of the Empirical Relationship between Small Amplitude Forbush Decreases and Solar Wind Disturbances

Study of Mars Magnetosheath Fluctuations using the Kurtosis Technique: Mars Express Observations

Planetary magnetosheaths are characterized by high plasma wave and turbulence activity. The Martian magnetosheath is no exception; both upstream and locally generated plasma waves have been observed in the region between its bow shock and magnetic boundary layer, its induced magnetosphere. This statistical study of wave activity in the Martian magnetosheath is based on 12 years (2005–2016) of observations made during Mars Express (MEX) crossings of the planet’s magnetosheath — in particular, data on electron density and temperature data collected by the electron spectrometer (ELS) of the plasma analyzer (ASPERA-3) experiment on board the MEX spacecraft. A kurtosis parameter has been calculated for these plasma parameters. This value indicates intermittent behavior in the data when it is higher than 3 (the value for a normal or Gaussian distribution). The variation of wave activity occurrence has been analyzed in relation to solar cycle, Martian orbit, and distance to the bow shock. Non-Gaussian properties are observed in the magnetosheath of Mars on all analyzed scales, especially in those near the proton gyrofrequency in the upstream region of the Martian magnetosphere. We also report that non-Gaussian behavior is most prominent at the smaller scales (higher frequencies). A significant influence of the solar cycle was also observed; the kurtosis parameter is higher during declining and solar maximum phases, when the presence of disturbed solar wind conditions, caused by large scale solar wind structures, increases. The kurtosis decreases with increasing distance from the bow shock, which indicates that the intermittence level is higher near the bow shock. In the electron temperature data the kurtosis is higher near the perihelion due to the higher incidence of EUV when the planet is closer to the Sun, which causes a more extended exosphere, and consequently increases the wave activity in the magnetosheath and its upstream region. The extended exosphere seems to play a lower effect in the electron density data.

On the relationship of power lines outages caused by thunderstorms with Forbush decreases of cosmic rays

It is known that power lines outages often occur during thunderstorms. Here are the results of comparing of power lines outages in Yakutia from 2012 to 2018 with the database of Forbush-Storm events. This database contains information on geomagnetic storms and Forbush-decreases of cosmic rays from 1996 to 2018. There are 3 classes of the events: if these two ground-based manifestations of solar wind disturbances occur simultaneously (Forbush with Storm, F+S) or separately (Forbush without Storm, F-S and Storm without Forbush, S-F). For 7 years in the summer time, 73 power lines outages associated with thunderstorms were recorded. It is shown that in 56 cases these outages occurred simultaneously with (F-S) class, 16 – with (F+S) class, and only in 1 case lightning outages were not associated with Forbush-Storm events (-F-S). In 19 cases of (S-F) class, not a single lightning outage was recorded. This means that lightning outages on power lines are mainly associated with decreases in the cosmic rays intensity, and during geomagnetic storms, power transmission disruptions occur when storms are simultaneous with Forbush-decreases of cosmic rays. Apparently, this indicates the significance of the effect of cosmic rays on atmospheric electricity, and it is more significant than the effect of geomagnetic storms.

Influence of Interacting Solar Wind Disturbances on the Variations in Galactic Cosmic Rays

Influence of Interacting Solar Wind Disturbances on the Variations in Galactic Cosmic Rays

Radio bursts related geomagnetic storms with coronal mass ejections, x-ray solar flares and solar wind disturbances: a survey

Radio bursts related geomagnetic storms with coronal mass ejections, x-ray solar flares and solar wind disturbances: a survey