Interplanetary Magnetic Field Vector Research Articles

Structure and Dynamics for Graphs of Interplanetary Magnetic Field Vectors

Structure and Dynamics for Graphs of Interplanetary Magnetic Field Vectors

Exploring the relationship between space weather parameters and cosmic ray muons observed at high cut-off rigidity site: A correlation, artificial neural network, and spectral analysis

The objective of this study was to examine the relationship between cosmic rays (CR) and various solar activity parameters, including the interplanetary magnetic field (B), solar radio emission flux at 10.7 cm (F10.7), solar wind speed (V), solar wind density (N), solar wind pressure (P), and the variance of the interplanetary magnetic field vector (σF). The CR data collected from 2007 to 2013 were obtained using a muon detector situated at King Abdulaziz University (KAAU) in Jeddah, Saudi Arabia, with a rigidity cutoff of 14.8 GV. To explore the correlation between the CR data and the selected parameters, three distinct methods were employed: regression analysis, artificial neural network (ANN), and power spectral analysis.Regression analysis revealed significant positive correlations between CR muons and plasma pressure (R = 0.1, p < 0.05), as well as solar wind speed (R = 0.1, p < 0.05). On the other hand, negative correlations were observed between CRs and radio flux (R = 0.75, p < 0.05), as well as interplanetary magnetic field (R = 0.1, p < 0.05). However, no significant correlations were found between CRs and plasma density or the variance of the interplanetary magnetic field vector (p > 0.05). Furthermore, multivariable correlation analyses were conducted to explore the relationship between CR muons and the considered parameters, resulting in only marginal improvement.For comparison purposes, data from the King Abdulaziz City for Science and Technology (KACST) muon detector in Riyadh, Saudi Arabia (with a rigidity cutoff of 14.4 GV), as well as CR data from Oulu NM (with a rigidity cutoff of 0.3 GV), were utilized for the same period as the KAAU data. The correlation results indicated that the relationships between the CR data from the three detectors and some of the considered parameters were consistent. However, the strength of the correlations and the magnitudes of the slopes exhibited variations.ANN procedures were also employed to compare the efficiency of neural network analysis in forecasting CR muons based on solar activity parameters. The Multilayer Perceptron (MLP) Module trained using the backpropagation learning algorithm was utilized to build a neural network model and assess its accuracy. The results indicated that the ANN method provided slightly more accurate predictions compared to regression analysis.Finally, Fast Fourier Transform (FFT) analyses were conducted to examine the presence of periodicities between the CRs and the variables under consideration. The analysis revealed several shared periodicities, including cycles spanning 270–277 days, 146–158 days, 89–95 days, 66–73 days, and 21–31 days.

Planar Magnetic Structures Downstream of Coronal Mass Ejection–driven Shocks in the Inner Heliosphere

Planar magnetic structures (PMSs), characterized by interplanetary magnetic field vectors remaining parallel to a specific plane, are commonly observed in the solar wind, especially in the sheath region of interplanetary coronal mass ejections (ICMEs). In this study, PMS events in the 2 hr regions downstream of ICME-driven shocks were investigated to reveal the relationship between PMS formation and shock environment using data collected by the Parker Solar Probe, Solar Orbiter, and Venus Express spacecraft in the inner heliosphere. PMS events are identified in the majority (around 93%) of the postshock 2 hr regions, with transit times ranging from 10 to 120 minutes, which demonstrates their common occurrence associated with ICME-driven shocks. About 33% of the detected PMS events cover the whole 2 hr intervals, called full PMS events. Most of the full PMS events are observed in the downstream region of quasi-perpendicular shocks. In addition, statistical results show that full PMS events occurring in the downstream region of quasi-perpendicular shocks are generally associated with higher magnetic compression ratios, which implies that full PMS events are more likely to be formed in the downstream region of strong quasi-perpendicular shocks.

