SOLAR-C Mission Saku Tsuneta (NAOJ) International ISAS/JAXA SOLAR-C WG

Hinotori/ASTRO-A （ 1981–1982 ） Yohkoh/SOLAR-A （ ） Hinode/SOLAR-B （ 2006– ） SOLAR-C Systems approach to understand solar and heliospheric magnetic activities and to develop algorithm for activity prediction Solar flare observations in X & γ-rays Hard X-ray Flares & soft X-ray corona Photospheric magnetic fields Solar physics from space in Japan 188kg 390kg 900kg Open issues in solar physics Fundamental plasma processes (SOLARC) Chromospheric and coronal heating (SOLAR-C) Acceleration of fast solar wind (SOLAR-C) Local dynamo process (SOLAR-C/D) Internal structure and flow (SOLAR-D) Global dynamo process (SOLAR-D)

Proposed mission definition Mission: to understand solar and heliospheric magnetic activities and to develop algorithm for solar activity prediction by understanding the magnetic coupling of convection zone-photosphere-chromosphere- transition region and corona Imaging spectroscopy instruments: Science cases: 1.3D-magnetic structure with neutral sheets 2.Heating of chromosphere and corona 3.Acceleration of fast solar wind 4.Prediction of solar flares 5.Fundamental plasma processes such as reconnection, waves, shocks, particle acceleration and turbulence 6.Global and local dynamo 7.Sun’s influence to Earth climate UV: high-throughput telescope x10 more sensitive with seamless coverage in temperature Visible: 1.5m-class telescope to obtain 3D magnetic structure from photosphere to corona with x10 more photons, and x3 resolution with high cadence X-ray/EUV: photon- counting or ultra-high resolution EUV telescopes Key requirements: 1.High spatial resolution to see elemental structure inferred by Hinode 2.High time resolution to freeze rapidly changing chromospheric phenomena 3.Chromospheric magnetic observations 4.Seamless spectroscopic imaging observations from photosphere to corona 5.Wide FOV to connect local and global, and to cover AR

How do we observationally connect these regions with such different appearances? Photosphere ? Interface region Chromosphere 2-5MK corona Questions to determine model instrument specifications How do we determine chromospheric magnetic structure? How do we determine coronal magnetic structure? Can we identify neutral sheet structures? Can we identify waves in chormosphere? What is the smallest scale size inferred from filling factors in all layers? What is the source of EIS line broadening; flows or turbulence or waves? How do we confirm or reject the Parker and type-II spicule conjectures on coronal heating? 4

Lesson learned from Hinode for Solar-C Our guiding principle is that small scale plasma processes associated with magnetic emergence, waves, shocks, and magnetic reconnection dictate the evolution of the global phenomena of the Sun and the heliosphere. Observations so far made indicate that observations of small scale structures and processes are within our reach. Hinode is blind to the chromosphere in terms of diagnostics capability, and misses the key elements in the system. Hinode’s spatial resolution in the corona does not match the high resolution of the photospheric observations. 5

Approach to implement objective is through High 3 (spatial resolution, cadence, and throughput) imaging spectroscopy for the entire solar atmosphere without gaps in temperature coverage. Hinode clearly showed that the combination of high spatial resolution and spectroscopy (including spectro-polarimetry) is a powerful tool for obtaining magnetic and plasma information. This is inevitably achieved with larger telescopes with highest possible throughput for more photons and higher spatial resolution. High S/N is critical in order to retrieve information from spectral profiles. 6

Science case 1. Reveal 3D magnetic structure from photosphere to corona Fundamental for all mission objectives Requires direct chromospheric magnetic observations Infer coronal magnetic field indirectly To have acceptable photon statistics, we need >1m telescope To freeze fast changing chromosphere, we need filtergraph as well as 2D spectro-polarimeter (IFU). To cover AR and have connectivity with global phenomena, we need large FOV close to 200 arcsec Issues – Size of telescope (currently 1.5m) – Carefully chosen set of observing lines – Spatial resolution vs number of photons

Science case 1. magnetic structure from photosphere to corona Science case 2. chromospheric and coronal heating mechanism Science case 3. mechanism of fast solar wind acceleration Establish magnetic connectivity (on terms of both space and time) from photosphere all the way to corona via photometric (non-magnetic) approach – We need three telescopes for seamless coverage in temperature – LEMUR is critical for this purpose Issues: – Do we have observables that guarantee info. on the connectivity between corona and photosphere with the model instruments?

