Neutron Monitor Database Research Articles

Seven Decades of Neutron Monitors (1951–2019): Overview and Evaluation of Data Sources

AbstractThe worldwide network of neutron monitors (NMs) is the primary instrument to study cosmic‐ray variability on time scales of up to 70 yr. Since the 1950s, 147 NMs with publicly available data have been in operation, and their records are archived in and distributed through different repositories and data sources. A comprehensive analysis of all available NM data sets (300 data sets from 147 NMs) is performed here to check the quality and consistency of the data. The data sources include World Data Center for Cosmic Rays, the Neutron Monitor Database, the Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation (IZMIRAN) and individual station/institution databases. It was found that The data from the same NM can be nonidentical and of different quality in different sources. We give and tabulate here a recommendation for the optimal data source of each NM. We also present here a list of 29 “prime” stations with the longest and most reliable data. Verified data sets for these prime stations are provided as supplementary information.

Spectral Analysis of Forbush Decreases Using a New Yield Function

The Forbush decreases of the cosmic ray intensity observed on 24 December 2014 and on 8 September 2017 were chosen for cosmic ray spectral analysis. At first an analytical study of the solar and geomagnetic parameters of these events was carried out due to the fact that both are typical cosmic ray events. Hourly cosmic ray data of the neutron monitor stations obtained from the high-resolution neutron monitor database were used for calculating the cosmic ray density and anisotropy variations. Following the method of the coupling coefficients, the galactic cosmic ray spectral index was calculated using the technique of Wawrzynczak and Alania (Adv. Space Res. 45, 622, 2010). A newly presented yield function by Mishev, Usoskin, and Kovaltsov (J. Geophys. Res. 118, 2783, 2013) including a geometrical correction factor, already used in the spectral analysis of the cosmic ray ground level enhancements, was applied for the first time to the case of Forbush decreases. A comparison of these results during the events is performed by using two other coupling functions: the function presented in the work of Clem and Dorman (Space Sci. Rev. 93, 335, 2000) and the one in the work of Belov and Struminsky (Proc. 25th Int. Cosmic Ray Conf. 1, 201, 1997). The latter includes an extension for neutron monitor stations with rigidity $1~\mbox{GV} < R < 2.78~\mbox{GV}$ . The obtained spectral index and the calculated cosmic ray intensity in the heliosphere during the two Forbush decreases after the coupling by these three functions are presented and discussed.

A new approximate coupling function: The case of Forbush decreases

We attempt the derivation of a new coupling function between ground level and primary cosmic rays for the case of Forbush decreases. The calculations for the new function are based on basic Quantum Field Theory theoretical tools, something that has not been attempted till now in other widely used cosmic ray coupling functions. The use of Quantum Field Theory calculations in cosmic rays events in general, is expected to be a suitable frame of work since it describes well the high energy particle interactions which result in variations to the total number of the particles involved through annihilation or creation of particles. The newly computed function is tested to the case of two events of Forbush decreases, February 2011 and March 2012, using data from the high resolution neutron monitor database. Results for the primary particle intensity values obtained from this function are compared directly to the corresponding ones from the use of the Dorman's widely accepted coupling function. The two sets are discussed in detail in order to deduce the possible suitability of Quantum Field Theory tools to cosmic ray events.

An Extended Study of the Precursory Signs of Forbush Decreases: New Findings over the Years 2008 – 2016

In spite of the fact that the current Solar Cycle 24 is close to its end now, it is a less active Solar Cycle, during its time period (2008 – 2016) and a lot of Forbush decreases of cosmic ray intensity with rigidity 10 GV and amplitude greater than 2% were recorded by the ground-based neutron monitors. Among these events, the ones associated with sudden geomagnetic storm commencements (SSCs) and presenting a first harmonic of cosmic ray anisotropy greater than 0.8% were examined. Cosmic ray data recorded at the neutron monitor stations were obtained from the European high resolution neutron monitor database, while the Forbush decreases, accompanied by their characteristics were accessed from the updated Database of the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN). Solar, interplanetary and geomagnetic characteristic parameters of each event separately have been studied in detail and analyzed. It was shown through the usage of the “ring of neutron monitor stations” method that, in some cases, precursory signals before the main phase of the event appeared. After an extended study of the Forbush decreases precursors during the examined period, the appearance of pre-decreases and/or pre-increases of the cosmic ray intensity before the beginning of the events, acting as precursory signals, were identified in almost half of the cases studied. In combination with other parameters, their common features are discussed, with the purpose of monitoring and possibly forecasting the space-weather conditions.

