Observational programs at Istituto Ricerche Solari Locarno (IRSOL)

Transcription

1 Observational programs at Istituto Ricerche Solari Locarno (IRSOL) Renzo Ramelli and IRSOL collaborators IRSOL Locarno, Switzerland Suzhou, China 24th July 2009

2 Scientific Collaborators affiliated to IRSOL Dr. Michele Bianda Prof. Jan O. Stenflo (ETHZ/IRSOL) Dr. Renzo Ramelli Dr. Daniel Gisler (IRSOL/ETHZ) Lucia Kleint (PhD student) (IRSOL/ETHZ) + Collaborations with people from other institutes worldwide

3 IRSOL Germany France Zurich Switzerland Austria Italy IRSOL = Istituto Ricerche Solari Locarno Observatory specialized in polarimetry

4 Outline Introduction: Scientific interest of polarimetry Instrumentation (Overview) Summary of observational programs Future goals

5 Polarimetry Polarimetry allows to get information about the magnetic fields Zeeman effect: Polarization signals up to serveral tens of % Zeeman effect allows to extract the tridimensional information of strong oriented magnetic fields.

6 Scattering polarization and the Hanle effect The improvement in the polarimetric accuracy (at 10-4 level or better) opened a new window in the observation of scattering polarization (mainly) near the limb Scattering polarization profiles in spectral lines are also sensitive to weak and mixed-polarity magnetic fields through the Hanle Effect (which mainly manifests itself as depolarization and ev. a rotation of plane of polarization) Powerful tool to get information about weak and (unresolved) mixed polarity magnetic fields (to which Zeeman effect is blind)

7 First two volumes of Gandorfer s Atlas obtained at IRSOL (2000, 2002) Second solar spectrum

8 The IRSOL instrumentation Telescope Telescope: Gregory - Coudé, evacuated Diameter of primary mirror: 45 cm Total focal length: 25 m Spectrograph: focal length: 10 m grating 18 cm 36 cm 316 lines / mm blaze 63 Fabry Perot filter system: Bandwidth ~ 30 ma Novel configuration with FP+spectrograph Adaptive optics: Tip-tilt DM with 37 actuators ZIMPOL polarimeter (see next slides)

9 ZIMPOL polarimeter ZIMPOL-polarimeter (Zurich Imaging Polarimeter, previously developed at ETH- Zurich and now at SUPSI Lugano) allows precise full Stokes measurements free from seeing induced spurious effects (modulation 42 khz / 1kHz). Polarimetric accuracy depends primarily on photon statistics level can be reached with long enough exposure time. ZIMPOL - setup

10 ZIMPOL3 New generation camera system which is being implemented for observations at IRSOL

11 ZIMPOL3 Improvements with respect to ZIMPOL2: more flexible and compact system adaptable to different cips new cips for UV with microlenses more efficient and faster exposure and readout simultaneously based on newer technology (replace components available on the market) more functions (readout modes, binning, subframe readout, different demodulation schemes, electronic compensation of telescope pol. offset) night astronomy application possible: longer integration time, better cooling

12 Advantages of GCT at IRSOL + ZIMPOL Very good polarimetric and spectral accuracy Large amount of observing time available: Flexibility, fast reaction to particular solar events Good for synoptic type programs or for projects requiring long observation time Good for testing and development of new instrumentation to be used also in dedicated campaigns at larger observatories (Thémis, Gregor,...) Measurements down to the near UV (ca. 380 nm) Instrumental polarization is small and almost constant over one day of observations (easy to correct depends on declination only)

13 Examples of scientific results obtained at IRSOL Hanle effect measured in the quiet chromosphere (Bianda et al., 1998) 2 Volumes of Second Solar Spectrum Atlas (Gandorfer, 2000/2002) Determination of novel constraints on impact polarization in solar flares (Bianda et al., 2005) Discovery of vast amount of hidden magnetism in the solar photosphere (Trujillo Bueno et al.- Stenflo, Nature 2004); Measurements of polarization in molecular lines (e.g. Afram et al. 2007; Berdyugina et al ; Asensio Ramos et al. 2004) Measurements of full Stokes profiles in prominences in Hα, He-D3 and Hβ (Ramelli et al., 2005) He-D3 full Stokes spectropolarimetric measurements in spicules (Ramelli et al., 2005) BaII D2 line observations to verify the theoretical predictions of Belluzzi et al. (Ramelli et al., 2007) Study of the origin of spatial variations of scattering polarization in the wings of the Ca I 4227 A line (Sampoorna et al., 2009)...

14 Examples of on-going projects: Inversion of prominence profiles with Hazel code preliminary (Ramelli et al.) (Hazel code: Asensio Ramos, Trujllo Bueno and Landi degl Innocenti, ApJ, 2008)

15 Examples of on-going projects: Inversion of prominence profiles with Hazel code preliminary (Ramelli et al.) (Hazel code: Asensio Ramos, Trujllo Bueno and Landi degl Innocenti, ApJ, 2008)

16 Examples of on-going projects: Inversion of profiles of spicules with HaZel code preliminary (Ramelli et al.) (Hazel code: Asensio Ramos, Trujllo Bueno and Landi degl Innocenti, ApJ, 2008)

17 Examples of on-going projects: Inversion of profiles of spicules with Hazel code preliminary (Ramelli et al.) (Hazel code: Asensio Ramos, Trujllo Bueno and Landi degl Innocenti, ApJ, 2008)

18 Examples of on-going projects: Synoptic program (Kleint et al.) Monthly observations at different N - Position angles (N, NW, W, SW, S) - wavelengths (5141 A, 5206 A, 4383 A) Slit parallel to the limb, at µ=0.1 (5 from limb) S

19 Synoptic program: profile modeling at 5141 (Kleint et al.) Calculate amplitude ratios R1 / R2 R3 / R2 R2 / P

20 mall all e re is => =>! Synoptic program: Variation with position angle? ve ve far far r No dependence from position angles e R R Measurements from 12/2007 until 2009 (Kleint et al.)

21 Main goals: Future research at IRSOL Different observing programs on solar magnetism and polarimetry Synoptic type programs (eg. Variations of the Hanle-effect signatures with respect to heliographic latitude and solar cycle phase) Development of novel instrumentation Collaboration with observatories with larger telescopes (Gregor, Thémis, EAST,...)

22 Thanks for your attention!