[Crater-team] Albedo from slopes; Carmageddon in the Pacific

[Jody Wilson]

Very interesting results, Mark!   The spectral change at the angle 
corresponding to the surface roughness kind of makes intuitive sense; 
looking at the horizon in this case means looking at the tops of hills 
with 15 degree slopes, so we see a spectrum corresponding to 15 degrees 
below the horizon for the flat Moon case.

I think we are NOT having the CRaTER telecon today - Harlan/Sonya please 
correct me if I'm wrong.

-Jody


On 2/20/2019 10:34 AM, Mark D Looper wrote:
>
> Hello—
>
> A landslide Monday took out the main highway from this side of the 
> island to downtown, and as a result traffic on the remaining routes is 
> awful.  Unfortunately, it is no longer feasible for my wife to take 
> both kids to school, and so I am losing half a working day on the road 
> taking one of them in the morning and picking them both up.  (I know 
> people have worse commutes in L.A., but still…)  We hope this will 
> revert to normal next week, but today I may not make it back in time 
> to dial in to the telecon, though I’ll try.
>
> Partly as a result of losing such a big chunk of yesterday, I didn’t 
> quite finish a brief PPTX I wanted to send reporting the results of my 
> calculations of albedo from sloping surfaces.  I attach a couple of 
> figures that will go into it when I finish it later today; these are 
> my usual energy-angle plots for proton albedo produced by all GCRs 
> (solar minimum spectra) from a dry FAN surface.  One is a repeat of 
> the results from a horizontal target surface; the other shows what you 
> get when you (1) tilt the simulation by 15 degrees, (2) discard albedo 
> particles coming out below horizontal or due to primary GCRs coming in 
> from below horizontal in the new coordinate system, and (3) average 
> over all azimuths around the new vertical.  Implicitly, this amounts 
> to the assumptions that the target surface has 15 degrees of slope 
> everywhere, in random azimuths, and that the individual patches that 
> slope in the same azimuthal direction are small compared to the sensor 
> FOV and large compared to the size of the contained GCR showers (about 
> 1 meter, from previous work).
>
> You can see that the strong hardening and intensification of the 
> spectrum near the limb in the 0 degree (horizontal) baseline plot is 
> lost because most of those particles are cut out by step (2) above – 
> only a band going across the slope is left with grazing GCRs coming in 
> and near-horizontal albedo coming out.  The near-vertical albedo (left 
> side of the plot) has a similar distribution but is diluted by the 
> discarding of some primary GCRs, and past the 75 degree zenith angle 
> where the line of sight starts to run into the ground you see the 
> lower, more isotropic fluxes from the more vertical directions in the 
> baseline simulation being averaged over the azimuths that are nearer 
> to horizontal in the tilted simulation.  I have produced, but not 
> quite yet collected into a plot, comparisons of damp (10 cm of 10% H) 
> vs. dry albedo in the same energy/angle bands I showed earlier (Geant4 
> meeting, AGU meeting), for a range of tilts from 0 to 30 degrees; I 
> will send this out in a PPTX later today. I expect that steeper slopes 
> will make everything resemble the near-vertical direction from the 
> original level simulations.
>
> Hope to talk to you on the telecon, but not taking bets—
>
> --Mark Looper
>
> Mark D. Looper
> Space Sciences Department
> The Aerospace Corporation
> M/S M2-260
> P.O. Box 92957
> Los Angeles, CA 90009-2957
> Mobile: 310-529-3406
> Voicemail: 310-336-6302
>
>
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-- 
Jody Wilson
Space Science Center
University of New Hampshire
---
Did you buy $ilver today?

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