CONTENTS

Annex 1     
 1     Introduction    
 2     Background    
 3     Prime degradations due to background ionizations       
        3.1     TEC
                  3.1.1     IRI-based method           
                  3.1.2     NeQuick-based method  
                  3.1.3     Model accuracy   
        3.2     Faraday rotation   
        3.3     Group delay         
        3.4     Dispersion
        3.5     TEC rate of change          
 4     Principal degradation due to irregularities         
        4.1     Scintillation          
        4.2     Geographic, equinoctial and solar dependence of scintillations  
        4.3     Ionospheric scintillation model    
        4.4     Instantaneous statistics and spectrum behaviour 
                  4.4.1     Instantaneous statistics   
                  4.4.2     Spectrum behaviour        
        4.5     Geometric consideration  
                  4.5.1     Zenith angle dependence
                  4.5.2     Seasonal-longitudinal dependence         
        4.6     Cumulative statistics        
        4.7     Simultaneous occurrence of ionospheric scintillation and rain fading     
        4.8     Gigahertz scintillation model       
 5     Absorption
        5.1     Auroral absorption           
        5.2     Polar cap absorption         
 6     Summary