Monitor Count Research Articles

On Designing a New Control Chart Using the Generalized Conway–Maxwell–Poisson Distribution to Monitor Count Data

Many researchers employed Poisson distribution-based control charts to monitor count data. Nevertheless, these charts can handle count data that deviate from the Poisson assumption of equal mean and variance. This paper suggests a new control chart (CC) that uses the generalized Conway–Maxwell–Poisson (GCOMP) distribution, which can deal with count data that have different levels of dispersion and zero-inflation (ZI). The proposed chart is designed considering the total number of counts. The main advantage of this study is that it pays attention to the tails of the count data when monitoring the process. The performance is measured by the average run length using L control limits at different sample sizes and parametric settings. The findings demonstrate that, for count data with varying tail behaviors, the proposed chart performs better compared to existing CCs. ZI count data can also be monitored with the proposed chart. The proposed chart can be applied in a variety of fields, as verified by the examples provided in this paper.

Analysis of neutron monitor count rates and timing distributions from latitude surveys

Neutron monitors continuously record the hadronic part of secondary atmospheric radiation on the ground, which originates from primary cosmic rays. In Thailand, we developed a mobile neutron monitor housed inside a standard-size shipping container named “Changvan.” It contains three neutron-sensitive proportional counters set up in the typical NM64 layout. However, the central counter doesn’t have the lead producer, leading us to refer to it as a “semi-leaded” neutron monitor. We examined cosmic ray spectral variations on two latitude surveys during 2018-2019 and 2019-2020. This work examines the ratio of count rates between leaded and unleaded setups, which shows notable variation based on geomagnetic cutoff rigidity, suggesting a sensitivity to the cosmic ray spectrum. This measurement could be implemented at stationary stations. The unleaded counter, shielded by the reflector with a higher count from nearby lead, may have advantages over a bare one. Furthermore, we explore alternative techniques to identify spectral changes in Galactic cosmic rays using Changvan data. We analyze using time delay histograms to determine the leader fraction (L) of neutrons that are not preceded by another neutron from the same primary cosmic ray. We also examine other parameters, including the alpha (α) parameter and pulse rate (PR), which can be compared with count rates (CR). Our findings indicate that the ratios of L and α are not significantly affected by geomagnetic cutoff rigidity. In contrast, CR and PR exhibit significant dependency and show opposite trends.

Monte Carlo Simulation and measurement of Calibration Neutron Monitor count rate dependence on proximity to water

Due to their global availability, neutron monitors play a crucial role in measuring time variations in the Galactic cosmic ray flux. A portable calibration neutron monitor (CalMon) is useful for intercalibrating various neutron monitors to ensure accurate measurements. A common technique to ensure that the calibration is done in a consistent environment is to place the CalMon at some height above a wide container (such as a portable swimming pool) filled with water. This study investigates the impact of CalMon height and water depth on the count rate ratio relative to a standard 18NM64 count rate recorded nearby (CalMon/18NM64). We compare simulated data from the FLUKA Monte Carlo package to experimental data from [1] to demonstrate the statistical accuracy of our simulation. Using the simulation results, we then extend the study of the proximity-to-water effect on the counting rate. In this work, we present a preliminary empirical model by analyzing the CalMon/18NM64 as a function of CalMon to water distance. Overall, our study enhances understanding of the response of calibration monitors (now often called “mini-neutron monitors”) operated in various locations worldwide, and validates the Monte Carlo techniques used to model the response of the global neutron monitor network.

Solar Magnetic Polarity Effect on Neutron Monitor Count Rates: Comparing Latitude Surveys and Antarctic Stations

The Galactic cosmic-ray spectrum manifests pronounced variations over the 11 yr sunspot cycle and more subtle variations over the 22 yr solar magnetic cycle. An important tool to study these variations is repeated latitude surveys with neutron monitors (NMs) on board icebreakers in conjunction with land-based references. We revisit 13 annual latitude surveys from 1994 to 2007 using reference data from the Mawson NM instead of McMurdo NM (which closed in 2017). We then consider two more latitude surveys (2018 and 2019) with a monitor similar to the 3NM64 in the previous surveys but without lead rings around the central tube, a so-called “semi-leaded neutron monitor.” The new surveys extend the linear relationship among data taken at different cutoff rigidity ranges. They also confirm the “crossover” measured near solar minima during epochs of opposite solar magnetic polarity and the absence of a crossover for epochs having the same solar magnetic polarity.

