Jop leader:  Eberhard Wiehr


Version:     27-Mar-00 (draft), 17-May-00 (1)

Scientific objective:

The condition for He+ emissions in quiescent solar prominences is not yet fully understood, in particular, in connection with the neutral He emission. A possible origin for the He+ emission is a transition layer between the cool prominence and the hot corona.

Scientific jusitification:

Spectroscopy of optical emissions yield narrow line profiles corresponding to kinetic temperatures near 8000 K and non-thermal broadenings near 5 km/s, as well as macro shifts up to 15 km/s. Space observations show EUV emissions of lines up to 300000 K with macro shifts of the same order and at the same spatial locations within the prominence as the optical lines, however, with larger non-thermal broadenings.

Emission lines from atomes in different ionization states should yield the same temperatures and velocities if formed in the same volume elements. This should be true for neutral and ionized He, and for other lines as e.g. CI and CIV. Similarly, the Lyman and the Balmer emissions should show the same behaviour.

We observe from ground the time variation of the prominence fine-structure, of macro-shifts, and of the gas-pressure to get an idea about the behaviour of the structure of the cool body, and see whether we can decide from EUV observations what type of transition layer may be realistic to explain the hot EUV emissions:

i) a hierarchy of threads with different temperature or
ii) threads with hot shells around a cool interior.

Our previous work shows that(Balmer) faint quiescent prominences are hot(8000 K) with relatively high He-emission and structured; whereas (Balmer-) bright prominences are cooler (6500 K) with lower He-emission and denser, but not structured. The absorption of hot EUV lines below the Lyman continuum (as e.g. Fe XII 195 A) should then be higher in the (Balmer- and Lyman-) bright prominences, whereas (Balmer- and Lyman-) faint prominences should occur less dark in Fe XII 195 A. The He+304 A emission is supposed to correlate with the optical He-brightness.

Observing procedure:

Observation of time series of quiescent prominences in Balmer, He- and Ca+ emission lines as two-dimensional intensity and, resp., Doppler maps: H-alpha shall be observed over about two hours as speckle reconstructed integrated intensity (DOT) and as Doppler series (VTT) for comparison of Doppler and intensity oscillations. This may allow to investigate possible variations of the number density of threads along the line-of-sight. Simultaneous observations of the pressure sensitive intensity ratio of Ca+8542/H-beta (SVST) shall indicate possible relations with the magnetic field. The He 10830 emission at selected slit positions shall be taken together with Ca+8542 (GCT) to separate the kinetic temperature and the non-thermal velocity.

At the same time, SUMER will measure for one slit position

(a)    the Lyman limit, higher Lyman lines and S VI at 910--950 A;
(b)    S IV, N II and He II at 1070--1100;
(c)    OI and CII lines at 1300--1340;
(d)    OIV 790 (in 2nd order) and CIV 1548;
(e)    OV 690.

The slit shall be 1'' times 120'', integr. time 115 s.

EIT will observe an area corresponding to 10x10 blocks (about 14'x14') with full resolution in He+ 304 with 12 minute cadence, plus one image in Fe XII 195 at the beginning (7:13 UT) and at the end (13:13 UT).

TRACE will observe two-dimensional images in 171, 1216, 1550, 1600, and 1700.

The campaign runs from Sunday, July 2 to Wednesday, July 12.

The daily programme runs from 9:00 to 13:00 UT. Except for July 2, the targets for the next day will be selected during Canary island afternoon hours (around 12:00 UT). Due to the constraints on the SUMER pointing only targets in the eastern hemisphere will be possible.

It is suggested to switch to submode 5 on Friday, June 30 and back to submode 6 in the evening hours of July 12.


P.Sütterlin (Utrecht) at Dutch-Open/LaPalma: H-alpha speckle bursts
H.Balthasar (Potsdam) at VTT/Teneriffa: FPI-Doppler maps in H-alpha
E.Wiehr at Schwedish SVST/LaPalma: simultaneous Ca+ and H-beta images
G.Stellmacher (Paris) at Gregory/Teneriffa: He10830 and Ca+8542 spectra
I.Dammasch (MPAe/Lindau): EUV data reduction.

GBO contact person: ewiehr@tt.iac.es / ewiehr@uni-sw.gwdg.de

EOF contact person: curdt@linmpi.mpg.de / curdt@sumop1.nascom.nasa.gov

SUMER planners: W. Curdt (week 27), U Schühle (week 28)

Existing publications:

DeBoer, Stellmacher, Wiehr: A&A 334, p. 280 (1998)
Stellmacher, Wiehr: Sol.Phys. (in press ; preprints available under