Issue |
A&A
Volume 402, Number 1, April IV 2003
|
|
---|---|---|
Page(s) | 361 - 372 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20030220 | |
Published online | 07 April 2003 |
On the nature of the chromospheric fine structure
I. Dynamics of dark mottles and grains
1
National Observatory of Athens, Institute for Space Applications and Remote Sensing, Lofos Koufos, 15236 Palea Penteli, Greece e-mail: kostas@space.noa.gr; georgia@space.noa.gr
2
Observatoire de Paris, Section de Meudon, LESIA, 92195 Meudon Principal Cedex, France e-mail: pierre.mein@obspm.fr
Corresponding author: K. Tziotziou, kostas@space.noa.gr
Received:
2
December
2002
Accepted:
24
January
2003
We analyze a time series of forty high spatial and
temporal resolution two-dimensional intensity and Doppler velocity
images at different wavelengths within the Hα line. The
observations were obtained with the Multichannel Subtractive
Double Pass (MSDP) spectrograph at THEMIS. We study the morphology
of dark mottles and grains as seen in different wavelengths and
examine their relation to the MDI magnetic field topology. We
determine some physical properties of dark mottles with an
inversion technique based on an iterative cloud model method with
constant source function, giving the optical thickness , the Doppler width
, the velocity v
and the source function S distribution along a structure. The
obtained global properties of mottles as well as the spatial and
temporal evolution of several physical parameters along the axes
of individual mottles are discussed. The derived velocities in
mottles as a function of space and time (time slice images)
exhibit a quasi-periodic, bi-directional pattern. It is suggested
that magnetic reconnection is the mechanism responsible for their
formation and dynamics. Furthermore, a similar quasi-periodic
behaviour of the Doppler velocity variations in dark grains and
their morphological characteristics both suggest the similarity of
dark mottles and grains.
Key words: Sun: chromosphere / lines: formation / radiative transfer
© ESO, 2003
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