Author: Gabriela Bagalá (gbagala@cds.plasma.mpe-garching.mpg.de)
First Draft: December, 1998; revised: March, 1999. Post-running update:
July, 1999.
Instruments involved
CDS, TRACE. Ground based: HASTA, MICA. Synoptic: MDI, LASCO, EIT, SXT.
Participants involved
M.P.E. (Germany): G. Bagalá, G. Haerendel (Prof.), A. Czaykowska, G. Rank.
Lockheed-Stanford Institute for Space-Research (USA): K. Schrijver, B. De Pontieu.
M.P.Ae. (Germany): R. Schwenn (Prof.), G. Stenborg.
I.A.F.E. (Argentina): C. Mandrini, R. Fernández, M. Rovira (Prof.).
Outline
Scientific Justification
The onset phase of CMEs and the physical evolution of prominences are subjects that have been outlined in JOPs 3, 12, and other campaigns (see for example Wiik etal, 1997, for a Joint Observation with CDS, SUMER and LASCO). But the proposed program has a new motivation in taking advantage of the capabilities of the TRACE instrument. The objective here is focused on the investigation of the conditions of the eruption of a prominence often associated with the CME. We will focus on the "more propitious" filament (the longer one, or the one lying in an AR with emerging flux, or the one between connected ARs, etc). We propose a 5-days study of the filament/prominence, with 3-4 days observing the disk and 1-2 days observing the limb. While on disk, we will look for the eruption signatures in two ways: by studying the physical conditions in the filament and its surroundings (densities, temperature, abundances), and by looking at the magnetic topology changes. While at the limb, we will wait with luck for an eruption. If it does happen, LASCO (and MICA (Mirror Coronagraph for Argentina, Stenborg etal, 1999)) observations will study if there exists an associated CME.
Method
The CDS instrument can provide information on filaments and their environments at various spectral lines corresponding to temperatures from 10,000 K to about 2 MK. With these data we will calculate temperature, densities, Doppler shifts and abundances to know from where the main amount of material comes, and to look for changes before or after a eruption.
From MDI and TRACE observations, we will try to derive the magnetic conditions which may be necessary and/or sufficient for the eruption. To do that, we will extrapolate the magnetic field taken with MDI, trying to follow the behavior of the loops observed with TRACE, as an outlining of the coronal magnetic field. We have experience in this, looking for the topology of the magnetic field through a force-free extrapolation of magnetograms (Bagalá etal, 1995, Mandrini etal, 1996, Démoulin etal 1997, and others), but the new TRACE data is a challenge for our work. We will use a new extrapolation method (based in earlier works of Low, 1991, 1992), that take into account the interaction between the plasma and the magnetic field, and the gravitational scale height of the plasma (CDS will help us to put the correct values). Application of this new development are actually in press (Aulanier etal, 1999 and Mandrini etal, 1999).
The LASCO instrument can provide information of the CME, if it occurs. It is possible that the Channel C1 from LASCO don't return to full functionality. In this case, the MICA instrument will complement LASCO's C2 and C3 looking at the corona at lower hight (between 1.05 and 2 solar radii, equivalent to the failed C1). If C1 resumes operation, MICA also will complement LASCO taking images with better temporal resolution, during and after the eruption of the prominence. Also LASCO could detect halo CME if the filament erupt and a CME develops while it is on disk.
HASTA (H Alpha Solar Telescope for Argentina, Bagalá et al, 1999a) instrument will help before the JOP start, in choosing the adequate filament, and during the JOP with images of the evolution of the filament/prominence. During the on-limb study, they could determine the onset of CME, measuring in the wings of H-alpha (with a temporal resolution of 1 sec). As MDI only takes longitudinal magnetograms, HASTA will also help us in adjusting the shear of the region, taking the direction of chromospheric fibrils.
We would use also synoptic data from SXT (on-board Yohkoh) and EIT (from SOHO), to see the features in higher temperatures.
Alternative Program
In the case that no "appropriate" quiescent prominence were present, we could choose an Active Region (AR) showing the most complex coronal activity. Par example, we could choose an AR with a recent emerged flux and look for an associated halo CME, as recent research suggest (see e.g. van Driel_Gesztelyi et al. 1999). We could continue the JOP in that way till the AR reaches the limb, and the AR loops were visible for TRACE.
What we will need from SOHO
CDS: we are requesting high-resolution observations in several lines as a measure of temperature, density diagnostics and atomic abundances. We want to cover the full range of CDS's temperatures, from transition region to the corona. We are requesting high-spatial resolution images within a 4 x 4 arc-minute field-of-view.
MDI : We will request high-resolution magnetograms (our target area falling within the fixed MDI area) for the first days of observation, and full-disk magnetograms for the last days.
LASCO, EIT: Synoptic data will be enough.
What we will need from TRACE
We will request images from coronal lines, maybe images in 171 A (Fe 9-10). We want to consider the 1216 Lyman Alpha line off the limb for studying prominences as well. The temporal resolution could be 2 minutes.
What we will need from MICA and HASTA
From MICA full-disk images. From HASTA we will need alternative images in the center and in the blue and red wings of the line. For both instruments, the short temporal cadence as possible.
What we will need from SXT (Yohkoh)
Synoptic data will be enough.
References
Aulanier etal, 1999: Solar Physics, in press
Bagalá etal, 1995: Solar Physics, 161, 103
Bagalá etal, 1999a): ESA SP-448, to be submited
Bagalá etal, 1999b): ESA SP-446, submited
Démoulin etal, 1997: A&A, 325, 305
Low, 1991: ApJ, 370, 427L
Low, 1992: Apj, 399, 300L
Mandrini etal, 1996: Solar Phys, 168, 115
Mandrini etal, 1999: Pub. Astron. Soc. Pacific C.S., in press
Stenborg etal, 1999: Proc. of the Solar Wind 9, S. Habal (ed.) Conf. Proc. 471 AIP, in press.
van Driel_Gesztelyi et al. 1999: Pub. Astron. Soc. Pacific C.S., in press
Wiik J., Schmieder B., Kucera T. et al, 1997: Solar Phys. 175, 411.
JOP 099 First-running
JOP 099 ran for the first time between the 8th and the 14th April, 1999. We looked for an active region (AR), with a filament, near the center of the sun, because we planned to follow the region to the limb during six days, in order to observe the prominence. In this first run, JOP 099 studied for 6 days AR 8507, located at N11 W01 on the first day.
MDI was running that dates the Continuous Dynamics program, so it did not get high-res magnetograms twice a day as we had expected. In consequence, at the moment we are processing full-disk magnetograms. A zoom of the MDI longitudinal magnetogram shows that AR 8507 is bipolar, with the preceeding, positive spot more intensive, and an elongated negative spot. We took H-alpha images with HASTA every minute both in the wings and in the center of the line. A bright plage region lies close to the positive spot, and the filament is located not on the main magnetic neutral line, but along the one dividing the AR and the quiet zone, encircling the whole region. TRACE data show a very potential region the first day.
As the JOP finished only 3 months ago the data analysis is preliminar. However, we can say that no important ejection of material happened in the region during the observing program. Nevertheless, we are studying at the moment some jets that CDS observed at the limb the last day of the JOP. In the Proceedings of the past SOHO 8 Workshop we have presented the status of our study (Bagalá etal, 1999b).