Comparison of the measured and modeled electron densities, and electron and ion temperatures in the low-latitude ionosphere during 19-21 March 1988

摘要

We have presented a comparison between the modeled NmF2 andhmF2, and NmF2 and hmF2 which were observed at the equatorial anomaly crestand close to the geomagnetic equator simultaneously by the Akita, Kokubunji,Yamagawa, Okinawa, Chung-Li, Manila, Vanimo, and Darwin ionospheric soundersand by the middle and upper atmosphere (MU) radar at Shigaraki(34.85°N, 136.10°E, Japan) during the 19-21 March 1988geomagnetically quiet time period at moderate solar activity nearapproximately the same geomagnetic meridian of 201°. A comparisonbetween the electron, T_e, and ion, T_i, temperatures measured bythe MU radar and those produced by the model of the ionosphere andplasmasphere is presented for 19-21 March 1988. It is shown that there isa large disagreement between the measured and modeled hmF2 from about07:00 UT to about 11:00 UT if the equatorial ExB drift given byScherliess and Fejer (1999) is used. The required equatorial upward ExB drift is weaker from 03:14 UT to 11:14 UT than that given by Scherliessand Fejer (1999) for the studied time period. The required modification ofthe ExB drift weakens the effect of the fountain in NmF2 bringing themodeled and measured hmF2 and NmF2, into reasonable agreement. The depth ofthe equatorial NmF2 trough in the calculated NmF2 is approximatelyconsistent with the measured depth if the modified equatorial ExB drift is used. It has been found that the north-south asymmetries in theobserved NmF2 and hmF2 about the geomagnetic equator are mainly caused bythe asymmetry in the neutral wind about the geomagnetic equator. In theNorthern Hemisphere, the meridional neutral wind taken from the HWW90 windmodel and the NRLMSISE-00 atomic oxygen density are corrected so that themodel results agree with the ionospheric sounders and MU radar observations.A theory of the primary mechanisms causing the latitude dependence of themorning and evening peaks in T_e is developed. The latitude dependenceof the magnitudes of these peaks in T_e is interpreted in terms ofthe corresponding dependence of the electron density. The relative role ofthe ExB drift and the plasma drift caused by the neutral wind in theformation and the dependence of the magnitudes of the morning andevening electron temperature peaks on the geomagnetic latitude is studied.