Interplanetary Magnetic Field Magnitude Research Articles

Magnetopause location modeling using machine learning: inaccuracy due to solar wind parameter propagation

An intrinsic limitation of empirical models of the magnetopause location is a predefined magnetopause shape and assumed functional dependences on relevant parameters. We overcome this limitation using a machine learning approach (artificial neural networks), allowing us to incorporate general, purely data-driven dependences. For the training and testing of the developed neural network model, a data set of about 15,000 magnetopause crossings identified in the THEMIS A-E, Magion 4, Geotail, and Interball-1 satellite data in the subsolar region is used. A cylindrical symmetry around the direction of the impinging solar wind is assumed, and solar wind dynamic pressure, interplanetary magnetic field magnitude, cone angle, clock angle, tilt angle, and corrected Dst index are considered as parameters. The effect of these parameters on the magnetopause location is revealed. The performance of the developed model is compared with other empirical magnetopause models. Finally, we demonstrate and discuss the inaccuracy of magnetopause models due to the inaccurate information about the impinging solar wind parameters based on measurements near the L1 point. This inaccuracy imposes a theoretical limit on the precision of magnetopause predictions, a limit that our model closely approaches.

Martian bow shock and magnetic pileup boundary models based on machine learning

Traditional Martian bow shock and magnetic pileup (magnetopause) boundary models are based on the fitting of free parameters in a prescribed formula. The form of the formula, fitted data, and considered controlling parameters distinguish the individual models from each other. However, all these models have one thing in common: the shape of the boundary and the parametric dependence assumed are fixed by the prescribed formula. The fitted data set typically consists of individual identified boundary crossings. This approach can suffer from a significant bias, as the boundary crossings are more likely to be identified in regions where a spacecraft spends more time. In this study, we use an automated region classification of the data measured by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft to solar wind, magnetosheath, or magnetosphere. This is achieved by applying the Support Vector Machine method to individual spacecraft half-orbits (from periapsis to apoapsis or vice versa). Two different models of the locations of the bow shock and magnetic pileup boundaries are then constructed based on neural networks: i) a model trained using the classified data, and ii) a model trained using individual identified boundary crossings. As compared to formal empirical modeling efforts, the neural network models do not assume any prescribed shape/distance formula. Optimal model parameterization (considering the solar wind dynamic pressure, solar ionizing flux, crustal magnetic field magnitude, Alfvén Mach number, and interplanetary magnetic field magnitude) is discussed and the model performance evaluated.

Latitudinal dependence of Pc3-4 amplitudes across the dip equator along the 210º Magnetic Meridian

Studying Pc3-4 geomagnetic pulsations at equatorial and very low latitude regions is an important issue to understand their generation and propagation mechanisms. Pc3-4 amplitudes and their latitudinal dependency across the dip equator up to low latitudes (± 25°) are investigated using geomagnetic data simultaneously obtained by the MAGDAS/CPMN stations along the 210° Magnetic Meridian (MM) chain. Forty-five Pc3 events and thirty-two Pc4 events were selected for this study. Our results show a clear dependence of Pc3-4 amplitudes on geomagnetic latitudes. At the dip equator, most of the selected Pc3 events (~75%) showed an enhancement in amplitudes, while the rest (~25%) showed an attenuation. After that, the amplitudes decreased gradually by increasing latitudes. These results suggest mixed generation and propagation mechanisms for the equatorial and very low latitudes Pc3s. For better understanding, the Interplanetary Magnetic Field (IMF) and solar conditions are examined during the selected events. Results indicate that Pc3 events with enhanced amplitudes at dip equator are mainly occurred in daytime with no preference to IMF (magnitude and direction) and solar parameters, which suggests the ionospheric currents model as a generation and propagation mechanism for these events. While the attenuation observed in the other Pc3 events was associated with intense and abrupt fluctuations in the IMF and solar parameters, which in turn suggests the compressional wave model for generating these Pc3 events. On the other hand, these two models can explain the observed enhancement in the Pc4 amplitudes at the dip equator. Therefore, our obtained results clarified the origin of equatorial Pc3-4 pulsations.