Interplanetary Magnetic Field By Controls the Magnetopause Location

AbstractWe present a statistical study of interplanetary magnetic field (IMF) effects on the magnetopause location based on nearly 15,000 magnetopause crossings identified in the THEMIS A‐E, Magion 4, Geotail, and Interball‐1 satellite data. In order to exclude the dominant controlling role of the solar wind dynamic pressure, differences between observed and empirical model magnetopause distances are analyzed. We find that the magnetopause distance is significantly controlled by the IMF clock angle, not considered in the used empirical models. Furthermore, during very low Alfvén Mach numbers (MA &lt; 4), IMF By component can induce a considerable dawn‐dusk asymmetry of the magnetopause shape. The magnetopause distance is found to be larger in the direction of the IMF vector, that is, not only the magnitude but also the orientation of the IMF By component is eventually important. The obtained results are qualitatively consistent with a magnetohydrodynamic model run at the Community Coordinated Modeling Center.

Comparison of Observed and Modeled Magnetic Fields in the Earth's Magnetosheath

AbstractObservations of the magnetic field for two passages through the Earth's magnetosheath are used for comparison with two simple models of the magnetosheath field that describe it as a potential field. We apply the Kobel and Flückiger (1994, https://doi.org/10.1029/94JA01778) model and the Romashets and Vandas (2019, https://doi.org/10.1029/2006JA012072) model complemented with the Jelínek et al. (2012, https://doi.org/10.1029/2011JA017252) empirical determination of the bow shock and magnetopause shapes and positions. The models yield a satisfactory match to observations when the positions and shapes of the bow shock and the magnetopause are controlled by the instantaneous solar wind upstream dynamic pressure and the instantaneous upstream interplanetary magnetic field vector is taken into account.

Effect of large-scale inhomogeneity of solar wind velocity on distribution of directions of interplanetary magnetic field vector

Using data with hourly resolution obtained in near-Earth heliosphere in 1965–2014, we have calculated statistical characteristics of the angles describing the direction of the interplanetary magnetic field (IMF): root-mean-square deviations of azimuthal and elevation angles, asymmetries of their distributions, and coefficient of correlation of the angles. It has been shown that the above characteristics varied in the course of solar cycle, and some of them changed their signs when solar polar magnetic field reversed. The results obtained from the experimental data analysis were compared with a model describing transport of large-scale disturbances of IMF lines by the inhomogeneous solar wind. The comparison has shown that the variations in the angular distribution of IMF in the course of solar cycle probably occur due to the appearance of the large-scale latitudinal gradient of solar wind velocity during solar minima. In addition, the angular distribution of IMF has been found to be substantially affected by the longitudinal velocity gradient in trailing parts of high-speed streams and short-term local-scale variations in velocity gradients.

A Proxy for the Upstream IMF Clock Angle Using MAVEN Magnetic Field Data

AbstractWithout an upstream monitor at Mars to provide a contemporaneous measurement of solar wind conditions, it is useful to have techniques of inferring the upstream solar wind conditions using downstream data. We develop a method to estimate the upstream interplanetary magnetic field (IMF) clock angle, defined as the orientation of the IMF vector in the plane perpendicular to the solar wind velocity, at Mars using magnetometer data from the Mars Atmosphere and Volatile Evolution (MAVEN) mission. The technique fits MAVEN magnetometer data from within the Martian magnetosheath to a model of the draped magnetic field direction in a coordinate system aligned with the motional electric field. The results provide a proxy for the clock angle that agrees with upstream measurements and reproduces the observed distribution of clock angles. Even if upstream observations are available for a given orbit, the proxy provides an estimate of the clock angle at the time when the spacecraft is in the magnetosheath, which may correct for inherent temporal variability, because the solar wind varies on timescales shorter than the 4.5‐hr MAVEN orbit. The clock angle proxy can be applied for any orientation of the MAVEN orbit, even when MAVEN does not traverse into the upstream solar wind.

