Sources of longitudinal variations in the high-middle latitude ionosphere over Eurasia

摘要

In the present study we analyze the relation of longitudinal effects in the mid-latitude and subauroral ionosphere with neutral atmosphere dynamics during quiet and disturbed geomagnetic conditions. Particularly, we analyze the large scale ionospheric effects that are initiated by large scale processes both in strato-mesosphere and in geomagnetic field. Comparing to our previous studies, we focus on processes in winter strato-mesosphere in quiet geomagnetic conditions and on lower thermosphere disturbances generated during the disturbed magnetosphere conditions. The disturbances under consideration are caused by different sources. The first source is active during quiet geomagnetic conditions in winter Northern Hemisphere, it is generated by a jet stream in strato-mesosphere. The difference between critical frequencies for the ionosondes spaced longitudinally by only 15-20 degrees could reach about 1.5-2 MHz, depending on the observation point location as related to the jet stream which usually has the specific zones of upward and downward fluxes. Second process that highly depends on neutral gas dynamics was previously analyzed on the basis of the ionosphere response to the March 2015 severe geomagnetic storm. It was shown that some unexpected longitudinal dynamics of the middle latitude ionosphere arose, while the storm-associated [O]/[N