We propose a mechanism for the origin of the Galactic ridge X-ray background that naturally explains the properties of the Fe K line , specifically the detection of the centroid line energy below 6.7 keV and the apparent broadness of the line .
Motivated by recent evidence of nonthermal components in the spectrum of the Galactic X-ray/ \gamma -ray background , we consider a model that is a mixture of thermal plasma components of perhaps supernova origin and nonthermal emission from the interaction of low energy Cosmic ray electrons ( LECRe ) with the interstellar medium .
The LECRe may be accelerated in supernova explosions or by ambient interstellar plasma turbulence .
Atomic collisions of fast electrons produce characteristic nonthermal , narrow X-ray emission lines that can explain the complex Galactic background spectrum .
Using the ASCA GIS archival data from the Scutum arm region , we show that a two-temperature thermal plasma model with kT \sim 0.6 and \sim 2.8 keV , plus a LECRe component models the data satisfactorily .
Our analysis rules out a purely nonthermal origin for the emission .
It also rules out a significant contribution from low energy Cosmic ray ions , because their nonthermal X-ray production would be accompanied by a nuclear \gamma -ray line diffuse emission exceeding the upper limits obtained using OSSE , as well as by an excessive Galaxy-wide Be production rate .
The proposed model naturally explains the observed complex line features and removes the difficulties associated with previous interpretations of the data which evoked a very hot thermal component ( kT \sim 7 keV ) .