Solar Wind Plasma Velocity Research Articles

Solar Wind Plasma Parameters in Relation with Good Quality Magnetic Cloud Related Geomagnetic Storms

We have analyzed magnetic cloud related geomagnetic storms detected during the period of solar cycle 23 and 24 with disturbances in solar wind plasma parameters. We have observed that all the MC related geomagnetic storms are accompanying with disturbances in solar wind plasma parameters. The magnitude of magnetic cloud related geomagnetic storms is soundly correlated with peak disturbances values of solar wind plasma parameters solar wind plasma velocity (SWPV), solar wind plasma density (SWPD), solar wind plasma temperature (SWPT), interplanetary magnetic fields (IMFB) and southward component of interplanetary magnetic fields (IMFBz). Large positive correlation with correlation coefficient 0.60 have found between magnitude of MC related GMS and peak value of related disturbances in IMFB and 0.67 between magnitude of MC related geomagnetic storms and peak value of associated disturbances in IMFBz. Additionally positive correlations with correlation coefficient 0.54 have been found between magnitude of MC related GMS and peak value of associated disturbances in solar wind plasma temperature ,0.40 between magnitude of MC related GMS and peak value of associated disturbances in solar wind plasma velocity, 0.27 between magnitude of MC related geomagnetic storms and peak value of disturbances in soar wind plasma density.

Effect of strong geomagnetic storms and their association with solar wind plasma temperature and IMF during solar cycles 23 and 24.

Strong interaction of CMEs with Earth’s environment causes serious space weather effect through the coupled magnetosphere system. A geomagnetic storm is a global disruption of the earth’s magnetic field, and usually occurs in response to abnormal conditions in the IMF and solar wind. In this paper we present the consequences on interplanetary causes of strong geomagnetic storms (Dst ≤ -200nT), that occurred during solar cycle 23 and 24. It was found that the positive correlation with correlation coefficient (0.46) between the magnitude of strong geomagnetic storm and magnitude of solar wind plasma temperature, (0.54) between the magnitude of strong geomagnetic storm and magnitude of solar wind plasma velocity, (.58) between the magnitude of strong geomagnetic storm and magnitude of southward component of interplanetary magnetic field (IMF Bz) and (0.54) between strong geomagnetic storm and magnitude of interplanetary magnetic field (IMF Btotal).The correlation between magnitude of strong geomagnetic storm and magnitude of interplanetary magnetic field (with positive correlation coefficient 0.58) is higher, as compared with magnitude of strong geomagnetic storm and magnitude of solar wind plasma temperature (0.46). It has been verified that strong geomagnetic storm intensity is correlated well with the interplanetary magnetic field IMF (Btotal and Bz) better than with its solar parameters.

Influence of Solar Wind Plasma Parameters on the Intensity of Isolated Magnetospheric Substorms

Parameters of the interplanetary magnetic field and solar wind plasma during periods of 163 isolated substorms have been studied. It is shown that the solar wind velocity V and plasma density N remain approximately constant for at least 3 h before substorm onset Т o and 1 h after Т o . On average, the velocity of the solar wind exhibits a stable trend toward anticorrelation with its density over the whole data array. However, the situation is different if the values of V and N are considered with respect to the intensity of substorms observed during that period. With the growth of substorm intensity, quantified as the maximum absolute value of AL index, an increase in both the solar wind plasma velocity and density, at which these substorms appear, is obsreved. It has been found that the magnitude of the solar wind dynamic pressure P is closely related to the magnetosphere energy load defined as averaged values of the Kan–Lee electric field EKL and Newell parameter dΦ/dt averaged for 1 h interval before Т o . The growth of the dynamic pressure is accompanied by an increase in the load energy necessary for substorm generation. This interrelation between P and values of EKL and dΦ/dt is absent in other, arbitrarily chosen periods. It is believed that the processes accompanying increasing dynamic pressure of the solar wind result in the formation of magnetosphere conditions that increasingly impede substorm generation. Thus, the larger is P, the more solar wind energy must enter the Earth’s magnetosphere during the period of the growth phase for substorm generation. This energy is later released during the period of the substorm expansion phase and creates even more intense magnetic bays.

