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HMI OBSERVATIONS OF TRANSIENT PHENOMENA Juan Carlos Martínez Oliveros Space Sciences Laboratory, UC Berkeley Charles Lindsey, Hugh Hudson, S. Couvidat,

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Presentation on theme: "HMI OBSERVATIONS OF TRANSIENT PHENOMENA Juan Carlos Martínez Oliveros Space Sciences Laboratory, UC Berkeley Charles Lindsey, Hugh Hudson, S. Couvidat,"— Presentation transcript:

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  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 Kosovichev and Zharkova, 1998

4 4 LoHCo Workshop, Stanford University February 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 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 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 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

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 Martínez-Oliveros et al., 2011

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

11 A black light flare? 11 LoHCo Workshop, Stanford University February

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 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 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

15  To avoid the pre-flare artifacts introduced by the negative weighting, NRT data was used. 15 LoHCo Workshop, Stanford University February 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

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

18 A transient Blue shift! 18 LoHCo Workshop, Stanford University February  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

20 The role of GONG 20 LoHCo Workshop, Stanford University February  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.


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