Geomagnetic Cutoff Rigidity Research Articles

Modeling the Atmospheric Ionization Rate During a Geomagnetic Reversal

AbstractThe Matuyama‐Brunhes reversal of Earth's magnetic dipole field took place 0.78 Ma ago, and detailed temporally resolved paleomagnetic data are available for this period. A geomagnetic reversal is expected to impact the cosmic ray flux, which in turn affects atmospheric ionization rates. To assess the magnitude of this effect, three preexisting models are used in tandem to yield 3D time series of the atmospheric ionization rates for the entire globe during the reversal. Specifically the time variable paleomagnetic field data is input into a particle trajectory calculator to produce geomagnetic cutoff rigidity maps for the entire globe. This is combined with an empirical model of the local interstellar cosmic ray spectrum and ionization yield functions based on Monte Carlo atmospheric particle simulations to produce novel time variable 3D atmospheric ionization rates during the reversal. As the dipole field weakens, the atmospheric ionization increases at low latitudes. The increase is ca. 25% at the surface and up to a factor of 5 in the upper atmosphere. Globally, ionization rates increase around 13% at the surface and up to a factor of 2 in the upper atmosphere, whereas polar regions are largely unaffected. Finally, the change in ionization due to the solar 11‐year cycle is greatly affected by the reversal. The relative change in atmospheric ionization between solar‐minimum and solar‐maximum varies between 2 and two orders of magnitude.

The capability of water Cherenkov detectors arrays of the LAGO project to detect Gamma-Ray Burst and high energy astrophysics sources

Gamma-Ray Bursts (GRBs) are one of the brightest transient events detected, with energies in their prompt phase ranging from keV to GeV. Theoretical models predict emissions at higher energies in the early times of the afterglow emission, and recently GRB190114C was the first GRB detected at TeV energies by the MAGIC experiment. The Latin American Giant Observatory (LAGO) operates a network of water Cherenkov detectors (WCD) at different sites in Latin America. Spanning over different altitudes and geomagnetic rigidity cutoffs, the geographic distribution of the LAGO sites, combined with the new electronics for control, atmospheric sensing, and data acquisition, allows the realization of diverse astrophysics studies at a regional scale. LAGO WCDs located at high altitudes possess good sensitivity to electromagnetic secondary radiation, which is the main expected signature of this kind of high-energy event on the ground. Due to the characteristics of the WCD and the wide field of view, LAGO possesses a large aperture high-duty cycle. In this work, we present the results of the sensitivity of LAGO small arrays of WCDs for the detection of events like GRB190114C. Also, we extend the study to other TeV galactic emitters, such as pulsar wind nebulas, TeV-halos, and some additional sources with unidentified categorizations. These are interesting sources to study taking advantage of the long-term monitoring capabilities of LAGO. We use a dedicated simulation process: ARTI, a toolkit developed by LAGO for high-energy air showers, MEIGA, a framework to simulate the response of the detectors, and oneDataSim, the new high-performance computing and cloud-based implementation of our simulation framework.

Estimation of the neutron monitors’ effective energies based on the 27-day galactic cosmic rays variations

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.

Monitoring of heliosphere, magnetosphere and atmosphere via cosmic ray effects in August 2018

Using data of ground-level cosmic ray measurements on the neutron monitor network, along with data of Yakutsk muon telescope complex and muon hodoscope URAGAN (Moscow) uncorrected for temperature, we used modified spectrographic global survey method for an August 2018 event to split cosmic ray variations into components of primary, magnetospheric and atmospheric origin. Time evolutions of isotropic primary flux for different rigidities, pitch-angle anisotropy of cosmic rays, interplanetary magnetic field orientation were obtained, variations in geomagnetic cut-off rigidity in Irkutsk and average-mass temperature over charged components’ measurement sites were also shown.

