The new Athens center on data processing from the neutron monitor network in real time

International audienceThe ground-based neutron monitors (NMs) record galactic and solar relativistic cosmic rays which can play a useful key role in space weather forecasting, as a result of their interaction with interplanetary disturbances. The Earth's-based neutron monitor network has been used in order to produce a real-time prediction of space weather phenomena. Therefore, the Athens Neutron Monitor Data Processing Center (ANMODAP) takes advantage of this unique multi-directional device to solve problems concerning the diagnosis and forecasting of space weather. At this moment there has been a multi-sided use of neutron monitors. On the one hand, a preliminary alert for ground level enhancements (GLEs) may be provided due to relativistic solar particles and can be registered around 20 to 30 min before the arrival of the main part of lower energy particles responsible for radiation hazard. To make a more reliable prognosis of these events, real time data from channels of lower energy particles and X-ray intensity from the GOES satellite are involved in the analysis. The other possibility is to search in real time for predictors of geomagnetic storms when they occur simultaneously with Forbush effects, using hourly, on-line accessible neutron monitor data from the worldwide network and applying a special method of processing. This chance of prognosis is only being elaborated and considered here as one of the possible uses of the Neutron Monitor Network for forecasting the arrival of interplanetary disturbance to the Earth. The achievements, the processes and the future results, are discussed in this work

THE GROUND-LEVEL ENHANCEMENT OF 2012 MAY 17: DERIVATION OF SOLAR PROTON EVENT PROPERTIES THROUGH THE APPLICATION OF THE NMBANGLE PPOLA MODEL

In this work, we apply an updated version of the Neutron Monitor (NM) Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model, in order to derive the characteristics of the ground-level enhancement (GLE) on 2012 May 17 (GLE71), the spectral properties of the related solar energetic particle (SEP) event, the spatial distributions of the high-energy solar cosmic ray fluxes at the top of the atmosphere, and the time evolution of the locationoftheGLEsource.Ourmodeling,baseduniquelyontheuseofground-levelNMdata,leadstothefollowing mainresults.TheSEPspectrumrelatedtoGLE71wasrathersoftduringthewholedurationoftheevent,manifesting some weak acceleration episodes only during the initial phase (at " 01:55‐02:00UT) and at " 02:30‐02:35UT and " 02:55‐03:00UT. The spectral index of the modeled SEP spectrum supports the coronal mass ejection‐shock driven particle acceleration scenario, in agreement with past results based on the analysis of satellite measurements. During the initial phase of GLE71, the solar proton source at the top of the atmosphere was located above the northernhemisphere,implyingthattheasymptoticdirectionsofviewingofthenorthernhemisphereNMsweremore favorably located for registering the event than the southern ones. The spatial distribution of the solar proton fluxes at the top of the atmosphere during the main phase manifested a large variation along longitude and latitude. At the rigidity of 1GV, the maximum primary solar protonflux resulted on the order of" 3# 10 4 part. m $2 s$ 1 sr $1 GV$ 1

Derivation of relativistic SEP properties through neutron monitor data modeling

The Ground Level Enhancement (GLE) data recorded by the worldwide Neutron Monitor (NM) network are useful resources for space weather modeling during solar extreme events. The derivation of Solar Energetic Particles (SEPs) properties through NM-data modeling is essential for the study of solar-terrestrial physics, providing information that cannot be obtained through the exclusive use of space techniques; an example is the derivation of the higher-energy part of the SEP spectrum. We briefly review how the application of the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al. 2010), can provide the characteristics of the relativistic SEP flux, at a selected altitude in the Earth's atmosphere, during a GLE. Technically, the model treats the NM network as an integrated omnidirectional spectrometer and solves the inverse problem of the SEP-GLE coupling. As test cases, we present the results obtained for two different GLEs, namely GLE 60 and GLE 71, occurring at a temporal distance of ~ 11 years

Applications and usage of the real-time Neutron Monitor Database

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Spectral Analysis of Solar and Geomagnetic Parameters in Relation to Cosmic-ray Intensity for the Time Period 1965 – 2018

