Observations of transition
region and chromosphere
Suguru Kamio
Hinode Science Center
National Astronomical Observatory of Japan

Outline• Why are the transition region and thechromosphere important?
• Hinode observations- explosive events in the transition region- photospheric magnetic fields.
• Desired features for the future mission- high throughput UV/EUV spectrometer- magnetic fields in the chromosphere- high sensitivity magnetogramBehavior of spectra

Line broadenings
and Doppler shift
Up to 100 km/s

CoronaFe XII (T=6.1)
positionTransition region
He II (T=4.7)

Smooth structureλ• The transition region and the chromosphere arehighly structured and dynamic.
• Something changes between the transition region
and the corona

Explosive events• Explosive events are UV-spectrum broadening
events frequently occur in transition region.
• Bi-directional flows caused by reconnection.
• But their relation to magnetic fields in thephotosphere have not established yet.

Brueckner & Bartoe (1983)

Innes et al. (1997)

Radiance

Doppler shift

Properties of He II spectra• Radiance, Doppler shift, and width were
derived from He II spectra.
• Spectral width in He IIexplosive event: 174 km/s
normal:93 km/s
(EIS instrumental width: 67 km/s)

Line width

Locations of explosive events• Markers indicate explosive event inside SOT FOV.
• They occurred near the boundary of network.
consistent with previous studies
e.g. Chae (2000), Madjarska & Doyle (2003)

SOT magnetogram• Stable observation ofSOT allows to study
dynamic behavior ofmagnetic fields in aquiet region.
• Fields are gatheringin network region.

Flow divergence• Divergence derived
from horizontal flows• Explosive events
preferably occur inconverging region of
mixed polarities.
• Line indicates EIS slit
converge

diverge

Red: positive flux
Black: negative flux
Green: explosive events

Need for higher cadencetimeInnes et al. (1997)• 10 sec cadence is not sufficient totrace the evolution of the transition
region.
• High throughput UV/EUV
spectrometer will allow us toobserve with 1 sec exposure.
• One-order improvement in temporal
resolution will boost our
understanding of the transition
region.

Importance of internetwork fields• Classical picture:
Network field dominant• Internetwork fields occupy
significant fraction of corona?

Magnetic canopy
Gabriel (1976)

Jendersie and Peter (2006)

Fields in the chromosphere• Magnetic field measurements in the photosphereprovide only lower boundary condition.
• Field measurements in the chromosphere will give us
vital information on the connection between thephotosphere and the corona.
• In addition, morphological study of fibril structures will
help to understand the magnetic field configuration.

Sensitivity to internetwork fields• SP can detect weaker magnetic fields than NFI.
• High sensitivity is essential to study weak internetwork
fields.

Spectropolarimeter (SP)Narrowband Filter (NFI)

Summary• The transition region and the chromosphere is highly
structured and dynamic.
• They are crucial to understand magnetic fieldconnectivity.
• Desired features for Solar-C- High throughput UV/EUV spectrometer for
better temporal resolution- Magnetic field measurement in the chromosphere- Sensitivity to weak internetwork fields in thephotosphere