Participant attention on the intervention target during repetitive passive movement improved spinal reciprocal inhibition enhancement and joint movement function

This study aimed to evaluate the effects of the participant’s attention target during repetitive passive movement (RPM) intervention on reciprocal inhibition (RI) and joint movement function. Twenty healthy adults participated in two experiments involving four attention conditions [control (forward attention with no RPM), forward attention (during RPM), monitor attention (monitor counting task during RPM), ankle joint attention (ankle movement counting task during RPM)] during 10-min RPM interventions on the ankle joint. Counting tasks were included to ensure the participant’s attention remained on the target during the intervention. In Experiment 1, RI was measured before, immediately after, and 5, 10, 15, 20, and 30 min after the RPM intervention. In Experiment 2, we evaluated ankle joint movement function at the same time points before and after RPM intervention. The maximum ankle dorsiflexion movement (from 30° plantar flexion to 10° dorsiflexion) was measured, reflecting RI. In Experiment 1, the RI function reciprocal Ia inhibition was enhanced for 10 min after RPM under all attention conditions (excluding the control condition. D1 inhibition was enhanced for 20 min after RPM in the forward and monitor attention conditions and 30 min after RPM in the ankle joint attention condition. In Experiment 2, the joint movement function decreased under the forward and monitor attention conditions but improved under the ankle joint attention condition. This study is the first to demonstrate that the participant’s attention target affected the intervention effect of the RI enhancement method, which has implications for improving the intervention effect of rehabilitation.

A new exponentially weighted moving average control chart to monitor count data with applications in healthcare and manufacturing

Attribute control charts are widely used to monitor count data. Many distributions are proposed to model and monitor count data. This article has developed an exponentially weighted moving average (EWMA) control chart under Generalized Conway–Maxwell–Poisson (GCOMP) distribution and named as the GCOMP-EWMA chart. The GCOMP distribution is an extension of the Conway–Maxwell–Poisson (COMP) distribution and is a longer-tailed model than the COMP distribution. The GCOMP distribution can also model the shorter tail behaviour in count data. Considering the tail behaviour, the in-control and out-of-control performance of the GCOMP-EWMA chart have been evaluated for over- and under-dispersed count data. Without using the zero-inflation property, the GCOMP-EWMA chart performs efficiently in monitoring zero-inflated count data compared to existing zero-inflated models-based control charts. Finally, illustrative examples demonstrate the practical applications of the GCOMP-EWMA charts in different fields.

Charge-Sign Dependent Cosmic-Ray Modulation Observed with the Calorimetric Electron Telescope on the International Space Station.

We present the observation of a charge-sign dependent solar modulation of galactic cosmic rays (GCRs) with the Calorimetric Electron Telescope onboard the International Space Station over 6yr, corresponding to the positive polarity of the solar magnetic field. The observed variation of proton count rate is consistent with the neutron monitor count rate, validating our methods for determining the proton count rate. It is observed by the Calorimetric Electron Telescope that both GCR electron and proton count rates at the same average rigidity vary in anticorrelation with the tilt angle of the heliospheric current sheet, while the amplitude of the variation is significantly larger in the electron count rate than in the proton count rate. We show that this observed charge-sign dependence is reproduced by a numerical "drift model" of the GCR transport in the heliosphere. This is a clear signature of the drift effect on the long-term solar modulation observed with a single detector.

Study of the Relationship Between Sunspot Number and the Duration of the ≈ 1.6 – 2.2 Year Period in Neutron Monitor Counting Rates