Fine structure of the interplanetary shock front according to measurements of the ion flux of the solar wind with high time resolution

According to the data of the BMSW/SPEKTR-R instrument, which measured the density and velocity of solar wind plasma with a record time resolution, up to ~3 ×10–2 s, the structure of the front of interplanetary shocks has been investigated. The results of these first investigations were compared with the results of studying the structure of the bow shocks obtained in previous years. A comparison has shown that the quasi-stationary (averaged over the rapid oscillations) distribution of plasma behind the interplanetary shock front was significantly more inhomogeneous than that behind the bow-shock front, i.e., in the magnetosheath. It has also been shown that, to determine the size of internal structures of the fronts of quasi-perpendicular (θBN > 45°) shocks, one could use the magnetic field magnitude, the proton density, and the proton flux of the solar wind on almost equal terms. A comparison of low Mach (МА < 2), low beta (β1 < 1) fronts of interplanetary and bow shocks has shown that the dispersion of oblique magnetosonic waves plays an essential role in their formation.

Voyager 2 solar plasma and magnetic field spectral analysis for intermediate data sparsity

AbstractThe Voyager probes are the furthest, still active, spacecraft ever launched from Earth. During their 38 year trip, they have collected data regarding solar wind properties (such as the plasma velocity and magnetic field intensity). Unfortunately, a complete time evolution of the measured physical quantities is not available. The time series contains many gaps which increase in frequency and duration at larger distances. The aim of this work is to perform a spectral and statistical analysis of the solar wind plasma velocity and magnetic field using Voyager 2 data measured in 1979, when the gap density is between the 30% and 50%. For these gap densities, we show the spectra of gapped signals inherit the characteristics of the data gaps. In particular, the algebraic decay of the intermediate frequency range is underestimated and discrete peaks result not from the underlaying data but from the gap sequence. This analysis is achieved using five different data treatment techniques coming from the multidisciplinary context: averages on linearly interpolated subsets, correlation without data interpolation, correlation of linearly interpolated data, maximum likelihood data reconstruction, and compressed sensing spectral estimation. With five frequency decades, the spectra we obtained have the largest frequency range ever computed at five astronomical units from the Sun; spectral exponents have been determined for all the components of the velocity and magnetic field fluctuations. Void analysis is also useful in recovering other spectral properties such as micro and integral scales.

GROUND LEVEL ENHANCEMENTS IN RELATION WITH ENERGETIC SOLAR FEATURES AND DISTURBANCES IN SOLAR WIND PLASMA PARAMETERS

Ground Level Enhancements (GLEs) in cosmic ray intensity observed during the period of 1997-2012 have been studied with energetic solar features and disturbances in solar wind plasma parameters and it is seen that all the GLEs have been found to be associated with coronal mass ejections, hard X-ray solar flares and solar radio bursts. All the GLEs have also been found to be associated with sudden jumps in solar proton ux of energy of ≥ 60 Mev. A positive correlation with correlation coecient of 0.48 has been found between the maximum percentage intensity (Imax%) of Ground Level Enhancements and the peak value of solar proton ux of energy (≥ 60Mev). All the Ground Level Enhancements have been found to be associated with jumps in solar wind plasma velocity (JSWV) events. A positive correlation with correlation coecient of 0.43 has been found between the maximum percentage intensity (Imax %) of Ground Level Enhancements and the peak value of solar wind plasma velocity of associated (JSWV) events. All the Ground Level Enhancements have been found to be associated with jumps in solar wind plasma pressure (JSWP) events. A positive correlation with correlation coecient of 0.67 has been found between the maximum percentage intensity (Imax %) of Ground Level Enhancements and the peak value of solar wind plasma pressure of associated (JSWP) events and of 0.68 between the maximum percentage intensity (Imax %) of Ground Level Enhancements and the magnitude of the jump in solar wind plasma pressure of associated (JSWP) events.

Coronal Mass Ejections And Disturbances In Solar Wind Plasma Parameters In Relation With Geomagnetic Storms

