Comparison of Anyang digisonde NmF2 and hmF2 with IRI-2007 model

Abstract

The Total Electron Content (TEC) which make GPS signal time delay in ionosphere is important to determine the GPS range error correction. The GPS users calculate TEC with ionospheric models in which the fixed ionospheric pierce point (hmF2) and NmF2 are used as important parameters. We analyzed the NmF2 and hmF2 data measured in Anyang digisonde station which is located in 37.4N, 127.0E and the geomagnetic latitude is 27.7N from April 1998 through April 2008, covers almost one solar cycle. For the variation with solar activity, we divided Anyang data for low, moderate, high geomagnetic activity conditions for each month in the 1 hour local time bin. While the NmF2 and hmF2 variations have linear relationship with F10.7, the NmF2 pattern in summer differs from other seasons. While the NmF2 calculated from IRI-2007 follows well with digisonde data except high solar activity condition, the IRI hmF2 shows large discrepancy with Anyang data. For the local time and seasonal variation, we sorted our data into 9 combined cases of solar and geomagnetic activity conditions. Local time variations of the NmF2 show the typical diurnal variation with the peak appearing at 12 &#8211

&#8211

16 LT except in summer. The hmF2 show the similar semi-diurnal variation for all cases with the 100 km variation in a day. For the seasonal variation, Anyang data show the semi-annual and winter anomaly of NmF2 and semi-annual anomaly of hmF2 and IRI model show the discrepancy with measurements in hmF2 rather than NmF2 especially in high solar activity conditions. We expect our research will contribute to the construction of an improved ionospheric model over Korean peninsula and Asian mid-latitude.