ar077.schmieder04 Posted: 16-Jan-95 Updated: 3-Sep-95, 18-May-96 Events specified: See text
Schmieder B., Mein P., Mein N., van Driel-Gesztelyi L., Malherbe J.M. (Meudon), Kalman (Debrecen), Alexander, D. and Lemen, J. (Yohkoh chief observers), La Palma group, and interested members of the Yohkoh Team.
Events specified: Formation of an Arch filament System and the overlying coronal loops in NOAA AR 7785, which emerged in the close vicinity of AR 7784 on October 5 1994. We intend to utilise multiwavelength data obtained during the coordinated observing campaign between Tenerife and Yohkoh in the period of Sept. 25-Oct. 7, 1994.
Category: AR evolution (emerging flux); formation of chromospheric arch filaments and coronal loops
Motivation: It is well known that emerging flux leads to
the formation of an arch filament system in the chromosphere
due to the compression of the cool plasma by the growing magnetic
loops above the emerging flux.
The loops, represented by the arch filament system, are rising
in the chromosphere with a speed of 10 km/s (Bruzek, 1969).
As those magnetic loops rise into the corona, they are heated up
by some unknown mechanism and form bright coronal loops
(see e.g. Kawai et al, 1992).
An analysis of the arch filaments and the related coronal loops
above new plage, then pores of opposite polarity may help to
understand whether the heating of the coronal loops is due
to a magnetic reconnection mechanism or something else, e.g.
electric current dissipation.
The location and configuration of cold and hot loops
as well as an analysis of the proper motions of the photospheric
features (spots, pores and minor magnetic hills) could provide
information on the twisting or shearing regime of the magnetic
field lines and could provide a clue whether the new flux emerges
with or without inherent twist, i.e. currents.
An extrapolation of the magnetic field lines could indicate whether
the emerging magnetic field configuration is potential or
force-free.
We have already analysed associated cold and hot loops utilising
MSDP(H-alpha) and SXT observations, but in those cases the problem
was different.
(i) it was during the gradual phase of a flare on June 26, 1992
Schmieder et al, 1995a),
(ii) the cold plasma was ejected along a very large loop
and it formed a surge on Oct 7, 1991 (Schmieder etal 1995 b)
(iii) a minor arch filament system was associated with an XBP on
May 1, 1993, which was interpreted as due to reconnection
(van Driel-Gesztelyi et al., 1995).
Data and Method to be Used:
The combination of H-alpha (MSDP on the German VTT) and
line-of-sight magnetic field
observations (Gregory telescope), taken on the Canary Islands,
photospheric observations taken at Debrecen, and the Yohkoh SXT
PFIs ans FFIs allow us to follow the evolution of this new region
(S06W08- AR 7785) for more than 24 hours.
The Multichannel Double Pass Spectrograph (MSDP) provides the
dynamics of the events. The comparison of the H-alpha observations
with the Yohkoh SXT images would provide a diagnostics of the
relationship between the chromospheric and the coronal events.
DATA Available during the coordinated campaign:
MSDP (H alpha)
AR 7784 S06 E 20 Oct 4 1994 08:51-10:31 a round sunspot
S06 E 06 Oct 5 1994 08:56-09:20
AR 7785 S09 W 08 Oct 5 1994 07:54-08:55
09:24-10:34
11:27-12:13
SXT PFI
Debrecen WL
La Palma WL
Tenerife GCT magnetograms
References:
Bruzek: 1967, Solar Physics, 2. 451.
Kawai, Kurokawa, Tsuneta, Shimizu, Shibata, Acton, Strong, Nitta:
1992, PASJ, 44, L193.
Schmieder, Heinzel, Kotrc, Wiik, Lemen, Hiei: 1995, Solar Physics
(in press)
Schmieder, Shibata, van Driel_-Gesztelyi, Freeland: 1995b,
Solar Physics (in press)
van Driel, Schmieder, Cauzzi, Mein N, Hofmann, Nitta, Kurokawa,
Mein, P, Staiger: 1995, Solar Physics, submitted
Update 18-May-96
We made the following steps in analysing the data:
(1) we have analysed the data of 5 October 1994 obtained with SXT.
(2) we have reduced the data obtained at Tenerife with the MSDP on the VTT.
(3) The Germans have analysed their magnetic data obtained simultaneously with the Gregory telescope at Tenerife.
These coordinated observations pointed out: (i) during the emergence of magnetic flux we have the well known chromospheric arch filament system.Dark threads perpendicular to the inversion lines (ii) in X-rays we observed similar loops but bright. Why there are bright that is really not yet explained. (iii) just before a subflare the connectivity of loops cahnge so the energy could be stored and released during the subflare that we observed in Halpha and with SXT.
The first results have been presented during the Yohkoh Meeting at Bath, England last March (see ar078.vandriel01).
Update 3-Sep-95
We have made progress first of all with the data reduction:
(i) analysed the evolution of the related active region in the photosphere between 3-8 October 1994, measured the position and proper motion of sunspots.
(ii) reduced most of the H-alpha observations taken with the MSDP at Tenerife on the VTT taken between 08:01-08:55 UT on 5 Oct. 1994.
(iii) obtained vector magnetograms taken at the NAO, Mitaka, Japan on 5 Oct.
(iii) obtained vector magnetograms taken at Mees Observatory, Maui, Hawaii, on 4 and 5 Oct.
(iv) made overlays between Yohkoh SXT FFIs and MSDP H-alpha observations at around 08 and 17 Ut on 5 Oct.
(v) prepared the Yohkoh SXT data for more detailed analysis.
We find that in the AR new flux emerged on 5 Oct, which is shown by the presence of a well-developed arch filament system. An interection between the new and a pre-existing magnetic fields seemed to lead to flare activity observed at 08:42 UT. The multiwavelength data is prepared, we plan to carry out a detailed analysis of the evolution of the magnetic field, H-alpha arch filaments and coronal loops connecting the new spots, as well as a 3D computation of the magnetic topology to compare theory to observations.