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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0229

Evolutionary behaviors of small magnetic elements in an active region remnant rushing to the south pole

plan term


@ @


 name : Iida, Shimizu @  e-mail : iida[at]eps.s.u-tokyo.ac.jp

contact person in HINODE team

 name : Iida @  e-mail : iida[at]eps.s.u-tokyo.ac.jp

 abstract of observational proposal
The polarity reversal of polar fields is one of the most important observational targets for better understanding of the solar cycle, i.e., details of the dynamo mechanism. One of observational approaches is to track magnetic flux patches as long as possible and determine how each magnetic flux patch behaves in the high latitude region where the polarity reversal may be on going. In the proposer(Iida)'s dissertation (Iida 2012),  he developed an auto-patch tracking algorithm and continuously tracked a huge amount of magnetic flux patches (1016.5 - 1019 Mx) in Quiet Sun with very long time (~5 days in new year holiday period) series of FG magnetogram observations. He determined how frequently each of four surface behaviors, i.e., splitting, merging, cancellation and emergence, is observed in Quiet Sun. The same analysis would be useful for the high latitude region where the polarity reversal may be on going. Hinode SOT has never acquired such long period series of observations for the high latitude region and this HOP proposal is to acquire such a unique dataset.  

The target region will be an active region remnant rushing to the poles, which induces the polarity reversal at the high latitude. The old-cycle polarity is still dominant in the south pole, but it is expected that the polarity reversal at the south pole will happen within one year. That means that the magnetic behaviors important for the polarity reversal are NOW on-going near the pole-side edge of the active region remnant rushing to the poles.

HOP 81 and HOP 206 have been regularly monitoring the magnetic field at the polar region, but the temporal cadence of SP maps is poor and we cannot investigate how each magnetic patch behave, such as merging and canceling. A long time series of FG magnetograms with a medium cadence will allow us to monitor how they behave. Since a lot of magnetic patches exist on the solar surface, a statistical study with tracing a lot of magnetic patches in high latitude may draw a new insight to the polarity reversal process. The long time series of SDO/HMI magnetograms is also useful for tracking, but it is only for magnetic patches larger than patches resolved with SOT. Magnetic patches experience patch behaviors in the time scale much shorter than 1 hour and a large amount of patch-patch interactions (splitting and canceling) are observed more frequently in smaller magnetic flux elements that can be resolved only with SOT (Iida et al 2012). Thus, high spatial resolution data from SOT has a great advantage over HMI data.

A continuous long-time observation is essential for archiving the purpose. Longer than 2 days. Hopefully 3 days. Also, this April (April 2013, B0 angle still 4-6 deg) would be the last chance for acquiring this kind of unique dataset with Hinode, because the polarity reversal is still on-going at the south pole. North pole in September-October is too late because of its polarity reversal situation.

Our proposed observables and their scientific targets are briefly summarized below, but this unique dataset can be used more extensively for other studies.

1. FG magnetogram - Track behaviors of magnetic patches and determine the frequency of, especially, cancellations

2. FG Dopplergram, EUV spectra and images - Where canceled magnetic flux goes? Submerging or upwarding?

 request to SOT
The most important observables come from SOT. The required data is a series of NaIVDG data, with acquisition of a few SP deep maps during the FG observation. It is noted that a careful consideration may be needed for interpretation of magnetograms taken at the high latitude. For the interpretation, magnetic field vector information from SP maps would be helpful.

Observable - NaIVDG (seq: 0x39d; with Full FoV)
FOV - It depends on the target but 160" x 160" or larger for the statistical analysis. Please include global PIL zone between the approaching negative polarity of AR remnant and positive polarity in the south pole.
Spatial resolution - 2x2 summing
Time cadence - 4 minutes. It can be reduced up to 5 minutes. Longer than 5 minutes is not allowed, for tracking magnetic behaviors properly with the algorithm. Larger FOV is higher priority than higher time cadence.
Telemetry estimate - It depends on the FOV, but the estimate is ~2.5 Gbits/day with 160"x160" (2Kx2K, 2x2 summing), 4 minutes cadence, the pointing at 600" off from disk center.

Observable - Fast (1.6s) mode
FOV - 164"x164", 2x2 summing.
Q factor &#8211; 75
Timing for run - Anytime during this HOP period is acceptable. Please obtain more than one map per day and in SAA free period.
Telemetry - ~250Mbits per one scan

 request to XRT
No request for this specific purpose. But we think the series of XRT data would be useful for studying coronal features at the high-latitude region.

 request to EIS
Slit-scan data is useful rather than slot data, because Doppler information in upper atmosphere is helpful to know the motions and also because high-temporal SDO/AIA images are available.
No specific EIS study number requested. The preferable slit-scan data has a time cadence of less than 30 minutes, which is shorter than the typical time scale of large patch cancellation (30 minutes). The preferable data covers the SOT field of view, but a partial coverage is acceptable. Or, sparse-raster scan is acceptable.

 other participating instruments
SDO/HMI and AIA. Please avoid the period when SDO plans no observations, if such periods exist.

- A continuous long period support is essential. Longer than 2 days. Hopefully 3 days.

- 10 minutes interruption by regular synoptic disk center pointing twice per day is acceptable for this observation.

- Execution in April 2013 (B0 angle still 4-6 deg) is proposed because the polarity reversal is still on-going at the south pole. April 2014 (next year) will be late. North pole in September is also late because of its polarity reversal situation.

- The proposer (Iida) will be a postdoc at ISAS/JAXA from April 2013 and he plans to analyze this dataset as soon as possible. He will attend the daily meeting on site to discuss the target, pointing, and FoV for planning.

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