P. Paschalis

Estimation of the cosmic ray ionization in the Earth's atmosphere during GLE71

DYASTIMA is an application, based on Geant4, which simulates the cascades of particles that are generated due to the interactions of cosmic ray particles with the atmospheres of the planets. The first version of DYASTIMA has been successfully applied to the Earths atmosphere, providing results that are in accordance with the publications of other models. Since then, important improvements and extensions have been made to the application, including a graphical user interface environment that allows the more effective management of the configuration parameters. Also, the actual modelling of the atmosphere has been changed allowing the definition of more complex cases and at the same time providing, in a more efficient way (with respect to the programs previous version) enhanced outputs. In this work, we combine the new version of DYASTIMA with the NMBANGLE PPOLA model, that estimates the spectrum of SEPs during relativistic proton events using ground level neutron monitor data from the worldwide network. Such a joint model has as a primary scope the simulation of a SEP event and of its secondary products at different altitudes in the Earths atmosphere, providing at the same time estimation of the respective ionization rates and of their spatial and temporal dependence. We apply this joint model to GLE 71, on 17 May 2012, and we discuss the results.

Recent Research applications at the Athens Neutron Monitor Station

The ground based neutron monitor measurements play a key role in the field of space physics, solar-terrestrial relations, and space weather applications. The Athens cosmic ray group has developed several research applications such as an optimized automated Ground Level Enhancement Alert (GLE Alert Plus) and a web interface, providing data from multiple Neutron Monitor stations (Multi-Station tool). These services are actually available via the Space Weather Portal operated by the European Space Agency (http://swe.ssa.esa.int). In addition, two simulation tools, based on Geant4, have also been implemented. The first one is for the simulation of the cosmic ray showers in the atmosphere (DYASTIMA) and the second one is for the simulation of the 6NM-64 neutron monitor. The contribution of the simulation tools to the calculations of the radiation dose received by air crews and passengers within the Earths atmosphere and to the neutron monitor study is presented as well. Furthermore, the accurate calculation of the barometric coefficient and the primary data processing by filtering algorithms, such as the well known Median Editor and the developed by the Athens group ANN Algorithm and Edge Editor which contribute to the provision of high quality neutron monitor data are also discussed. Finally, a Space Weather Forecasting Center which provides a three day geomagnetic activity report on a daily basis has been set up and has been operating for the last two years at the Athens Neutron Monitor Station.

Primary Data Processing Algorithms for Neutron Monitors

The primary data processing of the neutron monitors is a necessary procedure in order to provide the worldwide network of neutron monitors with high quality data. The procedure should be performed in a real time code which means that it should be fast and make use only of the past measurements of a neutron monitor. In general, the data correction algorithms are based on the comparison among the different channels of the detectors. Such methods, which are used currently by the Athens neutron monitor station as well as by many other stations are the Median Editor and the Super Editor. In this work, two new algorithms that are currently being developed in the Athens Station are presented. The first one is based on an Artificial Neural Network model, while the second one is based on a pure statistical model.

An online application for the barometric coefficient calculation of NMDB stations

One of the most important data corrections related to the primary data processing of the neutron monitors is the pressure correction due to the barometric effect. This effect induces considerable variation in the counting rate of a cosmic ray detector which is not related to the real variation of the cosmic rays flux but only to the local atmospheric pressure of the station. In order to provide the worldwide neutron monitor network with good quality data, a correction has to be made that requires the calculation of the barometric coefficient. A new method that effectively calculates the barometric coefficient for a station using data of a reference station in order to subtract the primary variations of cosmic rays is presented in this work. Moreover, this method is the prototype of an online tool that uses data of the NMDB stations and calculates the barometric coefficient for any available station. This tool is also presented.