Neutron monitor counting rates show periodicities in the ≈ 1.6 – 2.2-year range. These periodicities have been associated with a solar origin affecting the cosmic ray propagation conditions through the heliosphere. Our hypothesis is that the periodicities in the ≈ 1.6 – 2.2-years range correspond to a single periodicity that changes its duration over time.López-Comazzi and Blanco (Astrophys. J.927(2), 155, 2022) found that the duration of the ≈ 1.6 – 2.2-year period (tau ) is linearly related to the average sunspot number (SSN_{a}) in each solar cycle. The relationship shows that shorter ≈ 1.6 – 2.2-year periods occur during stronger cycles when SSN_{a} is higher. Therefore, the duration of this period varies from one solar cycle to another. This study focuses on this relation. For obtaining this relation, the values of the duration of the ≈ 1.6 – 2.2-year period in global neutron monitor counting rates (a virtual station determined by averaging of the different neutron monitor counting rates along the world) along the Solar Cycles 20 – 24 have been used. We extend the sample by adding the duration of the ≈ 1.6 – 2.2-year period in Huancayo neutron monitor counting rates along Solar Cycle 19 to this linear relationship. Once the linear relationship is extended, tau for the current Solar Cycle 25 is computed giving ≈ 2.24 years. Drawing on this more accurate relationship given by SSN_{a} = (-120 pm 10) : tau + (320 pm 20), we computed tau for the cycles previous to the existence of neutron monitors (Solar Cycles 7 – 18).These ≈ 1.6 – 2.2-year periodicities in neutron monitor counting rates could be produce by variations in the solar magnetic field due to an internal mechanism of the solar dynamo called Rossby waves. Concretely, the harmonic of fast Rossby waves with m=1 and n=8 fit with the detected ≈ 1.6 – 2.2-year periodicity. In addition, the variation of the solar magnetic-field strength from weaker to stronger solar cycles could explain the different periods detected in each cycle. Based on the detected periodicities using the dispersion relation for fast Rossby waves, a solar tachocline magnetic-field strength of ≈ 7 – 25 kG has been estimated.

The time profile of relativistic solar particle events as observed by neutron monitors

The most energetic particles accelerated in solar eruptive events are protons and nuclei with energies that may reach a few tens of GeV. They can be detected on the Earth through the secondaries they produce when interacting with the atmosphere. Solar energetic particle events where this happens are called Ground-Level Enhancements (GLEs). Their study is relevant on the one hand because the high particle energies pose particularly strong challenges to the understanding of the acceleration processes. On the other hand, the secondary particles constitute a source of radiation in the atmosphere that may temporarily exceed the permanent dose rate from galactic cosmic rays. This makes the monitoring of radiation doses received by aircrew from GLEs one issue of space weather services for civil aviation. This study addresses the time profiles of GLEs, in the search for commonalities that can be used to constrain models of acceleration and propagation and to forecast the evolution of an ongoing event. We investigate historical GLEs (1971–2012) with the worldwide network of neutron monitors, comparing the rise and the decay as observed by the neutron monitor with the strongest response. The sample comprises 23 events. We evaluate statistical correlations between rise time and decay time inferred from fits to the time profiles and compute a normalised median GLE time profile. An empirical correlation reported in earlier work between the observed rise times and decay times of the neutron monitor count rate profiles is confirmed. We find indications of a statistical relationship between the rise times and the parent eruptive activity. We discuss ideas on the mechanisms behind the correlation of rise and decay times and on its usefulness for space weather services.

A Metaheuristic Algorithm for Vertex Cover based Link Monitoring and Backbone Formation in Wireless Ad hoc Networks

Wireless ad hoc networks (WANETs) are infrastructureless networks and are used in various applications such as habitat monitoring, military surveillance, and disaster relief. Data transmission is achieved through radio packet transfer, thus it is prone to various attacks such as eavesdropping, spoofing, and etc. Monitoring the communication links by secure points (monitors) is an essential precaution against these attacks. Also, deploying monitors provides a virtual backbone for multi-hop data transmission. However, adding secure points to a WANET can be costly in terms of price and time, so minimizing the number of secure points is of utmost importance. Graph theory provides a great foundation to tackle the emerging problems in WANETs. A vertex cover (VC) is a set of vertices where every edge is incident to at least one vertex. The minimum weighted connected VC (MWCVC) problem can be defined as finding the VC of connected nodes having the minimum total weight. MWCVC is a very suitable infrastructure for energy-efficient link monitoring and virtual backbone formation. In this paper, we propose a novel metaheuristic algorithm for MWCVC construction in WANETs. Our algorithm is a population-based iterated greedy (PBIG) approach that is very effective against graph theoretical problems. We explain the idea of the algorithm and illustrate its operation through sample examples. We implement the proposed algorithm with its competitors on a widely used dataset. From extensive measurements, we obtain that the algorithm produces WCVC with less weight at the same time its monitor count and time performances are reasonable.

Ultradian Near 2-4-h Rhythms of Body Temperature in Laboratory Rodents Depend on External Environmental Heliogeophysical Factor Reflected by Neutron Monitor Count Rate.

