C. Guillermo Giménez de Castro (a.k.a. Guigue)

Transcription

1 A Panorama on High Energy Solar Physics. Observa8ons, Instrumenta8on and Theory at THz frequencies. C. Guillermo Giménez de Castro (a.k.a. Guigue) Centro de Rádio Astronomia e Astrofísica Mackenzie Universidade Presbiteriana Mackenzie São Paulo, Brazil FAPESP Week, London, 2019 February 11-12

2 Who we are? Center for Radio Astronomy and Astrophysics Mackenzie (CRAAM) It is a research center of the Instituto Presbiteriano Mackenzie located in the city of São Paulo, Brazil, with almost 60 years of continuum activity. It performs technical and scientific researches in Radio Sciences, Solar Physics, Solar-Terrestrial Physics and Space Weather, Earth Atmosphere, Space Geodesy, Stellar Activity, Exoplanets, Instrumentation, Terahertz Technology. It operates a number of instrumental facilities in different countries of South America, mostly in Brazil and Argentina. It supports the graduate programs in Geo-Space Sciences and Applications (CAGE) and in Electrical Engineering and Computing (EEG) of the School of Engineering (Mackenzie). School of Physics and Astronomy, University of Glasgow (SUPA)

3 CRAAM Instruments CRAAM tradi8on is to build its own instruments, always on the edge of the current technology. Now CRAAM operates a large and diversified set of telescopes from khz to THz and Cosmic Rays detectors.

4 People People involved in this research project. CRAAM Adriana Valio: staff researcher and professor. Jean-Pierre Raulin: staff researcher and professor. Paulo José de Aguiar Simões: staff researcher and professor 1. Sérgio Szpigel: staff researcher and professor. Jordi Tuneu: CAGE graduate student, now staying at UoG. Daneele Saraçol Tusnski: former CAGE graduate student. University of Glasgow Alexander MacKinnon: staff researcher and professor. 1 Un8l December 2018 at UoG.

5 Background

6 Nuclear Reactions during Solar Flares. First indirect evidences. Cosmic Rays detectors at the Earth surface have detected strong enhancements temporally coincident with solar flares (1942).

7 Nuclear Reactions during Solar Flares. First direct evidences. γ-rays spectrum taken with a detector in outer space reveals the occurrence of nuclear reac8ons during solar flares.

8 Sola Flares General Characteris>cs. Most energe8c phenomena in the Solar System: E T erg. Take place in the Ac-ve Regions of the solar atmosphere. Energy source: magne8c fields. Time Scale: from seconds to hours. Heat the local plasma, accelerate charged par8cles. Observed radia8on at all wavelengths: m λ 10-4 Å. Cosmic Rays.

9 The Solar Flare cartoon Borrowed from Kontar et al., Phis. Rev. Let., 2017, 118,

10 Flare Nuclear Reactions

11 Solar Flares at micro-waves Micro-waves: 1 ν 50 GHz 300 λ 6 mm Gyrosynchrotron from accelerated electrons 1 γ L 3 dn/de E -δ N total B G Par8ally polarized

12 Solar Flares at micro-waves Bremsstrahlung from thermal electrons Depends on Plasma Density, Temperature Unpolarized Usual model for homogeneous fully ionized sources.

13 Solar Flares at micro-waves Un8l ~ 90s there were very few observa8ons > 30 GHz. In 1984, the 13.4 m single dish Itape8nga antenna (CRAAM facility) discovered a new kind of flares at high frequencies. No physical explana8on was known at that 8me (nor now!). Kaufmann et al., 1985, Nature, 313, 380 Kaufmann etal. 1986, Astron. & Astrophys., 157, 11

14 Solar Flares at micro-waves In 1999, the Solar Submillimeter Telescope (CRAAM facility) had its first light. With its 212 and 405 GHz receivers is the only solar dedicated instrument in the world at these frequencies. It started to collect more strange flares, a.k.a. THz events.

