Magnetic Variability Imposed by the Quasi-16-Day Wave (Q16DW)

Abstract:

It is now well-accepted that vertically-propagating waves from the lower atmosphere exert significant variability on the ionosphere. The first interaction occurs within the so-called “dynamo region” (ca. 100-150 km), where winds, plasma and Earth’s magnetic field interact to generate electric fields and currents. These electric fields map to higher altitudes and impose spatial-temporal variability on the F-region ionospheric plasma. The accompanying dynamo-region electric currents induce ground magnetic perturbations measured by magnetometers distributed over the globe, and thus provide important insights into the nature of this neutral-plasma interaction. For instance, one might ask: what kind of longitude variability is imposed by planetary waves? In this study, we analyze the northward component of geomagnetic solar quiet (Sq) variations in an attempt to identify the zonal wave number content of planetary-wave (PW) signals in the Sq field. Data from five northern-hemisphere mid-latitude ground-based magnetometer stations distributed in longitude around one latitudinal circle are analyzed for the solar minimum period of 2009. The Q16DW and its zonal wave number components 0, ± 1 and ±2 are extracted and form the focus of this particular study. Results are interpreted in terms of the longitude variation of the total Q16DW, its connection with the Q16DW in the neutral atmosphere, and possible influences of the longitude dependence of Earth’s magnetic field.