Verification of ionospheric sensors

Abstract

Abstract. Ionospheric products from sensors and models were compared to investigate strengths and limitations of each. Total electron content data from computerized ionospheric tomography (CIT) and TOPEX sensors in the Caribbean region in 1997 were compared to estimates produced by models Parameterized Ionospheric Model (PIM) and Raytrace/ICEDBent-Gallagher (RIBG) and global maps from GPS. A 5 total electron content unit (TECU) bias was observed in TOPEX. CIT and TOPEX confirmed the location and structure of the equatorial anomaly. A GPS map confirmed the location of the anomaly but did not reproduce structure less than 1000 km in latitude and 1500 km in longitude and underestimated TEC by at least 11 TECU or 25%. PIM positioned the anomaly 13 ø equatorward of its observed location and greatly underestimated (-50%) the rise in content over 5ø-25øN range. RIBG overestimated the latitudinal extent of the anomaly and underestimated TEC at the peak by 40%. Additional comparisons were made using CIT and ionosonde sensors at midlatitude during the summer of 1998. Fourteen days of TEC, hmF2, NmF2, and half-thickness comparisons showed reasonable agreement between CIT and ionosonde for TEC and NmF2. The hmF2 and half-thickness comparisons were contaminated by noise, which accounted for a significant portion of the ionospheric variation. Daytime cases where CIT overestimated maximum density were attributed to underestimating layer thickness. Finally, TOPEX and multiple GPS sensors were compared to verify regional ionospheric conditions associated with occurrence of nighttime ionospheric depletions in the Caribbean during Combined Ionospheric Campaigns in June of 1998. From 0300 to 0800 UT on June 26, GPS and TOPEX showed elevated nighttime content over the entire Caribbean region. Vertical TEC approached 25 TECU in some places with interspersed depletions, which in some cases evacuated nearly the entire ionospheric content.

Scientific Investigations Using IDA4D and EMPIRE

“…IDA4D has been well validated [Coker et al, 2001;Watermann et al, 2002; and used in a number of scientific investigations Bust and Mitchell, 2008;Garner et al, 2006;Yin et al, 2006;Mitchell et al, 2005]. IDA4D is an objective analysis data assimilation algorithm based closely on the Navy Research Laboratories meteorological 3DVAR algorithm [Daley and Barker, 2000].…”

“…While validation of IDA4D has been performed [Coker et al, 2001;Watermann et al, 2002], these validations have either been comparisons against independent observations of TEC or case studies with ISRs. Recently, a long term multiple-month statistical analysis was carried out comparing in situ observations of electron density from the CHAMP satellite Plasma Languin Probe (PLP) instrument [Cooke et al, 2003] with IDA4D estimates of electron density that are interpolated in space and time onto the CHAMP observation points.…”

Deducing storm timeFregion ionospheric dynamics from 3-D time-varying imaging

“…IDA4D has been primarily used as a 3‐D electron density imaging algorithm. It has been well validated [e.g., Coker et al , 2001; Watermann et al , 2002] and applied to several scientific investigations, in particular, the investigation of the ionospheric response to major geomagnetic storms [ Bust et al , 2007; Bust and Mitchell , 2008], including the formation and evolution of storm enhanced density (SED).…”

Ionospheric Data Assimilation Three‐Dimensional (IDA3D): A global, multisensor, electron density specification algorithm

“…The horizontal resolution obtainable with CIT arrays can be as small as a few kilometers, while experimental investigations [Watermann et al, 2002;Coker et al, 2001] have demonstrated that the vertical resolution is $20-50 km (limited by the minimum elevation angle). When used in this fashion, CIT represents an inexpensive unique data source that provides high resolution spatial imaging of the ionosphere.…”