High Latitude Magnetic Impulse Events (MIEs): Polarization Peculiarities and Excitation Conditions

Polarization characteristics (polarization type, ellipticity e, tilt angle τ of the polarization ellipse’s major axis) of high-latitude magnetic impulse events (MIEs) observed at the latitude of the dayside polar cusp are studied. It is established that all impulses are elliptically polarized, being right-polarized in 43% of cases (R-type) and left-polarized in 57% of cases (L-type). The right-polarized MIEs on the ground are more pronounced in the azimuthal direction, whereas the left-polarized events are more clearly marked in the meridional direction. The MIEs of both polarization types have the properties of intermittent processes. It is shown that diurnal and seasonal variations in the occurrence frequency and amplitudes of the events depend significantly on the type of their polarization. The R- and L-type impulse events are predominantly observed during the descending and ascending phase of the solar cycle, respectively. Solar wind high-speed streams (HSSs) are more favorable for exciting right-polarized impulses, whereas left-polarized impulse events are more efficiently excited by coronal mass ejection (CME). It is established that R-type impulses emerge in the conditions when the orientation of the interplanetary magnetic field vector is close to the radial direction against the development of moderate magnetospheric substorms whereas the L-type impulses appear when IMF is perpendicular to the Sun–Earth line in the absence of substorms. The behavior of the characteristics of impulse events significantly depends on the value of the IMF Bz-component and on the angle θxB = arccos(Bx/B). It is conjectured that excitation of the two groups of impulses is caused by the IMF structures in the solar wind stream with the characteristic configuration in the ecliptic plane, which determine the polarization type and properties of MIEs.

Statistical Study of the Characteristics of Isolated Bursts of Midlatitude Pi2 Geomagnetic Pulsations

The characteristics and interplanetary excitation conditions of isolated bursts of Pi2 geomagnetic pulsations observed during the development of magnetospheric substorms (substorm Pi2) and in its absence (nonsubstorm Pi2) on the night side of the Earth are comparatively analyzed. It is shown that, regardless of the local time and season, the amplitude of isolated Pi2 substorm bursts is always higher than that of the nonsubstorm ones, and the periods and duration of the wave packets of substorm Pi2 bursts are less than those of nonsubstorms. Diurnal and seasonal variations in the characteristics of the two groups of Pi2 bursts differ in the form and position of maxima and minima. It is found that the start of excitation of isolated Pi2 bursts, during substorms and in its absence, is controlled by the preferred direction of the interplanetary magnetic field (IMF) vector perpendicular to the Sun–Earth line (angle θxB = arccos(Bx/B) → 90°). It is assumed that isolated Pi2 bursts of both groups are triggered by reorientation of the IMF vector in the ecliptic plane and the plane perpendicular to it ~15 min before their onset. The most likely source of midlatitude isolated Pi2 bursts during substorm development and in its absence are bursty bulk flows (BBFs) in the plasma sheet of the magnetospheric tail, the regularities of which coincide in many respects with the observed features of Pi2 bursts.

Magnetospheric access for solar protons during the January 2005 SEP event

The early phase of the extraordinary solar energetic particle 20 January, 2005 event having the highest peak flux of any SEP in the past 50 years of protons with energies &gt; 100 MeV is studied. Solar energetic particles (&gt;16 MeV) entry to the Earth’s magnetosphere on January 20, 2005 under northward interplanetary magnetic field conditions is considered based on multi-satellite data analysis and magnetic field simulation. Solar wind parameters and interplanetary magnetic field data, as well as calculations in terms of the A2000 magnetospheric magnetic field model were used to specify conditions in the Earth’s environment corresponding to solar proton event. It was shown that during the early phase of the event energetic particle penetration into the magnetosphere took place in the regions on the magnetopause where the magnetospheric and interplanetary magnetic field vectors are parallel. Complex analysis of the experimental data on particle fluxes in the interplanetary medium (data from ACE spacecraft) and on low-altitude (POES) and geosynchronous (GOES) orbits inside the Earth’s magnetosphere show two regions on the magnetopause responsible for particle access to the magnetosphere: the near equatorial day-side region and open field lines window at the high-latitude magnetospheric boundary. Calculations in terms of A2000 magnetospheric magnetic field model and comparison with SuperDARN images support the link between high-latitude solar energetic particle precipitations and the region at the magnetopause where the magnetospheric field is coupled with northward IMF, allowing solar particles entrance into the magnetosphere and access to the northern polar cap.