Variations in cosmic ray cutoff rigidities during the March 8–11, 2012 magnetic storm (CAWSES II period)

The geomagnetic cutoff rigidity of cosmic rays (CRs) is the main factor regulating the arrival of CR particles at a given point on Earth's surface or inside the magnetosphere. To study the relationship between cutoffs and near-Earth space parameters, we have selected the strongest magnetic storm that occurred on March 8–11, 2012 during the CAWSES-II interval, recommended by SCOSTEP for detailed studies of solar-terrestrial relations. We have found the geomagnetic cutoffs by two methods: 1) by trajectory calculations in the magnetic field of the perturbed magnetosphere according to the Ts01 model and 2) by the spectrographic global survey method according to the data from the world network of neutron monitors. The largest drop in the cutoffs (−1.1 GV) obtained by the latter method was observed during the recovery phase of the storm. Apparently, this is due to the influence of the supersubstorms that occurred at that time. The analysis has shown that the closest connection of variations in the cutoffs can be traced with the geomagnetic activity index Dst, which indicates the determining contribution of the ring current to the transport of CRs. In addition, we have found a significant connection with the electromagnetic field parameters (with the Bz component of the interplanetary magnetic field and the azimuthal component of the electric field Ey). The dynamic solar wind parameters practically do not control variations in CR geomagnetic cutoff rigidities.

Изменения жесткостей обрезания космических лучей во время бури 8–11 марта 2012 г в период CAWSES-II

The geomagnetic cutoff rigidity of cosmic rays (CRs) is the main factor regulating the arrival of CR particles at a given point on Earth's surface or inside the magnetosphere. To study the relationship between cutoffs and near-Earth space parameters, we have selected the strongest magnetic storm that occurred on March 8–11, 2012 during the CAWSES-II interval, recommended by SCOSTEP for detailed studies of solar-terrestrial relations. We have found the geomagnetic cutoffs by two methods: 1) by trajectory calculations in the magnetic field of the perturbed magnetosphere according to the Ts01 model and 2) by the spectrographic global survey method according to the data from the world network of neutron monitors. The largest drop in the cutoffs (−1.1 GV) obtained by the latter method was observed during the recovery phase of the storm. Apparently, this is due to the influence of the supersubstorms that occurred at that time. The analysis has shown that the closest connection of variations in the cutoffs can be traced with the geomagnetic activity index Dst, which indicates the determining contribution of the ring current to the transport of CRs. In addition, we have found a significant connection with the electromagnetic field parameters (with the Bz component of the interplanetary magnetic field and the azimuthal component of the electric field Ey). The dynamic solar wind parameters practically do not control variations in CR geomagnetic cutoff rigidities.

Simulation of cosmic rays inside an aircraft: spectral perturbation and dose reduction due to aircraft structures and contents.

In this study, an intricate combinatorial geometry model of a Boeing 777-300ER aircraft was constructed for Monte Carlo transport simulations. The aircraft-induced perturbations of the energy spectra and effective doses of secondary cosmic rays at a typical civil aviation altitude (10km) were investigated on a component-by-component basis, which included neutrons, protons, photons, electrons, positrons, muons and charged pions. Two geomagnetic cutoff rigidities (1.35 and 15.53 GV) and two solar modulation parameters (430 and 1360 MV) were considered in the aforementioned simulations. The characteristics of various cosmic-ray components at six locations along the fuselage were assessed and compared with those of an unperturbed radiation field in the atmosphere. Aircraft structures and contents reduced the effective doses of personnel inside the aircraft to varying degrees, up to an ~32% reduction in the middle section of the passenger cabin. On average, the dose reduction was ~12-16% depending on geomagnetic and solar conditions. Quantifying the aircraft's self-shielding effects can further improve the estimation accuracy of aircrew and passengers' exposure to cosmic radiation. Information regarding the perturbed energy spectra of cosmic rays may be useful for designing onboard experiments or analyzing onboard measurement data.

Cosmic ray cutoff rigidity governing by solar wind and magnetosphere parameters during the 2017 Sep 6–9 solar-terrestrial event

For the 2017 Sep 6–9 geomagnetic disturbance, we calculated (within the Tsyganenko magnetospheric magnetic field model Ts01) the cosmic ray (CR) geomagnetic cutoff threshold rigidities. We also compared those values with the calculation results obtained from ground-based observations at the global network of neutron monitors (GNNM) through the spectrographic global survey (SGS). Shown is a satisfactory correlation between the geomagnetic cutoff threshold rigidity variations obtained based on the Ts01 model and those obtained from the GNNM ground-based observations. An intercorrelation of the CR geomagnetic threshold variations with the parameters for geomagnetic activity, for solar wind, and for the interplanetary magnetic field (IMF) was established to be different at different stages of the magnetospheric-geomagnetic disturbance. This is because such an intercorrelation is caused by the dynamics of current systems, whose intensifying and damping occur differently over different time intervals. During the storm main phase, the geomagnetic cutoff rigidity threshold variation is shown to be governed, mainly, by the Dst and by the solar wind velocity, as well as by the IMF southern component and by the electric field azimuth component.