Coronal Mass Ejections (CMEs) are the drastic solar events in which huge amount of solar plasma materials are ejected into the heliosphere from the sun and are mainly responsible to generate large disturbances in solar wind plasma parameters and geomagnetic storms in geomagnetic field. We have studied geomagnetic storms, (Dst ≤-75nT) observed during the period of 1997-2007 with Coronal Mass Ejections and disturbances in solar wind plasma parameters (solar wind temperature, velocity, density and interplanetary magnetic field) .We have inferred that most of the geomagnetic storms are associated with halo and partial halo Coronal Mass Ejections (CMEs).The association rate of halo and partial halo coronal mass ejections are found 72.37 % and 27.63 % respectively. Further we have concluded that geomagnetic storms are closely associated with the disturbances in solar wind plasma parameters. We have determined positive co-relation between magnitudes of geomagnetic storms and magnitude of jump in solar wind plasma temperature, jump in solar wind plasma density, jump in solar wind plasma velocity and jump in average interplanetary magnetic field with co-relation co-efficient 0 .35 between magnitude of geomagnetic storms and magnitude of jump in solar wind plasma temperature, 0.19 between magnitude of geomagnetic storms and magnitude of jump in solar wind density, 0.34 between magnitude of geomagnetic storms and magnitude of jump in solar wind plasma velocity, 0.66 between magnitude of geomagnetic storms and magnitude of jump in average interplanetary magnetic field respectively. We have concluded that geomagnetic storms are mainly caused by Coronal Mass Ejections and disturbances in solar wind plasma parameters that they generate.

Symmetrie Cosmic Ray Intensity Decreases in Relation with Coronal Mass Ejections and Disturbances In Solar Wind Plasma Parameters

We have studied symmetric cosmic ray intensity decreases (V Shape, and U Shape) magnitude ≥ 2.0%, observed at Oulu super neutron monitor, during the period of 1986-2006 with coronal mass ejections CMEs), interplanetary shocks and disturbances in solar wind plasma parameters (solar wind temperature, velocity, density). We have found that 76.92% V shape symmetric cosmic ray intensity decreases are associated with halo and partial halo coronal mass ejections (CMEs). The association rate between halo and partial halo coronal mass ejections are found 40.00%and 60.00% respectively. Most of the V Shape symmetric cosmic ray intensity decreases are related to interplanetary shocks (61.53%) and the related shocks are forward shocks. We have also found positive co-relation with co-relation co-efficient 0.54 between magnitude of V shape symmetric cosmic ray intensity decreases and speed of associated coronal mass ejections. From the further study it is concluded that V shape symmetric cosmic ray decreases are strongly related to the disturbances in solar wind plasma parameters. Negative co-relation has been found between magnitudes of V Shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma density of associated JSWD events with co-relation co-efficient -0.152 between these two events. Negative co-relation has also been found between magnitude of V Shape asymmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma velocity of the associated JSWV events with co-relation co-efficient -0.48 between these two events. From the study of U Shape symmetric cosmic ray intensity decreases and disturbances in solar wind plasma parameters, we found negative co-relation with correlation coefficient, -0.473 between magnitude of U shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma temperature of associated JSWT events, -0.468 between magnitude of U shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma density of associated JSWD events and -0.26 between U shape symmetric cosmic ray intensity decreases and magnitude of jump in solar wind plasma velocity of associated JSWV events.

Effect of the solar wind and IMF parameters on the formation of long-period irregular pulsation burst regimes

The excitation of long-period irregular pulsations in the 2.0–6.0 mHz range (ipcl pulsation series) in the Earth’s magnetosphere, depending on the set of solar wind plasma and IMF parameters, has been studied experimentally. It has been found that burst regimes are observed when the solar wind dynamic pressure and velocity are higher than V ∼ 320 km/s and P ∼ 1 nPa, respectively. It has been indicated that the dynamics of the ipcl pulsation intensity and fractal structure largely depend on the solar wind plasma velocity and magnetic pressure, respectively. An analysis of the relationship between the appearance of ipcl pulsation burst series and large-scale solar wind streams and polar coronal holes made it possible to identify solar geoeffective regions, which can cause solar wind streams and Alfven waves that promote the generation of burst regimes. On the basis of the studied conditions of the interplanetary medium, favourable for the excitation of ipcl pulsation burst series, and generalization of morphological patterns, the possible mechanisms of their generation have been considerded. It has been demonstrated that ipcl burst regimes are most probably generated as wind instability in hydrodynamics (the Miles-Phillips mechanism). The Miles-Phillips instability is related to different factors in the solar wind stream, among which turbulence, the threshold velocity value, and pressure fluctuations play a defining role. Precisely these regularities are typical of the ipcl burst regime generation conditions.

Recovery of data on interplanetary medium parameters based on the aa index of geomagnetic activity

The average annual values of the electric field and parameters of the solar wind and IMF from our time to 1868 have been estimated based on the statistical relation between the aa index of geomagnetic activity and the interplanetary medium parameters. This estimation indicates that the relative variations during the 20th century were observed in the electric field (25 ± 3%), the IMF vector component transverse with respect to the velocity (16 ± 3%), and the solar wind plasma velocity (9 ± 1%, 37 ± 4 km/s). The modulus of the IMF vector radial component increased by 9.0 ± 2.5% during this period.

