HOP 0333

abstract of observational proposal

Main Objective:
ALMA-Hinode-IRIS coordinated observations of several quiet Sun regions to study the center-tolimb variation.

Scientific Justification:
We intend to carry out center-to-limb observations of the quiet Sun with ALMA at two frequencies (100 and 230 GHz) and perform detailed tests of 3D models of the quiet chromosphere. These observations will shed light on the thermal structure of the quiet chromosphere by comparing them with state-of-the-art radiative MHD simulations and simultaneous imaging and spectral observations from Hinode and IRIS. Several spectral lines observed by IRIS are formed at about the same height as the mm continua observed with ALMA, but probe different plasma properties.

Hinode EIS spectral data will provide information about higher layers while Hinode SOT data will provide information about the photosphere. We will assess whether the models can reproduce the observations and in case of discrepancies we will investigate their origin and how the models could be adjusted. The comparison of observations and models will also help us clarify the role of spicules in the limb brightening.

request to SOT

Regular fast maps: 3.8 s for one position (2 cycles, 1.6 s). The maps should be 45''-wide, therefore for 150 positions (0.3'' x 150 = 45'') 9.5 minutes will be required.

Point of contact for SOT: Toshifumi Shimizu (shimizu.toshifumi@isas.jaxa.jp)

request to EIS

EIS Requests:
The study to be used is an_alma_eis_s01v01. Each EIS raster will be 10 minutes in duration. The spacing between exposures will be 3", we will use 40 s exposure time, and the width of the scanned region will be 45''.

Point of contact for EIS: Harry Warren (harry.warren@nrl.navy.mil)

other participating instruments

IRIS Requests:
Bart De Pontieu recommends:
For the time of the 230 GHz observations:
3620254068 | Medium dense 128-step raster 42.2x60 128s Deep x 2 FUV spectrally r | 422.56 | 625.95 | 1.0 | 3.3+/-0.1 | 423+/-0 | 13.2+/-0.0 | 13.2+/-0.0 | 13.2+/-0.0 | 13.2+/-0.0

For the time of the 100 GHz observations:
3640500016 | Medium dense 4-step raster 1x60 4s FUV spectrally rebinned x 4 | 15.92 | 15.32 | 0.7 | 2.0+/-0.1 | 8.0+/-0.0 | 15.9+/-0.0 | 15.9+/-0.0 | 15.9+/-0.0 | 15.9+/-0.0

Different IRIS programs will be executed during the 230 GHz and 100 GHz observations because the cadence of the 100 GHz observations will also be appropriate for the study of weak transient activity. Therefore, it is desirable during that time interval to obtain IRIS data at high cadence, as well.

Additional instrument coordination: ALMA, BBSO

remarks

Dates: The ALMA observations will take place somewhere from March 11 to March 25.

Time window:
We have asked for one 4-hour session of ALMA observations. Solar observing at ALMA in March will take place from 13:30 UT to 19:30 UT. We request synoptics to be shifted before or after our observations. We also request IRIS to not be in eclipse during our observations.

Target(s) of interest:
At both ALMA frequencies, seven regions from disk center to the North Pole will be observed, each one for 10 minutes, with breaks for calibration lasting 3 minutes. The location of these regions will be at $mu=[1.0, 0.9, 0.8, 0.7, 0.5, 0.3, 0.0]$. In the first half of the observing period, the targets will be observed at 230 GHz and in the second half they will be observed at 100 GHz.