Angular distribution of low momentum atmospheric muons at ground level

We report measurements of the angular distributions of low momentum atmospheric muons at 38 m above sea level for zenith angles θ between -60 and 60 degrees in the south-north direction. The muon detection was performed with two NaI(Tl) scintillation detectors mounted in coincidence. An adjustable lead thickness placed between the detectors allowed to select muons with a minimal momentum ranging from 0.3 to 0.9 GeV/c. The integrated and the differential muon flux were determined by analyzing the deposited energy spectra in the scintillators backed up by a Geant4 simulation of the experimental setup. The results are consistent with the cos n (θ) distribution in good agreement with the literature. These data contribute to fill the gap in the geomagnetic cutoff rigidity interval 8 GV < Pc < 14 GV where no similar measurements were performed before. We found that n = 1.88 - 0.12 Pμ c in this domain of muon momenta cutoff Pμ c < 1 GeV/c. The present measurements are useful for many muon studies requiring an accurate integrated flux.

Probing solar storms with GRAPES-3 scintillator detectors

The GRAPES-3 muon telescope in Ooty, India detected a 2-h burst of cosmic ray muons (Eμ⩾1GeV) on 22 June 2015 upon the arrival of a strong coronal mass ejection which triggered a G4 class geomagnetic storm. A detailed study of this event with the aid of Monte Carlo simulations suggests that the observed excess muons are due to a weakening of Earth’s magnetic field caused by reconnection of the strong Bz component of interplanetary magnetic field with that of Earth (Mohanty, 2016). This caused a lowering of the geomagnetic cutoff rigidity and led to the entering of excess threshold cosmic rays into the Earth’s atmosphere. The event was also analyzed with the data recorded by the GRAPES-3 scintillator detector array. These detectors record cosmic ray shower particles above a few MeV energy in contrast to GeV threshold of the muon telescope, but they lack directional information. Here, we will present these results and compare them with the results from the muon telescope. We will discuss the relevance of these results to the space weather prediction.

A proposal to extend the spectrographic global survey method

We present a modified spectrographic global survey method to split the cosmic ray variations into components of the interplanetary, geomagnetospheric, and atmospheric origin from ground-based observations of the cosmic ray intensity. We show a possibility to use all the available suite of ground-based instrumentation recording cosmic rays (global network of the neutron monitors located at different locations and altitudes, ground- and underground-based muon telescopes, etc.) for such studies without involving the data from aerologic atmospheric sounding. As a demonstration of the method functionality, we provide the calculation results for the variations in the isotropic flux, pitch angle anisotropy of primary cosmic rays in the interplanetary space, changes in the planetary system of geomagnetic cutoff rigidities for every observational hour, as well as the atmosphere temperature above the point of observation of cosmic ray charged components for selected time intervals.

Study of the Ground Level Enhancements effect on atmospheric electric properties and mineral dust particle charging

The effect of Ground Level Enhancements (GLEs) on the atmospheric and dust particles electrical properties is studied. It has been found that in the case of fair weather conditions, GLE events enhance the atmospheric electrical conductivity, reduce the columnar resistance, and modify the fair weather electric field, air–earth conduction current, and possibly the Ionospheric Potential (IP) in a way that depends on the geomagnetic cut-off rigidity of the location and the altitude. If a dust particle layer is present, GLE events tend to cancel its electrical effects in the ambient atmosphere. This means that the enhancement of the electric field and the reduction of atmospheric electrical conductivity, caused by the ion attachment to dust particles, not only tend to return to their ambient fair weather values, but they can be further modified as if the dust layer was not present. Finally, in terms of dust particles’ electrical properties, GLE events tend to modify the ion attachment mechanism, and in principle, the particle net charge, and the electric field “sensed” by them, increase. Nevertheless, since the electrical force magnitude is up to six orders of magnitude less than gravity, the increase of the particles’ electrical properties is not sufficient to modify the particle settling dynamics and settling velocities.

