| Calculation Mode, Area, Granularity: |
Parameter Notes: |
| Satstress run mode: |
|
- snapshot: calculates the stresses at a single instant.
- max_tens: records the largest tensile (or least compressive) stress experienced
by each point on the surface over the course of an orbit.
- max_comp: records the largest compressive (or least tensile) stress experienced
by each point on the surface over the course of an orbit.
- failure: records the "first" time each point on the surface exceeds a certain
threshold stress (the tensile strength of the ice, set below). Results will vary depending
on where in the orbit you start your run. If you choose too high of a tensile strength, you
may get a null result, since it's possible that nowhere on the surface ever experiences a
stress as high as your threshold.
- onepoint: outputs a time series of the stresses experienced at a single point on the
surface. Choose the co-latitude of the calculation by setting θmin and
θmax to the same value, and similarly choose the east positive longitude of the
calculation by setting φmin and φmax to the same value.
|
| Orbital spacing of calculations: |
° |
Controls the temporal resolution of the calculation. The smaller this number is the more computationally
intensive the calculation is. Ignored in snapshot mode. |
| Geographic spacing of calculations: |
° |
Controls both the latitudinal and longitudinal resolution of the grid of calculations. If you're planning
using your output to make a vector plot, 10° or even 15° is good (if the calculation is global).
For scalar plots, 5° will give you a decent idea of what the field looks like, and 1° is good for
publication (again, for global calculations). |
| Initial location of satellite in orbit: |
° |
For those modes which do calculations at a variety of orbital locations, this determines where in the
orbit the calculation is started. In snapshot mode, this determines where in the orbit that one
calculation is done. Zero is defined as periapse. |
| θmin: |
° |
These parameters define the geographic bounds of your calculation.
θ represents co-latitude, that is, the angle southward from the north pole.
Thus, θmin is the northern bound of your calculation window and
θmax is the southern bound of your calculation window. θ values
must be between 0° and 180°
φ represents east-positive longitude, so φmin is the western boundary
of your calculation window, and φmax is the eastern boundary. φ values can
be positive or negative, but must be no more than 360° apart from each other.
|
| θmax: |
° |
| φmin: |
° |
| φmax: |
° |
| Planet and Satellite: |
Parameter Notes: |
| Mass of parent planet: |
[kg] |
|
| Mass of satellite: |
[kg] |
|
| Radius of the satellite: |
[m] |
|
| Semi-major axis of the satellite's orbit: |
[m] |
|
| Eccentricity of the satellite's orbit |
|
Because only the first order terms in e were used in the expansion of the gravitational
potential, the math underlying the model is only valid when e is small. Eccentricities greater
than 0.25 will result in substantial errors. |
| Non-synchronous rotation (NSR) period: |
[years] |
Length of time it takes for the (decoupled) ice shell to undergo one
complete rotation relative to the tidally locked core. Ojakangas and
Stevenson (1986) calculate that this should be on the same order as the
thermal diffusion timescale for the ice shell. This value should not be
greater than about 109 years since if gamma
(Pforcing/Trelaxation) becomes too large, the Love
number code breaks down, as it is not intended to deal with truly "fluid"
behavior. |
| Degrees of NSR the shell has undergone: |
° |
In the Melosh et al. "flattening" method, this parameter is required to
specify how many degrees of rotation the shell has undergone from an
initial, unstressed, orientation. In that model as the shell rotates, and
deforms to maintain Europa's figure, it is effectively acting like an
elastic spring, and storing stresses. The flattening model assumes that
there are some stresses initially (due to the formation of the bulge),
which must be subtracted from the final stresses (since in reality those
stresses would have relaxed away already).
In the potential based method, however, the magnitude and pattern of the
NSR stresses are independent of the amount of shell rotation that has taken
place (even in the elastic case) and this parameter acts only to shift the
position of the stress pattern longitudinally. |
| Material Properties: |
Parameter Notes: |
| Ice Rheology to use: |
elastic solid
maxwell solid
|
The Elastic solid rheology is unrealistic for any ice shell of
significant thickness, and its use is deprecated. It is provided for
comparison with previous elastic models. At present, if you specify the
elastic rheology, you must also provide your own elastic Love
numbers below.
