1. HMI OBSERVATIONS OF TRANSIENT PHENOMENA Juan Carlos Martínez Oliveros Space Sciences Laboratory, UC Berkeley Charles Lindsey, Hugh Hudson, S. Couvidat, J. Schou, Säm Krucker, P. Scherrer

2. Outline LoHCo Workshop, Stanford University February 8-9 2011 2  Motivation  The 12 June 2010 event  Black-light flares  Some results  The role of GONG

3. Motivation  The flare-interior relation was first discovered by Kosovichev and Zharkova (1998).  Sunquakes are the fingerprints of flares in the solar photosphere.  How is this phenomenon produce?  How is it related to the flare energy?  What are the roles of the chromosphere and magnetic field geometry? 3 LoHCo Workshop, Stanford University February 8-9 2011 Kosovichev and Zharkova, 1998

4. 4 LoHCo Workshop, Stanford University February 8-9 2011 Flare Excitation mechanism Motivation

5.  Why only a few flares are seismically active?  Till today a couple of tens of sunquakes have been detected.  What make seismically active flares “special”? 5 LoHCo Workshop, Stanford University February 8-9 2011 Motivation Is it the flare?Is it the Beam? The excitation mechanism?

6. Several mechanisms of seismic waves have proposed:  Chromospheric shocks  Photon bombardment (back-warming)  Penetrating particles  Magnetic field variations 6 LoHCo Workshop, Stanford University February 8-9 2011 Motivation

7. How to find these sunquakes? 1. Looking for waves in the Doppler data. 2. Looking for signatures associated with the seismicity, namely:  White-light kernels (almost always)  γ -emission (not always this are detected)  Impulsiveness in HXR and microwaves 7 LoHCo Workshop, Stanford University February 8-9 2011 Motivation Martínez-Oliveros et al., 2008 Martínez-Oliveros et al.,2007

8. The 12 June 2010 event  The flare studied was a GOES M2.0 event in NOAA active region11081, located approximately at N22W45  This was the first γ -ray flare of the new cycle.  It was a highly impulsive event So, this could be a good candidate. 8 LoHCo Workshop, Stanford University February 8-9 2011

9. Transient Phenomena  A first analysis of SDO/HMI data revealed a decrease of the intensity continuum during the impulsive phase of the flare. 9 LoHCo Workshop, Stanford University February 8-9 2011 Martínez-Oliveros et al., 2011

10. 10 LoHCo Workshop, Stanford University February 8-9 2011 Transient Phenomena No RHESSI imaging, due to Crab Nebula operations.

11. A black light flare? 11 LoHCo Workshop, Stanford University February 8-9 2011

12. A black light flare? II  We now know that the white-light continuum probably is enhanced in all flares, but that for the weaker ones the signal is lost in the glare and fluctuations of the photosphere.  Generally a dimming signature might imply: a) momentary obscuration by overlying material; b) thermal perturbations causing an increased opacity in the relatively cool chromosphere, hence increased absorption of radiation from the hot underlying photosphere; c) a non-thermal effect not accessible to standard modeling techniques but with a similar effect (Hénoux et al. 1990). 12 LoHCo Workshop, Stanford University February 8-9 2011 From Hénoux et al. 1990

13.  This kind of dimming or dip was reported before for observations of stellar flares (e.g. Cristaldi et al. 1980)  In the Sun is still unclear if this rare phenomenon really occurs.  This should be an achievable task for SDO/HMI. 13 LoHCo Workshop, Stanford University February 8-9 2011 From Cristaldi et al. 1980

14. Transient Phenomena It was truly a black light flare? Sadly, the answer is NO.  The HMI Dopplergrams and intensities data consist of a spatial- temporal interpolation, using 12 filtergrams at six different wavelengths and two polarization states, for each observable.  These interpolations, in conjunction with the scanning of the 6173 A Fe I line, were devised to minimize the effects of aliasing (unwanted time-series noise) in p-mode signals.  Because of this, the response of the standard Dopplergrams to a sufficiently rapid white-light flare can be an apparent reduction in intensity preceding the flare, i.e., an apparent “black-light flare” preceding the white-light. 14 LoHCo Workshop, Stanford University February 8-9 2011

15.  To avoid the pre-flare artifacts introduced by the negative weighting, NRT data was used. 15 LoHCo Workshop, Stanford University February 8-9 2011 Martínez-Oliveros et al., 2011

16. A transient Blue shift!  The blue shifted transient could signify a photospheric medium moving toward SDO, shifting the absorption line.  Could be also the results of down-flowing heated chromospheric material.  This kind of behavior is atypical.  Hudson (2011) report a red shift using EVE 304Å observations. 16 LoHCo Workshop, Stanford University February 8-9 2011

17. A transient Blue shift!  The blue shifted transient could signify a photospheric medium moving toward SDO, shifting the absorption line.  Could be also the results of down-flowing heated chromospheric material.  This kind of behavior is atypical.  Hudson (2011) report a red shift using EVE 304Å observations. 17 LoHCo Workshop, Stanford University February 8-9 2011

18. A transient Blue shift! 18 LoHCo Workshop, Stanford University February 8-9 2011  The blue shifted transient could signify a photospheric medium moving toward SDO, shifting the absorption line.  Could be also the results of down-flowing heated chromospheric material.  This kind of behavior is atypical.  Hudson (2011) report a red shift using EVE 304Å observations  Can He II move down rapidly while the photosphere is moving up slowly?

19. The role of GONG  Spurious Doppler and intensity signals can be controlled by comparison with GONG observations.  To achieve this cross- calibrations, techniques of cleaning should be applied to GONG data (Lindsey and Donea, 2008).  This techniques must compensate the noise introduced by atmospheric seen. 19 LoHCo Workshop, Stanford University February 8-9 2011

20. The role of GONG 20 LoHCo Workshop, Stanford University February 8-9 2011  Spurious Doppler and intensity signals can be controlled by comparison with GONG observations.  To achieve this cross- calibration, techniques of cleaning should be applied to GONG data (Lindsey and Donea, 2008).  This technique must compensate the noise introduced by atmospheric seen.