3. The Draft Model
The proposed ISO draft magnetic field model of the magnetosphere is intended to
satisfy all of the requirements set forth in Section 2. Although this standard
is intended to characterize the inner magnetosphere, the model must also merge
smoothly into magnetic field generated in other regions of Earth's environment
such as the core, the ionosphere, the distant tail, near-magnetopause regions
and interplanetary space. Therefore, the International Geomagnetic Reference
Field (IGRF) model, which describes the magnetic field generated by the
Earth's core and which is produced by International Association of
Geomagnetism and Aeronomy (IAGA) and updated by IAGA every 5 years is included
as part of the proposed magnetospheric model. The total magnetic field is
calculated as a sum of magnetic fields of internal (B1) and magnetospheric
(B2) sources:
A model of the magnetic field generated by field-aligned currents, which
connect the magnetosphere to the ionosphere, is also included as part of the
magnetospheric model, as is a model of the magnetosheath magnetic field which
takes into account the Interplanetary Magnetic Field (IMF) penetration into
the magnetosphere. The model further includes a set of auxiliary physical
models that characterize the magnetic field associated with various current
systems on he magnetopause and within the magnetosphere itself. These include
a model for the fields generated by Chapman-Ferraro currents on the
magnetopause that screen the primarily dipole field of the Earth characterized
by the IGRF model, a model characterizing fields generated by the geomagnetic
tail current system, a model characterizing fields generated by the Ring
Current system, and a model characterizing fields generated by those
magnetopause currents that screen the Ring Current. The overall model is
referred to as the Paraboloid Model A99 (Alexeev 99, described most completely
in [Alexeev et al., 1996; Alexeev and Feldstein, 2001]). In A99 magnetospheric
magnetic field induction Bm is represented in the form:
|
B2=Bsd(y,R1)+Bt(y,R1,R2, F¥)+Br(y,bR)+Bsr(y,R1,bR)+Bfac(I
||) |
where
- Bsd is the magnetic field of Chapman-Ferraro
currents on the magnetopause screening the dipole field;
- Bt is the
geotail current system magnetic field;
- Br is the ring current magnetic
field;
- Bsr is the magnetic field of the magnetopause currents screening the
ring current;
- Bfac is the field of Region 1 field-aligned currents.
The model has as its set of input parameters those listed in section 2, item 6.
All the input parameters depend on empirical data such as Solar Wind data
(which can be taken from the ACE or Wind satellites), Auroral Oval data, and
the AL and Dst magnetic indices computed from various geomagnetic
observatories scattered around the Earth's surface. The different Submodels
may be used to calculate the input parameters. The model user can choose his
own Submodel which describe some input parameter dynamics based on his own data
set. The model magnetic field sources depend on empirical data via input
parameters (model parametrization). Thus, the paraboloid Model consists of
three basic elements: Empirical data, Input Parameters, and the Model itself.
It should be noted that the submodels are not assumed to be
standardization objects since
they are created on the base of physical models. They are subject of
the scientific investigations and can be changed in terms
of the calculation techniques presented in Working Draft.
Three-level structure of the model,
ëxperimental data - the parameters of the magnetospheric
current systems - magnetospheric field", allows flexible taking
into account the structure of the data available, allowing to
provide calculations even for the cases when part of data is absent.
It is possible to use the other models for
R1, R2, br, for example the empirical models of
[Roelof, Sibeck, JGR, 1993, 98, 21421;
Shue et al., JGR, 1997, 102, 9497; Kalegaev, Lyutov, 2000, Adv. Space Res.,
25, 1489] for R1 calculations
via solar wind dynamic pressure and IMF Bz value. Such
approach allows flexible satisfy the user requirements involving
them in the development of the model appropriated for their own needs
and containing their own "physics".
Model is dynamic in the sense that it can function in real-time or near
real-time depending on the availability of the empirical data. It functions
through the full range of geomagnetic activity, from Solar Quiet conditions to
severe magnetic storm conditions, and in the whole magnetosphere. Other
magnetospheric models are commonly limited in their range of applicability with
respect to geomagnetic activity and/or by the region of applicability in space.
3.1 Demonstration of model
Demonstration of model and methods' needs and
opportunities for model development are presented in
Appendix
1 and
Appendix
2.
3.2 The model availability
The model is available at WWW site
http://alpha.sinp.msu.ru/lvm/dynamod.html.