SOHO Joint Operations Programme 94 SPICULES Authors: B. De Pontieu (CDS/Tenerife), O. von der Luehe (Tenerife), C.J. Schrijver (TRACE), T. Tarbell (MDI), F. Budnik (SUMER). Version: First Draft June 1998 Objective: Investigation of the relationship between the photospheric magnetic field, chromospheric disk-spicules and their influence on the overlying transition region/corona. Secondary Objective: Investigation of influence of limb-spicules on transition region. Scientific Justification: Both the origin and driving mechanism of disk-spicules (H-alpha mottles) and limb-spicules remain a mystery. Recent preliminary findings of Suematsu (Coronal Jets conference in Guadeloupe, Feb. 1998) suggest an association between photospheric field strength and formation/decay of Halpha mottles. We aim to investigate the origin of spicules by looking at the influence of the photospheric magnetic field (with MDI in hi-res mode) on the formation and decay of Halpha mottles (from Tenerife) and the UV counterparts (SUMER and CDS). Recent observations of TRACE show dark, short-lived, spicule-like features in the 171 Angstrom band when TRACE if pointed away from disk-center. The Tenerife observations can tell us whether the features in the TRACE data really are spicules. The secondary objective is an extension of the work found by De Pontieu et al. (to be published in the Guadeloupe proceedings,1998). A correlation was suggested between Doppler velocities in Halpha spicules (at the limb) and Oxygen V structures in CDS data. The velocities in the TR are considerably higher than in the chromosphere, which might shed light on the acceleration and driving mechanism of spicules. For this we aim to study Halpha spicules at the polar limb from Tenerife and study the same region with TRACE and CDS. This work will improve statistics on the results found earlier. Pointing: We suggest three different pointings (to be determined at the time of observations) due to the constraints of the instruments involved and the observability of the structures. Pointing 1: a region around the SUMER pointing, as long as it is quiet sun and in the MDI-hi res region. All instruments are involved. Pointing 2: a quiet sun region with considerable emission in 171 and more off towards the limb, to enable identification between Halpha mottles and the TRACE 171 dark structures. If this is outside of the MDI hi-res region, magnetic measurements of the region at a cadence of 1 minute would be very valuable. Pointing 3: at the northern polar limb with Tenerife, CDS and TRACE. Instruments: (all dates are inclusive) H alpha ------- Observing time available at the VTT in Tenerife on the following dates (1998): July 25 to August 2: 8h to 11h UT and 15h30 to 17h30 UT August 3 to 6: 15h30 to 17h30 UT (and probably also August 11 to August 18: 8h to 11h UT) We will use the Fabry-Perot interferometer and in the period of Aug.11 to 18 try to do phase-diversity (A. Tritschler) Observers: B. De Pontieu & O. von der Luehe & A. Tritschler SUMER ----- Require coverage of transition region-to-chromospheric temperature region lines in a high cadence mode (~20 sec) in the 'sit-and-stare' mode from 15h30 to 17h30 UT on August 3 to 6 and perhaps also from Aug. 11 to 18? Contact: F. Budnik MDI --- Require magnetic field measurements of MDI in the high resolution mode during (some of) the Tenerife observing times. Would very much like MDI support when SUMER observes. Contact: T. Tarbell TRACE ----- Require 171 with high cadence and some UV images for alignment. Observing program to be determined. Contact: C.J. Schrijver CDS --- Rapid scans with 2x240 slit of area with 20 width with high cadence. Lines include He584, OV630 and OIV554. Will use something along the lines of G_SPIC_1 with higher cadence. A new study will be suggested soon. Contact: B. De Pontieu (bdp@blackadder.lmsal.com)