Study on Long-Term Variation Characteristics of Geomagnetic Cutoff Rigidities of Energetic Protons Caused by Long-Term Variation of Geomagnetic Field

As a parameter that quantitatively measures the shielding effect of the Earth’s magnetic field on energetic particles, the geomagnetic cutoff rigidities will change significantly with the long-term change of geomagnetic field. In this article, by using the numerical simulation method, combined with the variation trend of the Earth’s main field International Geomagnetic Reference Field (IGRF) model and the energetic particles’ windows (EPWs), the variation characteristics of the cutoff rigidities of geomagnetic energetic particles in the vertical direction from 1965 to 2025 were studied. The study found that there is a close relationship between the cutoff latitude corresponding to the cutoff rigidities and the background magnetic field intensity, but they are not in a simple linear relationship. The changes of the cutoff rigidities and geomagnetic field in the northern and southern hemispheres are asymmetric. The weakening of the geomagnetic field will push the cutoff latitudes toward the near equatorial region in the southern hemisphere, but for northern hemisphere the phenomenon is not always credible. In the northern hemisphere, the areas of EPWs will decrease at a relative rate of 0.03%/yr, but in the southern hemisphere, it will increase at a rate of about 0.05%/yr to 0.12%/yr. The long-term trajectory of the positions of the EPWs’ central points do not correspond to geomagnetic poles, nor the magnetic dip poles, relatively speaking, its position is closer to the geomagnetic poles. The study can be used for a long-term forecasting of cutoff rigidities caused by background geomagnetic field variations.

Cosmic Radiation Exposure of Aircraft Crew under the Impact of Geomagnetic Vertical Cutoff Rigidity: Case Study of International Flights from Suvarnabhumi Airport, Thailand

Aircrew members are occupationally exposed to higher levels of galactic cosmic radiation than the general population in most parts of the world. The International Commission on Radiological Protection (ICRP) is concerned by the exposure of aircrews to cosmic radiation. The cosmic radiation intensity in the Earth atmosphere depends on many factors, e.g., the solar activity, altitude, and geomagnetic vertical cutoff rigidity on Earth. This study aimed to calculate the occupational radiation dose for aircraft crews during the solar minimum and maximum on fl ights from Suvarnabhumi Airport (BKK), Thailand, to 11 destinations worldwide. Based on the Monte Carlo simulation code of CARI-7 and JISCARD GUI, the cosmic radiation doses on fl ights was calculated. The maximum dose of a roundtrip fl ight (Bangkok–Helsinki) during the solar minimum condition was approximately 97.4 μSv (CARI-7) and 84.7 μSv (JISCARD GUI). The maximum radiation dose corresponded to 110 and 20 roundtrips for general aircraft crew and pregnant crew, respectively. This fi nding indicates that the polar-latitude region of Helsinki fl ights at low vertical cutoff rigidity ranges is of concern in terms of high-exposure cosmic radiation. The uncertainty associated with the result of the two codes was less than 30%. Therefore, the results were in reasonable agreement, and the codes could be used to calculate the exposure of aircraft crew to cosmic radiation.

Effects of the Laschamps Excursion on Geomagnetic Cutoff Rigidities

AbstractToday'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.

Geomagnetic field shielding over the last one hundred thousand years

The geomagnetic field prevents energetic particles, such as galactic cosmic rays, from directly interacting with the Earth’s atmosphere. The geomagnetic field is not static but constantly changing, and over the last 100,000 years, several geomagnetic excursions occurred. During geomagnetic field excursions, the field strength is significantly decreased and the field morphology is strongly influenced by non-dipole components, and more cosmic ray particles can access the Earth’s atmosphere. Paleomagnetic field models provide a global view of the long-term geomagnetic field evolution, however, with individual spatial and temporal resolution and uncertainties. Here, we reconstruct the geomagnetic shielding effect over the last 100,000 years by calculating the geomagnetic cutoff rigidity using four global paleomagnetic field models, i.e., the GGF100k, GGFSS70, LSMOD.2, and CALS10k.2 model. We compare results for overlapping periods and find that the model selection is crucial to constrain the cutoff rigidity variation. However, all models indicate that the non-dipole components of the geomagnetic field are not negligible for estimating the long-term geomagnetic shielding effect. We provide a combined record of global cutoff rigidities using the best available model for individual time intervals. Our results provide the possibility to estimate the cosmogenic isotope production rate and cosmic radiation dose rate covering the last 100,000 years according to the best current knowledge about geomagnetic field evolution, and will be useful in further long-term solar activity and climate change reconstruction.

