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In this paper, we propose that the accelerated electrons in the quiet Suncould collide with the solar atmosphere to emit Hard X-rays (HXRs) vianon-thermal bremsstrahlung, while some of these electrons would move upwardsand escape into the interplanetary medium, to form a superhalo electronpopulation measured in the solar wind. After considering the electron energyloss due to Coulomb collisions and the ambipolar electrostatic potential, wefind that the sources of the superhalo could only occur high in the corona (ata heliocentric altitude $\gtrsim 1.9$ R$_\odot$ (the mean radius of the Sun)),to remain a power-law shape of electron spectrum as observed by STEREO at 1AUnear solar minimum (Wang et al., 2012). The modeled quiet-Sun HXRs related tothe superhalo electrons fit well to a power-law spectrum, $f \sim\varepsilon^{-\gamma}$, with an index $\gamma$ $\approx$ 2.0 - 2.3 (3.3 - 3.7)at 10 - 100 keV, for the warm/cold thick-target (thin-target) emissionsproduced by the downward-traveling (upward-traveling) accelerated electrons.These simulated quiet-Sun spectra are significantly harder than the observedspectra of most solar HXR flares. Assuming that the quiet-Sun sources cover 5%of the solar surface, the modeled thin-target HXRs are more than six orders ofmagnitude weaker than the RHESSI upper limit for quiet-Sun HXRs (Hannah et al.,2010). Using the thick-target model for the downward-traveling electrons, theRHESSI upper limit restricts the number of downward-traveling electrons to atmost $\approx$3 times the number of escaping electrons. This ratio isfundamentally different from what is observed during solar flares associatedwith escaping electrons where the fraction of downward-traveling electronsdominates by a factor of 100 to 1000 over the escaping population.

Simulation of Quiet-Sun Hard X-rays Related to Solar Wind Superhalo Electrons