The study collated oscillations of body temperature of С57BL/6 mice and Roborovski hamsters (Phodopus roborovskii) in the period range of 100-240 min and fluctuations of the secondary cosmic rays reflected by neutron count rate of a neutron monitor at the Earth's surface. Cross-correlation of body temperature and neutron count rate data revealed their strong association only for simultaneous measurements. Collation of the phase of neutron count rate fluctuations with maxima of body temperature oscillations revealed the coincidence of the phases of both processes. There was a temporary connection between the periods of body temperature elevation and neutron count rate rise. Thus, not only the spectral parameters of biological and physical processes, but also their phases coincided, which corroborates the hypothesis on stimulating effect of increasing neutron count rate on activity of the animals.

Cosmic-ray atmospheric cutoff energies of polar neutron monitors

The atmospheric cutoff, similarly to the geomagnetic cutoff, is the lower energy limit for cosmic ray particles that can reach a given location on the ground and be registered by a detector there, e.g., by a neutron monitor. It is caused by the decreasing intensity of a cosmic-ray cascade in the lower atmosphere. Although the geomagnetic cutoff is higher than atmospheric over the most of the Earth’s surface, the latter is dominant and therefore defines the neutron monitor count rate in the polar regions. The atmospheric cutoff decreases with the altitude, and this provides additional sensitivity of high-altitude polar neutron monitors to low-energy particles, mainly solar energetic protons during the so-called ground-level enhancement events.In this work, we quantitatively estimated the atmospheric cutoff energies for 21 polar neutron monitor stations in conditions without a significant solar energetic particle event. The cutoff value can be as low as about 300 MeV for protons (VOSTOK and DOMC/DOMB stations), which is notably lower than about 430 MeV at sea level. In addition to that, we estimated the worst case scenario of the strongest-ever observed ground-level enhancement event GLE#05, occurred on the 23rd of February, 1956, and showed that the atmospheric cutoff becomes as low as about 100 MeV. In other words, some neutron monitor stations can register particles with energies of even about 100 MeV during an exceptionally strong solar particle event. It is explained by the highly intensive and soft spectrum of the event in its early delayed phase.

Diurnal anisotropy of polar neutron monitors: Dome C looks poleward

Galactic cosmic rays (GCR) exhibit a small local anisotropy observed as diurnal variability of ground-based neutron monitor (NM) count rates. Since the asymptotic directions of various NMs are different, their ability to observe the GCR diurnal variation also varies. Here we show that the Dome C (DOMC) NM is hardly sensitive to the diurnal variation, with its amplitude being 0.03%, in contrast to other polar NMs whose sensitivity to the diurnal variability ranges from 0.16 to 0.4%. We argue that this is related to the fact that DOMC NM has a narrow asymptotic-direction cone looking nearly to the South pole (geographic latitude above 75°). This makes the DOMC NM a unique detector being the only existing NM accepting cosmic-ray particles originating from the off-equatorial region. This is important for detailed studies of cosmic-ray transport in the vicinity of Earth, specifically for anisotropic solar energetic particle events.

Метод автоматической коррекции данных нейтронного монитора на осадки в виде снега в реальном времени

We have carried out an experimental study of the influence of precipitation in the form of snow on measurements of the neutron flux intensity near Earth's surface. We have examined the state of the snow cover and its density, and found out that the density depends on the depth of the snow cover. Using the experimental results, we estimate the neutron absorption path in the snow. Changes in snow cover by 10–12 cm at a depth of 80 cm are shown to cause variations in the monitor count rate with an amplitude of 0.9 %. At the snow depth of 80 cm, the neutron monitor count rate decreases by about 8 %. The observed variations should be attributed to the meteorological effects of cosmic rays. The absorption coefficient of neutrons in the snow was also found from the correlation between the count rate of the neutron monitor and the amount of snow above the detector. We propose a real-time correction of the neutron monitor data for precipitation in the form of snow. For this purpose, we implement continuous monitoring of the amount of snow cover. The monitoring is provided by a snow meter made using a laser rangefinder module. We discuss the results obtained.