15 Solar Flares at micro-waves Krucker, A., et al., Astron. & Astrophys. Rev.,2013, 21, 58

16 Positrons and Solar Flares

17 Can positrons explain the strange flares? In a series of papers in 1967, Lingenfelter & Ramaty computed the produc8on of e + during a flare. γ e+ 70 e + can survive enough 8me to emit Synchrotron and Bremsstrahlung. Lingenfelter, R.E. & Ramaty, R., Planet. Space Sci., 1967, 15,1303.

18 Nuclear Simulations We use the Monte Carlo simulator of par8cle transport and interac8ons in maoer FLUKA. We simulate a Solar Atmosphere and compute the secondary par8cles produc8on. We found that the secondary electrons are relevant too, and that transport affects the energy distribu8on.

19 Nuclear Simulations We computed the secondaries synchrotron emission for SOL to see whether positrons and secondary electrons may jus8fy the THz events. The answer is no: the number of primary protons needed is 2 orders of magnitude greater than it was inferred from the observa8ons. Tuneu et al., IAU: Living Around Ac-ve Stars, 2017,328, 120.

20 How can we detect positrons?

21 How can we detect positrons? A compound view Accelerated protons, and therefore positrons, are present in almost every flare. Positrons produce γ-rays by Bremsstrahlung with a broad peak around 60 MeV. Bremsstrahlung is not an efficient radia8on mechanism. γ-ray detectors are not quite sensi8ve. Synchrotron radia8on is stronger and detectors are cheaper and more sensi8ve. However, there are different concurrent radia8on processes that may difficult the detec8on.

22 A compound view Spectrum for SOL The proton number is es8mated using the primary electron number as a proxy. Ver8cal bars represent the present instrumenta8on, with their frequency band and sensi8vity. LLAMA

23 After flare detection? γ-ray emission was detected arer the official end of a flare. Without the primaries Gyrosynchrotron emission, secondaries emission may be detected. Ajello, M. et al., Astrophys. Jour., 2014, 789, 20.

24 What we need? More realis8c simula8ons, Beoer diagnos8cs, New instrumenta8on.

25 Better Simulations Present simula8ons consider the solar atmosphere as a square box, without magne8c fields. The transport is limited to par8cle interac8ons. Magne8c interac8ons may play a significant role in the transport resul8ng in emission sources located at different places for different species (as it was observed!).

26 Better Simulations New simula8ons now include magne8c fields, and Lorentz force. We are using Geant4, and the Guiding Center approxima8on.

27 We don t forget the thermal emission Primary electrons precipita8ng to the Chromosphere lost their energy in collisions with the environment. Ambient plasma gets heated and increases its thermal emission. The process is very dynamic. The effect may be stronger for 10 < λ < 100 μm Simões et al., Astron. & Astrophys., 2017, 05, A125.

28 New Instrumentation We need to fill the gap THz. Is challenging because detectors are in the technology fron8er, the Earth Atmosphere is a strong limita8on.

29 The THz Solar Flare Balloon Experiment: Solar-T It flew in piggyback of the GRIPS γ-rays detector over Antarc8ca between January 19 and 30, Full-Sun telescope, with Golay cell detectors (bolometers) and passband filters for the frequencies: 3 and 7 THz. CRAAM design and development. Sun-THz: projected spectrometer for the ISS with receivers for THz (Collabora8on LPI and CRAAM)

30 The High Altitude THz Solar Photometers: HATS Full Sun telescope with Golay cell detector. Frequency: 15 THz. To be installed at 2500 m.a.s.l. (OAFA Observ., Argen8na) Expected first light on July 2020.

31 The upper end: 30 THz Cameras Mid-IR (λ = 10 µm) commercial cameras installed in the focus of small telescopes. Typical space resolu8on 10 arcsec, sensi8vity 50 K, 8me resolu8on 1 s. Giménez de Castro et al., Space Weather, 2018, 16,1261.

32 New Filters and detectors In order to discriminate between Synchrotron and Thermal emission we need to know the wave Polariza-on. Detectors based on Graphene: are very sensi8ve at THz. can detect polariza8on, can be electronically tuned (spectral scanner ), and may be arranged in a focal array (camera). Experiments started at Mackenzie Graphene Laboratory (Mackgraphe) to produce THz detectors and passband filters for Solar observa8ons.