Identification of Penetration and Disturbance Dynamo Electric Fields and Their Effects on the Generation of Equatorial Plasma Bubbles

AbstractA very challenging task in ionospheric studies is to determine the separate contributions of penetration and disturbance dynamo processes in the generation of equatorial plasma drift during magnetic storms. In this study, we analyze the ion drift measured by the Communications/Navigation Outage Forecasting System satellite during the magnetic storm on 15–16 July 2012. A unique feature of this storm is the exceptionally long period of continuous southward interplanetary magnetic field (IMF) for 32 hr. The storm‐induced net change of the meridional/vertical ion drift, the difference drift between the storm time and the quiet time, is derived during the storm main phase and the first 20 hr of the recovery phase with southward IMF. The difference drift during the recovery phase cannot be explained by the disturbance dynamo effect alone. A new method is used to separate the drifts caused by the penetration and disturbance dynamo processes. The penetration drift is represented by an empirical pattern of penetration electric field and depends on the IMF magnitude, and the disturbance dynamo drift is obtained by subtracting the penetration drift from the measured difference drift. The derived disturbance dynamo drift is in good agreement with previous statistical pattern. This is the first effort to identify the separate contributions of the penetration and disturbance dynamo processes to the total drift from observed data. The results have important implications in identifying storm‐time penetration and disturbance dynamo electric fields and their effects on the generation and evolution of plasma bubbles.

Solar Wind Parameters Influencing Magnetosheath Jet Formation: Low and High IMF Cone Angle Regimes

AbstractMagnetosheath jets are localized flows of enhanced dynamic pressure that are frequently observed downstream of the Earth's bow shock. They are significantly more likely to occur downstream of the quasi‐parallel shock than the quasi‐perpendicular shock. However, as the quasi‐perpendicular geometry is a more common configuration at the Earth's subsolar bow shock, quasi‐perpendicular jets comprise a significant fraction of the observed jets. We study the influence of solar wind conditions on jet formation by looking separately at jets during low and high interplanetary magnetic field (IMF) cone angles. According to our results, jet formation commences when Alfvén Mach number MA ≳ 5. We find that during low IMF cone angles (downstream of the quasi‐parallel shock) other solar wind parameters do not influence jet occurrence. However, during high IMF cone angles (downstream of the quasi‐perpendicular shock) jet occurrence is higher during low IMF magnitude, low density, high plasma beta (β), and high MA conditions. The distribution of quasi‐parallel (quasi‐perpendicular) jet sizes parallel to flow peaks at ∼0.3 RE (∼0.1 RE). Some quasi‐perpendicular jets formed during high β and MA are particularly small. We show two examples of high β and MA quasi‐perpendicular shock crossings. Jets were observed in the transition region, but not deeper in the magnetosheath. A more detailed look into one jet revealed signatures of gyrating ions, indicating that gyrobunched ions near the shock may produce jet‐like enhancements. Our results suggest that jets form as part of the quasi‐perpendicular shock dynamics amplified by high solar wind MA and β.

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.

An Interpretable Machine Learning Procedure Which Unravels Hidden Interplanetary Drivers of the Low Latitude Dayside Magnetopause

AbstractIn this study, we propose an interpretable machine learning procedure to unravel the importance of multiple interplanetary parameters to the Earth's magnetopause standoff distance (MSD). We construct the interpretable procedure based on SHapley Additive exPlanations. A magnetopause crossings database from the Time History of Events and Macroscale Interactions during Substorms satellites and the multiple interplanetary parameters from OMNI during the period of 2007–2016 are utilized. The solar wind dynamic pressure and the interplanetary magnetic field (IMF) BZ are widely suggested as the important two interplanetary parameters that drive the MSD. However, the examination of the interpretable procedure suggests that the magnitude of the IMF is the second significant parameter after the dynamic pressure. Although the magnetic pressure, which is the function of the IMF magnitude was considered in previous studies, the importance of the IMF magnitude was underestimated. The interpretable procedure also reveals that the IMF magnitude and the BZ have different effects on the MSD. Their joint effect is the formation of the MSD sag near BZ = 5 nT. This is for the first time the interpretable concept is being applied to construct a machine‐learning magnetopause model.

