SOTSP: CORE (HOP0046): Synoptic SOT Irradiance Scans
2009-11-29T11:04:00 to 2009-11-29T11:20:00
Science Goal: CORE (HOP0046): Synoptic SOT Irradiance Scans
Program: Normal map 30 arcsec, Shorter Irradiance: DO NOT MODIFY!
Target: Active Region
xcen=-10 ycen=-733
Instrument: SOTSP
HOP/JOP: 79
Description:
Request to SOT HOP Number 0079 Method: perform 2 scan programs on a monthly basis. Program 1: N-S central meridian scan. 30 arcsecond SP Normal maps at each position in the scan. (SP prog. 0x008a) All BFI continuum plus G-band and Ca I I H-line at each scan position, 4k x 2k 2x2 summed. (FG prog. 0x0261) Program 2: E-W activity belt scans. All BFI continuum plus G-band and Ca I I H-line at each scan position, 4k x 2k 2x2 summed (FG prog. 0x0261) Other Instruments: eventual use of ACRIM and SORCE TIM irradiance measurements during analysis phase. No specific requests for coordinated operations since these instruments operate continually. Scientific Objectives: 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. Objective: 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.
