Wednesday, May 23rd 2012, 6:37 AM EDT
PUNE: A recent research by the Radio Astronomy Centre, National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research (TIFR) has found that there has been a steady weakening of the Sun's magnetic field and its associated solar wind in the interplanetary space. According to the study, these changes can have a greater impact on the earth's atmosphere than previously thought.
If such a steady weakening of the Sun's magnetic energy continues for one or two solar cycles, it may lead to a 'mini'-ice age kind of situation, similar to that which occurred in the 17th Century, states the study. According to the researchers, highly energetic charged particles, which are otherwise prevented by the Sun's strong magnetic field, now plunge into the magnetically weak inner space. Thus, during this deep minimum phase, space becomes a more dangerous place to travel for astronauts.
The Sun, our energy source, goes through phases of violent (maximum phase) and quiet (minimum phase) activity every 11 years, which is called one solar cycle. The effects of minimum activity of a solar cycle are seen for about a year. However, the study reveals that the minimum activity was seen for more than four years in the recently concluded solar cycle. Thus, it was the longest and quietest minimum in the past 100 years.
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This is supported by the unusually large number of sunspot free days (800 days) between the years 2005 and 2009, as against only 300 days in the earlier solar cycle, which indicates heavy reduction in magnetic brilliance of the Sun. It suggests that sunspots may be going into an inactive or hibernation mode. In addition, during this longest and deepest minimum (between 2005 and 2009), the energy of solar wind was considerably low compared to its previous minimum of the solar cycle.
The study, led by P K Manoharan, head of the Radio Astronomy Centre of the NCRA, using the Ooty Radio Telescope built and operated by NCRA, reveals the remarkable changes in the Sun-Earth space. He said the highly energetic charged particles plunging into the magnetically weak inner space can affect electronic devices in spacecrafts or satellites and the strong radiation emitted from the charged particles can lead to health problems for astronauts, during this deep minimum phase.
According to him, further studies will give more details on the forthcoming period of Sun's quiet behaviour and whether we are heading towards a mini-ice age period that was observed in the 17th Century. "During the mini-ice age period, there were practically no sunspots over prolonged time. In this period, the average temperatures in the northern hemispheres of the earth dropped by 2-3 degrees Celsius," he said.
The recent study has observed that the number of charged particles expelled by the sun has steadily declined from the year 1985 to 2012, during which overall low-speed wind also dominated the heliosphere (bubble of charged particles in the space surrounding the solar system). Manoharan said the study makes it clear that the reduction in the particle emission from the sun observed in the extreme minimum phase closely correlates with the steady weakening in the strength of the magnetic field above the Sun's surface due to absence of sunspot activity. This study has been accepted and will be soon published in an international journal, he added.
The Ooty Radio Telescope
The telescope is built and operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research, Pune. Operating at 327 MHz, it is 530m long in the north-south direction and 30m wide in the east-west direction. It is equatorially mounted on a hill slope in the Nilgiri hills in Tamil Nadu. A novel technique developed by the ORT team observes twinkling of large number of radio sources which provides the view of the density and speed of solar wind distribution in the three-dimensional space as well as its evolution over a long period of time.
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