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

[Anthony Case]

I concur with the previous statements about this likely being thermal.  At
least that's what we decided last time we discovered this feature.
Does anybody have an easy way to plot temperature(s) over the course of the
entire mission?  That'd be a nice confirmation.

Tony


---------------------------------------------------------------------

Anthony Case

Astrophysicist

High Energy Astrophysics Division (HEAD/SSXG)

Center for Astrophysics | Harvard & Smithsonian

Cell: (617) 304 0768

60 Garden Street | MS 58 | Cambridge, MA 02138


On Mon, May 17, 2021 at 1:43 PM Jody Wilson <jkwilson at guero.sr.unh.edu>
wrote:

> There was also a 6-month periodicity in the old proton swoosh summation,
> and there's a 6-month periodicity in the SEPI components (individual
> detectors, Andrew is investigating this further) that is indistinguishable
> from a longitudinal variation.  Mark's explanation may be the reason for
> all of these - I just wanted to point out that 6-month periodicities have
> shown up before.
>
> -Jody
>
>
> On 5/17/2021 1:28 PM, de Wet, Wouter wrote:
>
> 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> <mark.d.looper at aero.org>
> *Date: *Monday, May 17, 2021 at 1:11 PM
> *To: *"de Wet, Wouter" <wouter.dewet at unh.edu> <wouter.dewet at unh.edu>,
> "crater-team at lists.sr.unh.edu" <crater-team at lists.sr.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>
> <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>
> <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
>
>
>
>
>
> Figure 2: Flux Ratio vs. LET vs. Time (3-Dimensioal)
>
>
>
>
>
>
>
> Figure 3: Flux Ratio vs. LET vs. Time (2-Dimensioal)
>
>
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