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Iratius Radiman
Astronomy, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology
Mathematics

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The Temporal Variations in Sunspot Number, Geomagnetic aa index and Southern Oscillation Index Iratius Radiman; Hiroshi Miyake; Chatief Kunjaya; Yoji Takeoka; Muhamad Irfan Hakim; Zadrach L. Dupe
Jurnal Matematika & Sains Vol 7, No 1 (2002)
Publisher : Institut Teknologi Bandung

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Abstract

A study of three monthly solar-terrestrial indices of mean sunspot number, geomagnetic aa index, and Southern Oscillation Index during period of 1882 to 2000 was carried out to find any consistent short –term periodicities. We found 19, 22, and 26-month periodicities persistently occur in the above data, i nstead of 11-year pattern. We suggest that they might have solar activity origin.
On the Periodical Nature of Annual Variation of the Regressions of the Martian Polar Caps Using the Phase Dispersion Minimization-(PDM) Method Iratius Radiman; Chatief Kunjaya; Andreas Widjaja
Jurnal Matematika & Sains Vol 3, No 2 (1998)
Publisher : Institut Teknologi Bandung

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Data observations of the regressions of the Martian Polar Caps from 1905 to 1988 were reinvestigated through the Stellingwerf’s Phase Dispersion Minimization-(PDM) method. The results indicate that the annual variations of the regressions of the Martian Polar Caps is seen to have a periodical nature. The main period is found to be approximately 40 years while other periodical components of shorter duration seen in the data also exist. The shorter periods are 3, 6 and 8 years respectively. The 3 years period may be attributed to the systematic effect of 2-3 years interval in which the data was acquired. The 6 years may be a subharmonic component of the 3 years period, though it is blended. The 8 years period cannot be attributed to the same effects of observations, such as the cyclic appearances of each polar caps in the Martian epoch of observations. Irregularity of the epoch interval of observations prevent such a systematic effect to be seen. Therefore, we like to point out that the 8-years period is a real physical phenomenon of the annual variations of the polar regressions. This strongly support the findings of Iwasaki and Ebisawa on sizes of the South Polar Cap. The PDM-method is sufficiently general to analyze small sets of data involving missing observations and non-sinusoidal time variations. The method was used to ascertain results obtained previously through time-series calculations which involved missing observations. Discussions on probable relations between changes in solar radiation which might affect the annual regressions of the polar caps are also examined.
Solar Cycle Variations and its Effects on El Niño/La Niña Behaviour Iratius Radiman; Dhani Herdiwidjaja; Zadrach L. Dupe; Chatief Kunjaya; Muhammad Irfan Hakim
Jurnal Matematika & Sains Vol 8, No 2 (2003)
Publisher : Institut Teknologi Bandung

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Variations in the Solar Cycle has been known for a long time. The Solar Cycle is observed to vary from 14 to 8 years in length. The reconstructions of the annual solar total irradiance since the beginning of Maunder Minimum (from year 1600) to year 2000 show that there are envelopes of groups sunspot numbers. The intensities delineated by the envelopes are consistent with the range of CaII brightness. The timelength of the envelopes corresponds to long term variabilities such as the Gleissberg Cycle of 88 and 124 years period. A close correlation between total irradiance and sunspot number from 1610 to 2000 is found to be 0.88. Although the work of Labitzke and van Loon has clearly shown the existence of an oscillation in many atmospheric parameters with a period in the vicinity of 11 years and a phase that is related to that of solar activity, there is reluctance to accept a relationship to the 11-year solar cycle. Therefore this study aimed to pursue the investigations further by determining the correlation coefficients to lower trophospheric layers. Our studies reveal to results, which we summarized as follows: A weak correlation at 27 month delay is found between solar activities and the El Niño/La Niña phenomena. The next El Niño/La Niña event is expected to occur from year 2002 until mid 2003. A major change in the pattern of the solar cycle since 1700 appears. The sun is seen to be more frequent in its active states over the last 100 years. The length of the cycle is becoming shorter. The solar cycles modulate from 5, 8, 12 and 25-year period obtained from its total irradiance plot. The 5-year period coincides very well within the El Niño/La Niña period of 2 to 7-year. The El Niño/La Niña phenomenon has a 10-12 month duration. Every El Niño/La Niña event is separated from 24 to 84 months duration in an irregular pattern. Every El Niño/La Niña event is unique. These conclusions are drawn after decomposing the SST Anomaly Index through applied Fourier Transform. The effect of the solar cycle variations is to generate long period harmonics in the coming El Niño/La Niña events. We expect that more variability in climate will occur in the coming decade.
Are El Ninõ and La Nina Phenomena Influenced by Solar Activities ? Chatief Kunjaya; Iratius Radiman; Zadrach Dupe; Dhani Herdiwidjaja; M. Irfan Hakim
Jurnal Matematika & Sains Vol 6, No 1 (2001)
Publisher : Institut Teknologi Bandung

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El Ninõ and La Nina phenomena have caused disasters in many countries. Many million dollar losses has suffered by millions of people in several regions. However the exact cause of the phenomena is still unclear. The Sun plays the central role in determining the earth climate, therefore it is reasonable to think that changes in the Sun behaviour may influence the climate on earth including the El Ninõ and La Nina phenomena. Based on this consideration we tried to find any relationship between the indicator of solar activity, i.e. sunspots, and the indicator of El Ninõ and La Nina phenomena, i.e. Southern Oscilation Index (SOI).
The Motion of Solar Wind Charged Particle in a Sinusoidal Vibrating Magnetic Field Iratius Radiman
Jurnal Matematika & Sains Vol 12, No 4 (2007)
Publisher : Institut Teknologi Bandung

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Abstract

The motion of solar wind charged particle in a small perturbed magnetic field lines of magnitude B1 is derived througha perturbed Lorentz force. By introducing a small sinusoidal velocity perturbation v1 in transverse direction to theoriginal velocity field vo, a small perturbed magnetic field is resulted from the original magnetic field of magnitude B0. Asystem of simultaneous differential equations describing the perturbed Lorentz force in Cartesian coordinates isobtained. These equations, denoted as RESY, are then treated numerically to follow qualitatively the behaviour of thecharge motion locally. The squared space velocity resulted from RESY are twice to three times larger than the initialvelocity squared in the case of constant magnetic field. Here the initial velocity was normalized to unity,whereas itsvalue may be estimated from the well-known Parker exponentially increased solar-wind velocity. Vibrating magneticfields might be one candidate to explain the observed very high velocities for some solar wind particles.
Co-Authors Andreas Widjaja Chatief Kunjaya Dhani Herdiwidjaja Hiroshi Miyake M. Irfan Hakim Muhamad Irfan Hakim Muhammad Irfan Hakim Yoji Takeoka Zadrach Dupe Zadrach L. Dupe