Ongoing Issues

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==NUMBER PROBLEM==
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==Number problem==
*closely tied to acceleration problem
*closely tied to acceleration problem
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==Pre-flare==
==Pre-flare==
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*What is the flare loop density before a flare?
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*What is the flare loop density before a flare? See the [http://sprg.ssl.berkeley.edu/~hhudson/drafts/dublin/ suggestions] that the loop about to flare is normally empty.
   
   
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==Spectral issues==
==Spectral issues==
*Break at 1 AU in SEP electron spectrum seem to be due to plasma wave (Kontar). Can the same phenomenon also explain the break in flare X-ray spectra? (We already know of several other possible candidates: non-uniform target ionization (Kontar et al., 2002) and return current (Zharkova et al., 2005) are at the top of the list)
*Break at 1 AU in SEP electron spectrum seem to be due to plasma wave (Kontar). Can the same phenomenon also explain the break in flare X-ray spectra? (We already know of several other possible candidates: non-uniform target ionization (Kontar et al., 2002) and return current (Zharkova et al., 2005) are at the top of the list)
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*Could X-ray emission from flares or escaping SEPs be detected at 10 Rs (Solar Probe), and help consolidate the previous model(s)? X-ray emission from escaping electron beams are beyond RHESSI capabilities, but apparently not from Solar Probe nor FOXSI (at least those at starts at <500 MHz).
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*Could X-ray emission from flares or escaping SEPs be detected at 10 Rs (Solar Probe), and help consolidate the previous model(s)? X-ray emission from escaping electron beams are beyond RHESSI capabilities, but apparently not from Solar Probe nor FOXSI (at least those that starts >500 MHz).
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==Type III emission==
==Type III emission==
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*threshold of electron density for Type III burst generation (Kontar)
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*threshold of electron density for Type III burst generation? (Kontar)
*Type III emission delay with respect to SEPs (up to 10 mins): ~1/3 of events are delayed, 1/3 on time, ~1/3 hard to say (Krucker).
*Type III emission delay with respect to SEPs (up to 10 mins): ~1/3 of events are delayed, 1/3 on time, ~1/3 hard to say (Krucker).
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==Gamma-rays==
==Gamma-rays==
*pair production in 1 MK plasma for 10 mins. How can plasma be so hot so low for such a long time? (Share)
*pair production in 1 MK plasma for 10 mins. How can plasma be so hot so low for such a long time? (Share)
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How can such a plasma not be detectable by other means? (Hudson)
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==HXR footpoint issues==
==HXR footpoint issues==
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0. Number: Why are there usually two hard X-ray footpoints when there are many more points, and ribbon-like structure, at other wavelengths in the impulsive phase?
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1. Timing:
1. Timing:
RHESSI should be able to do footpoint timing at the 0.1s level with visibilities (Hurford)
RHESSI should be able to do footpoint timing at the 0.1s level with visibilities (Hurford)
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Some other important mechanism is at play, most probably magnetic mirroring. Liu et al. (2008) basically agree, saying that neither a difference in column densities nor magnetic mirroring alone can explain all observations: we have interplay between the two (or there is even something else that comes into play).
Some other important mechanism is at play, most probably magnetic mirroring. Liu et al. (2008) basically agree, saying that neither a difference in column densities nor magnetic mirroring alone can explain all observations: we have interplay between the two (or there is even something else that comes into play).
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3. Are spectral breaks the same for both footpoints?
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==Flare T, EM==
==Flare T, EM==
Hottest temperatures in flares (45 MK) occur early in flare, at end of HXR emission (Neupert effect). EM goes on to rise and peaks much later (Caspi). In an event analysed by Saint-Hilaire et al. (2009), EM increases during more than 10 hours.
Hottest temperatures in flares (45 MK) occur early in flare, at end of HXR emission (Neupert effect). EM goes on to rise and peaks much later (Caspi). In an event analysed by Saint-Hilaire et al. (2009), EM increases during more than 10 hours.
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==Chromospheric Evaporation==
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Is chromospheric evaporation the main source of all the hot plasma seen in the corona? EIS observations at different temperatures can address this question.
==Neutral SEPs==
==Neutral SEPs==
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==Energetics==
==Energetics==
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*Ion energetics: how much energy if one assumes a cutoff near the ion thermal energies? (Shih)
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* The global flare energy problem: how does the field restructuring redistribute the magnetic energy?
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RHESSI has made an important contribution in terms of seeing the downward motions of early sources (Sui, Veronig, Ji).
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* Ion energetics: how much energy in ions if one assumes a cutoff near the ion thermal energies? (Shih)
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Latest revision as of 13:43, 15 May 2009

Contents

Number problem


Pre-flare


Spectral issues


Type III emission


Gamma-rays

How can such a plasma not be detectable by other means? (Hudson)


HXR footpoint issues

0. Number: Why are there usually two hard X-ray footpoints when there are many more points, and ribbon-like structure, at other wavelengths in the impulsive phase?

1. Timing: RHESSI should be able to do footpoint timing at the 0.1s level with visibilities (Hurford)

2. Flux ratios, spectral index differences: Double footpoint flares: do we have correlation between spectral index difference and flux ratios? --> Actually, some. Saint-Hilaire et al. (2008) have demonstrated that differences in column densities between leg of loops cannot explain all observed footpoint spectral index differences and flux ratios. Some other important mechanism is at play, most probably magnetic mirroring. Liu et al. (2008) basically agree, saying that neither a difference in column densities nor magnetic mirroring alone can explain all observations: we have interplay between the two (or there is even something else that comes into play).

3. Are spectral breaks the same for both footpoints?


Flare T, EM

Hottest temperatures in flares (45 MK) occur early in flare, at end of HXR emission (Neupert effect). EM goes on to rise and peaks much later (Caspi). In an event analysed by Saint-Hilaire et al. (2009), EM increases during more than 10 hours.


Chromospheric Evaporation

Is chromospheric evaporation the main source of all the hot plasma seen in the corona? EIS observations at different temperatures can address this question.

Neutral SEPs


Energetics

RHESSI has made an important contribution in terms of seeing the downward motions of early sources (Sui, Veronig, Ji).



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