Science case 1. magnetic structure from photosphere to corona Science case 2. choromospheric and coronal heating mechanism Science case 3. mechanism of fast solar wind acceleration AC and DC energy inputs to upper layers Energy input due to quasi-static deformation Poynting flux via Aflven waves 9

Waves In order to identify wave modes and propagation direction, the phase difference of has to be observed. To estimate the Poynting flux of Alfven wave: both magnetic and velocity field observations in the upper atmosphere are required. Issues – Do we need ＳＵＶＩＴ + ＣＬＡＳＰ ?

Science case 2. choromospheric and coronal heating mechanism Science case 3. mechanism of fast solar wind acceleration Science case 4. Prediction of solar flares Science case 5. Fundamental plasma processes 11 SUVIT Photoispheric Observable with Zeeman I+δI(t) B // +δB // (t), B ┴ +δB ┴ (t) V LOS +δV LOS (t) v 図のキャプション SUVIT Chromospheric Observable with Zeeman/Hanle? I+δI(t) B // +δB // (t), B ┴ +δB ┴ (t) V LOS +δV LOS (t) v CLASP TR Observable I+δI(t), V LOS +δV LOS (t) B+δB(t) LEMUR TR/Corona Observable I+δI(t), V LOS +δV LOS (t)

Science case 2. choromospheric and coronal heating mechanism Science case 3. mechanism of fast solar wind acceleration Science case 4. Prediction of solar flares Science case 5. Fundamental plasma processes Imada et al., 2011 Slow-mode Shock XIT photon counting spectrometer can address Does slow shock (SS) really exist? Does SS provide energy to ions or electrons? Are fast shocks associated with SS? Scanning time <100s

Key features for model instruments SUVIT – Maximum 1.5m-class large aperture for photons and resolution – Equipped with IR-detector system for HeI observations – Equipped with both spectro-polarimeter (SP) & filter- graph – SP requires IFU unit for high cadence observations. ＸＩＴ – Photon counting spectroscopy for coronal and flare plasmas or – EUV telescope with very high spatial resolution ＬＥＭＵＲ – High-throughput seamless temperature coverage

Science issues (1) What is the best set of diagnostic lines to infer chromospheric magnetic structures? Can we infer chromospheric magnetic fields as we have been doing for the photosphere? (2) What is the best way to use the chromospheric field information for coronal field extrapolation? It is important to understand influence of line formation in the corrugated atmosphere. How much improvement in accuracy is expected in coronal field extrapolation when we have measurements of chromospheric magnetic fields?

Science issues (continued) (3) Do the Hanle/Zeeman measurements with SUVIT provide diagnostic capability for studies of chromospheric waves? (4) Can LEMUR provide diagnostic capability to detect waves? (5) If we can not fly both types of X-ray/EUV telescopes, should we fly either photon counting X-ray telescope or high-resolution EUV telescope?

Summary SOLAR-C is a fundamentally new way of viewing the solar atmosphere because it observes the entire atmosphere with the same high spatial and temporal resolution, in addition to performing high resolution spectroscopic(polarimetric) measurements over all atmospheric regions. Solar-C should finally solve many outstanding solar physics problems such as chromospheric/coronal heating, solar wind acceleration, and storage and energy release in flares and CMEs. SOLAR-C is a very challenging mission to design, scientifically and technically. The mieesion definition is still in early phase. International collaborations among SOLAR-C, theory & simulation, and ground-based observations from early stage are very important and should be an integral part of the program. 16

Solar&helio physics roadmap : From SOLAR-C to SOLAR-D HINODE (Solar-B) Solar maximum Japan FY D B/C A Launch (Japan FY 2018) Pre-A Pre-A: Pre-Phase-A (WG activities) A: Phase-A (R&D) B/C: Phase-B/C (PM phase) D: Phase-D (FM phase) SSSC: Space Science Steering Committee SRRSDR PDR CDR Pre Project MDR WG Activities D B/C A Pre-A Launch Engineering mission (*) (ISAS small satellite series #3) ISAS/JAXA Solar-C WG JSPEC/JAXA out-of-ecliptic solar mission WG 11 March Launch (Japan FY 2017) D B/C A Pre-A In Orbit verification =Mission proposal to ISAS/JAXA (*) Verification of large ion engine and other technologies to be used for future deep space missions Solar-C High resolution spectroscopy (plan B-satellite) Solar-D Out-of-ecliptic mission (Success-guaranteed plan A-satellite)