  The quiet-Sun X-ray emission is important for deducing coronal heating
mechanisms, but it has not been studied in detail since the Orbiting Solar
Observatory (OSO) spacecraft era. Bragg crystal spectrometer X-ray observations
have generally concentrated on flares and active regions. The high sensitivity
of the RESIK (REntgenovsky Spectrometer s Izognutymi Kristalami) instrument on
the CORONAS-F solar mission has enabled the X-ray emission from the quiet
corona to be studied in a systematic way for the first time. Our aim is to
deduce the physical conditions of the non-flaring corona from RESIK line
intensities in several spectral ranges using both isothermal and multithermal
assumptions. We selected and analyzed spectra in 312 quiet-Sun intervals in
January and February 2003, sorting them into 5 groups according to activity
level. For each group, the fluxes in selected spectral bands have been used to
calculate values parameters for the best-fit that lead to a intensities
characteristic of each group. We used both isothermal and multitemperature
assumptions, the latter described by differential emission measure (DEM)
distributions. RESIK spectra cover the wavelength range (3.3-6.1 A). This
includes emission lines of highly ionized Si, S, Cl, Ar, and K, which are
suitable for evaluating temperature and emission measure, were used. The RESIK
spectra during these intervals of very low solar activity for the first time
provide information on the temperature structure of the quiet corona. Although
most of the emission seems to arise from plasma with a temperature between 2MK
and 3MK, there is also evidence of a hotter plasma (T approx. 10MK) with an
emission measure 3 orders smaller than the cooler component. Neither coronal
nor photospheric element abundances appear to describe the observed spectra
satisfactorily.