Global Asymmetry in ΔX Variations During the 06 April 2000 Geomagnetic Storm: Relative Roles of IMF Bz and By

AbstractThis investigation is directed to understand the asymmetry in ΔX variations caused due to the relative roles played by Interplanetary Magnetic Field (IMF) Bz and IMF By in a particular interval (22:22–22:55 UT), during the main phase of a strong geomagnetic storm event of 06 April 2000 (Ap = 236). Two pairs of antipodal stations, being part of the SuperMAG network, are considered here. Ionospheric convection maps from SuperDARN network are used to understand spatio‐temporal evolution of the DP2 ionospheric convection patterns over high‐latitudes. The two‐dimensional maps of equivalent currents are used to show signatures of global DP2 currents associated with the interplay effect between the two IMF components. Observations show increases in the difference in ΔX variations between nearly antipodal stations from the Japanese‐European/African sector with respect to the same between the nearly antipodal stations from the Pacific/American‐Indian sector. This asymmetry is observed during the period when the absolute magnitude of IMF By is larger than that of IMF Bz resulting in a significant and conspicuous enhancement in IMF |By/Bz|. It is suggested that the distortions in DP2 cells and associated rotation of electrodynamic day‐night divider, bring one pair of stations under the same DP2 cell and one station of the other pair under a different DP2 cell and throat flow region leading to the asymmetry in ΔX variations between the antipodal stations. Therefore, the work highlights the importance of the interplay between IMF Bz and IMF By in determining the ionospheric impact over low latitudes during strong geomagnetic conditions.

A comparative study on geoeffective and non-geoeffective corotating interaction regions

A long database of corotating interaction regions (CIRs) is used to investigate their geoeffectiveness. Among 290 CIR events identified during Solar Cycle 24 (2008–2019), 88 (30%) are found to be geoeffective in causing geomagnetic storms with the symmetric ring current index [SYM-H] peak ⩽-50nT, and 202 (70%) are non-geoeffective with the minimum SYM-H >-50nT. Based on a comparative study of the geoeffective and non-geoeffective CIRs, following results are obtained. Geoeffective and non-geoeffective CIRs have comparable duration (28±15hours, 26±14hours, respectively) and radial extent (0.33±0.17AU, 0.30±0.17AU, respectively), on average. While the mean solar-wind plasma speed during the geoeffective (503±70km s−1) and non-geoeffective (491±63km s−1) CIRs exhibits no statistical difference, the geoeffective CIRs have ≈25% higher peak plasma density, ≈45% higher ram pressure, ≈42% higher temperature, ≈39% higher interplanetary magnetic field (IMF) magnitude, ≈57% stronger IMF southward component, and ≈61% stronger reconnection electric field than the non-geoeffective events, on average. The auroral electrojet index [AE] and SYM-H are found to be, respectively, ≈58% and ≈192% stronger during the geoeffective CIRs than the non-geoeffective events. The typical characteristic solar-wind and geomagnetic activity parameters given in this article can be useful for space weather modeling and prediction purposes.

The Dependence of the Venusian Induced Magnetosphere on the Interplanetary Magnetic Field: An MHD Study

The influences of the interplanetary magnetic field (IMF) on the induced magnetosphere of Venus are investigated using a global multispecies magnetohydrodynamics (MHD) model. The simulation results show that the induced magnetosphere is controlled by the IMF components perpendicular to the solar wind velocity (B Y and B Z in the Venus Solar Orbital coordinate), rather than the IMF magnitude (∣B∣). With the increase of , the induced magnetosphere becomes stronger in field strength and thicker in spatial scale, and the bow shock locates farther from the planet. The parallel IMF component (B X ) has relatively small impacts on the magnetic barrier and the magnetotail, regardless of the various IMF magnitudes and orientations caused by different B X . The responses of the Venusian induced magnetosphere to the change of upstream IMF are also studied. The time-dependent MHD calculations show that the dayside magnetosphere responds quickly with a timescale of 10 s–10 minutes, depending on the considered magnetospheric region. For comparison, the timescale required for the adjustment of magnetotail as driven by an IMF rotation is derived to be ∼10–20 minutes.

