It is generally accepted that scintillation observed on satellite signals that have traversed the ionosphere are caused by electron density inhomogeneities.\u00a0 Because the primary manifestation of scintillation is irregular signal intensity variation statistical measures have been used to characterize scintillation.\u00a0 However, models that characterize scintillation start with phase variations, initially without accompanying intensity variations.\u00a0 Effectively, scintillation starts with a scaling of path-integrated total electron density (TEC).\u00a0 The EM processes that convert the initiating phase structure to intensity and phase scintillation are referred to as a refraction and diffraction, although Maxwell\u2019s equations make no distinction between refraction, diffraction, or even stochastic structure.<\/p>\n
In two companion summaries, Scintillation Theory Revisited<\/em><\/a> and Scintillation Models Revisited<\/em><\/a>, we emphasized scintillation as a complex modulation initiated by the cumulative interaction of the signal with electron density structure.\u00a0 In the absence of stochastic scintillation structure, the signal phase responds directly to TEC.\u00a0 Indeed, major contributions to modeling the state of the ionosphere come from routine or targeted TEC measurements.\u00a0 However, definitive characterizations of ionospheric structure do not go beyond inverse-power-law spatial scale distributions borrowed from turbulence theory.<\/p>\n The complexity of scintillation models that incorporate structure realization generally precludes routine applications.\u00a0 In Structure Characterization Revisited<\/em><\/a>\u00a0we demonstrate a robust efficient back-propagation procedure that provides a definitive characterization of the ionosphere electron density structure causing scintillation.\u00a0 The structure parameters resolve the otherwise ambiguous routine S4, Prms, and ROTI measurements.<\/p>\n However, our preliminary results show that intercepted structure varies among three inverse power-law types, which is difficult to reconcile with simulations based on the convective instability generally believed to be the source of the structure.\u00a0 We suspect the evolution of convective instability structure is influenced by the state of the ionosphere, particularly traveling ionospheric disturbances.\u00a0 These results are presented with the hope that they can be verified and will stimulate definitive structure analysis.<\/p>\n","protected":false},"excerpt":{"rendered":" It is generally accepted that scintillation observed on satellite signals that have traversed the ionosphere are caused by electron density inhomogeneities.\u00a0 Because the primary manifestation of scintillation is irregular signal intensity variation statistical measures have been used to characterize scintillation.\u00a0 … Continue reading