HMI OBSERVATIONS OF TRANSIENT PHENOMENAJuan Carlos Martínez OliverosSpace Sciences Laboratory, UC Berkeley

Charles Lindsey, Hugh Hudson, S. Couvidat, J. Schou, Säm Krucker, P. Scherrer

LoHCo Workshop, Stanford University February 8-9 2011

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Outline

Motivation The 12 June 2010 event Black-light flares Some results The role of GONG

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LoHCo Workshop, Stanford University February 8-9 2011

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?

Kosovichev and Zharkova, 1998

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LoHCo Workshop, Stanford University February 8-9 2011

Flare Excitation mechanism

Motivation

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LoHCo Workshop, Stanford University February 8-9 2011

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”?

Motivation

Is it the flare?Is it the Beam?The excitation mechanism?

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LoHCo Workshop, Stanford University February 8-9 2011

Several mechanisms of seismic waves have proposed:

Chromospheric shocks Photon bombardment (back-

warming) Penetrating particles Magnetic field variations

Motivation

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LoHCo Workshop, Stanford University February 8-9 2011

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

Motivation

Martínez-Oliveros et al., 2008

Martínez-Oliveros et al.,2007

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LoHCo Workshop, Stanford University February 8-9 2011

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.

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LoHCo Workshop, Stanford University February 8-9 2011

Transient Phenomena A first analysis of SDO/HMI data revealed a decrease of the

intensity continuum during the impulsive phase of the flare.

Martínez-Oliveros et al., 2011

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LoHCo Workshop, Stanford University February 8-9 2011

Transient Phenomena

No RHESSI imaging, due to Crab Nebula operations.

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LoHCo Workshop, Stanford University February 8-9 2011

A black light flare?

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LoHCo Workshop, Stanford University February 8-9 2011

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).

From Hénoux et al. 1990

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LoHCo Workshop, Stanford University February 8-9 2011

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.

From Cristaldi et al. 1980

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LoHCo Workshop, Stanford University February 8-9 2011

Transient PhenomenaIt 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.

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LoHCo Workshop, Stanford University February 8-9 2011

To avoid the pre-flare artifacts introduced by the negative weighting, NRT data was used.

Martínez-Oliveros et al., 2011

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LoHCo Workshop, Stanford University February 8-9 2011

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.

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LoHCo Workshop, Stanford University February 8-9 2011

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.

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LoHCo Workshop, Stanford University February 8-9 2011

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

Can He II move down rapidly while the photosphere is moving up slowly?

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LoHCo Workshop, Stanford University February 8-9 2011

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.

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LoHCo Workshop, Stanford University February 8-9 2011

The role of GONG 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.