A Two‐Spacecraft Study of Mars' Induced Magnetosphere's Response to Upstream Conditions

AbstractThis is a two‐spacecraft study, in which we investigate the effects of the upstream solar wind conditions on the Martian induced magnetosphere and upper ionosphere. We use Mars Express (MEX) magnetic field magnitude data together with interplanetary magnetic field (IMF), solar wind density, and velocity measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, from November 2014 to November 2018. We compare simultaneous observations of the magnetic field magnitude in the induced magnetosphere of Mars (|B|IM) with the IMF magnitude (|B|IMF), and we examine variations in the ratio |B|IM/|B|IMF with solar wind dynamic pressure, speed and density. We find that the |B|IM/|B|IMF ratio in the induced magnetosphere generally decreases with increased dynamic pressure and that a more structured interaction is seen when comparing induced fields to the instantaneous IMF, where reductions in the relative fields at the magnetic pile up boundary (MPB) are more evident than in the field strength itself, along with enhancements in the immediate vicinity of the optical shadow of Mars. We interpret these results as evidence that while the induced magnetosphere is indeed compressed and induced field strengths are higher during periods of high dynamic pressure, a relatively larger amount of magnetic flux threads the region compared to that available from the unperturbed IMF during low dynamic pressure intervals.

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.

Magnetograph Saturation and the Open Flux Problem

Abstract Extrapolations of line-of-sight photospheric field measurements predict radial interplanetary magnetic field (IMF) strengths that are factors of ∼2–4 too low. To address this open flux problem, we reanalyze the magnetograph measurements from different observatories, with particular focus on those made in the saturation-prone Fe i 525.0 nm line by the Mount Wilson Observatory (MWO) and the Wilcox Solar Observatory (WSO). The total dipole strengths, which determine the total open flux, generally show large variations among observatories, even when their total photospheric fluxes are in agreement. However, the MWO and WSO dipole strengths, as well as their total fluxes, agree remarkably well with each other, suggesting that the two data sets require the same scaling factor. As shown earlier by Ulrich et al., the saturation correction δ −1 derived by comparing MWO measurements in the 525.0 nm line with those in the nonsaturating Fe i 523.3 nm line depends sensitively on where along the irregularly shaped 523.3 nm line wings the exit slits are placed. If the slits are positioned so that the 523.3 and 525.0 nm signals originate from the same height, δ −1 ∼ 4.5 at the disk center, falling to ∼2 near the limb. When this correction is applied to either the MWO or WSO maps, the derived open fluxes are consistent with the observed IMF magnitude. Other investigators obtained scaling factors only one-half as large because they sampled the 523.3 nm line farther out in the wings, where the shift between the right- and left-circularly polarized components is substantially smaller.

Solar Wind ∼0.15–1.5 keV Electrons around Corotating Interaction Regions at 1 au

Abstract Here we present a statistical study of the ∼0.15–1.5 keV suprathermal electrons observed in uncompressed/compressed slow and fast solar wind around 59 corotating interaction regions (CIRs) with good measurements by Wind 3DP from 1995 through 1997. For each of these CIRs, we fit the strahl and halo energy spectra at ∼0.15–1.5 keV to a Kappa function with a Kappa index κ and kinetic temperature T eff. We find that the ∼0.15–1.5 keV strahl electrons behave similarly in both slow and fast wind: the strahl number density n s positively correlates with the solar wind electron temperature T e and interplanetary magnetic field magnitude ∣B∣, while the strahl pitch angle width Θ s decreases with the solar wind speed V sw. These suggest that the strahl electrons are generated by a similar/same process at the Sun in both slow and fast wind that produces these correlations, and the scattering efficiency of strahl in the interplanetary medium (IPM) decreases with V sw. The ∼0.15–1.5 keV halo electrons also behave similarly in both slow and fast wind: the halo parameter positively correlates with the corresponding strahl parameter, and the halo number density n h positively correlates only with T e . These indicate that the halo formation process in the IPM retains most of the strahl properties, but it erases the relationship between n s and ∣B∣. In addition, κ in compressed wind distributes similarly to that in uncompressed wind, for both the strahl and halo. It shows that CIRs at 1 au are not a significant/effective acceleration source for the strahl and halo.

Solar Wind Control of Magnetosheath Jet Formation and Propagation to the Magnetopause

