First European Space Weather Week, 29 / 11 to 3 / 12 2004, ESA-ESTEC, The Netherlands
The new Athens Center on data processing from the Neutron Monitor Network in real time
H. Mavromichalaki1, G. Souvatzoglou1, C. Sarlanis1, G. Mariatos1, M. Gerontidou1, A. Papaioannou1, C. Plainaki1, S. Tatsis1
A. Belov2, E. Eroshenko2, V. Yanke2
2 IZMIRAN, Russian Academy of Science, Moscow, Russia
The ground based neutron monitors (NM) records 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 fully functioned New Athens NM network is in place for research application and the main goal is to take advantage of this unique multidimensional devise 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, there can be preliminary alert of ground level enhancements (GLEs), due to relativistic solar particles, which can be registered around 20 to 30 minutes before the main part of lower energy particles responsible for the GLEs – providing the advantage of forth warning. While, on the other hand, by monitoring the precursors of cosmic ray (CR) we manage to have a forehand estimate on what events as geomagnetic storms and/or Forbush decreases should we expect. Apart from all, the network of NM is a unified multidirectional spectrograph/detector characterized by considerably accuracy, providing a significant tool of forecasting the arrival of interplanetary disturbances of the Earth. The achievements, the processes and the future results to come, are being discussed in this work.
Disturbances of the solar wind, magnetosphere and cosmic rays (CR) are closely related, since they are caused by the same active processes at the Sun. Therefore the effect of the solar wind disturbances on cosmic rays may extend to large distances and due to the their relativistic velocity, CR bring valuable information on these disturbances, well in advance of their arrival at the Earth. Characteristic signatures of CR can be selected by special methods from the neutron monitor network (NMN) and so real time data combined with developed and tested methods, should be used for successful prediction on Space Weather.
In our days Internet becomes one of the most important tool for researchers working on solar-terrestrial physics. There is a tight relation among internet and space weather. Information is updated every minute or less by many tens of instruments in order to provide valid characteristics of the solar, geophysical and interplanetary effects.
Athens Neutron Monitor Station
Cosmic ray measurements in Athens (37.58˚N, 23.47˚E) initiated in November 2000 with a standard 6NM-64 neutron monitor. Athens station was the sixth one to present both graphical and digital data in an online base. The measurements of the station are being elaborated automatically in order to be compatible to other stations data because of the necessity to compare a number of high rigidity stations in a good quality data which is required for a detailed study of CR variations and space weather conditions. The resolution of the measurements reaches as far as one second – which is uniquely worldwide. The station’s web site is: http://cosrays.phys.uoa.gr where all data are being provided. The functional block diagram of the station – Figure 1 – highlights the way that a Neutron Monitor station operates. It is clear that the 6NM-64 neutron monitor connects to a registration system where the accounting of the particles takes place. From there a computer stores all data and forwards them to the main server of the station. Followed by a display to the web site of the station.
Fig.1: Athens Neutron Monitor Block Diagram
Neutron Monitor Network data processed in Athens
Starting in July 1997 the Moscow NM Station was the first one, in the world, to present real time data to the internet. Since then, a number of other stations became involved operating in various latitudes around the world. At this point, there are 25 stations providing real or quasi-real time data which can be elaborated automatically, in order to be compatible to other stations. In that way a comparison of high rigidity stations in a good quality data can be achieved, required for a detailed study of CR variations. Nowadays a number of special programs as GSM (Global Survey Method), RSM (Ring Station Method) - and others - allows the derivation of the CR density , anisotropy and CR-pitch angle distribution at any moment, by using as many neutron monitors as possible. The use of all stations as a unified multidirectional detector, made the accuracy of the measurements substantially higher (< 0.1% for hourly data). Twenty-five NM stations provide their data in real time, in digital and/or graphical form (Mavromichalaki et al, 2001).