Open and partially closed models of the solar wind interaction with outer planet magnetospheres: the case of Saturn

Abstract. A wide variety of interactions take place between the magnetized solar wind plasma outflow from the Sun and celestial bodies within the solar system. Magnetized planets form magnetospheres in the solar wind, with the planetary field creating an obstacle in the flow. The reconnection efficiency of the solar-wind-magnetized planet interaction depends on the conditions in the magnetized plasma flow passing the planet. When the reconnection efficiency is very low, the interplanetary magnetic field (IMF) does not penetrate the magnetosphere, a condition that has been widely discussed in the recent literature for the case of Saturn. In the present paper, we study this issue for Saturn using Cassini magnetometer data, images of Saturn's ultraviolet aurora obtained by the HST, and the paraboloid model of Saturn's magnetospheric magnetic field. Two models are considered: first, an open model in which the IMF penetrates the magnetosphere, and second, a partially closed model in which field lines from the ionosphere go to the distant tail and interact with the solar wind at its end. We conclude that the open model is preferable, which is more obvious for southward IMF. For northward IMF, the model calculations do not allow us to reach definite conclusions. However, analysis of the observations available in the literature provides evidence in favor of the open model in this case too. The difference in magnetospheric structure for these two IMF orientations is due to the fact that the reconnection topology and location depend on the relative orientation of the IMF vector and the planetary dipole magnetic moment. When these vectors are parallel, two-dimensional reconnection occurs at the low-latitude neutral line. When they are antiparallel, three-dimensional reconnection takes place in the cusp regions. Different magnetospheric topologies determine different mapping of the open-closed boundary in the ionosphere, which can be considered as a proxy for the poleward edge of the auroral oval.

Planar magnetic structures in coronal mass ejection-driven sheath regions

Abstract. Planar magnetic structures (PMSs) are periods in the solar wind during which interplanetary magnetic field vectors are nearly parallel to a single plane. One of the specific regions where PMSs have been reported are coronal mass ejection (CME)-driven sheaths. We use here an automated method to identify PMSs in 95 CME sheath regions observed in situ by the Wind and ACE spacecraft between 1997 and 2015. The occurrence and location of the PMSs are related to various shock, sheath, and CME properties. We find that PMSs are ubiquitous in CME sheaths; 85 % of the studied sheath regions had PMSs with the mean duration of 6 h. In about one-third of the cases the magnetic field vectors followed a single PMS plane that covered a significant part (at least 67 %) of the sheath region. Our analysis gives strong support for two suggested PMS formation mechanisms: the amplification and alignment of solar wind discontinuities near the CME-driven shock and the draping of the magnetic field lines around the CME ejecta. For example, we found that the shock and PMS plane normals generally coincided for the events where the PMSs occurred near the shock (68 % of the PMS plane normals near the shock were separated by less than 20° from the shock normal), while deviations were clearly larger when PMSs occurred close to the ejecta leading edge. In addition, PMSs near the shock were generally associated with lower upstream plasma beta than the cases where PMSs occurred near the leading edge of the CME. We also demonstrate that the planar parts of the sheath contain a higher amount of strong southward magnetic field than the non-planar parts, suggesting that planar sheaths are more likely to drive magnetospheric activity.

