We investigate the long-term evolution of X-ray coronae of solar analogs based on high-resolution X-ray spectroscopy and photometry with XMM-Newton .
Six nearby main-sequence G stars with ages between \approx 0.1 Gyr and \approx 1.6 Gyr and rotation periods between \approx 1 d and 12.4 d have been observed .
We use the X-ray spectra to derive coronal element abundances of C , N , O , Ne , Mg , Si , S , and Fe and the coronal emission measure distribution ( EMD ) .
We find that the abundances change from an inverse-First Ionization Potential ( FIP ) distribution in stars with ages around 0.1 Gyr to a solar-type FIP distribution in stars at ages of 0.3 Gyr and beyond .
This transformation is coincident with a steep decline of non-thermal radio emission .
The results are in qualitative agreement with a simple model in which the stream of electrons in magnetic fields suppresses diffusion of low-FIP ions from the chromosphere into the corona .
The coronal emission measure distributions show shapes characterized by power-laws on each side of the EMD peak .
The latter shifts from temperatures of about 10 MK in the most rapidly rotating , young stars to temperatures around 4 MK in the oldest target considered here .
The power-law index on the cooler side of the EMD exceeds expected slopes for static loops , with typical values being 1.5–3 .
We interpret this slope with a model in which the coronal emission is due to a superposition of stochastically occurring flares , with an occurrence rate that is distributed in radiated energy E as a power-law , dN / dE \propto E ^ { - \alpha } , as previously found for solar and stellar flares .
We obtain the relevant power-law index \alpha from the slope of the high-temperature tail of the EMD .
Our EMDs indicate \alpha \approx 2.2 - 2.8 , in excellent agreement with values previously derived from light curves of magnetically active stars .
Modulation with time scales reminiscent of flares is found in the light curves of all our targets .
Several strong flares are also observed .
We use our \alpha values to simulate light curves and compare them with the observed light curves .
We thus derive the range of flare energies required to explain the light-curve modulation .
More active stars require a larger range of flare energies than less active stars within the framework of this simplistic model .
In an overall scenario , we propose that flaring activity plays a larger role in more active stars .
In this model , the higher flare rate is responsible both for the higher average coronal temperature and the high coronal X-ray luminosity , two parameters that are indeed found to be correlated .