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Absence of Impact Polarization in H 

Absence of Impact Polarization in H . Michele Bianda Istituto Ricerche Solari Locarno (IRSOL) Switzerland Collaborators : A. Benz, D. Gisler, G. Küveler, R. Ramelli, J.O. Stenflo . Outline. Introduction to impact polarization Observations Technical setup

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Absence of Impact Polarization in H 

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  1. Absence of Impact Polarization in H Michele Bianda Istituto Ricerche Solari Locarno (IRSOL) Switzerland Collaborators: A. Benz, D. Gisler, G. Küveler, R. Ramelli, J.O. Stenflo

  2. Outline • Introduction to impact polarization • Observations • Technical setup • Difficulties in observing polarization • Polarimeter: ZIMPOL

  3. Impact polarization • Directed particle beam colliding with plasma impact polarization • Created in flares?

  4. 190 arc sec 140 arc sec Observations I Q/I • M1.0 flare • 2 August 2002 • 1051 UT • No impact polarization observed V/I

  5. 190 arc sec 140 arc sec Observations • M3.9 flare • 18 November 2003 • 0831 UT • No impact polarization observed I Q/I V/I

  6. Time evolution in flaring region

  7. Observations of X17.1 flare, 28 Oct 2003 • purple: slit position • green: TRACE 195 Å • yellow and blue: RHESSI

  8. Observations of X17.1 flare, 28 Oct 2003

  9. Observations of X17.1 flare, 28 Oct 2003

  10. Difficulties observing polarization in visible light • Polarization measurement: • Combining intensity images with different polarization properties • Difference of images • “polarization”, if not recognized as instrumental effect. • Impact polarization: • fast evolving structure • high intensity gradients

  11. I1 I2 I1 I2 R Polarimeter techniques • Two beam technique: + simultaneous −different optical paths −different CCDs • One beam technique: + same path + same CCD −not simultaneous ( seeing!)

  12. how? I1 0° switched at 42 kHz I2 90° ZIMPOL concept (1) • Fast polarization modulation and on-chip demodulation

  13. ZIMPOL concept (2) • Demodulation at 42 kHz • Same CCD pixel for different polarization states

  14. Conclusions • Impact polarization not detected by ZIMPOL at IRSOL; more than 30 events were observed

  15. Profiles from imaging observations

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