Study of Equatorial Ionospheric Irregularities with ROCSAT-1/IPEI Data for Assessment of Impacts of Communication/Navigation System (IV)
Abstract
Monthly variation of global equatorial density irregularity distribution has been obtained with data taken by ROCSAT-1 at the 600 km topside ionosphere from March 1999 to June 2004 during high to moderate solar activity periods. This complete global longitudinal distribution of monthly equatorial density irregularity occurrence variation provides not only the best spatial/temporal distribution existed so far but also fills the large gap of irregularity distribution missing over some Pacific regions where few ground observation is available. The 5-1/2 year result of the monthly occurrence pattern indicates a smooth variation across longitudes contrary to some beliefs that a drastic change in irregularity occurrence pattern can occur across some longitudes in the Pacific. Excellent agreement is noted for the current results with Aarons' conjectured sketch of global scintillation occurrence distributions [1993]. Furthermore, the seasonal/longitudinal (s/l) variations of quiet-time post-sunset vertical drift velocities are found to track closely with the s/l variations of irregularity occurrences except during the September equinox season. Linear regression analysis between the vertical drift velocity and the irregularity occurrence rate has been carried out to study the correlation between the two in seasonal as well as longitudinal variation. The results indicate that the vertical drift velocities at three different longitude regions of different magnetic declinations have good correlations with irregularity occurrences for all seasons. This implies that the vertical drift velocity alone can drive the occurrences of equatorial density irregularities in proportion even though its effectiveness has longitudinal variation.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 31, 2007
- Accession Number
- ADA476176
Entities
People
- Chao H. Liu
- Shin-yi Su
Organizations
- National Central University