Erratum to: Relationship of ground level enhancements with solar, interplanetary and geophysical parameters

Table 2 Correlation coefficients of GLE peaks and overall CRI of each GLE with simultaneous geomagnetic indices (SymH), interplanetary magnetic field (IMF-Btot), solar wind plasma velocity (Vsw), X-ray flux, and different energy channels of SEP fluxes. The correlations of GLE peaks (n = 6) with simultaneous solar, interplanetary and geophysical factors are examined. The data points (n = 6) of the GLE peak are taken for the rising part (n = 3) before peak point, peak point (n = 1) and descending after peak point (n = 2). The whole window of GLE event is taken as 24 hours that counted data number as n = 24 × 12 = 288 for 5-minute resolution. The correlations of the overall CRI of the selected GLE events are examined for the whole time window (n = 288)

On the relationship of cosmic ray intensity with solar, interplanetary, and geophysical parameters

The flux rate of cosmic rays incident on the Earth’s upper atmosphere is modulated by the solar wind and the Earth’s magnetic field. The amount of solar wind is not constant due to changes in solar activity in each solar cycle, and hence the level of cosmic ray modulation varies with solar activity. In this context, we have investigated the variability and the relationship of cosmic ray intensity with solar, interplanetary, and geophysical parameters from January 1982 through December 2008. Simultaneous observations have been made to quantify the exact relationship between the cosmic ray intensity and those parameters during the solar maxima and minima, respectively. It is found that the stronger the interplanetary magnetic field, solar wind plasma velocity, and solar wind plasma temperature, the weaker the cosmic ray intensity. Hence, the lowest cosmic ray intensity has good correlations with simultaneous solar parameters, while the highest cosmic ray intensity does not. Our results show that higher solar activity is responsible for a higher geomagnetic effect and vice versa.

Probing the solar wind-inner magnetospheric coupling: validation of relativistic electron flux models

High fluxes of relativistic electrons in the inner magnetosphere have been associated with a range of spacecraft anomalies, and therefore the modeling of the flux is of direct relevance to the development of space weather applications. Time variations of the electron flux at a given L shell are ultimately functions of interplanetary parameters as well as of internal magnetospheric dynamics. It is important to resolve which one of the two elements is important for modeling and to what extent. To that end we compare two models of the magnetospheric relativistic electron flux at 2–6 MeV spanning the range L = 1 –10 and driven by the solar wind plasma velocity, V SW . The finite-impulse-response (FIR) model represents the coupling of the flux to the solar wind velocity. It is part of an empirical model chain currently in development at the Center for Integrated Space Weather Modeling. The autoregressive moving-average (ARMA) model also includes a representation of the internal flux dynamics. The comparison is quantified in terms of the prediction accuracy, its variation with season and solar cycle phase, and its dependence on activity level. We find that the FIR model is more accurate than the ARMA model in most radial regions of the radiation belts, including the geosynchronous orbit. The results indicate that the long memory of the FIR model to past solar wind velocity inputs is more important in representing the effective coupling than ARMA's additional internal dynamics.

Modeling of geomagnetic field during magnetic storms and comparison with observations

This paper discusses: (a) development of the dynamic paraboloid magnetospheric field model, (b) application of this model for the evaluation of a variety of magnetospheric current systems and their contribution to the ground magnetic field variations during magnetic storms, (c) investigation of auroral electrojet dynamics and behavior of plasma precipitation boundaries, and (d) usage of the paraboloid magnetospheric field model for revealing relationships between geomagnetic phenomena at low altitudes and the large-scale magnetospheric plasma domains. The model's input parameters are determined by the solar wind plasma velocity and density, the IMF strength and direction, the tail lobe magnetic flux F ∞, and the total energy of ring current particles. The auroral particle precipitation boundaries are determined from, the DMSP particle observations; these boundaries are used to calculate the value of F ∞. The influence of the field-aligned tail, and ring currents on the magnetospheric field structure is studied. It is found that the polar cap area is strongly controlled by the tail current. The paraboloid magnetospheric field model is utilized for the mapping of the auroral electrojet centerlines and boundaries into the magnetosphere. Analysis of the magnetic field variations during magnetic storms shows that the contributions of the ring current, tail current, and the magnetopause currents to the D st variation are approximately equal.

