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% International conference
% "Sun at the Top of the Maximum and the Solar/Stellar Connection".
% Saint-Petersburg, Pulkovo, September 17-22, 2000
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% Please send your abstract before June 19, 2000 to:
% conf2000@gao.spb.ru | stepanov@gao.spb.ru
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{\large\bf { Disappearing filament inside a CH and associated
activity }}
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{\bf {I.M. Chertok$^1$, H.S. Hudson$^2$, E.I. Mogilevsky$^1$, V.N.
Obridko$^1$,\\ and N.S. Shilova$^1$ }}
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$^1$ {IZMIRAN, Troitsk, Moscow Region, Russia}\\ $^2$ {Solar
Physics Research Corporation, ISAS,  Sagamihara, Japan}\\

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% ABSTRACT

Based on Yohkoh/SXT, SOHO/EIT images and movies, as well as on
H-alpha, He I (10830 $\AA$) heliograms and other data, we analyze
an event of 28 December 1999 (Figure 1) which is interesting at
least in two aspects.\\ (1) A major horseshoe-shaped H-alpha
filament (F) appeared to be located within a large transequatorial
coronal hole (CH) in the east hemisphere.\\ (2) This filament
subsequently disappeared , with its eruption accompanied by a
number of dynamic phenomena including large-scale ones.



% FIGURES

\begin{figure}[here]
\begin{center}
\epsfig{file=1.eps,height=12.5cm} \caption[1]{(a,b) - The BBSO and
Meudon H-alpha heliograms illustrating the filament (F) and its
disappearance. (c,d) - Two Yohkoh/SXT images before and after the
filament eruption showing  the soft X-ray filament-associated
structure and post-eruption arcade inside the CH.    }
\end{center}
\end{figure}

The location of the filament inside the CH follows from the
Yohkoh/SXT data. At the same time, according to the Kitt Peak and
MLSO/HAO He I heliograms, the filament seemed to be located on the
south boundary of the CH. However based on source-surface model
calculations,  which show the footpoints of openmagnetic field lines
to correspond better to the Yohkoh/SXT CH, we conclude that the
filament truly was located within a CH.

Comparison of the BBSO and Meudon H-alpha pictures reveals that
the filament disappeared between 17:40 UT on 28 Dec and 09:03 UT
on 29 Dec. According to the detailed SOHO/EIT data at 195 $\AA$,
the filament eruption occurred at about 23 UT on 28 Dec. Similar
to many other events observed outside CHs, this filament eruption
was accompanied by formation of large post-eruption arcades
particularly visible in soft X-rays. These 195 $\AA$ data reveal
some hints that EUV coronal wave and dimming also took place in
this case. According to the LASCO C2/C3 data, a noticeable
south-polar CME was observed after 23:30 UT which appeared be
associated with filament eruption within the CH.

Starting at least from 19 UT on 28 Dec, a clear EUV large-scale
meridional emitting chain, crossing the CH and going from the
north-east active complex through the filament and then to the
south-east limb, was visible particularly at the SOHO/EIT
wavelengths 171 and 195 $\AA$. The evolution of the chain was
continuing during several hours after the filament eruption.

Thus, this event is an example of a CH with a significant large-scale
magnetic activity, including a disappearing filament and some other
dynamic phenomena, internal to its boundaries.  It allows us to
conclude that CHs may not be so simple and uniform structure as
normally believed and can contain local areas with low-altitude,
closed magnetic fields. The observed EUV meridional chain shows that
the erupted filament inside the CH was a part of a global evolving
magnetic structure associated with activity extending almost
throughout the whole east half of the disk.  We have noted similar
CH-interior activity in some other events which should be studied as
well.

It is reasonable to mention that the near-the-SE-limb region and
high-latitude filament channel, connected with the filament inside
the CH by the chain mentioned above, was a source of a significant
eruption and large CME that occurred later at ~15 UT on 29 Dec.

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