Comparative Study on Mass loss by the Sun and Energy Available for Utilization between two Tropical Stations in Nigeria

The electromagnetic radiation emitted from the Sun is called solar radiation. Almost all life on Earth evolved with the Sun as a major influence. The rising and setting Sun defined the daily cycle we still respond to biologically. This study investigates the yearly, monthly and daily variation of mass loss by the Sun for two locations; Gusau and Calabar situated across the Sahelian and Coastal climatic zones of Nigeria using daily, monthly and yearly global solar radiation meteorological data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 – June 2005). The energy available for utilization based on the mass loss by the Sun for the two locations was also investigated. The fluctuations in the results revealed that the mass loss by the Sun varies significantly from year to year, month to month and from day to day; thus, indicating that it is site dependent and strongly depends on the global solar radiation and solar activities in each of the locations. The highest yearly, monthly and daily mass losses by the Sun for Gusau are 6.3155 10 17 kg y -1 in 1985, 5.5691 10 16 kg m -1 in April and 2.3482 10 15 kg d -1 on April 21, 1985 respectively and the lowest yearly, monthly and daily mass losses by the Sun are 5.6423 10 17 kg y -1 in 1999, 4.2740 10 16 kg m -1 in December and 1.3031 10 15 kg d -1 on December 25, 1999 respectively. The highest yearly, monthly and daily mass losses by the Sun for Calabar are 4.6558 10 17 kg y -1 in 1984, 4.6451 10 16 kg m -1 in February and 2.0252 10 15 kg d -1 on February16, 1984 respectively and the lowest yearly, monthly and daily mass losses by the Sun are3.6806 10 17 kg y -1 in 1983, 2.5346 10 16 kg m -1 in August and 1.9546 10 14 kg d -1 on August7, 1983 respectively. The results indicated that the solar energy available for utilization for Gusau are greater than that of Calabar and this is a reflection of the abundant amount of global solar radiation received on a horizontal surface for Gusau as compared to Calabar. ________________________________________________________________________________________________________


INTRODUCTION
The Sun is the star closest to the earth, and its radiant energy is practically the only source of energy that influences atmospheric motions and our climate [1]. The Sun is a completely gaseous body composed mainly of hydrogen [1]. Its physical structure is complex and composed of several regions: the core, the interior, the convecting zone, the photosphere, the reversing layer, the chromosphere, and the corona [1]. The core is the innermost region and is the sun's hottest and densest part. The temperature of the core ranged from 15 x 10 6 to 40 x 10 6 K and is composed of highly compressed gases at a density of 100-150 g/cm 3 [1]. Above the core is the interior, which contains practically all of the Sun's mass; the core and the interior are thought of as a huge nuclear reactor and the source of almost all its energy. This energy is propagated mainly by radiation to the outer regions, which in turn transport this energy outward by convection and reradiation [1]. The surface of the Sun is called the photosphere, is the source of most visible radiation arriving at the earth's surface. This is the "crust," which can be seen through a blue glass by the naked eye. It is composed of very low-density inhomogeneous gases that form granulations and sunspots [1].The photosphere is the visible layer of the Sun, about 100 km thick [2]. Sunspots can be viewed in this layer, and the rotation of the Sun was first detected when the motion of these sunspots was observed [2].The temperature in this region is 4000-6000 K. The reversing layer extends for a few hundred kilometers: this layer contains vapors of almost all the familiar elements of the earth's crust. Above it, extending over a distance of about 2500 km, is the chromosphere, which, with the reversing layer, forms the sun's atmosphere. Composed mainly of hydrogen and helium, it is visible to the naked eye during an eclipse [1]. The relatively thin layer of the Sun called the chromosphere is sculpted by magnetic field lines that restrain the electrically charged solar plasma [2].The temperature of the chromosphere is several times higher than that of the photosphere [1]. The outermost portion of the sun is called the corona and is composed of extremely rarefied gases called the solar winds, which are thought to extend into the solar system. The coronal gases are considered to be at temperatures several times those of the photosphere [1].
The solar mass is a standard unit of mass in astronomy, equal to approximately . It is used to indicate the masses of other stars, as well as clusters, nebulae and galaxies. It is equal to the mass of the Sun [3 -4]. Sir Isaac Newton was the first person to estimate the mass of the Sun [5]. In his work Principia (1687), he estimated that the ratio of the mass of Earth to the Sun was about 1/28 700. The mass of the Sun has been decreasing since the time it formed. As the Sun loses mass its gravitational pull on the planets weakens slightly [6]. The Sun can't hold the planets as strongly as it used to, so the planets drift a bit further away from the Sun. At least that's the theory [6]. The shift of the planets is so small that it's difficult to measure [6].
The Sun loses mass in two major ways. The first is through solar wind. The surface of the Sun is hot enough that electrons and protons boil off its surface and stream away from the Sun, generating a "wind" of ionized particles [7]. When those particles strike Earth's upper atmosphere they can produce aurora [7]. The solar wind varies a bit in intensity, but from satellite observations, it is known that the Sun loses about 1.5 million tonnes of material each second due to solar wind [7].
The second way the Sun loses mass is through nuclear fusion [7]. The Sun is powered by the conversion of hydrogen into helium in its core, through the process of nuclear fusion [8] producing its life-giving glow over billions of years [7]. The production of helium transforms some of the hydrogen's mass into energy, which radiates away from the Sun in the form of light and neutrinos [7].This reaction results in a decrease in the Sun's mass, and in the release of energy through electromagnetic radiation and the solar wind [9]. By observing just how much energy the Sun radiates, and using Einstein's equation relating mass and energy, it was found that the Sun loses about 4 million tonnes of mass each second due to fusion [7].
So the Sun loses about 5.5 million tonnes of mass every second or about 174 trillion tonnes of mass every year [7]. That's a lot of mass, but compared to the total mass of the Sun it's negligible. The Sun will keep shining for another 5 billion years, and by that time it will have lost only about 0.034% of its current mass [7]. Several studies has been carried out by different researchers to calculate the mass loss by the Sun, this include Zuber and Smith [8], Kippenhahn [10] and Cox [11] to mention but a few.
The purpose of this study is to estimate and compare the mass loss by the Sun for Gusau and Calabar situated across the Sahelian and Coastal regions of Nigeria. The estimated mass loses for the locations were compared to those available in literatures. The study also investigates and compared the energy available for utilization based on the mass loss for the locations under investigation.