Magnetohydrodynamic turbulence in the solar wind

Low frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations may be thought of as originating near the Sun as nearly perfect Alfvén waves. Power spectra of these fluctuations from 10−7 Hz to several Hz to suggest that the medium is turbulent. Near 1 AU, fluctuations below 10−5 Hz have a relatively flat slope (∼−1) and contain most of the energy in the fluctuating fields. From 10−5 Hz to ∼0.1 Hz, the spectra exhibit a power law inertial range similar to that seen in ordinary fluid turbulence. At the highest frequencies, the rapid fall-off of the power suggests that strong dissipation is occurring. From in situ measurements, it is clear that the fluctuations emanate from the solar corona. The turbulent cascade appears to evolve most rapidly in the vicinity of velocity shears and current sheets. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics in both Cartesian and spherical geometry corroborate this interpretation. There are conflicting interpretations of observations suggesting that much of the power in magnetic field fluctuations resides in quasi-two-dimensional structures and simulations have helped to elucidate some of these issues.

Numerical simulation of Alfvénic turbulence in the solar wind

Low‐frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations can be thought of as nearly perfect Alfvén waves. Evidence from the Helios and Ulysses spacecraft suggest strongly that these fluctuations emanate from the solar corona with high correlation and flat power spectra (∼f−1). These fluctuations constitute a source of free energy for a turbulent cascade of magnetic and kinetic energy to high wave numbers, a cascade that evolves most rapidly in the vicinity of velocity shears and the heliospheric current sheet. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics (MHD) in Cartesian geometry showed that sharp gradients in velocity would decrease substantially the Alfvénicity of initially pure Alfvénic fluctuations; however, the effects of solar wind expansion on this turbulent evolution is, as yet, undetermined. We demonstrate that as was the case in Cartesian geometry, in an expanding volume, velocity shears and pressure‐balanced flux tubes still reduce the Alfvénicity of parallel propagating wave packets. These three‐dimensional spherically expanding simulations include velocity shears separating fast and slow flows, pressure‐balanced flux tubes, and a central current sheet which is the site of magnetic reconnection. Two‐dimensional spectra constructed in the r – θ plane resemble closely those resulting from similar initial conditions in Cartesian geometry.

Low frequency 1/&amp;lt;i&amp;gt;f&amp;lt;/i&amp;gt;-like fluctuations of the AE-index as a possible manifestation of self-organized criticality in the magnetosphere

Abstract. Low frequency stochastic variations of the geomagnetic AE-index characterized by 1/f b-like power spectrum (where f is a frequency) are studied. Based on the analysis of experimental data we show that the Bz-component of IMF, velocity of solar wind plasma, and the coupling function of Akasofu are insufficient factors to explain these behaviors of the AE-index together with the 1/f b fluctuations of geomagnetic intensity. The effect of self-organized criticality (SOC) is proposed as an internal mechanism to generate 1/f b fluctuations in the magnetosphere. It is suggested that localized spatially current instabilities, developing in the magnetospheric tail at the initial substorm phase can be considered as SOC avalanches or dynamic clusters, superposition of which leads to the 1/f b fluctuations of macroscopic characteristics in the system. Using the sandpile model of SOC, we undertake numerical modeling of space-localized and global disturbances of magnetospheric current layer. Qualitative conformity between the disturbed dynamics of self-organized critical state of the model and the main phases of real magnetospheric substorm development is demonstrated. It is also shown that power spectrum of sandpile model fluctuations controlled by real solar wind parameters reproduces all distinctive spectral features of the AE fluctuations.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions; storms and substroms).

On the excitation of the magnetosphere by the solar wind

In this note, evidence is presented to show that variations in the direction of V, the solarwind plasma velocity, produce a significant part of the activity that is measured by Kp. The activity produced by these variations in V/V may well be dominant during periods of low to moderate Kp. However, other solar-wind quantities may also be effective in producing geomagnetic activity. Most of the coupling mechanisms between the magnetosphere and the solar wind that have been proposed to date may be separated into two categories. In the first category are the mechanisms that produce the Kp component of geomagnetic activity in such a way that the level of activity depends upon the magnitude of some solar-wind quantity, or some function of more than one such quantity. Presumably, then, somewhere in the region of interaction between the solar wind and the magnetosphere, the transfer of the energy required for geomagnetic activity occurs at a rate determined by the magnitude of the controlling solar-wind quantity. Thus one would expect Kp and the magnitude of this controlling quantity, as measured in near-earth interplanetary space, to be correlated.