Understanding the Diurnal Cycle of Midlatitude Sporadic E. The Role of Metal Atoms

Midlatitude ionosonde observations show that there is a sporadic E (Es) diurnal cycle starts in higher altitudes at sunrise. This property labeled as the “Sporadic sunrise effect.” Given layers are composed of metal ions, effect implies atom solar photoionization could play role variability occurrence. possibility endorsed by Arecibo's incoherent scatter radar observations, showing weak ion lowest and uppermost D region heights appear to live during daytime, apparently coming out nighttime mesospheric layers. The atoms increases abundance ions available for Es layer generation whereas this absent nighttime. can explain why start or intensify all year round activity maximizes sunlit hours, has been reported many satellite radio occultation studies. significance on regular variation went unnoticed, despite existing evidence long time. present paper provides base better physical understanding pronounced 24-hr periodicity intensity places step toward improvement simulation models predictions characteristics.