Title: Chromospheric heating - signatures of waves and reconnection (Previously run with Campaign Number 7226 in the April 2007 SOHO/Hinode campaign) Authors: D.E. Innes, R. Attie, S.K. Solanki Intruments and POCs SOHO/SUMER: D.E. Innes SOHO/CDS: A. Fludra SOHO/MDI: TBD HINODE/SOT: H. Isobe HINODE/EIS: TBD HINODE/XRT: TBD TRACE: TBD STEREO: B. Inhester VTT (Tenerife): A. Lagg Huairou (China): H. Zhang Scientific Objectives: In the interface between the photosphere and the corona, the magnetic field plays a crucial role in guiding waves, in the build-up of magnetic stress and its dissipation through reconnection. One likely chromospheric heating mechanism is thought to be dissipation of hydro- magnetic shocks, especially in weak field and force-free regions of the chromosphere (e.g. De Pontieu & Erdélyi 2005, Nature, 430, 536). Most of the corona, transition region and chromosphere is force-free and currents are along field lines (parallel currents). Another possibility is direct magnetic field dissipation into plasma heat and flow, that is, by reconnection. This occurs in sheets of perpendicular current, where the resistivity is high enough to trigger dissipation. Distinguishing when, where and what the signatures of shocks and reconnection are, requires detailed high cadence, high resolution observations of all layers of the solar atmosphere. Until recently it was thought that brightenings with periods of 3-5 min indicated shock dissipation, but studies of explosive events suggest that reconnection may also be triggered by p-modes and then reconnection signatures would show the same 3-5 min periods expected from shock dissipation (Ning et al. 2004, A&A, 419, 114; Chen and Priest 2006, A&A, 238, 313). The goal of this proposal is to determine the heating associated with specific magnetic field structure or magnetic field evolution. Flux cancellation, emergence and merging can be seen in the photosphere and the structure in the transition region and corona extrapolated. This identifies regions known as Quasi-Separatrix Layers (QSLs) across which the magnetic connectivity changes (Démoulin et al. 1996, A&A, 308, 643) and current sheets form. Our plan is to use high cadence magnetic field, intensity and velocity SOT observations at different photospheric and chromospheric heights to determine wave fluxes and sites of energy dissipation such as Ca II bright points. These will be combined with SUMER and EIS observations of the chromosphere, transition region and lower corona to detect flows, and XRT images to find bright points in the corona. Both quiet and active region observations should be made. In active regions, the magnetic fields are stronger and more organized than in the quiet Sun so can be observed more easily, but there is likely to be more confusion in the chromosphere due to overlapping events. Operational Considerations: These observations do not require a special target. Their success lies in observing with many instruments simultaneously the same part of the Sun. Planning and target choice can be done days in advance which makes it a good program for multi-observatory observations. This HOP-JOP is also planned as a back-up for HOP-JOPs targeting specific features on the Sun such as active regions, filaments etc in the SOHO-Hinode-Ground campaigns. A typical observation is 6 hours. Proposed Dates: 2007 Oct 22 - Nov 4. We have been allocated time with VTT and SUMER is also planning a campaign to run at the same time. Detailed Observing sequences: SOHO/SUMER: map connection to chromosphere, pick up transition region and coronal flows. Quiet Sun - Rasters in Si I, N V, O V, Mg IX Active Region Rasters in C I, Si III, Ne VI, Ca X, Ca XIII, Fe XIX SOHO/CDS: Detect brightenings with high cadence Quiet Sun - wide slit in He I, O V, Mg IX exposure time 25s Active Region - wide slit He I, O V, Mg IX exposure time 10s SOHO/MDI: High Res when possible Hinode/SOT: Ca II, Blue continuum, magnetic field + SP scan and fast rasters Hinode/EIS: slot He II, Si VII, Fe VIII, Fe X, XI, XII, XIII, XIV, XV, XVI, FeXXIV Hinode/XRT: Structure of hot loops Quiet Sun - long exposures to show large scale magnetic linkage in corona Active Region - High cadence to pick up changes in magnetic linkage through the corona STEREO: Quiet Sun - extra 304 images to see chromosphere brightenings Active Region - High cadence, multiple filters TRACE: 171 images with 1700 for coalignment VTT: Chromospheric vector magnetic fields and flows (spectropolarimetry in He I 10830) Huairou: Vector magnetic fields