AbstractMagnetosheath jets are localized high‐dynamic pressure pulses originating at Earth's bow shock and propagating earthward through the magnetosheath. Jets can influence magnetospheric dynamics upon impacting the magnetopause; however, many jets dissipate before reaching it. In this study we present a database of 13,096 jets observed by the Time History of Events and Macroscale Interactions during Substorms spacecraft from 2008 to 2018, spanning a solar cycle. Each jet is associated with upstream solar wind conditions from OMNI. We statistically examine how solar wind conditions control the likelihood of jets forming at the shock, and the conditions favorable for jets to propagate through the magnetosheath and reach the magnetopause. We see that, for each solar wind quantity, these two effects are separate, but when combined, we find that jets are over 17 times more likely to reach and potentially impact the magnetopause when the interplanetary magnetic field (IMF) orientation is at a low cone angle, and approximately 8 times more likely during high speed solar wind. Low IMF magnitude, high Alfvén Mach number, and low density approximately double the number of jets at the magnetopause, while and dynamic pressure display no net effect. Due to the strong dependence on wind speed, we infer that jet impact rates may be solar cycle dependent as well as vary during solar wind transients. This is an important step towards forecasting the magnetospheric effects of magnetosheath jets, as it allows for predictions of jet impact rates based on measurements of the upstream solar wind.

Comparison of polar ionospheric behavior at Arctic and Antarctic regions for improved satellite-based positioning

Abstract In this paper, we investigate the hemispheric symmetric and asymmetric characteristics of ionospheric total electron content (TEC) and its dependency on the interplanetary magnetic field (IMF) in the northern and southern polar ionosphere. The changes in amplitude and phase scintillation are also probed through Global Ionospheric Scintillation and TEC monitoring (GISTM) systems recordings at North pole [Himadri station; Geographic 78°55′ N, 11°56′ E] and South pole [Maitri station; Geographic 70°46′ S 11°44′ E]. Observations show the range of %TEC variability being relatively more over Antarctic region (−40 % to 60 %) than Arctic region (−25 % to 25 %), corroborating the role of the dominant solar photoionization production process. Our analysis confirms that TEC variation at polar latitudes is a function of magnetosphere-ionosphere coupling, depending on interplanetary magnetic field (IMF) orientation and magnitude in the X ( B x Bx ), Y ( B y By ), and Z ( B z Bz ) plane. Visible enhancement in TEC is noticed in the northern polar latitude when B x < 0 Bx<0 , B y < − 6 nT By<-6\hspace{0.1667em}\text{nT} or B y > 6 nT By>6\hspace{0.1667em}\text{nT} and B z > 0 Bz>0 whereas the southern polar latitude perceives TEC enhancements with B x > 0 Bx>0 , − 6 nT < B y < 6 nT -6\hspace{0.1667em}\text{nT}<By<6\hspace{0.1667em}\text{nT} and B z < 0 Bz<0 . Further investigation reveals the intensity of phase scintillation being more pronounced than the amplitude scintillation during the disturbed geomagnetic conditions with excellent correlation with the temporal variation of TEC at both the stations. Corresponding variations in the parameters are studied in terms of particle precipitation, auroral oval expansion, Joule’s heating phenomena, and other ionospheric parameters. The studies are in line with efforts for improving ionospheric delay error and scintillation modeling and satellite-based positioning accuracies in polar latitudes.

Comparison of polar ionospheric behavior at Arctic and Antarctic regions for improved satellite-based positioning

Abstract In this paper, we investigate the hemispheric symmetric and asymmetric characteristics of ionospheric total electron content (TEC) and its dependency on the interplanetary magnetic field (IMF) in the northern and southern polar ionosphere. The changes in amplitude and phase scintillation are also probed through Global Ionospheric Scintillation and TEC monitoring (GISTM) systems recordings at North pole [Himadri station; Geographic 78°55′ N, 11°56′ E] and South pole [Maitri station; Geographic 70°46′ S 11°44′ E]. Observations show the range of %TEC variability being relatively more over Antarctic region (−40 % to 60 %) than Arctic region (−25 % to 25 %), corroborating the role of the dominant solar photoionization production process. Our analysis confirms that TEC variation at polar latitudes is a function of magnetosphere-ionosphere coupling, depending on interplanetary magnetic field (IMF) orientation and magnitude in the X ( B x Bx ), Y ( B y By ), and Z ( B z Bz ) plane. Visible enhancement in TEC is noticed in the northern polar latitude when B x < 0 Bx<0 , B y < − 6 nT By<-6\hspace{0.1667em}\text{nT} or B y > 6 nT By>6\hspace{0.1667em}\text{nT} and B z > 0 Bz>0 whereas the southern polar latitude perceives TEC enhancements with B x > 0 Bx>0 , − 6 nT < B y < 6 nT -6\hspace{0.1667em}\text{nT}<By<6\hspace{0.1667em}\text{nT} and B z < 0 Bz<0 . Further investigation reveals the intensity of phase scintillation being more pronounced than the amplitude scintillation during the disturbed geomagnetic conditions with excellent correlation with the temporal variation of TEC at both the stations. Corresponding variations in the parameters are studied in terms of particle precipitation, auroral oval expansion, Joule’s heating phenomena, and other ionospheric parameters. The studies are in line with efforts for improving ionospheric delay error and scintillation modeling and satellite-based positioning accuracies in polar latitudes.

