Sorry! This was written in 1995,

but it has been developed a lot since that.

Contact me for recent information about the model

but it has been developed a lot since that.

Contact me for recent information about the model

AIMM: Assimilative Ionospheric Model for Mid-latitudes## Principle:

The electron density and ion species O+, NO+, O2+ and N2+ are obtained numerically by solving the equations of continuity for all 4 ions and of momentum for O+. 21 chemical reactions are involved, with stable as well as meta-stable O+ considered. EUV91/EUVAC, MSIS86, HWM90/HWMMU and IRI95/Millstone Models are adopted in order to determine the background solar radiation flux and neutral composition, temperature and wind. Observed foF2 may be used to fit the simulated profile to the observed point at F2 peak.## Inputs:

geophysical location (for mid-latitudes), date of year, solar 10.7cm flux, Ap index, electron density at 500km (users can select Millstone Hill model, IRI95 values or observed foF2).## Output:

number density for electron as well as O+, NO+, O2+ and N2+, total contents within 100-500km and below the F2 peak, with the minimum time interval of 5 minutes for 24 hours, and minimum height interval of 2 km## Online Computations

Click here: http://www.haystack.edu/madrigal/Models/mim_form.html## For Ionospheric Data Assimilations (This part is NEW !)

It solves the O+ diffusion equation, derived from the continuity and the momentum equations of O+, and the mass continuity equation for NO+, O2+ and N2+ to compute Ne over 100--500 km altitude. The lower boundary is assumed to be in photochemical equilibrium. The upper boundary density is set to the measured electron density. Plasma temperatures are set to measured values. Photoelectron impact is considered with a formula for the ratio of secondary production to photoionization as given by Richards and Torr [1988]. We allow for the effects of vibrationally excited N2 by using the rate coefficient for the reaction of O+ with N2 as expressed by Buonsanto} [1995]. We use an empirical model of meridional ion drifts perpendicular to the geomagnetic field [ Zhang et al., 2000] to allow for the ExB drift contribution to the ion vertical motion. We use the MU radar wind climatology developed by Kawamura et al. [2000] to represent the values of the meridional wind used in the model. The neutral concentration and temperature are given by MSIS86 [Hedin, 1987] and the solar flux by EUVAC [Richards et al., 1994]. We modify each of these parameters, one or two or three at a time, for best fit between model and data. Our assimilation system also estimates the correlation coefficient if there are more than one variable being fitted. This helps examine the uniquness of the derived variables.

Zhang S-R, Xin-yu Huang, Yuan-zhi Su and S. M. Radicella, A Physical Model for One-dimensional and Time- dependent Ionosphere, Part I. Description of the Model, Annali di Geofisica, Vol 36, N.5-6, 1993 Zhang S-R and Huang, A numerical study of ionospheric profiles at midlatitudes Ann. Geophysocae, 13, 551-557,1995 Zhang S. R., S. Fukao and W. L. Oliver, Data modeling and assimilation studies with the MU radar J. Atmos. Solar-Terr. Phys., 61, 563-583, 1999 Zhang, S.-R., W. L. Oliver, S. Fukao, Y. Otsuka, A study of the forenoon ionospheric F2-layer behavior over the middle and upper atmospheric radar, J. Geophys. Res., 105, 15,823-15,833, 2000 Zhang, S.-R., W. L. Oliver, S. Fukao, S. Kawamura, Extraction of Solar and Thermospheric Information from the Ionospheric Electron Density Profile, J. Geophys. Res., 106, 12,821-12,836, 2001

Those interested users may contact the model author at the address below:

Dr. Shunrong Zhang MIT Haystack Observatory Route 40, Westford, MA 01886 Email: shunrong@haystack.mit.edu