OMNI Database Research Articles

Applicability of Bernoulli's theorem to upstream and downstream of the bow shock

In this research, the validity of Bernoulli's theorem for the solar wind crossing the Earth's bow shock has been investigated based on space explorations. Using solar wind plasma and interplanetary magnetic field data from the OMNI database, along with magnetosheath plasma and magnetic field data measured by the magnetospheric multiscale satellite in 2016 and 2018, 95 events were selected to study the Bernoulli invariant from the upstream to the downstream of Earth's bow shock (from the unshocked solar wind region to the shocked magnetosheath region). Statistical investigations show that the differences in the characteristic energy of plasmas between the solar wind region and the magnetosheath region are less than 5%, regardless of the upstream solar wind speed and the satellite's location in the magnetosheath. These results quantitatively support the generalization of Bernoulli's equation to the solar wind flowing through the bow shock, including the contribution of magnetic field energy.

On the northward shift of the heliospheric current sheet at the end of solar cycle 24

ABSTRACT Since solar cycle 16, the heliospheric current sheet (HCS) has been found to be shifted southward during the late declining to minimum phase. However, this trend is broken at the end of solar cycle 24. In this paper, we analyse the shift of the HCS by using information obtained from coronal model and in situ data provided by the near-Earth OMNI data base and the Parker Solar Probe (PSP). Coronal potential field source surface modelling results show that the northward shift is established at the beginning of 2018 and remains stable for about 2 yr. Interplanetary magnetic field data obtained from and within 1 au also support the northward shift, as the southern polarity T appears more frequently than the northern polarity A between 2018 and 2020. Both model results and in situ observation obtained by PSP imply that the HCS shift is established in the corona, and then propagates into the heliosphere. The quadrupole term still has a significant influence on the formation of the HCS shift.

The Response of the Earth Magnetosphere to Changes in the Solar Wind Dynamic Pressure: 1. Plasma and Magnetic Pressures

AbstractIn the present study, the influence of the solar wind dynamic pressure on the plasma and magnetic pressures of the magnetosphere is studied. We use 11‐year Time History of Events and Macroscale Interactions during Substorms (THEMIS) instruments for plasma and magnetic field measurements in the magnetosphere and the OMNI database for solar wind dynamic pressure and IMF data. We focus on the effects of the solar wind dynamic pressure (PSW) and consider only times in which the interplanetary magnetic field (IMF) components are within ±5 nT. We find that the plasma pressure inside the magnetosphere follows the solar wind dynamic pressure and that an increase in PSW also influence the day‐night pressure asymmetry. Our analysis also reveals the existence of ion and electron drifts from midnight toward the dusk and dawn sectors, respectively. We observe a local magnetic pressure minimum located near a plasma pressure maximum at around 11 RE on the nightside. Comparing the effect of PSW on both plasma and magnetic pressures, we observe trends which are consistent with the diamagnetic properties of plasmas. In general, the distribution of plasma pressure within the Earth's magnetosphere is an important criterion for evaluating the magnetostatic equilibrium and electric current system. The outcome of this study should provide additional methodologies for the characterization of key plasma characteristics within the magnetosphere.

Improving Enforcement Measures and Establishing Clear Criteria: A Content Analysis of Tobacco-Brand-Owned Instagram Accounts.