The Critical Factor in Controlling the Auroral Intensity in the Cusp Region as Revealed by a Statistical Study on Midday Gap and Non‐Gap Events

AbstractTaking advantage of the high spatial‐resolution and global coverage of Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations, we investigated the critical interplanetary factors in controlling the cusp auroral emission by dividing the midday auroras into the gap (weak emission) and non‐gap (intense emission) events. Although the cusp auroral intensity is essentially determined by a parameter related to the IMF (interplanetary magnetic field) direction, IMF magnitude (|By|), and solar wind speed (V), we found that the cusp aurora is statistically weak during the southward IMF but intense when the V and IMF |By| are greater. Further, we confirmed that even with V > 600 km/s, the intense‐aurora event still shows a minimum occurrence near the IMF |By| = 0. However, when the IMF |By| is greater, the V becomes less significant for the intense‐aurora occurrence. These results demonstrate that the IMF |By| is critical in controlling the cusp auroral intensity, most likely by producing an electric field which is given as .

The Influence of Hemispheric Solar Activity Features on the Interplanetary Plasma Parameters throughout 1967 ̶ 2017

In this article, we have examined the possible influence of hemispheric solar activity features on the interplanetary plasma parameters. For this purpose, the daily data of sunspot areas (SSAs) and sunspot numbers (SSNs) as well as the interplanetary plasma parameters (interplanetary magnetic field (IMF) magnitude B, plasma density n, plasma velocity V, plasma temperature T, and plasma dynamic pressure P) during the period 1967 2017 have been used. The daily data of each interplanetary plasma parameter has been classified into two groups, northern (N) and southern (S) sorted groups based on the dominance of hemispheric SSAs or SSNs. The yearly averages of the sorted N and S groups have been calculated for each plasma parameter. The asymmetry index (N-S) for each parameter between the northern and the southern sorted group has been calculated. The asymmetry of B over the solar activity cycles is not detectable, indicating that the solar cycles are magnetically symmetric, in agreement with the findings of (El-Borie et al., 2018a). During the solar cycles 20, 21, and 24, the solar plasma for the southern sorted group was faster (hotter) by 20.3 km/s (15.7×103 oK), 13 km/s (8×103 oK), and 29 km/s (14.5×103 oK) than that for the northern sorted group, respectively. In contrast, during the solar cycle 23, the solar plasma for the southern sorted group was slower (colder) by 7.4 km/s (7.2×103 oK) than that for the northern sorted one.

Forecasting SYM‐H Index: A Comparison Between Long Short‐Term Memory and Convolutional Neural Networks

AbstractForecasting geomagnetic indices represents a key point to develop warning systems for the mitigation of possible effects of severe geomagnetic storms on critical ground infrastructures. Here we focus on SYM‐H index, a proxy of the axially symmetric magnetic field disturbance at low and middle latitudes on the Earth's surface. To forecast SYM‐H, we built two artificial neural network (ANN) models and trained both of them on two different sets of input parameters including interplanetary magnetic field components and magnitude and differing for the presence or not of previous SYM‐H values. These ANN models differ in architecture being based on two conceptually different neural networks: the long short‐term memory (LSTM) and the convolutional neural network (CNN). Both networks are trained, validated, and tested on a total of 42 geomagnetic storms among the most intense that occurred between 1998 and 2018. Performance comparison of the two ANN models shows that (1) both are able to well forecast SYM‐H index 1 h in advance, with an accuracy of more than 95% in terms of the coefficient of determination R2; (2) the model based on LSTM is slightly more accurate than that based on CNN when including SYM‐H index at previous steps among the inputs; and (3) the model based on CNN has interesting potentialities being more accurate than that based on LSTM when not including SYM‐H index among the inputs. Predictions made including SYM‐H index among the inputs provide a root mean squared error on average 42% lower than that of predictions made without SYM‐H.