Analysis of sub-GLE and GLE events using NM data: space weather applications

Detailed study of solar energetic particle events is important to understand their acceleration and propagation in the interplanetary space and allows one to model various processes related to space weather and space climate e.g. radiation environment at flight altitudes and atmospheric ionization. A special class of events, called ground level enhancements, registered by ground based detectors, can dramatically change the radiation environment in the Earth’s atmosphere. New recently installed high-altitude polar neutron monitors NMs, namely DOMC/B and historically installed South Pole, have made the worldwide neutron monitor network more sensitive to strong solar energetic particle events, registered at ground level. The two high-altitude polar stations are able to detect lower energy events, which most likely would not be registered by the other (near sea level) neutron monitor stations. Here, using the worldwide neutron monitor database (NMDB) records and an optimization procedure combined with simulations, we assess the spectral and angular characteristics of a new class of events sub-GLEs. With the estimated spectral characteristics as an input, we evaluate the effective dose rate in polar and sub-polar regions at typical commercial flight altitude during such events as well as during GLEs.

Real‐Time Detection of the Ground Level Enhancement on 10 September 2017 by A.Ne.Mo.S.: System Report

AbstractOn 10 September 2017, a ground level enhancement (GLE) of cosmic ray intensity, identified as GLE72, was recorded by several stations of the worldwide neutron monitor network provided by the high‐resolution Neutron Monitor Database. The solar proton event that resulted in this GLE was associated with active region AR2673, which produced an X8.2 flare on the solar west limb. Protons were measured by the GOES satellites with energies above 10, 50, and 100 MeV, while particles at higher energies above 500 MeV were registered by ground‐based neutron monitors. This GLE event was successfully detected in real time by the GLE Alert plus System of the Athens Neutron Monitor Station (A.Ne.Mo.S.). In this work an overview of the GLE72 event is given, and a detailed analysis of the evolution of the GLE Alert signal issued by the GLE Alert plus System as well as a postevent summary are presented.

Unusual Cosmic Ray Variations During the Forbush Decreases of June 2015

Although the current Solar Cycle 24 is characterized by low solar activity, an intense geomagnetic storm (G4) was recorded in June 2015. It was a complex phenomenon that began on 22 June 2015 as the result of intense solar activity, accompanied by several flares and coronal mass ejections that interacted with the Earth’s magnetic field. A Forbush decrease was also recorded at the neutron monitors of the worldwide network, with an amplitude of 8.4%, and in its recovery phase, a second Forbush decrease followed, with an amplitude of 4.0% for cosmic rays of 10 GV obtained with the global survey method. The Dst index reached a minimum value of −204 nT that was detected on 23 June 2015 at 05:00 – 06:00 UT, while the Kp index reached the value eight. For our analysis, we used hourly cosmic-ray intensity data recorded by polar, mid-, and high-latitude neutron monitor stations obtained from the High Resolution Neutron Monitor Database. The cosmic-ray anisotropy variation at the ecliptic plane was also estimated and was found to be highly complex. We study and discuss the unusual and complex cosmic-ray and geomagnetic response to these solar events.

