ar078.vandriel03 Posted: 26-Jan-95 Updated: 3-Sep-95, 18-May-96 Events specified: A flare of 27-OCT-93 09:10 UT and active region AR 7608
van Driel-Gesztelyi L., Schmieder, B., Roudier T., Malherbe J.M. (Meudon), G. Cauzzi (Hawaii), Csepura (Debrecen), H. Zhang (Beijing), Lemen, J. (Yohkoh chief observer), and interested members of the Yohkoh Team
Category: Flare activity related to AR evolution (emergence of new flux in a pre-existing AR). We intend to utilise multiwavelength data (white-light, H-alpha, magnetic, X-ray) obtained during the coordinated observing campaign between Pic du Midi, Meudon and Yohkoh.
Motivation: There is a striking tendency of active regions to emerge near,
or even within, existing active regions (see e.g. Gaizauskas
et al, 1983). Such new flux emergence frequently leads to
the formation of a complicated magnetic configuration which is
known to be associated with enhanced activity, since the new flux
tends to reconnect with the pre-existing fields.
In AR 7608 there were at least two bipoles present on 27 Oct. 1993.
The positive polarity (f) part of the smaller bipole was embedded
in the negative polarity (p) part of the bigger, dispersed bipole.
Chromospheric activity was observed along the boundary of the
intruding polarity for several hours in the morning on 27 Oct.
We would like to analyse the activity combining photospheric,
chromospheric and coronal observations to learn about the
evolution of the flaring configuration and the eruption itself.
Utilising similar multiwavelenth data we have already studied a
serie of XBP flares related to a minor flux emergence in a
declining active region on 1 May 1993, and found evidence that
they were due to a macroscopic reconnection between the
pre-existing magnetic fields and the new bipole
(van Driel-Gesztelyi et al., 1995).
Data and Method to be Used:
The combination of H-alpha (MSDP at Pic du Midi), magnetograms
taken at Mees Observatory (Hawaii) and at Huairou (China),
photospheric observations taken at Debrecen, and the Yohkoh SXT
PFIs ans FFIs allow us to follow the evolution of this active region
(N09E40- AR 7608) and its flare activity 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) at Pic du Midi and Meudon 26 and 27 Oct.
Yohkoh PFIs and FFIs 26-28 Oct.
Stokes vector magnetograms (Mees Observatory, Hawaii) 27 Oct.
Magnetograms (Huairou, Beijing Astro. Obs.) 26 and 28 Oct.
Debrecen white-light full-disc photoheliograms 26-28 Oct.
References: Gaizauskas, Harvey, K, Harvey, J, Zwaan: 1983, ApJ. 265, 1056.
van Driel-Gesztelyi, 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:
(i) analysed the evolution of the related active region in the photosphere between 25-31 October 1993, measured the position and proper motion of sunspots.
(ii) reduced most of the H-alpha observations taken with the MSDP at Pic du Midi Observatory taken between 8:58-9:55 and 10:38-12:01 UT on 27 Oct. 1993.
(iii) reduced vector magnetograms taken at Mees Observatory, Maui, Hawaii with the Stokes Polarimeter and the IVM instrument on 27 Oct.
(iv) made overlays between Yohkoh SXT FFIs and a Kitt Peak magnetograms at times of flares (09:19 and 11:26 UT on 27 Oct.)
(v) in X-ray analysed emission measure and temperature evolution during the 2 flares.
We find that the AR consists of small intermittent spots, but the magnetic configuration, namely the presence of an included polarity, seems to be lasting. Two homologous small flares were observed related to the included polarity. The flares look like simple-loop flares, but a comparison with the H-alpha data reveals that in fact they consist of several tiny loops which have their footpoints in the H-alpha flare ribbons.
The first results have been presented during the Yohkoh Meeting at Bath, England last March. The abstract of the publication, which is submitted to the proceedings of the meeting:
Signatures of new emerging flux in the solar atmosphere}
B.Schmieder, J.M.Malherbe, P.Mein, N.Mein, L.van Driel-Gesztelyi, T.Roudier, N.Nitta, L.Harra-Murnion
The emergence of new flux in the low atmosphere leads to magnetic reconnection of field lines. In a stable phase the phenomenon is observed in the chromosphere by the formation of dark filaments (Arch Filament System). We show how bright loops visible in soft X-rays are co-aligned with the AFS. Different types of events appear as the released energy is increases. With less energetic phenomena than flares (E $<$ $10^{28}$ ergs cm$^{-3}$) we observe surges, jets or X-ray bright points, according to the configuration of the field lines (open/close). A low-level reconnection process is detectable as an X-ray bright point. If the energy is $\approx$ $10^{28}$ ergs cm$^{-3}$, we observe subflares.
We will document our statement by showing examples observed in coordinated observations obtained with the MSDP (Pic du Midi and Tenerife) and Yohkoh/SXT and BCS for the events occurring on Oct,5, 1994, Oct,27, 1993, May,1, 1993.
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 25-31 October 1993, measured the position and proper motion of sunspots.
(ii) reduced most of the H-alpha observations taken with the MSDP at Pic du Midi Observatory taken between 8:58-9:55 and 10:38-12:01 UT on 27 Oct. 1993.
(iii) reduced vector magnetograms taken at Mees Observatory, Maui, Hawaii with the Stokes Polarimeter and the IVM instrument on 27 Oct.
(iv) made overlays between Yohkoh SXT FFIs and a Kitt Peak magnetograms at times of flares (09:19 and 11:26 UT on 27 Oct.)
(v) prepared the Yohkoh SXT data for more detailed analysis.
We find that the AR consists of small intermittent spots, but the magnetic configuration, namely the presence of an included polarity, seems to be lasting. Three homologous C and B flares were observed related to the included polarity. The multiwavelength data is prepared, the interpretation of the results should be done soon.