Spectral analysis of solar and geomagnetic parameters as well as of cosmic-ray intensity was performed aiming to identify possible new periodicities and confirm the well-known ones. Specifically, short-, mid-, and long-term periodicities of these parameters such as sunspot number, Bz-component of the interplanetary magnetic field, geomagnetic Ap index, and cosmic-ray intensity over the time period 1965 – 2018, covering five solar cycles from Cycles 20 to 24, are presented. For this purpose, two different techniques, fast Fourier transformation and wavelet analysis, have been used in order to ensure accuracy in the frequency values and also their localization in the time series. The periodicities resulting from our comprehensive study, including the well-known 11-year and 27-day periods, the harmonics of the 5.5-year and of the 6-, 9-, and 13.9-day periods, respectively, and the ≈ 1.3-year and 1.7-year periods, were found in all of the above parameters except for the Bz-component of the interplanetary magnetic field. New periodicities such as the ≈ 10-month period for sunspot number and cosmic-ray intensity and the ≈ 3-year period for sunspot number, Ap index, and cosmic-ray intensity, were also determined. Furthermore, the newly introduced splitting of the 27-day periodicity into two adjacent peaks was confirmed in the Fourier spectra of the interplanetary magnetic field and the geomagnetic Ap index. It was concluded that several common periodicities appear in solar activity: the Ap index, and the cosmic-ray intensity. This result, in association with the fact that the spectral behavior of geomagnetic-activity parameters, provides invaluable information about the physical processes involved, and indicates that the Ap index might be used as a suitable index for space-weather forecasting. © 2019, Springer Nature B.V

Peak-Size Distributions of Proton Fluxes and Associated Soft X-Ray Flares

Abstract A database combining information about solar proton enhancements (SPEs) near the Earth and soft X-ray flares (GOES measurements) has been used for the study of different correlations through the period from 1975 to May 2006. The emphasis of this work is on the treatment of peak-size distributions of SXR flares and SPEs. The frequency of SXR flares and solar proton events (>10 and >100 MeV, respectively) for the past three solar cycles has been found to follow mainly a power-law distribution over three to five orders of magnitude of fluxes, which is physically correct beyond the "sensitivity" problem with the smallest peak values. The absence of significant spectral steepening in the domain of the highest peak values demonstrates that during the period considered, lasting 30 years, the limit of the highest flare's energy release has not yet been achieved. The power-law exponents were found to be −2.19 ± 0.04, −1.34 ± 0.02, and −1.46 ± 0.04, for the total SXR flare distribution and the total SPE distributions (for both E P > 10 MeV and E P > 100 MeV), respectively. For SPEs associated with flares located to the West of 20°W, the exponents are −1.22 ± 0.05 (E P > 10 MeV) and −1.26 ± 0.03 (E P > 100 MeV). The size distribution for corresponding flares follows a power law with a slope of −1.29 ± 0.12. Thus, X-ray and proton fluxes produced in the same solar events have very similar distribution shapes. Moreover, the derived slopes are not incompatible with a linear dependence between X-ray flare power and proton fluxes near the Earth. A similar statistical relation is obtained independently from the direct comparison of the X-ray and proton fluxes. These all argue for a statistically significant relationship between X-ray and proton emissions

High-Speed Solar Wind Streams and Geomagnetic Storms During Solar Cycle 24

An updated catalog is created of 303 well-defined high-speed solar wind streams that occurred in the time period 2009 – 2016. These streams are identified from solar and interplanetary measurements obtained from the OMNIWeb database as well as from the Solar and Heliospheric Observatory (SOHO) database. This time interval covers the deep minimum observed between the last two Solar Cycles 23 and 24, as well as the ascending, the maximum, and part of the descending phases of the current Solar Cycle 24. The main properties of solar-wind high-speed streams, such as their maximum velocity, their duration, and their possible sources are analyzed in detail. We discuss the relative importance of all those parameters of high-speed solar wind streams and especially of their sources in terms of the different phases of the current cycle. We carry out a comparison between the characteristic parameters of high-speed solar wind streams in the present solar cycle with those of previous solar cycles to understand the dependence of their long-term variation on the cycle phase. Moreover, the present study investigates the varied phenomenology related to the magnetic interactions between these streams and the Earth’s magnetosphere. These interactions can initiate geomagnetic disturbances resulting in geomagnetic storms at Earth that may have impact on technology and endanger human activity and health. © 2018, Springer Nature B.V

Statistical analysis of solar proton events

A new catalogue of 253 solar proton events (SPEs) with energy >10 MeV and peak intensity >10 protons/cm2.s.sr (pfu) at the Earth's orbit for three complete 11-year solar cycles (1970-2002) is given. A statistical analysis of this data set of SPEs and their associated flares that occurred during this time period is presented. It is outlined that 231 of these proton events are flare related and only 22 of them are not associated with Ha flares. It is also noteworthy that 42 of these events are registered as Ground Level Enhancements (GLEs) in neutron monitors. The longitudinal distribution of the associated flares shows that a great number of these events are connected with west flares. This analysis enables one to understand the long-term dependence of the SPEs and the related flare characteristics on the solar cycle which are useful for space weather prediction. © European Geosciences Union 2004