Cosmic ray solar diurnal and sidereal variations

• Main Author: Juwono, Alamsyah M
• Format: Thesis
• Language: English
• Published: 1997
• Subjects: Antarc*; Antarctica
• Online Access: https://eprints.utas.edu.au/20379/; https://eprints.utas.edu.au/20379/1/whole_JuwonoAlamsyahM1997_thesis.pdf

Data from underground cosmic ray observatories at Cambridge and Liapootah, Tasmania and Mawson, Antarctica, have been studied to determine the amplitudes of Solar Diurnal Variations for period of 11 years, 1982-1992, for Cambridge and Mawson observatories, and for 1992-1993 for Liapootah observatory. The amplitudes are estimated for either monthly average or yearly average, for ground based and free space as well. The monthly Solar Diurnal Variations have been shown to be contaminated by Sidereal component, and by using method of the sinusoidal fittings, the amplitudes of Solar Diurnal Variation and the Sidereal component of the variation have been extracted. The results of extracting the monthly Solar Diurnal Variations are (0.104 ± 0.004 %), (0.116 ± 0.006 %) for Cambridge, (0.090 ± 0.004 %) for Mawson and (0.060 ± 0.008 %) for Liapootah. The amplitudes of Sidereal component contaminating the Solar Diurnal Variations also have been found. These sidereal amplitudes are (0.043 ± 0.006 %) and (0.022 ± 0.008 %) for Cambridge, (0.019 ± 0.006 %) for Mawson and (0.0067 ± 0.012 %) for Liapootah. By using the Sidereal Variation component as detected in a deep underground station at Poatina as reference, i.e. that it is assumed to be purely galactic, the percentage of the Sidereal component detected by one of Cambridge's telescope which is due to North-South Anisotropy has been estimated. The result is that about 72% of total 0.043% Sidereal component detected in that telescope is due to North-South Anisotropy, and the other 28% is of galactic origin. Times of Maximum for monthly Solar Diurnal Variation detected by the two observatories, Cambridge and Mawson, are also discussed. The results show that in the ground-based observation Time of Maximum of Mawson tends to be later than those of Cambridge. Free Space analysis shows that there is good similarity among Times of Maximum of the monthly Solar Diurnal Variations detected by the two telescopes at Cambridge and one at Mawson, which in turn exhibits that cosmic ray particles which are detected in polar regions may undergo different magnetic bending than those detected in lower latitude regions. The free space analysis also gives the estimates of free space amplitudes of the Solar Diurnal Variations for corresponding Solar Diurnal Variation amplitudes as they observed in the ground. Yearly Solar Diurnal Variations at Cambridge and Mawson have also been studied. The wave-forms of the yearly plots during period of 1982-1993 show that they are consistent with the long-term modulations, either 11-year or 22- year modulation. In this case it is shown that the cosmic rays detected in those two observatories during 1985/1986 underwent a minor depression, i.e. a situation when 11-year and 22-year modulation waves are superposing with one out of phase to the other. The last part of this study concerns on North-South Asymmetry of the sidereal variation. Data from vertical telescope at Liapootah are used for this purpose. The 1992-1993 data of Liapootah have been compared to data from the vertical telescope at Matsushiro underground station. The result of the Sidereal Variation of (0.040 ± 0.007 %) from Liapootah is significantly larger than that found from Matsushiro which is (0.026 ± 0.008 %). This result confirms what previously reported by Munakata et al. (1994). Sidereal Variations from other telescope components of Liapootah station have also been studied. They are plotted against the latitudes of viewing of corresponding telescopes, to examine the presumption that there is NorthSouth Asymmetry of Sidereal Variation. The result of the plotting supports the presumption, and it exhibits that the line of symmetry may lie somewhere between equator and 20C S.