Ongoing Issues
From RHESSI Wiki
Contents |
NUMBER PROBLEM
- closely tied to acceleration problem
Pre-flare
- What is the flare loop density before a flare?
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)
- 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).
Type III emission
- 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).
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)
HXR footpoint issues
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).
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.
Neutral SEPs
- can they come from flares?
- could give information on ions < 1 MeV...
Energetics
- Ion energetics: how much energy in ions if one assumes a cutoff near the ion thermal energies? (Shih)
