3.1.2.7 How are so many electrons accelerated on such short time scales to explain the observed hard X-ray fluxes?
It is becoming increasingly clear that propagation of energetic electrons does not follow a simple collisional thick-target scenario, so more sophisticated models of electron transport are required including effects of non-uniform plasma ionization (e.g. Kontar et al. 2003), return current (e.g. Zharkova & Gordovskyy 2006), and beam-plasma interaction via various plasma waves (e.g. Kontar 2001). The deposited energy of the non- thermal electrons heats the chromospheric plasma and the resulting overpressure drives the hot plasma up the legs of the magnetic loops (e.g. Brown 1973) in the process termed chromospheric evaporation. Hard X-ray observations provide thermal diagnostics of the heated flare loops.
Observing plans for this objective should include in particular partially limb-occulted flare observations and observations of hard X-ray emissions associated with CMEs:
- Study coronal phenomena in hard X-rays associated with CMEs:
- Highly occulted events associated with fast backside CMEs (Krucker et al., 2007), non-thermal bremsstrahlung.
- Produced by flare-accelerated energetic electrons (>10 keV) trapped in magnetic structures related to the CME or
- Accelerated in CME current sheets or other coronal magnetic restructuring related to the CME.
- Highly occulted events associated with fast backside CMEs (Krucker et al., 2007), non-thermal bremsstrahlung.
- Explore the consequences of particle acceleration by Alfvén waves created by the magnetic reconfiguration during magnetic reconnection (Fletcher & Hudson, 2008).
- SoloHI: Contribute (mode: shock+synoptic), no min. obs time, all distances, w/EUI-STIX-METIS.
- EUI, EUI synoptic mode (S). EUI FD 174, 304, cadence 2 min. EUI HR 174 and Ly-alpha, cadence 1 min for 30 min before and during X-ray peak. Best when the solar limb from SO is connected to Earth, or other s/c.
- EPD: All sensors: spectra, composition, fluxes, directional information, together with IS instruments. Solar source identification by RS instruments (full disk imaging). Also coordinated multi-s/c SEP observation campaigns with SPP & other missions.
- METIS: Measurement of coronal outflow velocity and density in corona to identify the shock front. Measurement of shock passage timing relative to the flare occurrence.
- Products:
- CME velocity maps
- CME density maps
- CME directionality
- CME flag
- Modes:
- GLOBAL (before the event, if possible), min. obs time 2 hr, data volume ≤ 300 Mb.
- CMEOBS, starts after CME flag rise, min. obs time 1 hr (high cadence, 1 min), data volume ~ 2.137 Gb.
- GLOBAL (after the event), min. obs time 2 hr, data volume ≤ 300 Mb.
- Other instruments: PHI, EUI, STIX, SoloHI, MAG, SWA, EPD, RPW.
- Products: