The ionospheric scale heights derived from the incoherent scatter radar measurements Libo LIU Institute of Geology and Geophysics Chinese Academy of Sciences Beijing, CHINA Email: email@example.com Outline •Ionospheric scale heights Expressions of altitude profile of Ne Definitions of ionospheric scale heights •Incoherent Scatter Radar (ISR) data set •Result & Summary Functions of electron density profiles in the ionosphere Many mathematical functions: Chapman function, exponential, parabolic, Epstein functions, and … are used to describe the altitude profile of Ne. The scale height is evidently a key parameter in these functions to determine the shape of ionospheric Ne profiles. Related studies on ionospheric scale heights (1) Bottomside Scale heights are relatively easy to be deduced from ground-based ionosonde and other measurements [e.g., Huang and Reinisch, 2001; Reinisch and Huang, 2004]. (2) Topside Scale heights are derived from incoherent scatter radars, topside sounders [e.g., Belehaki et al., 2006; Kutiev et al., 2006], and radio occultation measurements [e.g., Stankov and Jakowski, 2006]. Ionospheric scale heights •Plasma scale height (Hp) Hp=kb(Ti+Te)/mig •Vertical scale height (VSH) •Effective scale height (Hm) Strictly speaking, VSH and Hm are virtually the distribution heights of electron density profiles. Fit with Chapman-α profile function O: observed exponential fit linear fit linear fit log10(Ne) (m-3) Figure. An example of ISR altitude profiles of Ne, Ti and Te within half an hour. Data Base Arecibo ISR data (1966-2002), which are archived in the NCAR CEDAR database, are analyzed without specifying the measurement modes. These data have a typical altitude resolution of about 23 km prior to 1985 and 37 km in subsequent years. Median ISR Ne, Te, and Ti profiles are determined within every 30 minute interval in each day. Thus more than 16,000 mean profiles are derived from more than 90,000 raw Ne profiles in the Arecibo ISR database. P=(F107+F107A)/2 8 Arecibo Local Noon 9 Arecibo Local Midnight 10 Geomagnetic activity effects Millstone Hill ISR, October 21 to November 5, 2002. Geomagnetic activity dependences of Hm over Wuhan (midday) [Liu et al., Annales Geophysicae, 2006] Relationship between VSH and Hp Arecibo Hp=kb(Ti+Te)/mig Figure. Diurnal variation of the ratios of VSH to Hp, VSH/Hp. Relationship between VSH and Hp Diffusion effect Thermal gradient [Liu et al., JGR, 2007] Nighttime Daytime Relationship between VSH and Hm Diurnal variation of the ratios of VSH to Hm, VSH/Hm. Arecibo The ratio of VSH to Hm changes from 3.2 at daytime to 2.7 at night. Summary •This investiagtion shows that the topside ionospheric scale heights VSH, Hp and Hm have appreciable diurnal and seasonal variations. •VSH, Hm, and Hp tend to increase with increasing solar flux. •Both the contributions from the topside thermal structure and diffusion processes can greatly influence the ratio of VSH to Hp. Thanks for your attention! Liu L., et al. (2007), An analysis of the scale heights in the lower topside ionosphere based on the Arecibo incoherent scatter radar measurements, J. Geophys. Res., 112, doi:10.1029/2007JA012250.