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HINODE Operation Plan (HOP)

accepted on


 HOP No.

 HOP title

HOP 0418

Joint GREGOR - Solar Orbiter/STIX observations of solar flares

plan term




 name : Battaglia, Podladchikova, Krucker    e-mail : andrea-battaglia[at]ethz.ch,   Elena.Podladchikova[at]pmodwrc.ch,  krucker[at]berkeley.edu

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: The main objective is to investigate the energetics and the effects of the precipitating electrons from the corona toward the lower solar atmosphere during solar flares, by combining spectral measurements through the IR, visible, UV and X-rays. We would like to request co-observations of IRIS and Hinode during our campaign of joint observations between GREGOR and STIX onboard Solar Orbiter.

Scientific Justification: In the standard flare model, the magnetic reconnection that occurs in the corona releases energy in the form of kinetic energy of particles. Herein, guided by the magnetic field lines, previously accelerated electrons travel toward the solar surface and by interacting with the dense chromosphere via Coulomb collisions, they heat the ambient plasma and trigger the production of the impulsive nonthermal bremsstrahlung emission in Hard X-rays (see Fletcher et al., 2011). Consequently, the heated chromospheric plasma expands upward into the flare loops, through the process known as chromospheric evaporation. This process produces enhanced thermal bremsstrahlung emissions in Soft X-rays and in the standard flare model it manifests as a gradual phase. The delay between the impulsive manifestation and the gradual phase that manifests in this scenario is better known as the Neupert effect.

However, generally, two different processes can lead to the chromospheric evaporation. The first one is related to the precipitating electron beam, which, depending on the power, can be distinguished between explosive and gentle. The second process triggering the chromospheric evaporation is due to the conductive energy flux in the absence of electron beams (Battaglia et al., 2015). Observations of different emission lines forming at different altitudes in the chromosphere, combined with STIX imaging and spectroscopy, are needed for unambiguous distinction between the type of energy input causing the evaporation (electron beam or conductive energy input) and its nature (explosive or gentle). With IRIS and Hinode, the purpose is to have a more complete temperature coverage to unambiguously distinct between chromospheric evaporations. Hence, our observation will focus on measuring the evolution of the flare ribbons.

Finally, spectral measurements through IR, visible, and UV of the proposed campaign, will allow us to investigate also the energetics of flares and the influence on the lower atmosphere. Indeed, the spectral shape and its evolution will allow us to deduce the energy that goes into the radiation and then it will be compared to the input energy of accelerated electrons derived from the STIX X-ray observations.

 request to SOT
We would like to request continuous IQUV SP rasters of the active region, centered on the neutral line, where the flare is most likely to occur, in a fast map mode. The FOV depends on the size of the AR (~100‘‘x164‘‘), ideally to be chosen such that the cadence is below 20 minutes.

 request to XRT
384x384 Thin-Be with a 30s - 1 min cadence (if telemetry allows), including a pre-flare buffer sequence. The usual multifilter flare response should be used.

 request to EIS
We would like to request the following study to run: qub_hi-cad_flare_v2 (ID: 530), with the number of rasters to be adjusted to fit within the orbital daylight period. The pointing should be centered with the IRIS pointing.

 other participating instruments
IRIS requests:
- 8 step raster in order to improve the chances to catch the flare ribbons;
- exposure time between 2 to 4 seconds (max. 4 seconds), or according AEC (Automatic Exposure Control)
- SJI: both Si IV 1400 A and Mg II h/k 2796 A will allow us to aligne IRIS with SDO 1600 and GREGOR, and study the flare ribbons. Moreover, this set of filters will help the AEC.
- SJ cadence: default, if possible
- Readout and compression as default for this type of programs
- Flare linelist

Case with very large raster (0.88 Mbit/s)
3660107434  |  Very large coarse 8-step raster 14x175 8s  Si IV   Mg II h/k Deep x 4   |      41.10 |52.99    |      0.88     |  5.1+/-0.1 | 41.1+/-0.0 |  0.0+/-0.0 | 10.3+/-0.1 | 10.2+/-0.1 |  0.0+/-0.0

Low data rate alternative: case with large raster (0.54 Mbit/s)
3660107433  |  Large coarse 8-step raster 14x120 8s Si IV   Mg II h/k Deep x 4 Spati  |      40.97 |32.86    |      0.54     |  5.1+/-0.1 | 41.0+/-0.0 |  0.0+/-0.0 | 10.3+/-0.1 | 10.2+/-0.1 |  0.0+/-0.0

Solar Orbiter/STIX


Dates: ToO program from May 24 to June 4. The purpose is to observe flares together with GREGOR and Solar Orbiter/STIX. The minimum would be to co-observe a flare, ideally several flares are desired.

Time window: Due to weather conditions, GREGOR normally observes between 8:00 to 11:00 UT. Very good seeing at GREGOR most often occurs from 8:00 to 10:00 UT. Since flares are difficult to predict, any interruption may potentially lead to miss some events or part of the events.

Target(s) of interest: During the observation campaign (May 24 to June 4), Solar Orbiter will be approximately 95 degrees away from Earth. This implies that there will be ~85 degrees overlap on the Sun and this overlap is toward the eastern limb (as seen from Earth). Our targets are flares occurring in active regions. The PI of this proposal will contact the planners for the AR of interests.

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