Study of the Cosmic-Ray Modulation During the Passage of ICMEs and CIRs

We compare the cosmic-ray response to interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) during their passage in near-Earth space. We study the relative importance of various structures/features identified during the passage of the ICMEs and CIRs observed during Cycle 23 (1995 – 2009). The identified ICME structures are the shock front, the sheath, and the CME ejecta. We isolate the shock arrival time, the passage of the sheath region, the arrival of ejecta, and the end time of their passage. Similarly, we isolate the CIR arrival, the associated forward shock, the stream interface, and the reverse shock during the passage of a CIR. For the cosmic-ray intensity, we utilize the data from high counting rate neutron monitors. In addition to neutron monitor data, we utilize near-simultaneous and same time-resolution data of interplanetary plasma and field, namely the solar-wind velocity, the interplanetary magnetic field (IMF) vector, and its variance. Further, we also utilize some derived interplanetary parameters. We apply the method of the superposed-epoch analysis. As the plasma and field properties are different during the passage of different structures, both in ICMEs and CIRs, we systematically vary the epoch time in our superposed-epoch analysis one by one. In this way, we study the role and effects of each of the identified individual structures/features during the passage of the ICMEs and CIRs. Relating the properties of various structures and the corresponding variations in plasma and field parameters with changes of the cosmic-ray intensity, we identify the relative importance of the plasma/field parameters in influencing the amplitude and time profiles of the cosmic-ray intensity variations during the passage of the ICMEs and CIRs.

The relationship between plasmapause, solar wind and geomagnetic activity between 2007 and 2011

Abstract. Taking advantage of the Cluster satellite mission and especially the observations made by the instrument WHISPER to deduce the electron number density along the orbit of the satellites, we studied the relationships between the plasmapause positions (LPP) and the following LPP indicators: (a) solar wind coupling functions Bz (Z component of the interplanetary magnetic field vector, B, in GSM system), BV (related to the interplanetary electric field; B is the magnitude of the interplanetary magnetic field vector, V is solar wind velocity), and dΦmp/dt (which combines different physical processes responsible for the magnetospheric activity) and (b) geomagnetic indices Dst, Ap and AE. The analysis is performed separately for three magnetic local time (MLT) sectors (Sector1 – night sector (01:00–07:00 MLT); Sector2 – day sector (07:00–16:00 MLT); Sector3 – evening sector (16:00–01:00 MLT)) and for all MLTs taken together. All LPP indicators suggest the faster plasmapause response in the postmidnight sector. Delays in the plasmapause responses (hereafter time lags) are approximately 2–27 h, always increasing from Sector1 to Sector3. The obtained fits clearly resolve the MLT structures. The variability in the plasmapause is the largest for low values of LPP indicators, especially in Sector2. At low activity levels,LPP exhibits the largest values on the dayside (in Sector2) and the smallest on the postmidnight side (Sector1). Displacements towards larger values on the evening side (Sector3) and towards lower values on the dayside (Sector2) are identified for enhanced magnetic activity. Our results contribute to constraining the physical mechanisms involved in the plasmapause formation and to further study the still not well understood related issues.

Field-aligned currents influence on the ionospheric electric fields: Modification of the Upper Atmosphere model

We have modified the electric field calculation block of the global three-dimensional time-dependent model of the Earth’s Upper Atmosphere (UAM) to study the influence of the interplanetary magnetic field (IMF) on the ionospheric electric fields. The spatial and temporal distributions of field-aligned currents (FACs) flowing between the ionosphere and the Earth’s magnetosphere are specified from the Lukianova empirical model, which is based on statistical distributions of FACs by Orsted, CHAMP, and Magsat satellites magnetometer data and takes into account the dependence of FACs on the IMF. The modified version of the UAM is verified with the help of model calculations of the global distribution of the electric field for two IMF vector orientations: By = Bz = 0 and By = 0, Bz =–5 nT. An analysis of calculated latitude–longitude FACs density and electric field potential distributions in geomagnetic coordinates at an altitude of 175 km shows that the modified version of the UAM makes it possible to take into account the dependence of ionospheric electric fields on the IMF, the influence of currents in Region 3, and the seasonal variation of FACs.

