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

[Justin Kasper]

Back in the day I think we looked and the correlation with temperature
seemed the strongest explanation.  There’s temperature in the housekeeping
data.

On Monday, May 17, 2021, Anthony Case <tonycase at cfa.harvard.edu> wrote:

> 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
>
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>
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>
> 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
>> M/S M2-260
>> P.O. Box 92957
>> Los Angeles, CA 90009-2957
>> Mobile: 310-529-3406
>> Voicemail: 310-336-6302
>>
>> Publications: https://www.loopers.org/curvitae.html
>> <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.loopers.org%2Fcurvitae.html&data=04%7C01%7Cwouter.dewet%40unh.edu%7Cb92713dc10334b5bc51308d91956d196%7Cd6241893512d46dc8d2bbe47e25f5666%7C0%7C0%7C637568683036598949%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=PrZiSAJ%2FSvnA8ZFavlyyMNgB8tdb%2BGMi7Bm469KVmqo%3D&reserved=0>
>>
>>
>>
>> *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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