The Maxwell solid rheology is the simplest viscoelastic
rheology, equivalent to a spring and dashpot in series. It allows
relaxation of stresses over time periods greater than the relaxation time
of the material in question.
Note that the viscoelastic model reproduces the elastic stresses well
for sufficiently high upper ice shell viscosities, and sufficiently short
NSR rotation periods (i.e. when ICE_UPPER_DELTA < 1.0)
|
| Density of ice: |
[kg/m3] |
|
| Viscosity of upper ice layer: |
[Pa sec] |
The viscosity of the upper ice layer is generally assumed to be higher (since this ice is
colder) than the lower layer. |
| Viscosity of lower ice layer: |
[Pa sec] |
| Tensile strength of ice: |
[Pa] |
Required only for tensile failure mode. |
| Shear modulus of ice (μice): |
[Pa] |
There are many elastic moduli that can be used to describe a material's elastic response. If you are more familiar with others such as:
you can easily calculate the equivalent shear and bulk moduli using the conversion table at the bottom of the
elastic modulus article at Wikipedia. All of the above
will be calculated and written to the diagnostic output for your convenience. |
| Bulk modulus of ice (κice): |
[Pa] |
| Shear modulus of silicate core (μcore): |
[Pa] |
| Bulk modulus of silicate core (κcore): |
[Pa] |
| Bulk modulus of ocean (κocean): |
[Pa] |
|
| Density of ocean: |
[kg/m3] |
|
| Satellite Internal Structure: |
Parameter Notes: |
| Thickness of the upper portion of the ice shell: |
[m] |
|
| Thickness of the lower portion of the ice shell: |
[m] |
|
| Global ocean: |
Yes
No |
Currently the model only works when the satellite has a global, decoupling ocean. |
| Depth of ocean: |
[m] |
This is the distance from the bottom of the solid ice shell to the surface of the rocky (or possibly icy)
interior. |
| Love Numbers: |
Parameter Notes: |
| H(Re, D) |
|
If you have your own Love number code, you can enter the Love numbers H
and L here explicitly. Subscript "Re" and "Im" indicate the real and
imaginary parts of the complex (frequency dependent) Love numbers.
Subscript "D" and "N" indicate which numbers pertain to diurnal and NSR
forcing periods. All Love numbers are degree 2.
If you elect to use your own Love numbers, you must provide non-zero
values for all of the fields at left. Also, note that if you use your own
Love numbers, then the values of the parameters (ice shell thickness,
viscosities, etc) entered elsewhere on this form, and listed in the
input/output files, which would have gone into calculating them
using our code, will not necessarily pertain to your calculation. |
| H(Im, D) |
|
| L(Re, D) |
|
| L(Im, D) |
|
| H(Re, N) |
|
| H(Im, N) |
|
| L(Re, N) |
|
| L(Im, N) |
|
| Helastic |
|
Alternatively, if you are using the (deprecated) elastic rheology, you may provide elastic Love numbers explicitly here. |
| Lelastic |
|
| Output: |
Parameter Notes: |
| Stress principal components: |
|
In this output mode, the stresses at each gridpoint are diagonalized
into their principal components, and output as a magnitude, and a unit
vector describing the direction. Both the most tensile, and least tensile
stresses are output. The θ (co-latitudinal) component of the
unit vectors is south positive, and the φ (longitudinal)
component of the unit vectors is east positive. This output allows
for easy plotting of σ1 and σ3.
|
| Undiagonalized stress tensor: |
|
Alternatively, you may output the undiagonalized stress tensor, which
describes the stresses with only three numbers at each gridpoint,
τθθ, τφφ, and
τθφ (= τφθ), the
co-latitudinal, longitudinal, and deviatoric components of the stress. |
|