The influence of solar wind variability on magnetospheric ULF wave power

Abstract. Magnetospheric ultra-low frequency (ULF) oscillations in the Pc 4–5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF) orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind–IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996–2004) of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature), plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind–magnetosphere coupling.

Geomagnetic storm intensity forecast caused by magnetic clouds of solar wind

Method of short-term forecast intensity of geomagnetic storms, expected by effect Solar wind magnetic clouds in the Earth’s magnetosphere is developed. The method is based calculation of the magnetic field clouds distribution, suitable to the Earth, the initial satellite measurements therein components of the interplanetary magnetic field in the solar ecliptic coordinate system. Conclusion about the magnetic storm intensity is expected on the basis of analysis of the dynamics of the reduced magnetic field Bz component clouds and established communication intensity of geomagnetic storms on Dst-index values and Bz component of the interplanetary magnetic field vector.

The influence of IMF clock angle timescales on the morphology of ionospheric convection

AbstractWe exploit a database of high‐latitude ionospheric electric potential patterns, derived from radar observations of plasma convection in the Northern Hemisphere from the years 2000–2006, to investigate the timescales of interplanetary magnetic field (IMF) control of ionospheric convection and associated magnetospheric dynamics. We parameterize the convection observations by IMF clock angle, θ (the angle between geocentric solar magnetic (GSM) north and the projection of the IMF vector onto the GSM Y‐Z plane), and by an IMF timescale, τB (the length of time that a similar clock angle has been maintained prior to the convection observations being made). We find that the nature of the ionospheric convection changes with IMF clock angle, as expected from previous time‐averaged studies, and that for τB∼30 min, the convection patterns closely resemble their time‐averaged counterparts. However, as τB increases we find that the convection evolves away from the time‐averaged patterns to reveal modified characteristic flow features. We discuss these findings in terms of solar wind‐magnetosphere‐ionosphere coupling and consider their implications for understanding the time‐dependent nature of magnetospheric dynamics.

Classification of space-weather complexes based on solar source type, characteristics of plasma flow, and geomagnetic perturbation induced by it

The space-weather complexes including characteristics of solar streams (parameters of the solar wind, components of the interplanetary magnetic-field vector) and temporal quantitative estimates of their geomagnetic effects (Dst index) are classified. Comparative and neural-network methods for this classification are developed. As a result of numerical neural-network experiments, types of solar streams responsible for generation of geomagnetic perturbations with different intensities are established. It is confirmed that, on the basis of the selected space weather complexes, it is possible to refine the influence of these streams on the electromagnetic state of the magnetic sphere and, hence, improve the accuracy of predictions of this state.

Hybrid simulation of the shock wave trailing the Moon

A standing shock wave behind the Moon was predicted by Michel (1967) but never observed nor simulated. We use 1D hybrid code in order to simulate the collapse of the plasma‐free cavity behind the Moon and for the first time to model the formation of this shock. Starting immediately downstream of the obstacle we consider the evolution of plasma expansion into the cavity in the frame of reference moving along with the solar wind. Well‐known effects as electric charging of the cavity affecting the plasma flow and counterstreaming ion beams in the wake are reproduced. Near the apex of the inner Mach cone where the plasma flows from the opposite sides of the obstacle meet, a shock wave arises. We expect the shock to be produced at periods of high electron temperature solar wind streams (Ti ≪ Te ∼ 100 eV). The shock is produced by the interaction of oppositely directed proton beams in the plane containing solar wind velocity and interplanetary magnetic field vectors. In the direction across the magnetic field and the solar wind velocity, the shock results from the interaction of the plasma flow with the region of the enhanced magnetic field inside the cavity that plays the role of the magnetic barrier. The appearance of the standing shock wave is expected at the distance of ∼7RM downstream of the Moon.