This study examines limitations of the current regulatory framework for tobacco advertising on Instagram. We first investigate compliance with Food and Drug Administration (FDA) warning label requirements for posts by tobacco-owned accounts. Next, we examine the prevalence of content that has been restricted in broadcast or print for its youth appeal, followed by content meeting more expansive criteria for youth appeal set forth in the FDA's guidance document. Posts by tobacco-brand-owned accounts between January 1, 2021, and February 14, 2022, were sampled from Mintel's Comperemedia Omni database. Instagram posts from 15 accounts were examined for violations of FDA warning label requirements and content that has been restricted on other mediums, including cartoons, sports branding, unauthorized claims, and young models (N = 1243). Finally, a subsample of n = 453 unambiguously branded posts was coded for themes that met the FDA's criteria of resonating with younger audiences, particularly that "adolescents rely on external information as they seek to shape their own identities." Only 12.8% of posts had fully compliant warning labels. Content that has been in some way regulated on other mediums, such as cartoons (1.6%), unauthorized health claims (<1%), sports branding (<1%), and young models (4.4%) were infrequent. However, a conservative analysis focusing only on branded posts found that posts frequently highlighted tech elements (45%), device customizability (24.5%), vaper identity (17.7%), stylized product photography (33.6%), social media engagement (32.2%), and memes (5.7%). Enforcement of existing regulations on Instagram is minimal. Explicit content restrictions applying evidence-based guidance on youth-appealing advertising are needed. This research has important implications for enforcing and expanding advertising regulations on social media. First, Instagram's self-imposed regulations are ineffective, permitting tobacco companies to post ads from brand-owned accounts despite claiming to restrict tobacco promotion on the platform. Second, policymakers should seek to apply FDA guidance on youth-appealing advertising informed by decades of research to create explicit enforceable content restrictions that extend beyond cartoons, sports figures, and young models to include content likely to situate tobacco use within the developing self-concept of vulnerable youth such as presenting e-cigarettes as hi-tech devices, highlighting vaper identity, or infiltrating online social media culture. Finally, greater resources for enforcement are needed given the only applicable regulation, warning labels, remains largely ignored.

Investigating the heliosphere, magnetosphere, atmosphere, and properties of cosmic rays during the 2018 Aug 25–26 strong geomagnetic storm

We investigated the conditions of the heliosphere, magnetosphere, and atmosphere from cosmic ray (CR) observations during the 2018 Aug 25–26 strong geomagnetic storm. The analysis involved the global survey (GS) and the spectrographic global survey (SGS) methods created and developed at the Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of the Siberian Branch of the Russian Academy of Sciences (ShICRA SB RAS) and at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS). Also, in our analysis, we used the data on direct measurements of the interplanetary medium parameters from the known OMNI database, CR measurements at the GOES geostationary satellites, from the global network of neutron monitors and muon detectors, from the Sayan spectrograph, and from the A.I. Kuzmin Yakutsk spectrograph of CR. When analyzing this event, the SGS enabled to obtain the data on the orientation of the mean interplanetary magnetic field, on the geomagnetic cutoff rigidity and its variations during the geomagnetic storm. Also, this method allowed us to estimate the bulk temperature over the point of recording CR, the ring current and the magnetopause current, as well as their contributions to the Dst-index, and also to establish differential rigidity spectra of CR at different stages of the magnetic storm evolution. Through the GS method, we determined the value and the directions for the first two spherical harmonics of CR distribution, and the direction to their anisotropy source. The results obtained through two different global survey methods are shown to be agree and mutually supplement each other. Using the Yakutsk spectrograph records enabled to determine the index for the power energy spectrum of variations in CR intensity during the investigated event.

Solar wind parameters in rising phase of solar cycle 25: Similarities and differences with solar cycles 23 and 24

Solar activity and solar wind parameters decreased significantly in solar cycles (SCs) 23–24. In this paper, we analyze solar wind measurements at the rising phase of SC 25 and compare them with similar data from the previous cycles. For this purpose, we simultaneously selected the OMNI database data for 1976–2022, both by phases of the 11-year solar cycle and by large-scale solar wind types (in accordance with catalog [http://www.iki.rssi.ru/pub/omni]), and calculated the mean values of the plasma and magnetic field parameters for the selected datasets. The obtained results support the hypothesis that the continuation of this cycle will be similar to that of cycle 24, i.e. SC 25 will be weaker than SCs 21 and 22

Параметры солнечного ветра на фазе роста 25-го солнечного цикла: сходства и различия с 23-м и 24-м солнечными циклами

Solar activity and solar wind parameters decreased significantly in solar cycles (SCs) 23–24. In this paper, we analyze solar wind measurements at the rising phase of SC 25 and compare them with similar data from the previous cycles. For this purpose, we simultaneously selected the OMNI database data for 1976–2022, both by phases of the 11-year solar cycle and by large-scale solar wind types (in accordance with catalog [http://www.iki.rssi.ru/pub/omni]), and calculated the mean values of the plasma and magnetic field parameters for the selected datasets. The obtained results support the hypothesis that the continuation of this cycle will be similar to that of cycle 24, i.e. SC 25 will be weaker than SCs 21 and 22

Prediction of Proton Pressure in the Outer Part of the Inner Magnetosphere Using Machine Learning