Method of automatic correction of neutron monitor data for precipitation in the form of snow in real time

We have carried out an experimental study of the influence of precipitation in the form of snow on measurements of the neutron flux intensity near Earth's surface. We have examined the state of the snow cover and its density, and found out that the density depends on the depth of the snow cover. Using the experimental results, we estimate the neutron absorption path in the snow. Changes in snow cover by 10–12 cm at a depth of 80 cm are shown to cause variations in the monitor count rate with an amplitude of 0.9 %. At the snow depth of 80 cm, the neutron monitor count rate decreases by about 8 %. The observed variations should be attributed to the meteorological effects of cosmic rays. The absorption coefficient of neutrons in the snow was also found from the correlation between the count rate of the neutron monitor and the amount of snow above the detector. We propose a real-time correction of the neutron monitor data for precipitation in the form of snow. For this purpose, we implement continuous monitoring of the amount of snow cover. The monitoring is provided by a snow meter made using a laser rangefinder module. We discuss the results obtained.

Uncertainty Characterization in PM2.5 Estimates Across the Contiguous US

BACKGROUND AND AIM: Accurate PM2.5 exposure assessment, often performed using statistical prediction models, is a critical component of health studies and regulatory action. Ensemble modeling is becoming increasingly popular as it improves accuracy by combining the unique strengths of different models. Identifying where prediction uncertainty is greatest can inform monitor deployment and model development. We fit an ensemble model integrating multiple existing PM2.5 prediction models, estimated location-specific uncertainty in predictions, and then identified factors contributing to uncertainty. METHODS: We predicted 2015 annual PM.5 concentrations at 0.01°×0.01° resolution across the contiguous US by combining three well-validated prediction models with the Bayesian Non-parametric Ensemble (BNE). Training data came from the US Environmental Protection Agency's Air Quality System database. We estimated model uncertainty, which captures disagreement between models, uncertainty of weights, and random error, as the standard deviations of predictions’ location-specific posterior predictive distribution. We analyzed how predicted PM2.5, AQS monitor count within a 50-km radius, summer- and winter-mean temperature, and population density vary with uncertainty via a generalized additive mixed model, with penalized splines and a random intercept for state. RESULTS:Mean (standard deviation; SD) predicted PM2.5 was 6.37 μg/m3 (1.78), with a spatial RMSE of 0.71 μg/m^3, and mean (SD) uncertainty was 0.47 (0.20) μg/m^3. We observed greater uncertainty in the Midwest and Great Lakes areas. Predicted concentration had a complex relationship with uncertainty, with a generally positive association above ~8 μg/m^3. Monitor density had a negative association. Winter temperature below 0°C was positively associated with uncertainty, and summer temperature was positively associated below 19°C and negatively above 19°C. Very high population density was associated with lower uncertainty. CONCLUSIONS:PM2.5 prediction uncertainty varied across space; uncertainty was greater in areas with more pollution, fewer monitors, colder winters, more moderate summers, and lower population density. Subsequent monitoring and prediction model development should consider prioritizing these areas. KEYWORDS: Exposure assessment, particulate matter, spatial statistics

Measurement and simulation of the neutron propagation time distribution inside a neutron monitor

Using a setup for testing a prototype for a satellite-borne cosmic-ray ion detector, we have operated a stack of scintillator and silicon detectors on top of the Princess Sirindhorn Neutron Monitor (PSNM), an NM64 detector at 2560-m altitude at Doi Inthanon, Thailand (18.59∘N, 98.49∘E). Monte Carlo simulations have indicated that about 15% of the neutron counts by PSNM are due to interactions (mostly in the lead producer) of GeV-range protons among the atmospheric secondary particles from cosmic ray showers, which can be detected by the scintillator and silicon detectors. Those detectors can provide a timing trigger for measurement of the propagation time distribution of such neutrons as they scatter and propagate through the NM64, processes that are similar whether the interaction was initiated by an energetic proton (for 15% of the count rate) or neutron (for 80% of the count rate). This propagation time distribution underlies the time delay distribution between successive neutron counts, from which we can determine the leader fraction (inverse multiplicity), which has been used to monitor Galactic cosmic ray spectral variations over ∼1-40 GV. Here we have measured and characterized the propagation time distribution from both the experimental setup and Monte Carlo simulations of atmospheric secondary particle detection. We confirm a known propagation time distribution with a peak (at ≈70 μs) and tail over a few ms, dominated by neutron counts. We fit this distribution using an analytic model of neutron diffusion and absorption, for both experimental and Monte Carlo results. In addition we identify a group of prompt neutron monitor pulses that arrive within 20 μs of the charged-particle trigger, of which a substantial fraction can be attributed to charged-particle ionization in a proportional counter, according to both experimental and Monte Carlo results. Prompt pulses, either due to neutrons or charged-particle ionization, are associated with much higher mean multiplicity than typical pulses. These results validate and point the way to some improvements in Monte Carlo simulations and the resulting yield functions used to interpret the neutron monitor count rate and leader fraction.

