Геомагнитное обрезание космических лучей во время магнитной бури 23–24 марта 2023 г.: связь с параметрами солнечного ветра и геомагнитной активностью с учетом широтных эффектов

Today's geomagnetic field can prevent energetic particles, including solar energetic particles and galactic cosmic rays, from directly hitting the Earth's atmosphere. However, when the geomagnetic field strength is significantly decreased during geomagnetic field excursions or reversals, the geomagnetic field shielding effect becomes less prominent. Geomagnetic cutoff rigidity, as a quantitative estimation of the shielding effect, can be calculated using trajectory tracing or theoretical equations. We use a recent high‐resolution continuous geomagnetic field model (LSMOD.2) to study the geomagnetic cutoff rigidity during the Laschamps excursion. Global grids of the geomagnetic cutoff rigidities are presented, in particular for the excursion midpoint when the geomagnetic field is weak and not dipole‐dominated anymore at Earth's surface. We compare the cutoff rigidity calculation results between a trajectory tracing program and theoretical equations and we find that the influence of the non‐dipole component of the geomagnetic field cannot be ignored during the excursion. Our results indicate that the exposure of Earth's atmosphere to energetic particles of cosmic and solar origin is high and nearly independent of latitude in the middle of the Laschamps excursion. Our results will be useful for future studies associated with cosmic radiation dose rate and cosmogenic isotope production rate during the Laschamps excursion.

The period of interplanetary, geomagnetic and solar disturbances of September 7–15, 2005, is characterized by two sharp increases of solar wind velocity to 1000 km/s and great Dst variation of the geomagnetic field (~140 nT). The time variations of theoretical and experimental geomagnetic thresholds observed during this strong geomagnetic storm, their connection with solar wind parameters and the Dst index, and the features of latitudinal behavior of geomagnetic thresholds at particular times of the storm were studied. The theoretical geomagnetic thresholds were calculated with cosmic ray particle tracing in the magnetic field of the disturbed magnetosphere described by Ts01 model. The experimental geomagnetic thresholds were specified by spectrographic global survey according to the data of cosmic ray registration by the global station network.

Cosmic ray variations due to changes in the magnetosphere are evaluated for severe magnetic storm on 20 November 2003 using data from the worldwide neutron monitor network and the global survey method. From these results the changes in the planetary distribution of magnetic cutoff rigidities during this disturbed period are obtained in dependence of latitude. A correlation between Dst index and cutoff rigidity variations was defined for each cosmic ray station. The maximum changes in cutoff rigidities occurred while Dst index was around −472 nT. Geomagnetic effect in cosmic ray intensity reached at some stations 6–8%, and it seems to be the greatest one over the history of neutron monitor observations. The latitudinal distribution shows a maximum changes at geomagnetic cutoff rigidities around 7–8 GV. This corresponds to unusually low latitudes for maximal effect. Cutoff rigidity variations were also calculated utilizing the last model of Tsyganenko for a disturbed magnetosphere (T01S). A comparison between experimental and modeling results revealed a big discrepancy at cutoff rigidities less than 6 GV. The results on the geomagnetic effect in cosmic rays can be used for validating magnetospheric field models during very severe storms.

It is well known that both the galactic and anomalous cosmic rays show positive intensity gradients in the outer heliosphere which are connected with corresponding pressure gradients. Due to an efficient dynamical coupling between the solar wind plasma and these highly energetic media by means of convected MHD turbulences, there exists a mutual interaction between these media. As one consequence of this scenario the enforced pressure gradients influence the distant solar wind expansion. Here we concentrate in our theoretical study on the interaction of the solar wind only with the anomalous cosmic-ray component. We use the standard two-fluid model in which the cosmic-ray fluid modifies the solar wind flow via the cosmic-ray pressure gradient. Then we derive numerical solutions in the following steps: first we calculate an aspherical pressure distribution for the anomalous cosmic rays, describing their diffusion in an unperturbed radial solar wind. Second, we then consider the perturbation of the solar wind flow due to these induced anomalous cosmic-ray pressure gradients. Within this context we especially take account of the action of a non-spherical geometry of the heliospheric shock which may lead to pronounced upwinddownwind asymmetries in the pressures and thereby in the resulting solar wind flows. As we can show in our model, which fits the available observational data, radial decelerations of the distant solar wind by between 5 to 11% are to be expected, however, the deviations of the bulk solar wind flow from the radialdirections are only slightly pronounced.

Nonlinear interdependence features in solar wind parameters influencing geomagnetic activity during geomagnetic storm

Development of a web monitor for the water Cherenkov detectors array of the LAGO project

The correlation between the variations of geomagnetic cutoff rigidity ΔR and interplanetary parameters and the Dst index of geomagnetic activity during one moderate and six strong storms of solar cycles 23 and 24 has been calculated. The ΔR values have been obtained with two methods: (1) the spectrographic global survey method (SGS), in which the determination of the cutoff rigidity RSGS is based on observational data from the neutron monitor network, and (2) a method in which the particle trajectories are calculated numerically in a model magnetic field of the magnetosphere to determine the cutoff rigidity Reff. In general, the results obtained by the two methods are in close agreement. The Dst index of geomagnetic activity has the greatest effect on ΔR, and the correlation increases with storm intensity. The sensitivity of ΔR to interplanetary parameters vary greatly for different storms. The most geoeffective interplanetary parameter is the solar-wind speed V. A significant anticorrelation of ΔR and V can be traced for almost all storms. The correlation of ΔRSGS with the Bz component of the interplanetary magnetic field is observed only for two storms, on November 7–14, 2003, and November 7–8, 2004, for which the absolute Bz value was very high (≈−50 nT). At the same time, there is a rather high correlation of ΔReff with Bz for most storms. The azimuthal component of the interplanetary field By and the solar-wind dynamic pressure P show almost no connection with ΔR.

