Day-to-day variations of migrating semidiurnal tide in the mesosphere and thermosphere

By using a general circulation model, we examine behavior of the migrating semidiurnal tide for solar cycle moderate and geomagnetically quiet conditions. We investigate day-to-day variabilities of the migrating semidiurnal tide in the mesosphere and thermosphere and their relation with the migrating semidiurnal tide generated in the lower atmosphere. The results show that day-to-day variations of the migrating semidiurnal tide are evident from the tropopause to the thermosphere. Fluctuations of the migrating semidiurnal amplitude with periods of 10-12 and 25 days are found at altitudes from 20 to 250km, indicating dynamical coupling between the mesosphere and thermosphere and the lower atmosphere

Day-to-day variations of migrating semidiurnal tide simulated by a general circulation model

By using a general circulation model, we examine behavior of the migrating semidiurnal tide for equinox during solar cycle minimum and geomagnetically quiet conditions. We investigate day-to-day variations of the migrating semidiurnal tide in the mesosphere and thermosphere, and their relation with the migrating semidiurnal tide generated in the lower atmosphere. The results show that day-to-day variations of the migrating semidiurnal tide are evident from the upper troposphere to the thermosphere. Fluctuations of the migrating semidiurnal tide amplitude with periods of 17-18 and 25 days are found at altitudes from 20 to 200 km height, indicating dynamical coupling between the mesosphere and thermosphere and the lower atmosphere

Neutral wind control of the jovian magnetosphere-ionosphere current system

[1] In order to clarify the role of neutral dynamics in the Jovian magnetosphere-ionosphere-thermosphere coupling system, we have developed a new numerical model that includes the effect of neutral dynamics on the coupling current. The model calculates axisymmetric thermospheric dynamics and ion composition by considering fundamental physical and chemical processes. The ionospheric Pedersen current is obtained from the thermospheric and ionospheric parameters. The model simultaneously solves the torque equations of the magnetospheric plasma due to radial currents flowing at the magnetospheric equator, which enables us to update the electric field projected onto the ionosphere and the field-aligned currents (FACs) depending upon the thermospheric dynamics. The self-consistently calculated temperature and ion velocity are consistent with observations. The estimated neutral wind field captures the zonally averaged characteristics in previous three-dimensional models. The energy extracted from the planetary rotation is mainly used for magnetospheric plasma acceleration below 73.5°latitude while consumed in the upper atmosphere, mainly by Joule heating at above 73.5°latitude. The neutral wind dynamics contributes to a reduction in the electric field of 22% compared with the case of neutral rigid corotation. About 90% of this reduction is attributable to neutral winds below the 550-km altitude in the auroral region. The calculated radial current in the equatorial magnetosphere is smaller than observations. This indicates that the enhancement of the background conductance and/or the additional radial current at the outer boundary would be expected to reproduce the observed current. Citation: Tao, C., H. Fujiwara, and Y. Kasaba (2009), Neutral wind control of the Jovian magnetosphere-ionosphere current system