Preliminary analysis of the Changvan neutron monitor operation in latitude surveys during 2019-2020

Within our solar system, space weather is influenced by the solar wind and the interplanetary magnetic field carried by the solar wind plasma. Severe solar storms can expose people to increased radiation levels, shut down electrical systems, and interfere with radio signals. Space weather probably affects the weather and climate on our planet, but we do not yet have a precise understanding of the influence. Some aspects of space weather can be monitored at ground level with a detector, such as a “neutron monitor,” that measures cosmic rays from outer space. We have developed a portable “Changvan” neutron monitor to investigate the energy spectrum of cosmic rays and its solar modulation, i.e., variations over the typically 11-year sunspot cycle. The Changvan monitor located inside the insulated shipping container comprises three proportional counters in the standard-design neutron monitors, but the central counter is deficient in the lead producer. This monitor records counting rates during passage through a range of geomagnetic latitudes, which this technique is called “latitude survey.” The ultimate goal of the latitude surveys is to help accurately interpret data from every neutron monitor in a space environment that is always changing. In this work, we show a preliminary analysis of Changvan monitor data collected from two latitude surveys during 2019-2020 on the Chinese icebreaker MV Xue Long from Shanghai, China to Zhongshan station, Antarctica and back. A strong anti-correlation can be observed between the Changvan monitor count rate and barometric pressure.

Access of Energetic Particles to a Magnetic Flux Rope from External Magnetic Field Lines

Abstract Cosmic-ray (CR) fluxes in the heliosphere are affected by the transient interplanetary coronal mass ejections (ICMEs), causing so-called Forbush decreases (FDs), characterized by a decline of up to 25% in the neutron monitor counts at the Earth’s surface, lasting up to over a week. FDs are thought to be caused by the ICME shock wave or the magnetic flux rope embedded in the ICME inhibiting CR propagation through the ICME structure. FDs are typically modeled as enhanced diffusion within the ICME structure. However, so far modeling has not considered the access of the CRs from the interplanetary field lines into the isolated magnetic field lines of the ICME flux rope. We study the effect of an ICME flux rope on particle propagation by using full-orbit particle simulations, with the interface between the external interplanetary magnetic field and the isolated flux rope field lines modeled analytically. We find that the particles can access the flux rope through the x-point region, where the external magnetic fields cancel the azimuthal component of the rope field. The transport through this region is fast compared to diffusive radial propagation within the rope. As a result, the propagation of CRs into the flux rope can be modeled as diffusion into a cylinder. The density cavity within the rope is asymmetric, and limited to the magnetic field lines isolated from the external field. Thus, in order to evaluate the role of the flux rope in FDs, one must analyze the extent of the region where the flux rope magnetic field lines are separated from the interplanetary magnetic fields.

Powerful Solar Proton Events of January 2005 and their impact on intensity of the stratospheric polar vortex

In January 2005, a series of powerful Solar Proton Events (SPEs) associated with an increase of flare activity on the Sun was observed. Increases of solar proton fluxes with energies 165-500 MeV allowing particles to reach stratospheric altitudes (∼30 km and below) were registered during the events starting on 15, 16 and 17 January. The strongest event, with particle energies exceeding 500 MeV, took place on 20 January and was accompanied by an increase of the neutron monitor counting rate (Ground Level Enhancement). The events under study resulted in a considerable increase of stratospheric ionization. In this work an impact of these events on intensity of the stratospheric polar vortex playing an important part in the mechanism of solar-atmospheric links is studied. A noticeable intensification of the vortex (increase of western wind velocity) was revealed at all the stratospheric levels in the course of the SPE series under study. It was shown that auroral activity (precipitations of auroral electrons generating bremsstrahlung X-rays) is also a possible factor of the vortex intensification. The obtained results provide evidence that ionization changes associated with powerful SPEs and auroral activity may influence the state of the stratospheric polar vortex on the day-to-day time scale. A possible cause of the vortex intensification seems to be temperature variations associated with changes of chemical composition of the polar stratosphere due to ionisation changes.