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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0248

Coronal rain diagnostics - thermal evolution, fine structure & MHD seismology

plan term

@ @


 name : Antolin, Katsukawa, De Pontieu, Okamoto, Kato @  e-mail : patrick.antolin[at]nao.ac.jp

contact person in HINODE team

 name : Katsukawa @  e-mail : yukio.katsukawa[at]nao.ac.jp

 abstract of observational proposal
Objective:  to determine the evolution and structure of thermal instability in loops and perform MHD seismology with coronal rain

Scientific Background:
Coronal rain corresponds to emission in both chromospheric and transition region lines from neutral or partially ionised material occurring in a time scale of minutes along coronal loops. The blobs composing the rain act as tracers of the magnetic field, and have provided insight into the elementary length-scales, field topology and thermal structuring in the solar corona (Schrijver 2001, Antolin & Rouppe van der Voort 2012). It has been difficult however to quantify a coherent length scale over which neighbouring loops will share a common thermodynamic evolution due to the lack of instrument coverage in the chromosphere to transition region temperature range. It is also unclear whether significant braiding or twisting exists, and how thermal instability evolves and produces fine thermal structuring. The difficulty lies in the very fast timescale of the instability and the subsequent fast dynamics of the rain, which requires high temporal, spatial and spectral resolutions for its detection.

The high spatial resolution windows offered by the rain further allows to detect small amplitude transverse  MHD waves in the corona. Both, observations and numerical simulations indicate a relatively high optical thickness and plasma-beta parameter for the coronal rain blobs, implying an interaction with the magnetic field through MHD wave generation/damping. This scenario constitutes a wealth of application for coronal seismology, which has yet to be exploited (Antolin & Verwichte, 2011).

Coordinated observations between IRIS and Hinode allows an excellent temperature coverage of the chromosphere and transition region at high spatial, temporal and spectral resolutions. Such combination represents a unique opportunity to study the evolution of thermal instability in loops and perform MHD seismology with unprecedented detail.

 request to SOT
- Ca II H at a cadence around 10 sec with exposure times long (~1.5s or more)
- Half CCD for higher cadence
- No 2x2 summing for higher spatial resolution
- ROI 3, include both disk and the off-limb regions. At least 80 arcsec off the limb should be visible at all times.
- E or W pointing (Active region)

 request to XRT

 request to EIS
EIS study 434 (VHH_SlowAR_SaS_1h6m), which does a sit and stare, 30 s  exposure time, with the 2 arcsec slit with a slit length of 296 arcsec. Slit should be parallel to limb. Context 40 arcsec slot before / after the sit-and-stare

 other participating instruments
Request to IRIS:
Six different observing modes:

A. Sit-and-stare with 8s exposure times, and both 2796/1400 slit-jaws (for total SJI cadence of ~20s)

B. Sit-and-stare with 8s exposure times, and 1330/1400 slit-jaws

C. Sit-and-stare with 8s exposure times, and 2796/1330 slit-jaws

D. Sit-and-stare with 4s exposure times, and 1330/2796/1400 slit-jaws (SJI cadence of ~18s)

E. Sit-and-stare with 4s exposure times, and 1330/1400 slit-jaws (SJI cadence of ~10s)

F. Two-step raster with 8s exposure times, and 2796/1400 slit-jaws (SJI cadence of ~20s)

These should all have linelist 0, non-simultaneous read-out (OBS-ID > 50) and run for at least 1 hour.

Each program should be run at least three times, for different roll angles so that the slit is perpendicular to the limb, at an angle of ~45 deg and parallel to the limb.

The SJI FOV should include both off-limb and on-disc regions. At least 90 arcsec off the limb should be visible at all times. When parallel to the limb the slit should always be at least 30 arcsec off limb.

Minimum duration of each run should be 1 hour, avoiding SAA; longer runs are desirable when telemetry allows.

The target should be an active region.  Note that the SOT FOV is internally shifted, independent of the usual SOT offset that is well-known to CPs and COs.  THEREFORE, HINODE POINTING (corrected for the usual SOT offset) SHOULD AIM 20-25 ARCSEC INSIDE OF THE LIMB AT THE TARGET POSITION PLANNED FOR IRIS.

The target coordinates could be chosen either by the Hinode or IRIS planners, depending on the phase of the Hinode planning cycle.  If the SAA-free periods are not used, then coordination between the planners to avoid SAA in both spacecraft is necessary.  IRIS SAA-free times are approximately 11-15 UT and 23 - 04 UT.

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