METHODOLOGY
The measured daily climatic data of global solar radiation utilized in this present work were obtained from the National Aeronautics and Space Administration (NASA) atmospheric science data centre under Surface meteorology and Solar Energy. The daily averaged data were aggregated to monthly data. Similarly, the monthly averaged data were aggregated to yearly data. The study area under investigation is Gusau (Latitude 12.17 0 N, Longitude 6.70 0 E and altitude 463.9 m above sea level) located in Sahelian zone of Nigeria and Calabar (Latitude 4.97 0 N, Longitude 8.35 0 E and altitude 61.9 m above sea level) located in the Coastal zone of Nigeria. To avoid possible misleading indications related to year to year variation in weather condition, the period under investigation is twenty two years (July 1983 -June 2005) so as to obtain a good climatological average. The quality assurance of the meteorological measurements was determined by checking the overall consistency of the daily, monthly and yearly average of the meteorological parameter used in the study areas. According to Olaniran [12] Nigeria is classified into four climatic zones; these are the Sahelian zone, Midland zone, Guinea savannah zone and the Coastal zone. The locations within the climatic zones are shown in Figure 1. The area, in of spherical shell centered on the Sun and passing through the Earth is given by [13] (1) where is the radius of the Earth from the Sun and is numerically given as .
The radiation per second in ( ) emitted from the Sun to a specific location on the Earth's surface is given by The energy radiated in one day, in ( ) is given by The energy radiated in one month, in ( ) is given by The energy radiated in one year, in ( ) is given by From the famous Einstein's mass energy relation [13], the mass loss by the Sun per day is given by ⁄ The mass loss by the Sun per month is given by ⁄ The mass loss by the Sun per year is given by where is the speed of light and is numerically given as    Figure 4 shows the yearly variation of mass loss by the Sun for Gusau during the period under investigation. The result indicated that the mass loss varies significantly from year to year; the highest value of mass loss was in 1985 with and the lowest was in 1999 with . Figure 5 shows the monthly variation of mass loss by the Sun for Gusau. It is obvious that the highest mass loss was in the month of April with and the lowest in December with . Figure 6 shows the daily variation of mass loss by the Sun in April, 1985 for Gusau. It can be seen that the mass loss varies significantly from day to day with the highest value on April 21, 1985 with and the lowest value on April 28, 1985 with .         Figure 11. Variation of mass loss per day for the minimum month during the period of investigation for Calabar Figure 11 shows the daily variation of mass loss by the Sun in August, 1983 for Calabar. It can be seen that the mass loss varies significantly from day to day with the highest value on August 18, 1983 with and the lowest value on August 7, 1983 with .

Figure 6. Variation of mass loss per day for the maximum month during the period of investigation for Gusau
In this study, the highest and lowest yearly values of mass loss by the Sun for Gusau are in 1985 and in 1999 respectively while for Calabar are in 1984 and in 1983 respectively. The results in this study are in line with those reported by Zuber and Smith [8] where they evaluated the mass loss by the Sun in one year to be . Kippenhahn [10], obtained the mass loss by the Sun in one year as . In another study, Cox [11], estimated the mass loss by the Sun in one year as .

CONCLUSION
This present study examines the yearly, monthly and daily variation of mass loss by the Sun and energy available for utilization in two locations; Gusau (Latitude 12.17 0 N, Longitude 6.70 0 E) located in Sahelian zone of Nigeria and Calabar (Latitude 4.97 0 N, Longitude 8.35 0 E) located in the Coastal zone of Nigeria using daily, monthly and yearly global solar radiation meteorological data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 -June 2005). The highest and lowest values of mass losses for the two locations considered are in close agreement with those reported in literature e.g., Zuber and Smith [8], Kippenhahn [10] and Cox [11] with the mass loss by the Sun for Gusau been higher than that of Calabar. However, the results in this study suggests that the mass loss by the Sun varies significantly from year to year, month to month and from day to day rather than having a single point value, therefore, indicating that the mass loss by the Sun is strongly dependent on the global solar radiation and solar activities of the location/region as it is site dependent. The energy available for utilization using the famous Einstein's mass energy equation as a direct relationship that exist with the mass loss by the Sun revealed that the solar energy available for utilization for Gusau are greater than that of Calabar and this is a reflection of the abundant amount of global solar radiation received on a horizontal surface for Gusau as compared to that of Calabar.