Onsets of Solar Proton Events in Satellite and Ground Level Observations: A Comparison

AbstractThe early detection of solar proton event onsets is essential for protecting humans and electronics in space, as well as passengers and crew at aviation altitudes. Two commonly compared methods for observing solar proton events that are sufficiently large and energetic to be detected on the ground through the creation of secondary radiation—known as ground level enhancements (GLEs)—are (1) a network of ground‐based neutron monitors (NMs) and (2) satellite‐based particle detectors. Until recently, owing to the different time resolution of the two data sets, it has not been feasible to compare these two types of observations using the same detection algorithm. This paper presents a comparison between the two observational platforms using newly processed &gt;100 MeV 1 min count rates and fluxes from National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite (GOES) 8–12 satellites, and 1 min count rates from the Neutron Monitor Database. We applied the same detection algorithm to each data set (tuned to the different background noise levels of the instrument types). Seventeen SPEs with GLEs were studied: GLEs 55–70 from Solar Cycle 23 and GLE 71 from Solar Cycle 24. The median difference in the event detection times by GOES and NM data is 0 min, indicating no innate benefit in time of either system. The 10th, 25th, 75th, and 90th percentiles of the onset time differences (GOES minus NMs) are −7.2 min, −1.5 min, 2.5 min, and 4.2 min, respectively. This is in contrast to previous studies in which NM detections led GOES by 8 to 52 min without accounting for different alert protocols.

Monitoring geomagnetic disturbance predictors using data of ground measurements of cosmic rays

Results from investigating the behavior of zonal components of the first two angular moments of the distribution of cosmic rays observed in 2015 are presented. The global survey approach developed at the Institute of Cosmophysical Research and Aeronomy, Siberian Branch, Russian Academy of Sciences, is used to determine the zonal harmonics. In this technique, the worldwide network of neutron monitors acts as a single multidirectional detector of cosmic rays. It is shown that sharp increases in the positive amplitudes of zonal harmonics, considered to be predictors of geomagnetic field disturbances with a probability of ~0.75, precede geomagnetic storms with Dst < −50 nT. A geomagnetic storm predictor becomes apparent in periods of time from several hours to 1.5 days. Geomagnetic disturbances are currently monitored in real time using the global survey approach based on data from the worldwide neutron monitor database (http://www.nmdb.eu). The initial results from forecasting can be found on the Internet (http://www.ysn.ru/~starodub/SpaceWeather/global_survey_real_time.html).

Latitudinal and longitudinal dependence of the cosmic ray diurnal anisotropy during 2001–2014

Abstract. The diurnal anisotropy of cosmic ray intensity for the time period 2001 to 2014 is studied, covering the maximum and the descending phase of solar cycle 23, the minimum between solar cycles 23 and 24, and the ascending phase and maximum of solar cycle 24. Cosmic ray intensity data from 11 neutron monitor stations located at different places around the Northern Hemisphere obtained from the high-resolution Neutron Monitor Database (NMDB) were used. Special software was developed for the calculations of the amplitude and the phase of the diurnal anisotropy vectors on annual and monthly basis using Fourier analysis and for the creation of the harmonic dial diagrams. The geomagnetic bending for each station was taken into account in our calculations determined from the asymptotic cones of each station via the Tsyganenko96 (Tsyganenko and Stern, 1996) magnetospheric model. From our analysis, it was resulted that there is a different behavior of the diurnal anisotropy vectors during the different phases of the solar cycles depending on the solar magnetic field polarity. The latitudinal and longitudinal distribution of the cosmic ray diurnal anisotropy was also examined by grouping the stations according to their geographic coordinates, and it was shown that diurnal variation is modulated not only by the latitude but also by the longitude of the stations. The diurnal anisotropy during strong events of solar and/or cosmic ray activity is discussed.

The Neutron Monitor Control Panel

This work presents the current status and future plans of the Neutron Monitor Control Panel (NMCP), a new software developed to aid the operator in typical station maintenance and configuration operations. This software is integrated with the new so-called NOAS data acquisition system and it can be accessed using a supported web browser. It features a visual inspection tool to help the operator to identify spikes in the data, trace the origin of the spike back to the raw readings of each counter tube and pressure reading, and mark the data as invalid in the Neutron Monitor Database if desired. The software also provides information about station operation status, some descriptive statistics about current data being recorded and, in the future, will provide an interface to configure station parameters.

