Abstract
Abstract F-region plasma dynamics has been one of the main foci of the ionospheric research community for decades. The mid-latitude F-region has been considered to be relatively calm; however recent observations using highly sensitive CCD imaging systems and Global Positioning System (GPS) receivers have revealed that mid-latitude F-region mesoscale electrodynamics are more complex and this region is more active than usually assumed. Here we report combined incoherent scatter radar (ISR), imager, and GPS observations of F-region Medium-Scale Traveling Ionospheric Disturbance (MSTID) structures over the Arecibo Observatory in Puerto Rico. In particular, the plasma structures seen in the narrow-beam ISR cannot be understood fully without the all-sky images, which provide the context for the radar results—specifically, the spatial and temporal properties of the mesoscale structure. The GPS-derived total electron content (TEC) data provide additional information on the intensity of the MSTIDs. Here we present analysis of two specific plasma depletion events, which we prefer to call “MSTID bands”. Important results on the 3D geometry of these structures were found using a newly developed observation technique. For the first time, it is shown that the southern part of MSTID bands reaches higher altitudes than the northern part (vertically tilted by 12° towards magnetic south). These results give a much broader perspective on nighttime, mid-latitude F-region structure and point to new ways of interpreting these structures and how they appear in ISR results.
Highlights
The Penn-State All-Sky Imager (PSASI) installed at Arecibo Observatory (AO: 18.3◦N, 66.75◦W, altitude 350 m, L = 1.43 at 300 km, dip angle 46◦, geomagnetic coordinates 31.5◦N, 8◦E) is a high-resolution optical all-sky imager which has been operating since April 2003
Numerical solutions of the Perkins equations for simulation of nighttime F-region electrodynamic processes indicate that the depletion/enhanced structures develop northwestto-southeast aligned “wave fronts” that propagate to the southwest in the northern hemisphere
Considering that the plasma depletion bands have a vertical extent, the MediumScale Traveling Ionospheric Disturbance (MSTID) bands affect total electron content (TEC) results to various degrees depending on the relative orientation of the band and the look angle (Makela et al, 2001a)
Summary
The Penn-State All-Sky Imager (PSASI) installed at Arecibo Observatory (AO: 18.3◦N, 66.75◦W, altitude 350 m, L = 1.43 at 300 km, dip angle 46◦, geomagnetic coordinates 31.5◦N, 8◦E) is a high-resolution optical all-sky imager which has been operating since April 2003. The imager is configured to primarily monitor mesoscale F-region processes using the 180◦ field-of-view (FOV) primary lens and 557.7-nm, 630.0-nm, and 777.4-nm narrowband filters. The all-sky imager data for more than three years is available online (allsky.ee.psu.edu) and is being used to study various ionospheric phenomena. More details on PSASI and all-sky imaging in general are available in Seker et al (2007)
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