Abstract
AbstractThe temporal change in height of a specific electron density can be used as a proxy for vertical plasma drift (PVPD) at the magnetic equator. The use of PVPDs as a predictor of low‐latitude ionospheric scintillation during the subsequent evening has previously been shown to have forecasting skill when using ionosonde data. The implementation of this approach using a physics‐based model is proposed to provide greater forecast antecedence without the need for local ionosondes. For the first time, the physics‐based model PVPD method is compared to another forecasting approach that uses a physics‐based model to calculate Rayleigh‐Taylor growth rates (RTGRs). In equinoctial test cases considered, when appropriate scintillation observation thresholds are selected, PVPD forecasting is shown to have skill similar to or better than the RTGR method using the same physics‐based model. PVPD forecasting requires only electron densities and corresponding altitudes. Therefore, this approach could be applied using an ionospheric data assimilation model whereas the majority of these models do not provide output for all variables required for RTGR forecasting. The forecasting skill in these test cases, the simplicity of physics‐based PVPD forecasting, and the suitability of this method for use of ionospheric data assimilation model output make this method attractive as a forecasting tool in an operational setting if skill can be further demonstrated for a wide range of conditions. However, both PVPD and RTGR forecasting skill are shown to be limited during solstitial months with high scintillation activity. This may be improved by using a data assimilation model.
Highlights
In the post-sunset low-latitude ionosphere, bubbles or plumes of depleted plasma can rise into regions with higher plasma density causing ionospheric plasma density irregularities (Woodman & La Hoz, 1976)
Yizengaw, et al (2014) showed that, using hourly average S4 values at Vanimo for 56 days in March and April 2000, Rayleigh-Taylor growth rates (RTGRs) forecasting could successfully predict that strong scintillation would occur on 17 days, successfully predict that strong scintillation would not occur on 31 days, predict strong scintillation which did not occur on 3 days, and predict that strong scintillation would not occur on 5 days for which strong scintillation was observed, i.e., whether strong scintillation would or would not occur was correctly predicted on 85.7% of days in the test case
Using the same S4 threshold, proxy for vertical plasma drift (PVPD) forecasting successfully predicted that strong scintillation would occur on 17 days, successfully predicted that strong scintillation would not occur on 29 days, predicted strong scintillation which did not occur on 5 days, and predicted that strong scintillation would not occur on 5 days for which strong scintillation was observed, i.e., whether strong scintillation would or would not occur was correctly predicted on 82.1% of days
Summary
In the post-sunset low-latitude ionosphere, bubbles or plumes of depleted plasma can rise into regions with higher plasma density causing ionospheric plasma density irregularities (Woodman & La Hoz, 1976) Signals passing through these plasma irregularities can undergo rapid fluctuations of amplitude or phase (scintillation) resulting in reduced signal quality (Kintner et al, 2007). At the same time (in the absence of sunlight), the lower ionosphere rapidly decays (through ion-electron recombination), and a steep vertical electron density gradient develops on the bottomside of the raised F layer This produces the necessary configuration for the Rayleigh-Taylor instability in which a heavy fluid is situated above a light fluid. These bubbles, and associated irregularities, can form plume-like structures as they rise through the denser regions above their initial location, extending to altitudes of more than 1,000 km (Woodman & La Hoz, 1976)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
