SOHO MDI AND SUMER SCIENCE PROPOSAL Local Helioseismology and Heating of the Chromosphere and Corona Main Investigator: R. Kariyappa, Jet Propulsion Laboratory, MS 169-506, 4800 oak Grove Drive, Pasadena, CA 91109, Email: rkari@simdac.jpl.nasa.gov; Phone: 818-393-3475; Fax: 818-354-8895 After August 15, 1996: Indian Institute of Astrophysics, Koramangala, Bangalore 560034 India, Email: rkari@iiap.ernet.in; RKariyappa@solar.stanford.edu; Phone: 91-80-553-0672; Fax: 91-80-553-4043 Co-Investigators: P. Scherrer, Stanford University, Center for Space Science & Astrophys. Stanford, CA 94305, USA, Phone: 415-723-1504 Fax: 415-725-2333; Email: pscherrer@solar.stanford.edu P. VenkataKrishnan, Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India, Email:pvk@iiap.ernet.in; Phone: 91-80-553-0672; Fax: 91-80-553-4043 A. Vigouroux, Observatoire de la Cote d'Azur, B.P. 229, F-06304, Nice Cedex 04, France Email: vig@purcell.obs-nice.fr K. Wilhelm, Max-Planck-Institut fur Aeronomie Postfach 20, 37189 Katlenburg-Lindau, Germany Phone: 49-5556-979423; Fax: 49-5556-979240 Email: kwilhelm@solar.stanford.edu Objectives: The main goal of the proposed research is to identify and understand the influence of localized inhomogeneties, like sunspots, flaculae, plages, network and intranetwork regions, on the solar oscillations and to explain the heating mechanisms of the chromosphere and corona. The SOHO/MDI/SOI experiments provide the measurements in high resolution and the full-disk images of the Sun in velocity, magnetic field, line intensity, and continuum intensity of the photosphere. Whereas the SOHO/SUMER experiment will provide the images of the Sun from the chromosphere through the transition region and to the inner corona and these observations provide detailed information on the various features. Combining the images of the Sun obtained from MDI and SUMER, will yeild to study the local helioseismology right from the low photosphere to the corona. We propose to apply the wavelet analysis technique to solar oscillations at different heights and different regions of the Sun. It is a very powerful tool to obtain information on the temporal behaviour of an oscillatory signals and the temporal lags between the signal of the different heights and at different regions of the Sun. Hence to explain the nature of the wave propagation and physical mechanisms of the heating of the chromosphere and corona. Scientific Rationale: Solar Oscillations provide a unique method of studying the interior structure of the Sun, however the observed signals convey information integrated over the depth of penetration of the mode studied. Thus low l value modes provide data on the deep interior, whereas high l modes only probe the surface layers. It is from a study of such data that a picture of the solar interior will emerge. Another penetration of depth separation may be obtained by studying different features on the Sun seen at the various levels in the solar atmosphere from low photosphere to corona. Hence local helioseismology will become a powerful tool for studying simultaneously about the inhomogeneous features, their properties and their period of oscillations as a function of height in the solar atmosphere. One of the major problems in solar physics is to understand the way the chromosphere and corona are heated and supported by the non-radiative energy from the layers below. Examine the dynamical processes of the various structures observed at the various levels in the solar atmosphere and to find out from the observational evidence how the energy requirements can be met. Proposed Research: Task (1): Study of Local Helioseismology We propose to study the solar oscillations in various features like sunspots, flaculae, plages, network and intranetwork regions, which are seen at the different heights in the solar atmosphere. This would be of great interest to establish spatial and temporal relations between the photosphere, chrompshere and the corona. This will explain the physical mechanisms of solar oscillations and for the existence of different periods at different heights in the solar atmosphere. For this purpose, we propose to segregate the various features from the images of the Sun in photosphere, chromosphere, transition region, and corona obtained with MDI/SOI and SUMER experiments. Then compare the period of oscillations at the locations of the features seen at various levels in the solar atmosphere. Task (2): Heating of the Chromosphere and Corona We propose to apply the Wavelet analysis technique to simultaneous observations obtained in different frequencies of the Sun. Using this analysing technique the temporal behaviour of oscillations at different frequencies will be studied in all features. It is essential to study the layers below the corona - photosphere and chromosphere - where the source of energy is avaiable, and to analyse the magnetohydrodynamic waves, which are good candidates to heat the chromosphere and corona. This diagnostic can be improved with the use of the wavelet transform. It is a very powerful tool to obtain information on the temporal behaviour of an oscillatory signal, to determine, from a precise investigation of energy variations, the temporal lags between the signals of the different levels in the solar atmosphere in various features. The results on the behaviour of Solar oscillations at different heights and different regions of the Sun can be evidenced. Task (3): Role of Magnetic Fields in Dynamical Processes of the Structures We propose to establish the relation between the brightness and the magnetic field strength in various features particularly in fine scale structures. Since the MDI and SUMER experiments produce the images of the Sun in Intensity and magnetic field, this study will help to understand the realtion between brightness and magnetic field and it may put a light on magnetic and non- magnetic waves to explain the heating mechanism of the chromosphere and corona. Task (4): Footpoints of the Fine Sacl Structures Since the observations are simultaneous in photosphere (from MDI/SOI), Chromosphere, Transition Region aand Inner Corona (from SUMER), we explain about the footpoints of the various fine scale structures with respect to the Photospheric Features. Also this explains to the question: What are the underlying physical mechanisms for solar oscillations ? Task (5): Solar Variability By integrating the brightness of the various features as well as for the whole disk observed at different frequences, we can estimate the individual contribution to total solar variability and to identify and understand the underlying physical mechanisms of solar variability. Task (6): Search for g-mode Oscillations and and Look for Giant Cells Reponsibilities: The proposed research will be a collaborative effort between the MDI and SUMER teams and other participating institutions. Analysis of the images and interpretation of the results will be the responsibility of R. Kariyappa. P. Scherrer and K. Wilhelm will provide the images and their expertise in the interpretation of the results. P. VenkataKrishanan will provide his expertise in the theoretical interpretation of the results. Application of Wavelet Analysis technique on Solar oscillations data will be the responsibility of A. Vigouroux.