TITLE: Detection of waves in the solar atmosphere AUTHORS: L. Teriaca (teriaca@mps.mpg.de), S.K. Solanki, D.S. Bloomfield, Max-Planck-Institut fuer Sonnensystemforschung, Katlenburg-Lindau, Germany D. Banerjee, G. Gupta, Indian Institute for Astrophysics, Koramangala, Bangalore, India S. Imada, National Astronomical Observatory of Japan, Tokyo, Japan PARTICIPATING INSTRUMENTS: SoHO/CDS SoHO/SUMER Hinode/EIS Hinode/XRT Hinode/SOT STEREO/EUVI TRACE VTT-TIP2 (Tenerife) SCIENTIFIC OBJECTIVE: We aim at searching for wave signatures in the radiance (VUV images) and spectral line radiance, shift and width (VUV spectra) in the polar coronal hole regions. During April 2007 (Campaign #7208), combined HINODE/SOHO observations have shown some evidence of radiance fluctuations propagating outward with a speed of about 60 km/s. The fluctuations seem to show a periodicity of 7 to 8 min. Based on the experience acquired by the analysis of the April 2007 data, we would like to apply for one or two 5 hours observing windows with instruments aboard SOHO, HINODE and TRACE. SCIENTIFIC JUSTIFICATION: Coronal holes have long been identified as the primary source regions of the fast solar wind, but only recently the fundamental solar roots of this system has been explored. SOHO on-disk observations have shown that the coronal velocity structure is linked with the chromospheric magnetic network, with the largest outflow velocities occurring along the chromospheric network boundaries. (Hassler et al. 1999, Science, 283, 810), in regions that appear dark in coronal lines (Wilhelm et al. 2000, A&A 353, 749; Xia et al. 2003, A&A 399, L5). EIT observations of the polar coronal holes have also raised the possibility that coronal jets produced by reconnection events in the network may provide a significant fraction of the solar wind mass flux (Wang et al. 1998; ApJ, 501, L145; Dobrzycka et al. 2002, ApJ, 565, 621). The precise connection between these important observations cannot be established without comprehensive observations of the whole atmosphere in lines/band-passes covering the temperature range from 10 kK to several MK. The coupling of existing instruments (SOHO, TRACE) with high-cadence, simultaneous measurements of the photospheric and chromospheric magnetic and velocity fields (from ground, German Vacuum Tower, and space, SOT/HINODE) and spectra of lines formed at temperatures around and above 1 MK, provided by the EIS spectrograph aboard HINODE will be ideally suited to resolve outstanding questions about the mechanism(s) responsible for heating and accelerating the ambient plasma in the open-field regions close to the Sun (within the sonic point). In particular, we would like to explore the possible roles of MHD waves and magnetic reconnection in heating and initially driving the coronal-hole plasma that is accelerated farther out to become the fast wind (Parker 1991, ApJ, 372, 719; Wang 1998, ApJ, 501, L145). The high sensitivity of EIS in lines formed at several MK and the high spatial resolution magnetograms would be a key tool in detecting signatures of magnetic reconnection. Slow MHD waves can carry significant energy flux on open field lines, so they may be important for the acceleration of the fast solar wind. Fast waves, on the other hand, dissipate more quickly, thus contributing to heating at lower heights. Thus far, only long period (10-70 min) radiance fluctuations have been detected in plumes and inter-plume regions, but nothing is known about higher frequency and/or lower amplitude variations (e.g. DeForest & Gurman 1998, ApJ, 501, L217; Banerjee et al. 2001b, A&A 380, L39). To establish the effects of MHD waves on the coronal plasma and possible contributions to the solar wind, we need to know whether the observed variations are truly due to MHD waves, whether different types of waves are found in different parts of coronal holes, whether they begin at the solar surface or higher up, and how they are generated and dissipated. Our proposal has the capabilities of greatly contributing in answering those questions. OPERATIONAL CONSIDERATIONS AND TARGET SELECTION: TARGET: The south or north coronal hole. The north coronal hole will be slightly (4 degrees) more tilted towards Earth. However, we shall recommend the hole that has larger spatial extent. DETAILED OBSERVING SEQUENCES: SOHO - SUMER: Use the 1"x120" slit centred on the limb in a Northern or Southern coronal hole (the best defined one at the time of observation). Main lines to be used Ne VIII 77 nm and O VI 103.2 nm and 103.7 nm. The Ne VIII line is formed at the base of the corona at a temperature (about 0.6 MK) where there still is enough plasma to in coronal holes to yield spectra with a good signal to noise. This line is unique of SUMER and it is perhaps the best diagnostic to study coronal holes. An additional line will be the O IV 79 nm, probing the transition region. The O VI lines have a measurable radiatively excited component that can be modulated by the outflow speed velocity. Obtain spectra of each target region with an exposure time of about 20s. Each sit-and-stare sequence is to be preceded by a small context raster (50"x120") to co-align with EIS. Total duration of the sequence is between 4 and 5 hours. SOHO - CDS: A 4'x4' opening raster (GENE: general intensity map), followed by two repetitions of SER75W (Line widths at limb #2) time series, followed by a closing 4'x4' raster (GENE). HINODE - EIS: Time series of slot images in strong isolated lines to study radiance oscillations at different temperatures. Exposure times of about 60 seconds. Context raster images are foreseen for context and for co-alignment with the other instruments. The slit will be centred at the north (south) limb, observing up to 256" above the limb. Estimated Study duration: about 5 h. HINODE - SOT: One or (better) two SP scans. Ca II H images. HINODE - XRT: High cadence (40s to 60s) observations in a single filter (Al-poly) with a 512"x512" field of view. VTT TIP-2: Repeated rasters in the He I multiplet at 1083 nm, recovering the four Stokes profiles. The data will be taken with the slit tangent to the limb, over a FOV of +/- 15" from the limb. The exposure time will be around 10 seconds, allowing a raster cadence of less than 10 minutes. Sit and stare sequences at given heights above the limb may be also added. TRACE: Images in the 171 band at 30s cadence. On-board 2x2 binning can be used if needed. STEREO/EUVI: Conext images at 171 every few minutes.