HJC 2022/02/16 by Aki Takeda

1. Introduction

Superflares (1033-1036 erg) can happen on Sun-like stars. Nature paper from Kepler obs.

Stellar and solar flares share a common driving mechanism : mangetic reconnection.

Multi-wavelength observation enables to probe :
Investigate "Sun-as-a-star light curves" : full-Sun integrated transit curves of as listed in Table 1 (NOTE: they are observed as an "almost" isolated structure during disk passage)

using the data from Caveat: applicability of the results to stars limited to Sun-like stars.

2. Data Analysis

2.1 SORCE/TIM

TIM data : 6 hourly mean TSI data, smoothed by filtering out 36hr components.

2.2 SDO/HMI

HMI data : Noise reduction by filter out < 36hr components

2.3 SDO/AIA

AIA synoptic data (Level 1.5), 4x4 binning, 1hr cadence, full-disk integrated signals.
cf. Table 2 and Figure 2.

2.4 Hinode/XRT

XRT data: Al_mesh and Al_poly filter images from the Synoptic Composite Image Archive at MSU.
Within ± 15-min from 6 and 18 UT. Full-disk integrated signals.
[my comments]
- SCIA data are composite images.
- 30 min window is too tight.
- stray light contamination on Al_mesh images.

2.5 GOES/XRS

XRS data: science quality data (Level 2). 1-8Å band 1-min averaged data.

3. Transit Light Curves

3.1 Sunspot AR 12699

Fig. 3 (plots) and Fig. 4 (movie)

3.2 Plage: return of AR 12713

Fig. 5 (plots) and Fig. 6 (movie)

3.3 EFR: AR 12733

Fig. 7 (plots) and Fig. 8 (movie)

4. Detailed Analysis of the Light Curve

4.1 Correlations between UV/EUV light curves and Magnetic flux

4.2 "Dip" and "Shoulder" in visible light curves

Explained using intensity histogram of 400x400" region.

4.3 Mistery of 171Å light curve

Explained from the AIA DEM study: DEM shift to higher temperature.