Fig. 2: A global presentation of all NM on-line stations
Space weather refers to conditions on the sun and in the solar wind, magnetosphere, ionosphere and thermosphere that can influence the performance and reliability of space and/or ground based technological systems. Characteristic signature in cosmic rays may be selected by special methods from neutron monitor network (NMN) data and input to space weather applications, while real time data in combination with selected methods can be used for successful prediction (Mavromichalaki et al, 2004)
The prospective goal of the network is to make possible receiving all data in real time in close sequence from all servers around the globe, in order to make a real time monitoring of space weather conditions, combining the potentiality given by the active cosmic ray groups working on the field. In Athens cosmic ray station, a data collection system has been developed, capable of gathering data from remote stations and able to present their data to Internet via FTP or HTTP servers. This system has been designed with the capability to support a large number of stations and therefore the upgrade of the system is rather flexible. It is important to outline that the designed collection system has the ability to provide reliable data, based on the issue that there are independent programs collecting simultaneously data from different stations in different ways. Until today there are 21 stations from which the described system collects data. In that point of mind a number of algorithms and programs has been developed. In particular a ‘scheduler’ algorithm has the ability to call various types of executable downloaders.
One of the most interesting aspects on this program was the presentation of data. The neutron monitor recording system transfers one minute and hourly data to their server and refresh their database every hour. A special program included in a scheduler creates a graphical file once per hour which is displaced on the web site of the station. Advanced processing system of 1-5-15-60 minute refreshes database which is operating in a number of stations providing both graphical and digital form of the measurements.
The early detection of Earth directed SEP event by NMs gives a very good chance of preventive prognosis of dangerous particle flux and can provide an alert with a very low probability of false alarm. The method developed in Villoreci et al. (2000) and Stoker et al. (2000) using 1-min NM data (Dorman et al. 2004) from a single observatory was applied to predict the spectrum of the approaching particles.
Data Collection System
Fig. 3: A schematic diagram of the Athens Center of the NM Network in real time
The overall process of data can be seen in the above figure. The properties of every station participating in the network are concentrated in one database program the: ‘Properties Database’. Within the same database the initialization parameters of the data collection on poling is being deposed for every station.
A ‘Scheduler’ program reads the properties of each station and makes the decision whether or not to make a data collection call to a station. For every different station there is a single data collection program which uploads the data from the specific remote station to the local database of the network in Athens.
The ‘Scheduler’ software has the ability to call many data collection programs in the same minute and in that way those programs run at the same time in a parallel mode. Every data collection program can bring on the latest data in a periodic scheme, of a specific time period automatically or even manually. Real time data are graphically presented and used in programs running in the same mode providing information and forecasting signals. Recently an effort to combine the results of the NMN and those presented by other sources has been achieved, urging us into going forth with an even more detailed analysis.
Fig. 4: Plots of real time data NM Network (left panel) and from other sources (right panel)
What are the applications of the NM Network used in Athens Center?
A reliable Neutron Monitor Network such as used in the Athens Center provides an operational monitoring able to forecast space weather effects. At this point the network is being used onward two directions. Specifically, (a) the first direction is a Ground Level Enhancement (GLE) prediction or ‘GLE Alert ’and (b) secondly the forecast of interplanetary shock arrival.
The network provides us with precursors from which we can be led to prediction. It is known that low energy protons are the most dangerous part of the solar energetic particle (SEP) spectrum for satellite electronics and crew. Maximal flux of such particles reaches the Earth several hours after the occurrence of the event on the Sun. High energy particles from the solar proton event reach the Earth with a velocity close to that of light. The flux can not be accurately measured by satellites because of their small detector square; while ground based NMs do measure the flux with highly statistical accuracy (in average 0.5% for 5 min) as GLEs. In that way we are in a position to develop methods in order to extract dependable forecast signals. It is essential to provide forecasting signals because of the high dependency of solar interplanetary events to human activities (Figure 5).
Fig. 5: Effects of the Sun to Human activities
Space Weather Forecasting
(a) GLE Onset
As can be obtained by figure 6, the profiles of particles of different energy during the powerful SEP event of April 15, 2001 clearly declares that the high-energy particle profiles registered at the Earth had already ended well before the main development of the low-energy particle profiles as recorded on board GOES.
