[Crater-team] Interesting Artifacts in CRaTER Data: 6-Month Periodicity in Low LET Fluxes (including a strange anti correlation)

[de Wet, Wouter]

Mark,

Ahh, yes that makes sense! When I cut everything below the peak the 6-month periodicity in the low LET flux data all but disappears.

Thanks for the quick response. It looks like I will need to cut everything below roughly 0.3 keV/micron out of the analysis.

Wouter

From: Mark D Looper <mark.d.looper at aero.org>
Date: Monday, May 17, 2021 at 1:11 PM
To: "de Wet, Wouter" <wouter.dewet at unh.edu>, "crater-team at lists.sr.unh.edu" <crater-team at lists.sr.unh.edu>
Subject: Re: Interesting Artifacts in CRaTER Data: 6-Month Periodicity in Low LET Fluxes (including a strange anti correlation)

Caution - External Email

If I remember correctly, that’s due to thermal noise in the lowest PHA channels, which is periodic because of the differing sun exposure as the orbit changes.  I will see if I can find some plots that I made near the beginning of the mission which showed this.  It is why I discard the lowest PHA channels and never look much below the proton peak – the data are not valid down there.

--Mark

Mark D. Looper
Space Sciences Department
The Aerospace Corporation
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From: Crater-team <crater-team-bounces at lists.sr.unh.edu>
Date: Monday, May 17, 2021 at 7:07 AM
To: crater-team at lists.sr.unh.edu <crater-team at lists.sr.unh.edu>
Subject: [Crater-team] Interesting Artifacts in CRaTER Data: 6-Month Periodicity in Low LET Fluxes (including a strange anti correlation)
All,

While working on the final processing of the observed CRaTER Flux vs. LET data, I have found an interesting artifact.

I have been looking at the Flux vs. LET vs Time data for the entire mission so far.


  *   For the smallest LET values, there seems to be a 6-month periodicity in the observed flux, see the ‘wavy’ red edge in Figure 1 below.
  *   When I divide everything by the flux observed in August 2009, I get the flux ratio shown in Figures 2 and 3 below. When looking at the flux ratio, the 6 month periodicity becomes very clear.
  *   One interesting thing I also notice is that it seems like there is an anti-correlation between the flux in lowest LET bins (< 0.25 keV/micron) and the slightly higher LET bins  (> 0.25 keV/micron).

Has anyone else observed this yet? Any thoughts about what is causing this?

Thanks,
Wouter


Figure 1: Flux vs. LET vs. Time
[cid:image001.png at 01D74B20.7B40A5F0]


Figure 2: Flux Ratio vs. LET vs. Time (3-Dimensioal)

[cid:image002.png at 01D74B20.7B40A5F0]


Figure 3: Flux Ratio vs. LET vs. Time (2-Dimensioal)
[cid:image003.png at 01D74B20.7B40A5F0]
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