AbstractThe information on plasma pressure in the outer part of the inner magnetosphere is important for simulations of the inner magnetosphere and a better understanding of its dynamics. Based on 17‐year observations from both Cluster Ion Spectrometry and Research with Adaptive Particle Imaging Detector instruments onboard the Cluster mission, we used machine‐learning‐based models to predict proton plasma pressure at energies from ∼40 eV to 4 MeV in the outer part of the inner magnetosphere ( = 5–9). Proton pressure distributions are assumed to be isotropic. The location in the magnetosphere, the property of stably trapped particles, and parameters of solar, solar wind, and geomagnetic activity from the OMNI database are used as predictors. We trained several different machine‐learning‐based models and compared their performances with observations. The results demonstrate that the Extra‐Trees Regressor has the best predicting performance. The Spearman correlation between the observations and predictions by the model is about 70%. The most important parameter for predicting proton pressure in our model is the value, which relates to the property of stably trapped particles. The most important predictor of solar and geomagnetic activity is F10.7 index. Based on the observations and predictions by our model, we find that no matter under quiet or disturbed geomagnetic conditions, both the dusk‐dawn asymmetry at the dayside with higher pressure at the duskside and the day‐night asymmetry with higher pressure at the nightside occur. Our results have direct practical applications, for instance, inputs for simulations of the inner magnetosphere or the reconstruction of the 3‐D magnetospheric electric current system based on the magnetostatic equilibrium.

Research on the Effect of Data Assimilation for Three‐Dimensional MHD Simulation of Solar Wind

AbstractAs an important part of space weather forecasting, the prediction of solar wind parameters in the near‐Earth space is particularly significant. The introduction of data assimilation (DA) method can improve the reliability of numerical prediction. In this study, we use a three‐dimensional (3D) magnetohydrodynamics (MHD) numerical model with Kalman filter to infer the impact of the DA on solar wind modeling. We use the 3D MHD numerical model with near‐Earth in situ observations from the OMNI database to reconstruct solar wind parameters between 21.5 solar radii and 1 AU. The period from 2018 to 2021 is simulated, when the solar activity in the decay of the 24th solar cycle to the rising of 25th solar cycle. The numerical model generates two separate results, one without DA and one with DA directly performed on the model‐only results. Statistical analysis of observed, modeled and assimilated solar wind parameters at 1 AU reveals that assimilating simulations provide a more accurate forecast than the model‐only results with a sharp reduction in the root mean square error and an increase of correlation coefficient.

PLATEAU REGIONS IN THE MAGNETOSPHERIC PLASMA PRESSURE DISTRIBUTION AND LARGE-SCALE FIELD-ALIGNED CURRENTS

The radial distribution of the magnetospheric plasma pressure frequently shows the existence of definite features such as local increases and decreases. Regions with near to constant radial plasma pressure distribution were observed using INTERBALL/Tail probe and THEMIS mission satellites. Such regions were named the plasma pressure plateaus. In spite of the simultaneous observations near the same plateau pressure distribution by two satellites at near the same orbits with time delay ~30 min, it is essential to precisely separate purely temporal pressure changes from spatial variations. We compare the results of THEMIS observations with the predictions of Tsyganenko and Mukai [2003] model of magnetotail plasma pressure distribution using observed IMF and solar wind conditions from the OMNI data base. We also determine the projection of the observed pressure plateau to Iijima and Potemra [1978] picture of field-aligned currents using TS01, TA16 models. We show that observed plasma pressure profile cannot be the result of the temporal pressure changes.

Helium Abundance Decrease in ICMEs in 23–24 Solar Cycles

Based on the OMNI database, the influence of the solar activity decrease in solar cycles (SCs) 23–24 on the behavior of the relative helium ions abundance Nα/Np inside interplanetary coronal mass ejections (ICMEs) is investigated. The dependences of the helium abundance on the plasma and interplanetary magnetic field parameters in the epoch of high solar activity (SCs 21–22) and the epoch of low activity (SCs 23–24) are compared. It is shown that Nα/Np significantly decreased in SCs 23–24 compared to SCs 21–22. The general trends of the dependences have not changed with the change of epoch, but the helium abundance dependences on some parameters (for example, the magnitude of the interplanetary magnetic field) have become weaker in the epoch of low activity than they were in the epoch of high activity. In addition, the dependence of the helium abundance on the distance from spacecraft to the ICME axis was revealed; the clearest dependence is observed in magnetic clouds. The Nα/Np maximum is measured at the minimum distance, which confirms the hypothesis of the existence of a helium-enriched electric current inside an ICME.

