an e magazine from ASSAM & NAGALAND      

Astrophysics is one branch of physical science, which even many physicists shun because of its complexity and inherent uncertainties, as many of its postulations cannot be established by direct experimentation.

By end of the last century many physicist understood that apart from the two easily appreciable forms of solar energy-light and heat, the sun emits a number of other forms of energy and only an infinitesimal part of such inter-planetary energy reaches the Earth's atmosphere, and again only a fraction of such energy can penetrate the Earth's magnetic and other shields (as ozone layer) and reach the Earth's surface. Different forms of interplanetary energy are collectively known as 'cosmic rays' or 'cosmic energy'.

In the Thirties of the Twentieth century serious studies on cosmic energy were taken up primarily to understand the phenomenon of auroral or polar illumination as it was noticed that the increase of auroral activities is directly related to period of enhancement of sunspots and stronger electromagnetic disturbances in the Earth's atmosphere. The second available tool was to study the deviation of comet tails by the pressure exerted by the solar wind.

Study of 'cosmic energy' received tremendous boost by the invention of radio-telescope and even more so when man made satellites started revolving around the Earth and could collect data from the upper level of atmosphere of the Earth and beyond.

The present author who is not an astrophysicist, has undertaken this ormidable job of explaining the behaviour of solar-terrestrial energy variation cycles uninitiated in non-technical language, hence a lot of omission and commission should be expected in this endeavour.

S. Chapman and V.C.A. Ferraro (Nature 126, 129. 1930) were the first (?) to establish that materials identical with the solar corpuscular radiation is emitted in the form of continuous stream with variable intensity and speed from the solar coronal part and collectively termed these energy streams as the 'solar wind'.

After sixty years of intensive study by many eminent scientists in various institutes of Physics and 'Space research laboratories', our knowledge about the solar wind is still meagre, and whatever is expounded, there are controversies galore. Universally accepted characters of the solar wind, which is also known as 'solar flux' and 'solar energy stream', are following:

1. Solar wind is a complex combination of energetic particles and rays, constituted by probably more than forty different forms of energy, some of which have been identified, some are yet to be identified, and quite probably existence of some forms may not yet be known to the science.

2. Eighty percent of the solar-flux is considered to be in the form of low, intermediate and high-energy protons. The rest, twenty percent is formed of alpha particles, electrons, X-rays; gamma radiation, ions, undetermined nuclei of atoms and interchanging forms of energy (one of the major problem in study of solar and cosmic energy flux is that they rapidly interchange forms).

3. As the solar wind leaves the Sun, within the interplanetary medium, numerous separate bundles of magnetic flux exists that are adjacent to and are in equilibrium with each other. A filament magnetic field structure is embedded in the solar wind. Due to the rotation of the Sun on its axis the solar field lines form an Archimedean spiral.

4. The density and speed of the solar flux as it leaves the Sun, and the part of it which reaches the Earth will depend upon the intensity of the solar radiation (flare) activities on the solar surface, therefore energy arrival on the Earth's surface is also not uniform and vary both chronologically and spatially. It is known, that there is one roughly 11 years long cycle of varying solar flares and sunspots on the solar surface, which results in increase or decrease of level of solar electromagnetic energy on the Earth's surface. The reasons behind these periodic changes are not yet properly understood.Astrophysicists agree that the change of energy regime on the Sun's surface is of two types, one continuous and non- eversible and the second is cyclic. They are:

1. Like any other star the Sun has also got a life history from its birth to death where the radiation level is continuously changing its age and it is non-repetitive. Because of extreme time length of each phase of change this has got little importance in your short-term study of the effects of solar radiation on biosphere of the Earth.

2. (a) Yet unproven but theoretically possible; a controversial but popular explanation for long time, the cyclic change of the intensity of solar radiation take place probably because the Sun has got its own binary partner star, provisionally named as 'Nemesis'. Both the stars are revolving around each other. While the two stars approach to a near orbit, because of mutual gravitational pull, huge tidal waves of energy are pulled out to interplanetary space, which gets 'supersaturated' with energy. Catastrophes in the planetary geology of the solar planets and in the biospheres of the Earth is envisaged during such close encounter.

There are few takes of the proposition forwarded by P. Seymour (1988) that the planetary alignments within the solar system cause increase of solar flares because of their 'combined gravity'.

(b) The Sun shows a cycle of enhanced energy dissipation which repeats roughly after each eleven and half terrestrial years, commonly known as 'eleven year sunspot cycle'. Actually these increase of intensity may take place within such a short period as seven and half years or the time gap may be as long as sixteen and half years. Generally accepted explanation is that, due to intense activities on the Sun's surface, huge energy flares are thrown to the coronal part of the Sun and there from to interplanetary space. Areas in photosphere wherefrom the energy is depleted will appear to terrestrial observers as comparatively less illuminated, dark spots, popularly known as sunspots.

(c) The 'centers of enhanced activity' on the Sun's surface are not uniformly distributed. The latitude of the solar energy flares (source of solar wind) are located only within 10 to 15 degrees from the center of the visible disk of the Sun (It is quite interesting to note that the 'deeptangsha' or the effective part of the Sun, in the Indian astrology is accepted to be only upto 10º from the equator of the visible orb of the Sun).