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Volume2, Issue1


EDITORIAL

Page 1PDF: Editorial

Sefer Bora Lisesivdin


ARTICLES

Page 2PDF: Effect of interplanetary disturbances on cosmic rays and interplanetary parameters

Rekha Agarwal, Rajesh Kumar Mishra

Abstract: In the present work analogous analysis has been made for the extreme events occurred during July 2005. Specifically, rather intense Forbush decrease was observed at different neutron monitors all over the world during 16 July 2005. It started some hours before arrival of a weak shock associated with a CME from 14 July 2005. It is rather a peculiar event, as it is not a ground level enhancement of solar cosmic rays and not a geomagnetic effect in cosmic rays. An effort has been made to study the effect of this unusual event on cosmic ray intensity as well as various solar and interplanetary plasma parameters. It is noteworthy that during 11 to 18 July 2005, the solar activity ranged from low to vary active. Especially low levels occurred at the 11, 15 and 17 July whereas high levels took place on the 14 and 16 July 2005. A series of Forbush effects took place from 12 July causing a decrease in cosmic ray intensity of about 2%, by the 16 July 2005. An intensive Forbush decrease of cosmic ray intensity observed on 16th July, 2005. The charac-teristics of this Forbush decrease on 16th July, 2005 indicate that it does not comprise ground level enhancement of solar cosmic rays neither a geomagnetic effect in cosmic rays. The Sun is observed active during 11 to 18 July 2005 and the interplanetary magnetic field intensity lies within 15 nT and solar wind velocity was limited to ~ 500 kms-1. The geomagnetic activity dur-ing this period remains very quite, Kp index did not exceed 5, the disturbance storm time Dst index remains ~ - 70 and no sudden storm commencement (SSC) has been detected during this period.


Page 7PDF: Relativistic dynamics without conservation laws

Bernhard Rothenstein, Stefan Popescu

Abstract: We show that relativistic dynamics can be approached without using conservation laws (conservation of momentum, of energy and of the centre of mass). Our approach avoids collisions that are not easy to teach without mnemonic aids. The derivations are based on the principle of relativity and on its direct consequence, the addition law of relativistic velocities.


Page 21PDF: Study of high amplitude anisotropic wave trains alongwith interplanetary plasma parameters

Rajesh Kumar Mishra, Rekha Agarwal

Abstract: The first three harmonics (diurnal/semi-diurnal/tri-diurnal) of high amplitude anisotropic wave trains of cosmic ray intensity over the period 1991-1994 have been investigated for Deep River neutron monitoring station. Our study reveals that the diurnal time of maximum i.e. phase remains in the corotational/18 Hr direction, whereas the time of maximum for semi-diurnal ani-sotropy has no definite trend as compared to the quiet days (days on which the transient magnetic variations are regular and smooth) annual average for majority of the HAE events. The phase of the tri-diurnal anisotropy significantly shifts towards later hours as compared to the quiet day annual average. It is noticed that these events are not caused either by the high-speed solar wind streams or by the sources on the Sun responsible for producing these streams such as polar cor-onal holes. The amplitude of tri-diurnal anisotropy for HAE events is observed to remain high for negative polarity of north-south component of interplanetary magnetic field (Bz), whereas it is found to remain slightly low for positive polarity of Bz showing a negative correlation. The amplitude of the tri-diurnal anisotropy is observed to increase with the decrease in the value of disturbance storm time index (Dst) showing a negative correlation.


Page 27PDF: Magnetic behaviour and critical phenomenon in spinels xCuCr2Se4 - (1-x)Cu0.5Ga0.5Cr2Se4 systems

Mohamed Hamedoun, Rachid Masrour, Khalid Bouslykhane, Ahmed Hourmatallah, Najib Benzakour

Abstract: We study the magnetic properties and the critical behaviour of the xCuCr2Se4 - (1-x)Cu0.5Ga0.5Cr2Se4 systems in the range0.6≤x≤1. The values of the nearest neighbour and next-nearest neighbour exchange interactionsJ1and J2 are calculated by a distribution probability adapted of the nature of dilution problem in B-spinel lattice. The critical region is studied by high-temperature series expansion extrapolated with the Padé approximants method. The critical temperature Tc and the critical exponents gammaand nu associated with the magnetic susceptibility and the correlation length , respectively, are deduced, by using the height temperature series expansions combined with the Padé approximants method. The obtained values of gamma and nu are insensitive to the dilution ratio and may be compared with other theoretical results based on 3D Heisenberg model.