The Solar Particle Acceleration Radiation and Kinetics (SPARK) Mission Concept

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This  paper present a mission concept of SPARK,  which have three payloads  such as LISSAN, FOXSI and SISA to detect the solar emissions as gama-rays, X-rays, and EUV regimes. This paper gives a good presentataion about SPARK in detail. And SPARK's observations will help to understand the particle acceleration mechanism during the solar eruption. I recommend this paper to be published in this journal as present form. 

Author Response

We thank the reviewer for spending the time to read over our article, and for their general support of the SPARK mission.  We appreciate that they were happy with the article in the present form.

Reviewer 2 Report

Comments and Suggestions for Authors

This paper proposes the concept and features of a new solar mission designed to study impulsive solar events and structures with particle acceleration. The scientific questions are extensively described and the concept of the instruments is clear. I recommend publication of this paper, which would support the mission in this phase. 

A few suggestions are listed in the following:

Sec.1: "current EUV imaging spectrographs (e.g.  Hinode/EIS [23] and Solar Orbiter/SPICE [24]) have provided intriguing images of the complex  structures associated with solar eruptive events but they have not been optimised for studying them." The authors might consider that approved MUSE and Solar-C/EUVST instruments will fill this gap.

Sec.1.2.2: Short-period oscillations of debated origin should not be confused with longer-period ones probably due to MHD waves

Sec.1.2.3: "SPARK will examine the coronal magnetic field strength" and Sec.1.4.2: "SPARK will also provide measurements of magnetic field strengths in active region loops, using the magnetically induced transition at 257.3 Å" Some more details would be appropriate.

Sec.2.1: missing information "(add reference 332 to LISSAN paper here)"

Sec.2.3: missing information "(add reference to SISA paper here)" 

Sec.2.3: "integral field spectrograph (IFS)": any reference?

Comments on the Quality of English Language

The quality of English is good, with a few minor issues below:

Sec.2.2: phrasing between lines 367-374 looks like a telegram and should be improved

Sec.1: acheived

Author Response

We thank the reviewer for spending the time to read through our article and providing some feedback.  We are pleased to hear their positive comments about the article.  Below we address their comments individually.

 

This paper proposes the concept and features of a new solar mission designed to study impulsive solar events and structures with particle acceleration. The scientific questions are extensively described and the concept of the instruments is clear. I recommend publication of this paper, which would support the mission in this phase. 

A few suggestions are listed in the following:

Sec.1: "current EUV imaging spectrographs (e.g.  Hinode/EIS [23] and Solar Orbiter/SPICE [24]) have provided intriguing images of the complex  structures associated with solar eruptive events but they have not been optimised for studying them." The authors might consider that approved MUSE and Solar-C/EUVST instruments will fill this gap.

 

Reply: We agree that MUSE and Solar-C/EUVST will help to fill this gap.  We have added the following text at the end of the paragraph to address this issue:

" The Solar-C Extreme-UV High-throughput Solar Telescope \citep[EUVST;][]{Shimizu2020} and Multi-Slit Solar Explorer \citep[MUSE;][]{DePontieu2020,DePontieu2022,Cheung2022} are highly complementary upcoming EUV missions %that %explicitly target solar eruptive events, and 
which will be transformative for flare science \citep{Cheung2022}. MUSE will provide high-cadence active region-scale imaging spectroscopy, sampling select key EUV lines by rastering its 35 slits. EUVST, with its single slit, will provide much broader temperature coverage with rich plasma diagnostics from a large number of lines. Both instruments are scheduled to launch within one year of each other and promise co-spatial observations of plasma in the solar atmosphere.  An instrument that would build upon their science legacy, one that co-observes with X-ray and $\textgamma$-ray instruments, should be the aim of a next-generation flare mission. That is, an instrument that combines rich plasma diagnostics with very high-cadence 2D spectral imaging."

 

Sec.1.2.2: Short-period oscillations of debated origin should not be confused with longer-period ones probably due to MHD waves

 

Reply: We have modified the text in this section to address the issue

 However, despite extensive research, the origins of these short-timescale modulations in flare emissions remain debated. While some studies suggest they may be a direct signature of a repetitive impulsive energy release process, the potential role of magnetohydrodynamic (MHD) oscillations in the flaring site or nearby, particularly in the context of longer-period pulsations, has yet to be fully determined. Similarly, a combination of these processes indeed could be at play (see \cite{Zimovets:2021} for an overview of proposed mechanisms). Moreover, it is quite likely that different classes of flaring pulsations (i.e. different periods, patterns, energies) are produced by different mechanisms.

 

Sec.1.2.3: "SPARK will examine the coronal magnetic field strength" and Sec.1.4.2: "SPARK will also provide measurements of magnetic field strengths in active region loops, using the magnetically induced transition at 257.3 Å" Some more details would be appropriate.

 

Reply: The science case sections were not intended to provide the justification of the different methods.  We had left that to the individual payload sections.  We have added a reference to the SISA payload section in 1.2.3 and we have added modified the text regarding the coronal magnetic field in section 2.3 as follows:

This wavelength range includes lines sensitive to coronal magnetic field strength \citep[Fe X 25.7 nm, see e.g.][] {DelZanna:Mason:2018,Landi:2020,Brooks:2021} that can be deduced using a ratio of magnetically sensitive Fe X lines, formed at 1 MK. 

 

Sec.2.1: missing information "(add reference 332 to LISSAN paper here)"

Reply: We have added the LISSAN reference

 

Sec.2.3: missing information "(add reference to SISA paper here)" 

Reply: Given that the SISA paper has not been published yet, we have removed this reference

 

Sec.2.3: "integral field spectrograph (IFS)": any reference?

Reply: We have added a reference to "Basic principles of integral field spectroscopy" by  Jeremy Allington-Smith

 

Comments on the Quality of English Language

The quality of English is good, with a few minor issues below:

Sec.2.2: phrasing between lines 367-374 looks like a telegram and should be improved

 

Reply:  We have rephrased the sentences as follows:

FOXSI will be able to reliably image faint thermal and non-thermal sources in the solar corona, even in the presence of brighter ones, for the first time.  Such images will enable FOXSI to elucidate a ground-breaking new understanding of particle acceleration and the evolution of solar eruptive events.  FOXSI will not intrinsically integrate images over preset time or energy intervals but instead records the energy, position and arrival time of individual photons, allowing images and spectra to be produced ex-post-facto in accordance with specific science goals.

 

Sec.1: acheived

Reply: Thanks, corrected