Program for Calculating the Geomagnetic Cutoff Rigidity of Cosmic Rays and the Trajectories of Their Motion

Program for Calculating the Geomagnetic Cutoff Rigidity of Cosmic Rays and the Trajectories of Their Motion

Technology for Location, Analysis and Interpretation of Magnetic Alterations as Precursors of Seismic Phenomena Update

To date, several studies have shown that the Earth's magnetic field suffers alterations at the local geographical location before an earthquake occur. Its study demonstrates that the Earth’s magnetic alterations at specific local geographical zone, is a local seismic precursor alerting a proximity of an earthquake with a margin of error of approximately 10%. The electromagnetic noise from background is very confusing, but that reason was necessary to identify these electromagnetic signal precursors by filtering a large amount of noise. To isolate the electromagnetic noise, was implemented a Magnetic North deflection detection in Smart Phones Magnetometers. Using it technology, was developed a mathematical algorithm that work in combination with the Smart Phones magnetometers. This research was based using in reference the study carried out by the Department of Physics of the Faculty of Physical Sciences and Mathematics (FCFM) of the University of Chile directed by Cordado, 2018[1], in the paper called “Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin”.

Accounting for meteorological effects in the detector of the charged component of cosmic rays

Abstract. In this paper, we discuss the influence of meteorological effects on the data of the ground installation CARPET, which is a detector of the charged component of secondary cosmic rays (CRs). This device is designed in the P.N. Lebedev Physical Institute (LPI, Moscow, Russia) and installed at the Dolgoprudny scientific station (Dolgoprudny, Moscow region; 55.56∘ N, 37.3∘ E; geomagnetic cutoff rigidity (Rc = 2.12 GV) in 2017. Based on the data obtained in 2019–2020, the barometric and temperature correction coefficients for the CARPET installation were determined. The barometric coefficient was calculated from the data of the barometric pressure sensor included in the installation. To determine the temperature effect, we used the data of upper-air sounding of the atmosphere obtained by the Federal State Budgetary Institution “Central Aerological Observatory” (CAO), also located in Dolgoprudny. Upper-air sounds launch twice a day and can reach an altitude of more than 30 km.

Long-term magnetic anomalies and their possible relationship to the latest greater Chilean earthquakes in the context of the seismo-electromagnetic theory

Abstract. Several magnetic measurements and theoretical developments from different research groups have shown certain relationships with worldwide geological processes. Secular variation in geomagnetic cutoff rigidity, magnetic frequencies, or magnetic anomalies have been linked with spatial properties of active convergent tectonic margins or earthquake occurrences during recent years. These include the rise in similar fundamental frequencies in the range of microhertz before the Maule 2010, Tōhoku 2011, and Sumatra–Andaman 2004 earthquakes and the dramatic rise in the cumulative number of magnetic anomalous peaks before several earthquakes such as Nepal 2015 and Mexico (Puebla) 2017. Currently, all of these measurements have been physically explained by the microcrack generation due to uniaxial stress change in rock experiments. The basic physics of these experiments have been used to describe the lithospheric behavior in the context of the seismo-electromagnetic theory. Due to the dramatic increase in experimental evidence, physical mechanisms, and the theoretical framework, this paper analyzes vertical magnetic behavior close to the three latest main earthquakes in Chile: Maule 2010 (Mw 8.8), Iquique 2014 (Mw 8.2), and Illapel 2015 (Mw 8.3). The fast Fourier transform (FFT), wavelet transform, and daily cumulative number of anomalies methods were used during quiet space weather time during 1 year before and after each earthquake in order to filter space influence. The FFT method confirms the rise in the power spectral density in the millihertz range 1 month before each earthquake, which decreases to lower values some months after earthquake occurrence. The cumulative anomaly method exhibited an increase prior to each Chilean earthquake (50–90 d prior to earthquakes) similar to those found for Nepal 2015 and Mexico 2017. The wavelet analyses also show similar properties to FFT analysis. However, the lack of physics-based constraints in the wavelet analysis does not allow conclusions that are as strong as those made by FFT and cumulative methods. By using these results and previous research, it could be stated that these magnetic features could give seismic information about impending events. Additionally, these results could be related to the lithosphere–atmosphere–ionosphere coupling (LAIC effect) and the growth of microcracks and electrification in rocks described by the seismo-electromagnetic theory.