Fig. 6: Powerful SEP event of April 15, 2001
A method of prognosis has been proposed on the physical bases of the above notice. Specifically, the method calls for four steps:
- Data from at least three NM stations at Earth (two high latitudinal and one – two low latitudinal) and two independent satellite channels, for example X-ray on GOES10 and GOES12, are processed to search for the start of ground level enhancement (GLE). If it is found, our computer sends a signal to collect data from all neutron monitors through the network. Also, calculates spectra and other parameters for estimation of the expected CR profiles for lower energies, at different altitudes several hours ahead.
- The obtained by such a way alert signal is used for sending out the forecasting by e-mail, and, mainly, to run a system of minute data collection from the whole NM network. In this case data on the network station are very important to be updated not rarer than every 5 minutes. The number of necessary stations should be about 10-20.
- While the minute data are collected the program of the proton enhancement analysis is running. The proton spectrum will be derived with more and more accuracy along the accumulation of new and new data.
- Solar relativistic particles registered at Earth have an essential property to bring information on solar and interplanetary conditions much earlier than low and mid energy solar particles. Due to their big diffusion coefficient high energy particles come from the Sun in 8-20 minutes after acceleration and escaping into solar wind, whereas the main part of lower energy particles, which cause dangerous situation for electronics and hazard radiation, usually come later in more than 30-60 minutes. Proton events registered at Earth (GLEs) have a complete profile well before the enhancement evolving in the lower energies. This fact can be used for the calculations of spectra and fluxes for lower energies at different levels in 20-30 minutes after the onset and improve these results along the time. In a whole it allows prognosis time behavior of non-relativistic solar protons up to 10-15 hours.
Fig. 7: Alert Method for prognosis of GLE Onset
(b) Geomagnetic Storms
A large heliospheric storm, indicated by different space weather parameters, is shown in figure 8 , where significant variations in CR density and in the first harmonic of the CR anisotropy, derived from ground level observations, occur simultaneously with dramatic changes in the interplanetary and geomagnetic parameters.Another aspect of the real-time ground level monitoring cosmic rays is the obtaining of the galactic CR characteristics for diagnosing a situation in the heliosphere to predict some dangerous events in Earth’s vicinity.
Fig. 8: Space Weather parameters on a large heliospheric storm
The proposed method on the prognosis of geomagnetic storms consists of the following steps:
- System of data collection in real time from neutron monitor network has been created and supports unlimited number of stations. In this listing should be included high latitudinal stations and mid and low latitudinal as well.
- After collection data for a current hour from at least 15 stations (optimum 30) the program of analysis by the global survey method (GSM) is run out. In result the CR density, spectral parameters of density, and three components of CR anisotropy vector is derived at this current hour.
- Amplitude of isotropic variation and characteristics of the CR anisotropy (first harmonic) are put at web site in real time and are the initial experimental data for analysis of the current heliospheric situation. To carry out more reliable analysis it would be desirable to use these results together with other data on solar and solar wind measurements
- H. Mavromichalaki , V. Yanke , L. Dorman , N. Iucci , A. Chilingaryan , O. Kryakunova Neutron Monitor Network in Real Time and Space Weather. Monograph NATO series for space weather infrastructure technology, Effects of Space weather on Technology Infrastructure, 301-317, 2004
- Mavromichalaki, H., C. Sarlanis, G. Souvatzoglou, S. Tatsis, A. Belov, E. Eroshenko, V. Yanke and A. Pchelkin. Athens Neutron Monitor and its aspects in the cosmic-ray variations studies. Proc. 27th ICRC 2001, 4099, 2001
- L.I. Dorman, L.A.Pustil’nik, A. Sternlieb, I.G. Zukerman, A.V. Belov, E.A. Eroshenko, V.G. Yanke, H. Mavromichalaki, C. Sarlanis, G. Souvatzoglou, S. Tatsis, N. Iucci, G. Villoresi, Yu. Fedorov, B. A. Shakhov, M. Murat, Monitoring and Forecasting of Great Solar Proton Events Using the Neutron Monitor Network in Real Time. IEEE for Plasma Science, 32,1478-1488, 2004