Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 34, 1053-1068, 2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Regular paper
21 Nov 2016
Latitudinal and longitudinal dependence of the cosmic ray diurnal anisotropy during 2001–2014
Anastasia Tezari1,*, Helen Mavromichalaki1, Dimitrios Katsinis1, Anastasios Kanellakopoulos1, Sofia Kolovi1, Christina Plainaki2,1, and Maria Andriopoulou3 1Nuclear and Particle Physics Department, Faculty of Physics, National and Kapodistrian University of Athens, Zografos, 15784 Athens, Greece
2INAF-IAPS, Via del Fosso del Cavaliere, 00133, Rome, Italy
3Space Research Institute, Austrian Academy of Sciences, Graz, Austria
* Invited contribution by A. Tezari, recipient of the EGU Outstanding Student Poster (OSP) Award 2015.
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.

Citation: Tezari, A., Mavromichalaki, H., Katsinis, D., Kanellakopoulos, A., Kolovi, S., Plainaki, C., and Andriopoulou, M.: Latitudinal and longitudinal dependence of the cosmic ray diurnal anisotropy during 2001–2014, Ann. Geophys., 34, 1053-1068, doi:10.5194/angeo-34-1053-2016, 2016.
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