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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0046

CORE: Synoptic SOT Irradiance Scans

plan term

once per month

@ @


 name : T. Berger @  e-mail : berger[at]lmsal.com

contact person in HINODE team

 name : T. Berger @  e-mail : berger[at]lmsal.com

 abstract of observational proposal
Scientific background:
The total solar irradiance varies by about 0.1% over the course of  
the solar cycle, primarily due to the influence of magnetic  
structures such as sunspots and faculae on the photospheric spectral  
irradiance.  Short-term irradiance variation (on the scale of days-to-
months) is well understood to be due to the balance of sunspots and  
facular areas as they cross the disk. However on the decadal scale of  
the solar cycle, questions remain as to why the irradiance variation  
can lead and/or lag the active region count over the course of the  
cycle. Explanations ranging from changes in the solar diameter in  
response to magnetic flux storage in the convection zone to changes  
in the surface area of the photosphere due to F-mode modulation have  
been put forward. Seeing-free observations of both granulation and  
magnetic flux on a large range of scales are now possible with the  
SOT SP/FG instrument combination. We propose to observe with SOT on a  
regular basis throughout the rise of Cycle 24 in order to better  
understand the variation of irradiance with rising flux levels in the  
photosphere. On 07-March-2007 we performed a test program which  
produced a N-S scan of the central meridian with full SP normal maps  
at 12 positions. In a separate program (08-March-2007) we produced E-
W scans of the +15 and -15 deg. latitude "active region" belts with  
BFI continuum filtergrams and NFI Fe I 630.25 nm magnetograms. Both  
of these programs produced unique data that are not possible to  
obtain from any other visible light solar instrument. If performed on  
a regular basis and ultimately analyzed with the data from the total  
irradiance measurement satellites such as ACRIM and SORCE, these  
observations have the potential to reveal new and important aspects  
of the relation between solar irradiance and magnetic flux emergence  
over the solar cycle.

Measure large-sample statistical granulation properties such as size  
and contrast in three continuum bands along with both line-of-sight  
and vector magnetic field measurements for a variety of disk  
positions over the course of Cycle 24. Ideally we would like to have  
full-disk observations of these properties, but since the SOT field-
of-view is limited, the number of disk positions observed is limited  
to the number of individual pointings that are practical in one  
observing period.

 request to SOT
Method:  perform 2 scan programs on a monthly basis.

Program 1: N-S central meridian scan.  50 arcsecond SP Normal maps
                  at each position in the scan.
All BFI filtergrams and NFI  Fe I 630.25 nm magnetograms at each  

Program 2: E-W activity belt scans. All BFI filtergrams as well as
                  NFI Fe I 630.25 nm magnetograms and H-alpha filtergram

SP: Normal maps of 50" scan width at each N-S meridian scan position.
FG: Irradiance scan program (0x89)

 request to XRT
Thin Al/Poly sub-field readout at each pointing position.

 request to EIS
Large-FOV observations in He I 256 at each pointing position.

 other participating instruments
eventual use of ACRIM and SORCE TIM  
irradiance measurements during analysis phase. No specific requests  
for coordinated operations since these instruments operate continually.

N-S meridian scan requires 12 pointings to cover the solar
       The E-W latitude scans each require 13 pointings.

Program 1: ~13 hours (about 1 hour at each pointing for
                          completion of the SP normal map plus overhead).
Program 2: ~6 hours (about 3 hours for each E-W scan).

Once per month for duration of the mission. Major flare watch
               would  cancel.

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