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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0446

Flare precursor event observations in coordination with Solar Orbiter and the Swedish Solar Telescope (SST)

plan term


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 name : Battaglia, Collier, Purkhart, Barczynski, Saqri, Harra, Veronig, Krucker @  e-mail : andrea.battaglia[at]fhnw.ch, hannah.collier[at]fhnw.ch, stefan.purkhart[at]uni-graz.at, Krzysztof.Barczynski[at]pmodwrc.ch, jonas.saqri[at]edu.uni-graz.at, Louise.Harra[at]pmodwrc.ch, astrid.veronig[at]uni-graz.at, samuel.krucker[at]fhnw.ch

contact person in HINODE team

 name : Savage, Watanabe, De Pontieu @  e-mail : sabrina.savage[at]nasa.gov, watanabe.tetsuya[at]nao.ac.jp, bdp[at]lmsal.com

 abstract of observational proposal
Main Objective: To investigate plasma diagnostics during flare precursor events.

Scientific Justification: Despite the standard picture describing solar flares can be considered a satisfactory approximation of reality, more sophisticated interpretations are needed in order to explain the observations. For instance, recently, Hudson et al. (2021) reported an unexpected common temperature behavior during the earliest detectable stages of solar flares. By means of GOES/XRS diagnostics, they reported temperatures between 10 and 15 MK. Moreover, by analyzing SDO/AIA images, they suggested that these early hot onset sources are mainly footpoints and low-lying loops that subsequently become parts of the structure of the flare. However, on the one hand, the limited GOES/XRS response does not allow to detect any potential X-ray emission produced by non-thermal bremsstrahlung during these early stages, i.e., flare accelerated electrons colliding with the chromosphere. On the other hand, SDO/AIA alone, due to the broad temperature response of its passbands, does not allow to properly constrain the origin of these hot sources.

In order to have a better temporal description of both temperature and location of these hot sources, X-ray imaging and spectroscopy in a broader temperature range is needed. The X-ray telescope on board Solar Orbiter, STIX, diagnoses and gives imaging information of thermal and non-thermal emission at high cadence for plasma at temperatures from about 8 MK and above. Moreover, the observations provided by XRT will allow us to constrain the high-temperature end of the SDO/AIA DEM, which, in combination with the STIX measurements, allow to clearly disentangle these hot sources in the EUV images provided by AIA.

Once the location of the hot sources is known, we aim to diagnose other plasma conditions and dynamics during the onset interval. High-resolution IRIS observations will allow us to study the emission at cooler temperatures, in particular at temperatures characteristic of the transition region and the chromosphere in such a way, we can analyze the response of the transition region in case of non-thermal emission detected by STIX (i.e., electron beams colliding and heating the chromosphere). Additionally, the plasmaparameters obtained from EIS and IRIS can be compared.

Therefore, for the motivations previously reported, we believe that such a coordination is of fundamental importance in order to shed some light on this matter.

 request to SOT
We would like to request continuous IQUV SP rasters of the active region, centered on the neutral line in a fast map mode. The FOV depends on the size of the AR (~100eex164ee), ideally to be chosen such that the cadence is below 20 minutes.

 request to XRT
We request to run the standard flare program with the highest cadence possible as soon as the flare flag triggers. In order to be able to detect possible flare onset events, before that the flare flag triggers, we would like to request a typical active region program with a cadence of about one minute.

 request to EIS
In order to get sufficiently high cadence, we would request the following study to run:
HH_Flare+AR_180x152 (ID: 461).
The pointing should be centered with the IRIS pointing.

 other participating instruments
IRIS requests:
The goal is to observe the flare dynamics with high cadence in the temperature minimum, chromosphere and transition region (raster +SJI). Zero roll angle (normal setup). The IRIS observation is divided into 2 parts:

PART A (observation repeated by first 80% of the observation time)
-high-data rate:
OBS 3622606133: Large coarse 8-step raster; tracker =ON
Large coarse 8-step raster 14x120 8s C II Si IV Mg II h/k Mg II w s Deep x 4 Spatial x 2, Spectral x 2 FUV spectrally rebinned x 4 SJI cadence 0.5x faster

-low-data rate:
OBSID: 3622606132: Large coarse 8-step raster; tracker =ON
Medium coarse 8-step raster 14x60 8s C II Si IV Mg II h/k Mg II w s Deep x 4 Spatial x 2, Spectral x 2 FUV spectrally rebinned x 4 SJI cadence 0.5x faster

PART B (observation repeated by last 20% of the observation time):
-high-data rate:
-OBSID: 3660259103, tracker =ON
Large sit-and-stare 0.3x120 1s C II Si IV Mg II h/k Deep x 8 FUV spectrally rebinned x 2

-low-data rate:
-OBSID: 3660259102, tracker =ON
Medium sit-and-stare 0.3x60 1s C II Si IV Mg II h/k Deep x 8 FUV spectrally rebinned x 2

Additional instrument coordination:
Swedish Solar Telescope (SST) & Solar Orbiter

Dates: ToO program in coordination with SST and Solar Orbiter from Oct 8 to Oct 17. During this period, Solar Orbiter will be at perihelion. We do not have constraints on the minimum number of observation days during the campaign, but to increase the chance to observe flares, the maximum number of possible days will be highly appreciated. For the proposed observations, it is not necessary to be on consecutive days.

Time window: Good seeing conditions at SST most often occur from 07:30-11:30 UT. If possible, we would appreciate it if the observation can be scheduled within this time range. In case of some particular constraints, please prioritize 08:00-10:00 UT.

Target(s) of interest: Flares, therefore complex active regions. The active regions of interest are located near the eastern limb, since we will coordinate the observing campaign with Solar Orbiter, which will belocated about 90-100 degrees, with respect to the Earth-Sun line, toward the eastern limb.

Previous HOPs:
HOP 0418: no solar flares observed in coordination with Solar Orbiter/STIX

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