Particle Acceleration in Solar Flares with Imaging-Spectroscopy in Soft X-rays

Particles are accelerated to very high, non-thermal energies during explosiveenergy-release phenomena in space, solar, and astrophysical plasmaenvironments. In the case of solar flares, it has been established thatmagnetic reconnection plays an important role for releasing the magneticenergy, but it remains unclear if or how magnetic reconnection can furtherexplain particle acceleration during flares. Here we argue that the key issueis the lack of understanding of the precise context of particle accelerationbut it can be overcome, in the near future, by performing imaging-spectroscopyin soft X-rays (SXRs). Such observations should be complemented by observationsin other wavelengths such as extreme-ultraviolets (EUVs), microwaves, hardX-rays (HXRs), and gamma-rays. Also, numerical simulations will be crucial forfurther narrowing down the particle acceleration mechanism in the contextrevealed by the observations. Of all these efforts, imaging-spectroscopy inSXRs, if successfully applied to large limb flares, will be a milestone in ourchallenge of understanding electron acceleration in solar flares and beyond,i.e. the Plasma Universe.