Understanding the Physics of Solar Flares: Measuring Physical Conditions with High-Resolution Spectroscopy

1. Understanding the Physics of the Acceleration Region of Solar Flares: Measurements of Physical Conditions in the Super-Hot Flare Component and Reconnection Region Using the Fe XXV and Fe XXVI Lines Near 1.8 Å by George Doschek Presented at the 10th RHESSI Workshop- Planning a New Mission, Contributed Science and Measurements 5-6 August, Annapolis, MD 2010

2. Solar Flares: The “Standard Reconnection Model” ~ Fe XII (inflows into the reconnection region) ~ Fe XXIV (loop top confined source) jets Evaporation: Fe XVIII – Fe XXIV He II (footpoints, hard X-ray proxy)

3. Measuring Physical Conditions in the Super-Hot Flare Component and the Flare Reconnection Region • Some estimates are available for the physical parameters of the super-hot component: temperature, density estimate based on volume, emission measure, time history and flare class association from RHESSI (e.g., Amir Caspi) and Hinotori (e.g., K. Tanaka). • But basically nothing is known about the physical characteristics in the flare reconnection region (it’s dark!) • The superhot plasma parameters can be improved by high resolution spectroscopy, and physical parameters in the reconnection region can be determined for the first time.

4. Drake et al. 2006, 443, 553 Temperatures? Densities? Turbulence? Anisotropic Velocities? Spatial Scale Distributions?

5. Unveiling the Microphysics of the Solar Corona • Particle acceleration • Magnetic reconnection • Ion-cyclotron wave heating • Turbulent cascades • Non-Maxwellian distributions Seeing the microphysics requires high spatial and spectral resolution coupled observations from the photosphere into the corona TRACE: 0.5” pixels SOHO/EIT: 2.6” pixels TRACE: 0.5” pixels Yohkoh: 2.45” pixels Plan B Solar-C: 0.1” – 0.3” spatial resolution will provide an exact match from the photosphere into the corona, thus allowing resolution of elementary heating events and traceability of footpoint mechanical energy into the coronal magnetic field and into consequent plasma heating. Elementary heating event in a polar coronal hole. This event is clearly unresolved at ~EIS/ TRACE spatial resolution. 5,800km Hinode/EIS: 1” pixels

6. High Resolution Bragg Crystal Spectroscopy • The high temperatures of the super-hot component and flare reconnection region (20-40 x 106 K) at present require observations of the He-like (Fe XXV) and H-Like (Fe XXVI) iron-line multiplets near 1.8 Å using Bragg crystal spectroscopy.

7. Solar Flare Iron Spectra

8. Plasma Diagnostics from Bragg Spectrometers • Electron temperature • From dielectronic to resonance line ratios • Independent of ionization equilibrium • Electron density • From ionization times • From ionization equilibrium conditions • Flows and Turbulence • From line profiles & wavelength shifts • Polarization • From line ratios • Non-Maxwellian Velocity Distributions

9. Electron Temperature – Fe XXV Complex

10. Electron Temperature – Fe XXVI Complex From Katsuo Tanaka, PASJ, 38, 225 (1986)

11. Ionization equilibrium and electron density in the reconnection region electron density = ~2x109 cm-3 - ~2x1011 cm-3 in the acceleration region

12. Flows and Turbulence: Direct Observation of Chromospheric Evaporation in Flares

13. Polarization Measurements Livermore Electron Ion Beam Trap (EBIT)

14. He-like Scandium (Z = 21) From Henderson et al. 1990, Phys. Rev. Letters, 65, 705 (Livermore EBIT)

15. Non-Maxwellian Velocity Distributions Seely, Feldman, & Doschek 1987, ApJ, 319, 541