1

The Coupled Magnetosphere-Ionosphere-Thermosphere Model, v.

2.0:Ionospheric Electrodynamics

Stan Solomon, Alan Burns, Jiuhou Lei, Astrid Maute, Art Richmond, Wenbin Wang, Mike Wiltberger, and Janet Zeng

High Altitude Observatory

National Center for Atmospheric Research

CISM Advisory Council Meeting • Boston University • 12 March 2007

2

CMIT v. 1.1

TING

E

LFM

Magnetosphere -Ionosphere Coupler

Jll, np,Tp

Conductivities:p

h,

Winds: Jw

PJll

-JwParticle precipitation:

Fe, E0

Electric Potential:tot

CMIT 1.0 (no Jw feedback)

delivered to CCMC

3

CMIT v. 2.0

TIE-GCM

E

LFM

Magnetosphere -Ionosphere Coupler

Jll, np,Tp

Conductivities:p

h,

Winds: Jw

PJll

-JwParticle precipitation:

Fe, E0

Electric Potential:tot

GSWMNeutral wind feedback standardIntercomm coupling standard

4

How is TIE-GCM different from TING?

Physical Differences:

TIE-GCM calculates the low-latitude electric field using the modeled neutral winds

Apex magnetic coordinate system employed (based on IGRF)

(TIGCM and TING used dipole magnetic field and empirical electric field)

TIE-GCM can use a lower boundary tidal specification from the GSWM

(Global Scale Wave Model)

TIE-GCM has a new solar ionization method and improved photochemistry

…and can be driven using measured solar EUV irradiance

TIE-GCM has improved validation with neutral density and ionospheric data

…a work in progress

Numerical Differences:

TING is a serial code

TIE-GCM is a MPI code with 2-D decomposition in geographic latitude, longitude

…but, the dynamo potential solver is in mag. coordinates, and still serial

Input/output files standardized in netCDF, graphics/analysis packages, etc.

High-resolution (2.5° x 2.5° x H/4) version in the works

5

Neutral Density Modeling using Measured Solar EUV

MSIS-00 TIE-GCM

mean 1.03 0.99

STD 0.22 0.15

6

Use of Solar Measurements Eliminates Solar Cycle Bias

7

Schematic Representation of Ionospheric Currents

8

Low-Latitude Dynamo Creates the Appleton Anomaly

a.k.a., equatorial ionization anomaly, intertropical arcs, tropical nightglow, etc.

9

Calculation of the Global Ionospheric Electric Potential

//)()( JJBuEbBuEJ MHP

Basic assumptions:Steady-state, electrostatic electric fieldNo electric field along magnetic field linesCurrent density in divergence-free

current density wind-driven “dynamo”

terms

magnetospheric term field-aligned

current

[ ˜ m ] R ˜ K m

s

m

(cosm

˜ K ms )

m

R2 cosmJmr

This results in the potential equation, which is solved for high latitudes in the M-I coupling module:

conductance field-line integral

wind-driven current field-line integrals

We would like to solve this equation at all latitudes, however, there are two problems:

The dynamo solver is hemispherically symmetric, but Jmr is notWe don’t yet have a full description of the region-2 current system

10

p[ ˜ ] (1 p) pR ˜ K m

s

m

(cosm

˜ K ms )

m

(1 p)m

Calculation of the Global Ionospheric Electric Potential

In CMIT 2.0, these difficulties are circumvented using the same approach used to combine an empirical or assimilated high-latitude potential with the TIE-GCM low-latitude dynamo:

global potential

mean high-latitude potential

p is a cross-over parameter: p=1 below magnetic latitude 60° and p=0 above 75°.

Using this formulation, we are getting a “partially shielded” low-latitude ionosphere that allows some penetration electric fields, but neglects the time-dependent aspect because there is no explicit region-2 current system.

When coupled with the LFM, we get a little more shielding, since the LFM does contain weak region-2 currents.

11

TIE-GCM Calculation of F2-Region Electron Density

12

Comparison with Ionospheric Measurements by COSMIC

Jiuhou Lei et al., “Comparison of COSMIC ionospheric measurements with ground-based observations and model predictions: preliminary results,” J. Geophys. Res., in press, 2007.

13

CMIT 2.0 Example — April 2004 CAWSES Campaign

14

CMIT 2.0 Example — April 2004 CAWSES Campaign

15

Equatorial Vertical Drift — Comparison with Jicamarca Data

Vertical Drift (m/s)

Vertical Drift (m/s)

16

Neutral Composition — Comparison with TIMED Data

17

Next Steps in the Development of a Global Potential Solver

Instead of using an applied potential at high latitudes and the cross-over function, apply magnetospheric field-aligned currents directly to the solver:

[ ˜ m ] R ˜ K m

s

m

(cosm

˜ K ms )

m

R2 cosmJmr

low latitudes

high lat. boundary

NH

SH symmetric

high latitudes

low lat. boundary

NH

low lat. boundary

SH

+

NH

SH

=

54

-54

interface

interface

equator

mag. latitude

-90

90

mag. longitude

-180 180

Then, solve the three regions separately, and iterate between solutions to obtain convergence at the two interfaces:

global potential

18

Next Steps in the Development of a Global Potential Solver

We have implemented and tested this iterative dynamo solver, but only for individual time-steps — it is not yet part of CMIT.

For this to work effectively, we need:

• Improved description of time-dependent region-2 current system

Complete integration of RCM into CMIT

• Improved efficiency of dynamo routine

Parallelize field-line integral calculations

Parallelize elliptical solver routine