It is a fascinating fact that a solitary star like the Sun emits
intense X-rays from its outer atmosphere. Observations with the Japan-
US Yohkoh satellite showed that all the sporadic heating from X-class
flares to ubiquitous tiny bursts in the solar corona is due to
magnetic reconnection; a process to efficiently annihilate magnetic
fields with opposite direction and generating jets, heats and non-
thermal particles.
These activities on the surface of the star are driven by magnetic
fields created by the interaction of flow and seed magnetic fields
inside the Sun (dynamo mechanism). The magnetic field strength on the
surface of the Sun exceeds 1kG, while that at the bottom of the
convection zone may exceed 100kG. They are too strong, far stronger
than the equi-partition magnetic field strength, the energy of which
is the same as that of the local convection motion. Though a dynamo
mechanism can amplify field strength upto the equi-partition field
strength, it is perceived possible to have field strength beyond that
threshold. Such too-strong magnetic fields can be found elsewhere in
the universe, namely pulsers (1012G), magneters (1015G), galaxies and
clusters of galaxies (a few micro G), which is again too strong in
terms of that in early universe (<10-15G). The dynamo mechanism for
the sun and these objects is poorly understood.
The Hinode spacecraft was successfully launched in September 2006
using a JAXA’s M-V launch vehicle. It comprises an observatory style
set of instruments that function together to answer the fundamental
questions of how magnetic fields are formed and how they dissipate to
create the solar corona. This subsequently addresses all the
phenomena that have an impact on the Sun-Earth system, such as the
formation of the solar winds, triggering of flares with intense non-
thermal acceleration and coronal mass ejections, and formation and
maintenance of filaments and prominences. The concept of Hinode is
that two X-ray and EUV telescopes observe the dissipation part of the
magnetic life-cycle, while the visible light telescope simultaneously
observes the generation and transport of magnetic field. Hinode is
the Japan’s third solar mission with participation of NASA and UK
STFC (then PPARC) and subsequently ESA.
Hinode has higher temporal, spatial and velocity resolution than any
satellite previously and is probing wavelength regimes that have
never had such continuous time coverage available. This has allowed
us to discover waves in spicules, prominences and on the photosphere,
ubiquitous jets in chromospheres, ubiquitous transient horizontal
magnetic fields on the photosphere suggesting turbulent dynamo
process, supersonic down-flow and convective collapse resulting in
super equi-partition magnetic field strength, emergence of large-
scale flux rope from below the photosphere, kG-magnetic patches in
the polar regions, identification of the origin of slow solar wind,
and enigmatic fine-scale flows in the prominence. This talk
summarizes how these new results from Hinode are addressing these
critical questions as well as probing fundamental physical processes
that will have applications in many other scenarios across the universe.