Investigation on contribution of neutron monitor data to estimation of aviation doses

We presented a new method of the neutron monitors’ (NM’s) effective energy estimation based on the 27‑day galactic cosmic rays (GCR) variations: using AMS-02 measurements we study rigidity dependance of 27-day variations’ amplitude and calculate the energy value so that the variability of the GCR particles at this energy is equal to that of the NM’s count rate. We examined how NM’s effective energy depends on the geomagnetic cutoff rigidity using data of several NM.

The Latin American Giant Observatory (LAGO) is a widespread cosmic ray observatory which uses water-Cherenkov Detectors (WCD) deployed in nine Latin American countries, being able to detect transient events or long term modulation effects simultaneously at places having different geomagnetic rigidity cut-offs and altitudes. In this work, results of studies on cosmic ray muon flux variations during the Forbush decrease of 22 June 2015 registered by the LAGO detector installed at the University of Campinas, Brazil, ${22^{o}49^{'}03^{}S, 47^{o}04^{'}11^{}W}$ at 650 m a.s.l., the TANCA detector, are presented. TANCA is a cylindrical polyethylene tank of 10 $m^2$ containing a sealed liner with a reflective inner surface. The liner contains 11400 liters of ultra-pure water. Cherenkov light produced by the passage of particles through the water is collected by three nine-inch-diameter photomultiplier tubes. The experimental setup and detector performance is also presented. The studies on Forbush decrease contain comparisons with neutron monitors and indices of Earth's magnetic activity.

Using data of satellite and ground-based cosmic ray (CR) observations at the worldwide network of neutron monitors, Forbush effects (FE) in November 2012 have been studied using the spectrographic global survey (SGS) method. The SGS method allows investigating variations in the rigidity spectrum, anisotropy, and changes in the geomagnetic cutoff rigidity during every hour of observations. Data of ground-based measurements on the worldwide network of neutron monitors (41 stations) averaged over 1-hour intervals, and data from the GOES-15 satellite were used for the analysis. Relative changes in CR intensity with R = 4 GV in the Geocentric Solar Ecliptic coordinate system for different time points of the period studied are presented.

Solar wind magnetosphere coupling: Predicted and modeled with intelligent hybrid systems

Quantitatively relating cosmic rays intensities from solar activity parameters based on structural equation modeling

We present a new parameterization of quintessence potentials for dark energy based directly upon the dynamical properties of the equations of motion. Such parameterization arises naturally once the equations of motion are written as a dynamical system in terms of properly defined polar variables. We have identified two different classes of parameters, and we dubbed them as dynamical and passive parameters. The dynamical parameters appear explicitly in the equations of motion, but the passive parameters play just a secondary role in their solutions. The new approach is applied to the so-called thawing potentials and it is argued that only three dynamical parameters are sufficient to capture the evolution of the quintessence fields at late times. This work reconfirms the arbitrariness of the quintessence potentials as the recent observational data fail to constrain the dynamical parameters.

A self‐consistent model was developed to study the stochastic acceleration (second‐order Fermi) of interstellar pickup ions in the quiet solar wind (SW) and inside corotating merged interaction regions (CMIRs) in the presence of the effects of wave coupling and the damping of magnetohydrodynamic waves by pickup ions. Our simulations of the solar wind wave spectrum show that (1) Pickup H+ is mainly responsible for wave damping at large wave numbers with pickup He+ contributing very little and pickup O+ contributing nothing. (2) Strong wave‐wave interactions wash out wave‐damping effects for radial distances r ≤ 10 AU from the Sun in the quiet solar wind and for r ≤ 23 AU inside corotating merged interaction regions. This is to be contrasted with previous work which calculated strong wave damping inside 10 AU from the Sun in the absence of wave coupling. For the simulated pickup ion spectra the main results are as follows: (1) The pickup He+ and O+ spectra are unaffected by the wave damping. (2) In contrast, the accelerated pickup H+ spectra have concave features for kinetic energies 1–5 KeV which become more pronounced with increasing radial distance. This suppression of the pickup H+ acceleration is attributed to the wave damping caused by the pickup H+. (3) Inside corotating merged interaction regions the preacceleration of pickup ions is stronger because of the enhanced heliospheric magnetic field. The suppression of pickup H+ acceleration is smaller and only starts to show for r > 23 AU. (4) Under the assumption that the seed population of anomalous cosmic rays should have speeds v > 400 km s−1 the H+/He+ density ratio in this population can be as low as ∼2.6 in the quiet solar wind and ∼13 inside corotating merged interaction regions. Compared with the observed ratio of ∼6 for anomalous cosmic rays (ACRs), our conclusion is that if CMIR and quiet SW regions are considered together, then the observed under abundance in ACR H+ could in principle be produced on average.