HOP 0089

abstract of observational proposal

Objectives: 1: To find a chromospheric counter part of the transient horizontal magnetic fields (THMFs) seen on the photosphere (THMF study). 2: To study the dynamics of Alfven waves propagating from photosphere to the corona (Alfven wave study).

Scientific Background:
1. THMF study: Spectro-polarimeter (SP) aboard Hinode found that granular-sized THMFs are ubiquitous all over the solar photosphere (Lites et al. 2008, Orozco Suarez et al. 2007, Centeno et al. 2007, and Ishikawa et al. 2008). Ishikawa and Tsuneta (2008, submitted) point out that the magnetic energy flux, with which THMFs provide the quiet Sun is comparable to total chromospheric energy loss estimated by Withbroe and Noyes (1977), and THMFs could contribute to the chromospheric and coronal heating (e.g., Abbett 2007; Isobe et al. 2008). A direct observation of chromospheric THMFs should be urgently done to understand the possible role of THMFs for the chromospheric and coronal heating. We would like to directly find THMFs on the chromosphere and the photosphere simultaneously. While we detect THMFs by the Hinode SP scans in 630.2 nm and by the NFI magnetograms taken in the Fe I 525.02 nm with a high time cadence less than 60 sec, IBIS performs the spectro-polarimetric observation in the chromospheric lines (eg. Ca II 854.2 nm) with the time cadence same as the Hinode NFI. EIS will complement the observations by making narrow-slot raster scans in transition region and lower corona lines to monitor response in these regions of the overlying atmosphere.

2. Alfven wave study
Fujimura and Tsuneta (2008, in preparation) discovered a propagating Alfven wave in the photosphere. Velocity fluctuation in the coronal loop has been detected by Van Doorsselaere et al. (2008), Mariska et al. (2008), Doschek et al. (2007), Hara et al. (2008)., Taroyan et al. (2008) using EIS. We are interested in the dynamics of Alfven wave propagating from photosphere to the corona. Therefore, we propose to observe magnetic field and velocity fluctuations simultaneously in the photosphere (Hinode SOT/SP), the chromosphere (IBIS, US National Solar Observatory), and the corona (Hinode EIS).
We would like to observe active region at the photosphere with SP, BFI, and NFI. SP performs a repeated scan with high time cadence, which allows us to observe apparent fluctuations of magnetic field and velocity at lower photosphere. IBIS performs a spectro-polarimetric observation in lines suitable for chromospheric diagnostics (e.g. CaII 854.2 nm) EIS will perform a repeated scan with the narrow slit to measure the occurrence and propagation of wave packets through analysis of Doppler velocity fluctuations in the transition region and lower corona.

request to SOT

1. THMF study:
BFI Ca II H:
FOV 55”x111”, 2x2 sum, 30 sec cadence, Q75 -> 130Mbit/1H Gb:
FOV 55”x111”, 2x2 sum, 3min cadence, Q75 -> 56Mbit/1H

NFI
Fe 5250 Sh-less IQUV (-60mA offset):
FOV 50”x81”, 2x2 sum, 30 sec cadence, Q75 -> ~170Mbit/1H

SOT-SP
Fast map, FOV 5"x82" (32 slit pos, 2x2 sum), 60s cadence, 2 side CCDs-> 600Mbit/1H

Note: The offset for NFI should be optimized for the detection of THMFs, and we need a test-run program to decide the suitable offset before the campaign. Our priority is BFI and NFI for the duration which we specified above, and at the beginning of the observation please run SP simultaneously as long as the telemetry permits. When the telemetry is not enough, decrease of the time cadence for BFI Ca and NFI up to 50 sec would also be available.

2. Alfven wave study
BFI/ Ca II H: FOV 55”x111”, 2x2 sum, 1 min cadence, Q75 -> 70 Mbits/hour
G-band: FOV 55”x111”, 2x2 sum, 1 min cadence, Q75 -> 100 Mbits/hour
NFI: Na I D 5896 IV (-160mA offset): FOV 55”x111”, 2x2 sum, 1 min cadence, Q75 -> 60 Mbits/hour

SP: Fast map, FOV 5”x82” (16 slit positions), 1min cadence, Q75-> 600Mbit/hour

Note: SP performs a repeated scan with high time cadence. 1 min’s scan is necessary for us to detect Alfven waves. We would also like to take BFI (CaII and G-band) and NFI (Na I D 5896) images, which are necessary for alignment with IBIS. Duration of the observation should be 1 hour or more. If the program described above reaches the telemetry limitation, decrease the time cadence of FG in all the lines.

request to EIS

Request for EIS:
1. THMF study
Use DRW_QS_THMF (to be verified) 40” slot raster with two slightly overlapping positions. Lines included will be: Mg VI, Mg VII, Si VII, Fe XI, Fe XII (x2), He II and Fe XVI. These include the strongest clean lines for EIS's narrow slot in the transition region. FOV will more than cover SOT FOV: EIS FOV will be 76” x 200”. Cadence is 60 seconds, using JPEG98 compression. Data rate estimate: 66 Mbit/hour.

2. Alfven wave study
Use DRW_Alf_01 (to be verified) Narrow continuous scan with six positions of the 2” slit (10 second exposures), giving FOV of 12”x152”, at relatively high cadence (60 seconds). Pointing centered on the centre of the SOT/SP FOV. Lines included will be: He II, Si VII, Fe XI, Fe XII, Fe XIII, Fe XV and Fe XVI. Fe XII 195 Å is the most frequently used line for EIS wave studies (van Doorsselaere et al., Erdelyi & Taroyan, Mariska et al.). However, as a baseline, we include the Fe XII 186A line (for density-sensitive ratios with 195A), Fe XI and XIII to examine neighbouring temperatures, and Mg VII to probe the transition region. Fe XV and XVI are included for co-alignment with XRT. JPEG98 compression. Data rate estimate: 67 Mbit/hour.

remarks

Time period: Our observation proposal for IBIS was accepted by National Solar Observatory, and we plan to perform the observation with IBIS from November 7 to November 17. We request these 11 consecutive days.

Time window: 15:30-17:30UT. Minimum duration is 2 hours (14UT-16UT) every day.

Target of interest:

1. The target of the THMF study is the quiet Sun at the disk center. However, if we cannot obtain any chromospheric Stokes Q/U signals corresponding to horizontal fields in the quiet Sun, we may go to the limb, where Stokes V signal
more sensitive to weaker line-of-sight magnetic field gives us the information of horizontal fields.

2. We prefer active regions to the quiet Sun for the Alfven wave study. We would like to contain pore in target region, because magnetic structure with life time longer than an hour is preferable for the study. The target region should be far away from the disk center (We would like μ-angle about 60°), because we use the Stokes V to detect transverse fluctuation of magnetic field and velocity.

For Alfven wave study please CT SERVO CYCLE OFF/ON every 1 hour.