Peculiarities of the Heliospheric State and the Solar-Wind/Magnetosphere Coupling in the Era of Weakened Solar Activity

Based on the data of the solar wind (SW) measurements of the OMNI database for the period 1976–2019, we investigate the behavior of SW types, as well as plasma and interplanetary magnetic field (IMF) parameters, for 21–24 solar cycles (SCs). Our analysis shows that with the beginning of the period of low solar activity (SC 23), the number of all types of disturbed events in the interplanetary medium decreased, but the proportion of magnetic storms initiated by CIR increased. In addition, a change in the nature of SW interaction with the magnetosphere could occur due to a decrease in the density, temperature, and IMF of solar wind.

Dynamical Coupling between Anomalous Cosmic Rays and Solar Wind in Outer Heliosphere

Voyager 2 (V2) observed that pickup ions (PUIs) and anomalous cosmic rays (ACRs) have a significant influence on the solar wind structures in the outer heliosphere. In particular, the maxima in energetic particle intensities often lagged behind the shock front, while the flow velocity in some cases featured a precursor in front of the shock. These two effects are believed to be caused by the cease of ACR injection from PUIs at large heliocentric distances, and the backward diffusion of ACRs, respectively. This paper investigates the dynamical coupling between the ACRs and the solar wind in the outer heliosphere by means of a time-dependent numerical MHD simulation, in which the ACRs are treated as a massless fluid that only contributes its pressure to the system. Two types of inner boundary conditions were used, namely a synthetic short-term shock event and an extended period of data-driven solar wind variability based on the OMNI database. The lag of the ACR pressure maximum relative to the shock front, and the extended shock precursor were reproduced by the numerical results. The increase rate of the lag is related to the corresponding diffusion coefficient and the injection efficiency from PUIs to ACRs. The model was also applied to the termination shock, where simulations likewise showed that the peak in the ACR distribution can be located a short distance downstream of the shock front, indicating that the time-dependent diffusive shock acceleration mechanism is a candidate to interpret the lag between the ACR pressure peak and the shock front observed by V2.

Multi-Variate LSTM Prediction of Alaska Magnetometer Chain Utilizing a Coupled Model Approach

During periods of rapidly changing geomagnetic conditions electric fields form within the Earth’s surface and induce currents known as geomagnetically induced currents (GICs), which interact with unprotected electrical systems our society relies on. In this study, we train multi-variate Long-Short Term Memory neural networks to predict magnitude of north-south component of the geomagnetic field (|BN|) at multiple ground magnetometer stations across Alaska provided by the SuperMAG database with a future goal of predicting geomagnetic field disturbances. Each neural network is driven by solar wind and interplanetary magnetic field inputs from the NASA OMNI database spanning from 2000–2015 and is fine tuned for each station to maximize the effectiveness in predicting |BN|. The neural networks are then compared against multivariate linear regression models driven with the same inputs at each station using Heidke skill scores with thresholds at the 50, 75, 85, and 99 percentiles for |BN|. The neural network models show significant increases over the linear regression models for |BN| thresholds. We also calculate the Heidke skill scores for d|BN|/dt by deriving d|BN|/dt from |BN| predictions. However, neural network models do not show clear outperformance compared to the linear regression models. To retain the sign information and thus predict BN instead of |BN|, a secondary so-called polarity model is utilized. The polarity model is run in tandem with the neural networks predicting geomagnetic field in a coupled model approach and results in a high correlation between predicted and observed values for all stations. We find this model a promising starting point for a machine learned geomagnetic field model to be expanded upon through increased output time history and fast turnaround times.

