Hinode Science Plan

Science Drivers

The Sun is our nearest star. Its proximity provides heat and light to maintain
life on Earth, as well as a unique laboratory to test our theories of stellar
evolution and galaxy formation.

It is crucial for our survival on Earth to understand the Sun's effect on the
near-earth environment and on the climate of the earth. Our ability to resolve
features on the Sun and study the physical processes occurring in detail helps
us to understand the processes occurring on other stars and astrophysical objects.
In turn, improving our understanding of other stars gives us information on the
long-term evolution of the Sun.

The Hinode mission will provide us with the opportunity to better understand
that aspect of the Sun that affects the climate on Earth and space weather:
solar activity.

Science Goals of Hinode

To determine the mechanisms responsible for heating the corona in active regions
and the quiet Sun.

One of the remaining unresolved questions in solar physics is why the temperature
of the atmosphere rises from 5780 K at the photosphere to millions K in the corona.
Clearly the second law of thermodynamics tells us that the temperature should fall as
you move away from a heat source (at the core of the Sun).

The fact that this happens only until we reach the photosphere suggests that an
additional non-thermal heat source is needed to explain and maintain the high
temperatures seen in the corona. Several mechanisms have been suggested and we
are confident that the energy must come from the magnetic field. However, there is
as yet no consensus on the details.

Hinode will be able to determine the physical mechanisms responsible for
coronal heating using a combination of spectroscopic and magnetic information
to determine how the magnetic energy is converted in the EUV and X-ray radiation
we see in the corona.

To determine the mechanisms responsible for transient phenomena, such as flares
and coronal mass ejections.

Flares and coronal mass ejections (CMEs) are the most energetic manifestations
of our Sun's activity and the most likely to directly affect our environment
on Earth. CMEs in particular when headed in our direction can cause major
magnetic disturbances when they reach the Earth's magnetopshere. The causes
of these explosions and expulsions of plasma are not yet fully understood.

Hinode will provide measurements of magnetic fields, electric currents and
velocity fields, which coupled with imaging of the corona will reveal the trigger
for both flares and CMEs. With an understanding of what triggers these events our
opportunities for reliable prediction increase substantially.

To investigate the processes responsible for energy transfer from the photosphere
to the corona.

The energy to maintain the high temperatures of the transition region and corona,
and for flares, CMEs and smaller scale activity observed in these parts of the
atmosphere must come from the magnetic field which originates below the Sun's
convection zone.

To determine how this energy is transferred from below the photosphere up to outer
atmosphere we need to be able simultaneously measure changes in the magnetic field
with the transition region and coronal response.

With Hinode we will be able to make this connection and understand how the energy
is transferred.

Get Involved with Hinode Science!

To be kept informed of science meetings and activities related to Hinode please
feel free to join our Hinode science mailing list. To do so please send an e-mail
to with subscribe solarb_science in the main
section of the e-mail (not in the subject header).

Last Revised: Monday, 04-Mar-2022

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