Optimizing the real‐time ground level enhancement alert system based on neutron monitor measurements: Introducing GLE Alert Plus

AbstractWhenever a significant intensity increase is being recorded by at least three neutron monitor stations in real‐time mode, a ground level enhancement (GLE) event is marked and an automated alert is issued. Although, the physical concept of the algorithm is solid and has efficiently worked in a number of cases, the availability of real‐time data is still an open issue and makes timely GLE alerts quite challenging. In this work we present the optimization of the GLE alert that has been set into operation since 2006 at the Athens Neutron Monitor Station. This upgrade has led to GLE Alert Plus, which is currently based upon the Neutron Monitor Database (NMDB). We have determined the critical values per station allowing us to issue reliable GLE alerts close to the initiation of the event while at the same time we keep the false alert rate at low levels. Furthermore, we have managed to treat the problem of data availability, introducing the Go‐Back‐N algorithm. A total of 13 GLE events have been marked from January 2000 to December 2012. GLE Alert Plus issued an alert for 12 events. These alert times are compared to the alert times of GOES Space Weather Prediction Center and Solar Energetic Particle forecaster of the University of Málaga (UMASEP). In all cases GLE Alert Plus precedes the GOES alert by ≈8–52 min. The comparison with UMASEP demonstrated a remarkably good agreement. Real‐time GLE alerts by GLE Alert Plus may be retrieved by http://cosray.phys.uoa.gr/gle_alert_plus.html, http://www.nmdb.eu, and http://swe.ssa.esa.int/web/guest/space‐radiation. An automated GLE alert email notification system is also available to interested users.

The First Ground-Level Enhancement of Solar Cycle 24 on 17 May 2012 and Its Real-Time Detection

Ground-level enhancements (GLEs) are defined as sudden increases in the recorded intensity of cosmic-ray particles, usually by neutron monitors (NMs). In this work we present a time-shifting analysis (TSA) for the first arriving particles that were detected at Earth by NMs. We also present an automated real-time GLE alert that has been developed and is operating via the Neutron Monitor Database (NMDB), which successfully identified the 17 May 2012 event, designated as GLE71. We discuss the time evolution of the real-time GLE alert that was issued for GLE71 and present the event onset-time for NMs that con- tributed to this GLE alert based on their archived data. A comparison with their real-time time-stamp was made to illustrate the necessity for high-resolution data (e.g. 1-min time res- olution) made available at every minute. The first results on the propagation of relativistic protons that have been recorded by NMs, as inferred by the TSA, imply that they are most probably accelerated by the coronal-mass-ejection-driven shock. Furthermore, the success- ful usage of NM data and the corresponding achievement of issuing a timely GLE alert are discussed.

Castilla-La Mancha neutron monitor

This work presents the ongoing development of the new Castilla-La Mancha Neutron Monitor located in the Science and Technology Park of Guadalajara (Spain). The instrument is integrated by fifteen proportional counter tubes. Three of them are old tubes of the well-known BP28 standard. The other twelve are the new tubes (model 2061) manufactured by LND Inc. (USA), which intend to provide a valid replacement for the old BP28 model. Testing results of the new detector cross calibration between BP28 and LND2061 counters and comparison with other stations in the Neutron Monitor Data Base are presented.

Optimization of neutron monitor data correction algorithms

Nowadays, several neutron monitor stations worldwide, broadcast their cosmic ray data in real time, in order for the scientific community to be able to use these measurements immediately. In parallel, the development of the Neutron Monitor Database (NMDB; http://www.nmdb.eu) which collects all the high resolution real time measurements, allows the implementation of various applications and services by using these data instantly. Therefore, it is obvious that the need for high quality real time data is imperative. The quality of the data is handled by different correction algorithms that filter the real time measurements for undesired instrumental variations. In this work, an optimization of the Median Editor that is currently mainly applied to the neutron monitor data and the recently proposed ANN algorithm based on neural networks is presented. This optimization leads to the implementation of the Median Editor Plus and the ANN Plus algorithms. A direct comparison of these algorithms with the newly appeared Edge Editor is performed and the results are presented.

