Data modeling and assimilation studies with the MU radar
Zhang SR, Fukao S, Oliver WL
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
61 (7): 563-583 MAY 1999


Abstract:
We report initial results of data modeling and assimilation studies for several MU radar experiments. Various inputs to a one-dimensional ionospheric model are adjusted to provide agreement with observation and also to learn the sensitivity of the model to their variations. Certain observations are also used directly in the model to anchor or constrain its behavior. In particular, studies of the electron density from 100 to 500 km altitude in the ionosphere are carried out with the help of a theoretical model of O+, NO+, O-2(+) and N-2(+) densities and MU radar observations of the power, ion-drift and plasma-temperature profiles. Four typical cases are selected to study quantitatively the effects of the (A) perpendicular-north component of the plasma drift (15 December 1986), (B) atmospheric composition (7 October 1986), (C) solar EUV flux (2 August 1989) and (D) upper-boundary O+ density (5 October 1989) on the model N(m)F2, h(m)F2 and N-e profile, as well as on the neutral wind calculation from h(m)F2 and drift data. It is found that the measured Vertical ion drift explains quantitatively well the measured h(m)F2 (particularly at low solar activity) while the model gives a better match with the measured N-e when it uses the h(m)F2-based wind rather than the measured plasma drift. Different model values of the atmospheric O/N-2 ratio and EUV flux and different values of the upper-bound O+ density may modify not only N(m)F2 markedly but also h(m)F2: a lower O/N-2 ratio results in higher h(m)F2; the EUVAC model gives higher h(m)F2 at high solar activity than does the EUV91 model, with a smaller upper-bound O+ density, h(m)F2 is lower by day but little changed by night. We specifically note that the meridional wind needed by the model to reproduce the observed h(m)F2 differed according to how well the model reproduced the observed N(m)F2. The uncertainties in the MSIS86 and EUV model predictions are also discussed. It is found that if the MSIS and EUV91 models are used together. the model gives an N(m)F2 higher than that measured at high solar activity. Thus the O/N-2 ratio needs to be reduced from the MSIS value if EUV91 is used. If EUVAC is used, no large modification is required. At equinox for low solar activity, modeling with either EUV model produces N(m)F2 values lower than those measured, and so the true O/N-2 ratio may be higher than that given by MSIS model. (C) 1999 Elsevier Science Ltd. All rights reserved.

KeyWords Plus:
UPPER-ATMOSPHERE RADAR, PEAK ELECTRON-DENSITY, SOLAR EUV FLUX, MILLSTONE-HILL, MIDLATITUDE IONOSPHERE, GEOMAGNETIC STORMS, MERIDIONAL WINDS, F-LAYER, THERMOSPHERE, MIDDLE

Addresses:
Zhang SR, Kyoto Univ, Ctr Radio Atmospher Sci, Kyoto 6110011, Japan
Kyoto Univ, Ctr Radio Atmospher Sci, Kyoto 6110011, Japan
CAS, Wuhan Inst Phys & Math, Wuhan 430071, Peoples R China
Boston Univ, Dept Elect & Comp Engn, Boston, MA 02215 USA
Boston Univ, Ctr Space Phys, Boston, MA 02215 USA

Publisher:
PERGAMON-ELSEVIER SCIENCE LTD, OXFORD

IDS Number:
226EQ

ISSN:
1364-6826