Validation of the use of THEMIS-B and THEMIS-C as a near-Earth solar wind monitor

Two THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft, B and C, began orbiting the Moon in 2011 and have since provided routine measurements of the plasma conditions in the lunar orbit. In this study, we systematically compare these measurements in near-Earth space with solar wind measurements obtained from the Lagrangian 1 (L1) point and propagated to the Earth, including measurements in the OMNI database and from the Wind spacecraft. A statistical comparison between THEMIS data and data from the OMNI database from September 2011 to December 2017 showed that the <em>Y</em> and <em>Z</em> components of the magnetic field and the flow speed are generally consistent between the two data sets. The ion number density and the dynamic pressure measured by THEMIS in near-Earth space are lower than those in the OMNI database, suggesting possible variation in the solar wind environment while propagating from the L1 point to near-Earth space. We further show two examples in which near-Earth solar wind measurements are applied in calculating the magnetopause location and in quantifying the magnetic field response to interplanetary shocks. Both examples suggest that using solar wind data from near-Earth space achieves better results than using solar wind data from the L1 point. These results provide validation of THEMIS-B and THEMIS-C as an alternative monitor of the near-Earth solar wind environment.

Potential of Regional Ionosphere Prediction Using a Long Short‐Term Memory Deep‐Learning Algorithm Specialized for Geomagnetic Storm Period

AbstractIn our previous study (Moon et al., 2020, https://doi.org/10.3938/jkps.77.1265), we developed a long short‐term memory (LSTM) deep‐learning model for geomagnetic quiet days (LSTM‐quiet) to perform effective long‐term predictions for the regional ionosphere. However, their model could not predict geomagnetic storm days effectively at all. This study developed an LSTM model suitable for geomagnetic storms using the new training data set and redesigning input parameters and hyper‐parameters. We collected 131 days of geomagnetic storm cases from January 1, 2009 to December 31, 2019, provided by the Japan Meteorological Agency's Kakioka Magnetic Observatory, and obtained the interplanetary magnetic field Bz, Dst, Kp, and AE indices related to the geomagnetic storm corresponding to each storm date from the OMNI database. These indices and F2 parameters (foF2 and hmF2) of Jeju ionosonde (33.43°N, 126.30°E) were used as input parameters for the LSTM model. To test and verify the predictive performance and the usability of the LSTM model for geomagnetic storms developed in this manner, we created and diagnosed the 0.5, 1, 2, 3, 6, 12, and 24‐h predictive LSTM models. According to the results of this study, the LSTM storm model for 24‐h developed in this study achieved a predictive performance during the three geomagnetic storms about 32% (10%), 34% (17%), and 37% (5%) better in root mean square error of foF2 (hmF2) than the LSTM quiet model (Moon et al., 2020, https://doi.org/10.3938/jkps.77.1265), SAMI2, and IRI‐2016 models. We propose that the short‐term predictions of less than 3 h are sufficiently competitive than other traditional ionospheric models. Thus, this study suggests that our model can be used for short‐term prediction and monitoring of the regional mid‐latitude ionosphere.

Drop of Solar Wind at the End of the 20th Century

AbstractVariations in the solar wind (SW) parameters with scales of several years are an important characteristic of solar activity and the basis for a long‐term space weather forecast. We examine the behavior of interplanetary parameters over 21–24 solar cycles (SCs) on the basis of the OMNI database (https://spdf.gsfc.nasa.gov/pub/data/omni). Since changes in the parameters can be associated with both changes in the number of different large‐scale types of SW and with variations in the values of these parameters at different phases of the solar cycle and during the transition from one cycle to another, we select the entire study period in accordance with the Catalog of large‐scale SW types for 1976–2019 (see the site http://www.iki.rssi.ru/pub/omni, [Yermolaev, Nikolaeva, et al., 2009, https://doi.org/10.1134/s0010952509020014], which covers the period from 21 to 24 SCs) and in accordance with the phases of the cycles, and average the parameters at selected intervals. In addition to a sharp drop in the number of interplanetary coronal mass ejections and associated sheath types, there is a noticeable drop in the value (by 20%–40%) of plasma parameters and magnetic field in different types of solar wind at the end of the 20th century and a continuation of the fall or persistence at a low level in the 23–24 cycles. Such a drop in the solar wind is apparently associated with a decrease in solar activity and manifests itself in a noticeable decrease in space weather factors.