Definition of parameters of daily anisotropy of cosmic rays according to the world network of neutron monitors

In our previous works we have created the method of determination of parameters of cosmic ray daily anisotropy in the interplanetary environment based on the data provided by only single station – cosmic ray spectrograph named after A.I.Kuzmin. This method allows to predict the ingress of the Earth into large-scale solar wind disturbances with a probability of more than 70% and in advance time of about from several hours up to 2 days. Now it became possible to use the data of the neutron monitor networks, which can be seen in the neutron monitor database (NMDB) in real time. In this case the well-known method of global survey is applied for determination of cosmic ray anisotropy. Usage of the data of the cosmic ray station network allows to determine parameters of daily cosmic ray anisotropy with a greater accuracy.

Online application for the barometric coefficient calculation of the NMDB stations

The primary processing of the neutron monitor data includes all the necessary actions and procedures that each cosmic ray station follows in order to provide the worldwide neutron monitor network with good quality data. One of the main corrections of the primary data is the pressure correction due to the barometric effect. The barometric effect induces variations to the measured data of the neutron monitors which are related to the variations of the local atmospheric pressure of the stations. This correction requires the definition of the barometric coefficient which is calculated experimentally. The accurate calculation of the coefficient is a prerequisite for the quality of the data. This paper presents the implementation of an online tool which calculates the barometric coefficient of a cosmic ray station, by taking advantage of the fact that most stations publish their data on the Neutron Monitor Data Base.

Identification of high energy solar particle signals on the Mexico City neutron monitor database

We performed a search for ground level solar cosmic ray enhancements on the full five minute database of the Mexico City neutron monitor using wavelet filters and two different statistical tests. We present a detailed analysis of the time series of November 2, 1992, where we found a previously unreported increment matching the onset time of the impulsive phase of GLE 54, thus providing evidence of an effective detection of high energy solar cosmic rays.

Search for solar energetic particle signals in the Mexico City neutron monitor database

AbstractWe performed a search for ground level solar cosmic ray enhancements on the full five minute database of the Mexico City neutron monitor using wavelet filters and two different statistical tests. We present a detailed analysis of the time series of November 2, 1992, where we found a previously unreported increment matching the onset time of the impulsive phase of the Ground Level Enhancement No. 54, thus providing evidence of an effective detection of high energy solar cosmic rays. This technique may help to find still undiscovered GLE signals in the Worldwide Neutron Monitor Database, to refine GLE spectra and, probably, to find a relationship between the latter and the solar cycle.

The effect of cosmic ray intensity variations and geomagnetic disturbances on the physiological state of aviators

Over the last few years various researches have reached the conclusion that cosmic ray variations and ge- omagnetic disturbances are related to the condition of the human physiological state. In this study medical data re- garding 4018 Slovak aviators were analyzed in relation to daily variations of cosmic ray and geomagnetic activity. Specifically daily data concerning mean values of heart rate which were registered during the medical examinations of the Slovak aviators, were related to daily variations of cos- mic ray intensity, as measured by the Neutron Monitor Sta- tion on Lomnicky Stit (http://neutronmonitor.ta3.sk/realtime. php3) and the high resolution neutron monitor database (http://www.nmdb.eu) and daily variations of Dst and Ap ge- omagnetic indices. All subjects were men in good health of age 18 60 yrs. This particular study refers to the time period from 1 January 1994 till 31 December 2002. Statistical meth- ods were applied to establish a statistical significance of the effect of geomagnetic activity levels and cosmic ray inten- sity variations on the aforementioned physiological param- eters for the whole group. The Pearson r-coefficients were calculated and the Analysis of Variance (ANOVA) method was applied to establish the statistical significance levels (p- values) of the effect of geomagnetic activity and cosmic ray intensity variations on heart rate up to three days before and three days after the respective events. Results show that there is an underlying effect of geomagnetic activity and cosmic ray intensity variations on the cardiovascular functionality.