Showing papers on "Solar cycle 24 published in 2003"

An Early Prediction of Maximum Sunspot Number in Solar Cycle 24

Abstract: A non-linear coupling function between sunspot maxima and aa minima modulations has been found as a result of a wavelet analysis of geomagnetic index aa and Wolf sunspot number yearly means since 1844. It has been demonstrated that the increase of these modulations for the past 158 years has not been steady, instead, it has occurred in less than 30 years starting around 1923. Otherwise sunspot maxima have oscillated about a constant level of 90 and 141, prior to 1923 and after 1949, respectively. The relevance of these findings regarding the forecasting of solar activity is analyzed here. It is found that if sunspot cycle maxima were still oscillating around the 141 constant value, then the Gnevyshev–Ohl rule would be violated for two consecutive even–odd sunspot pairs (22–23 and 24–25) for the first time in 1700 years. Instead, we present evidence that solar activity is in a declining episode that started about 1993. A value for maximum sunspot number in solar cycle 24 (87.5±23.5) is estimated from our results.

Wavelet analysis of several important periodic properties in the relative sunspot numbers

Abstract: We investigate the wavelet transform of yearly mean relative sunspot number series from 1700 to 2002. The curve of the global wavelet power spectrum peaks at 11-yr, 53-yr and 101-yr periods. The evolution of the amplitudes of the three periods is studied. The results show that around 1750 and 1800, the amplitude of the 53-yr period was much higher than that of the the 11-yr period, that the ca. 53-yr period was apparent only for the interval from 1725 to 1850, and was very low after 1850, that around 1750, 1800 and 1900, the amplitude of the 101-yr period was higher than that of the 11-yr period and that, from 1940 to 2000, the 11-yr period greatly dominates over the other two periods.

Solar control of meteor radar rates

Abstract: Meteor radar observations carried out in August-September 1953-84 at theOnsala Space Observatory in Sweden show long-term, as well as short termvariations in meteor radar rates. These rate variations are associatedwith position in the solar cycle, and with variations in the solar windsector structure. An inverse correlation is found between meteor radarrates and the solar cycle. The magnitude of this effect is quite large;about twice as many radar echoes are observed at solar minimum as atsolar maximum. We propose that this long-term inverse correlation withthe sunspot number is caused by a solar cycle controlled variation ofthe atmospheric density gradient at meteor ablation heights (90-110 km).Day-to-day variations in meteor radar rates, which correlate withshort-term geomagnetic activity have also been detected. A superposedepoch analysis based on solar wind sector boundaries as key dates showsthat a minimum in meteor radar rates occurs about 3 days after theEarth's passage of a solar wind sector boundary. (Less)

Super Solar Neutron Telescope for the Next Solar Maximum

Abstract: We propose a new type of solar neutron detector, the Super Solar Neutron Telescope, for the next solar cycle 24. The new detector should retain the function of the present solar neutron telescopes, i.e., the capability for energy measurement and determination of the arrival direction of solar neutrons with high detection efficiency. For this purpose the detector should be composed of scintillator blocks with dimensions of 5cm×10cm×300cm. Those scintillator blocks will be aligned to compose a tracker and the proposed dimensions of the Super Solar Neutron Telescope are 300cm×300cm×150cm. The energy and direction of 70% of incoming neutrons with kinetic energies >150MeV can be measured by this telescope. The performance of the Super Solar Neutron Telescope has been investigated by Monte Carlo calculation.

Large Indian Solar Observatory

Abstract: More than three decades back, Dr. M. K. V. Bappu, the father of modern Indian Astronomy, wrote the following paragraph in “Current Science”, about a solar physicist's dream. “On the solar side, the ground-based telescope still offers the maximum for the high-resolution study. The vacuum telescope located at a good site should be able to obtain spectra of features less than half a second of arc. Choice of site in a wide expansion of water holds much promise. Very small islands, less than a 100 meters across in an ocean, are a good possibility. Much careful study should be made in this regard before locating a large vacuum telescope of the order of 150 cm in aperture. A bright solar image of large scale under almost perfect conditions of seeing would be answer to the solar physicist's dream”. There have been several attempts, in the mean time; to build a large ground based solar telescopes during the last thirty years. At the same time, there have been great advances in the field of solar physics both from ground based and space observations. Specially the last decade have witnessed a great progress in solar research due to a host of space missions like Yohkoh, SOHO, TRACE and RHESSI. At the present time, the 50 cm solar space telescope, capable of 0.5 arc second spatial resolution, is being built for deployment in early 2006. There are two major ground based facilities, one 4 meter aperture solar telescope in USA “Advanced Technology Solar Telescope” and the other 1.4 meter aperture telescope in Germany “GREGOR” are being built to be operative in 2010 and 2005 respectively. Clearly, these two instruments will make great contributions in our understanding of the fine solar features. Besides these new instruments, there have been a number of telescopes that were equipped with instruments to correct the atmosphere induced effects for image distortion (adoptive optics) leading to very high spatial resolution observations of the sun. In the recent past, the Indian solar researchers have been seriously contemplating to make a large telescope for observational study of the solar features. Here, I describe various aspects of such an instrument and outline a possible scenario to realize it.