Solar wind temperature–velocity relationship over the last five solar cycles and Forbush decreases associated with different types of interplanetary disturbance

ABSTRACT The behaviour of the solar wind (SW) proton temperature and velocity and their relationship during Forbush decreases (FDs) associated with various types of solar source – coronal mass ejections (CMEs) and coronal holes (CHs) – have been studied. Analysis of cosmic ray variations, SW temperature, velocity, density, plasma beta, and magnetic field (from 1965–2019) is carried out using three databases: the OMNI database, Variations of Cosmic Rays database (IZMIRAN) and Forbush Effects &amp; Interplanetary Disturbances database (IZMIRAN). Comparison of the observed SW temperature (T) and velocity (V) for the undisturbed SW allows us to derive a formula for the expected SW temperature (Texp, the temperature given by a T–V formula, if V is the observed SW speed). The results reveal a power-law T–V dependence with a steeper slope for low speeds (V &amp;lt; 425 km s−1, exponent = 3.29 ± 0.02) and flatter slope for high speeds (V &amp;gt; 425 km s−1, exponent = 2.25 ± 0.02). A study of changes in the T–V dependence over the last five solar cycles finds that this dependence varies with solar activity. The calculated temperature index KT = T/Texp can be used as an indicator of interplanetary and solar sources of FDs. It usually has abnormally large values in interaction regions of different-speed SW streams and abnormally low values inside magnetic clouds (MCs). The results obtained help us to identify the different kinds of interplanetary disturbance: interplanetary CMEs, sheaths, MCs, corotating interaction regions, high-speed streams from CHs, and mixed events.

Differences in the Dynamics of the Asymmetrical Part of the Magnetic Disturbance during the Periods of Magnetic Storms Induced by Different Interplanetary Sources

The differences in the dynamics of the asymmetrical part of the geomagnetic disturbance at middle and low latitudes during magnetic storms initiated by different interplanetary sources are analyzed. The analysis is performed with the SYM-H, ASY-H, and Dst indices from the OMNI database during the periods of 58 intense magnetic storms with –270 ≤ Dstmin ≤ –90 nT that were recorded in 1995–2017 and initiated by one of the solar wind structures: compressed corotating interaction regions (CIRs); interplanetary coronal mass ejections (ICMEs) including magnetic clouds (MCs) and Ejecta “pistons”; and compressed Sheath regions in front of ICMEs. The interplanetary sources were identified on the basis of the catalog of large-scale solar-wind phenomena ( ftp://ftp.iki.rssi.ru/pub/omni/ ). A double superposed epoch analysis with reference points at the onset of the storm and during Dstmin was used. It is shown that the ASY-H values during Sheath-driven storms are, on average, 40% higher than for storms of other groups and that the ASY-H maximum occurs ~3 h earlier than Dstmin during Sheath-driven storms and 1–2 h earlier during MC-driven storms, which may indicate a more intense and uneven energy inflow during these periods. It is assumed that this energy inflow may be provided by the proton flux with energies of >10 MeV observed by the GOES geostationary satellites, which increases by more than two orders of magnitude in the intervals of Sheath-driven storms as compared to storms of other groups.

Temporal Evolution of the Rotation of the Interplanetary Magnetic Field Bx, By, and Bz Components

Abstract The daily interplanetary magnetic field (IMF) B x , B y , and B z components from 1967 January 1 to 2018 December 31 listed in the OMNI database are used to investigate their periodicity and study temporal variation of their rotation cycle lengths through continuous wavelet transform, autocorrelation, and cross-correlation analyses. The dominant rotation period in each of the daily B x , B y , and B z components is 27.4 days, implying the existence of rotational modulation in the three time series. The dependence of the rotation cycle lengths for both B x and B y components on solar cycle phase almost shows the same result. The rotation cycle lengths for both B x and B y components increase from the start to the first year of a new Schwabe cycle, then decrease gradually from the first to the fourth year, and finally fluctuate around the 27.4-day period within a small amplitude from the fourth year to the end of the Schwabe solar cycle. For the B z component, its rotation cycle length does not show such a solar cycle variation. The significant periods in the variation of B x rotation are 2.9, 3.4, 4.3, 4.9, 10.5, and 11.9 yr, and there exist significant periods of 3.4, 9.9, and 14.1 yr in the variation of B y rotation. The relationship of solar activity with B x and B y components is complex. The possible mechanisms for the temporal variation of the rotation period of the three components are discussed.