Inner heliospheric Interplanetary Scintillation signatures of the deepest solar minimum in the past 100 years.

Bisoi Susanta Kumar, bisoi.susanta@gmail.com, Physical Research Laboratory, Ahmedabad, India
Padmanabhan Janardhan, jerry@prl.res.in, Physical Research Laboratory, Ahmedabad, India

Abstract
We have used interplanetary scintillation (IPS) observations at 327 MHz spanning years 1983-2009 from the Solar Terrestrial Environment Laboratory (STEL), Japan to study micro-turbulence in the inner heliosphere. We find that the turbulence levels show a steady and significant drop in the entire inner heliosphere starting from around 1995. The fact that the solar polar fields, in recent times, also showed a similar declining trend implies that the large-scale IPS signatures provide a consistent result showing the buildup to the solar minimum between the solar cycles 23 and 24, the deepest in the past 100 years, actually began more than a decade earlier.