Multi-wavelength targets for a new flare/CME/SEP mission

1. Multi-wavelength targets for a new flare/CME/SEP mission Lyndsay Fletcher (University of Glasgow) & wisdom of all of RHESSI WG4 2002-2010

2. Flare plasma spectroscopic diagnostics The majority of of the flare radiative energy originates in the chromosphere and has a huge diagnostic potential SOHO/CDS and Hinode/EIS used for studies of chromospheric flare evaporation speeds. Hinode/EIS can also be used for flare densities One or two decent SOHO/SUMER flare observations! We need a better understanding of density, temperature, velocity & turbulence structure during the flare

3. Chromospheric plasma diagnostics In fact, most of the flare radiated power is in the optical and UV – comparatively little known about this observationally! One snapshot of an RHD flare model – heating by a time-varying electron beam (Allred et al 05) The best examples of broadband observations (Neidig 83, Hiei 82, Machado & Rust 74) (in here are the high order Balmer lines – can be used for Stark broadening measurements) • compare with predictions of radiative hydro models (cf quiet chromosphere) • understand where, when (and how?) chromospheric energy input happens • understand how optical continuum formed – photosphere or chromosphere?

4. Imaging of footpoints Do we need arcsecond scales to understand flares? (Emslie) Krucker et al. 2010 TRACE White light 1” resolution, 2s cadence TRACE 1216 Å channel • Correlations & context: Impulsive phase WL footpoints correlate in space and time with HXRs, and images show larger active region context. • Detail: from optical we know that footpoints are not simple! Optical imaging helps to interpret HXR measurements • Spatial scales – Hinode G-band observations -> brightest WL sources have sub arcsecond scales • Topology: UV ribbons/WL footpoints help decipher evolving coronal topology

5. Flare-CME relationship We need to understand the relationship between magnetic restructuring in the corona and particle acceleration • RHESSI lightcurves and SXR images pin down flare and beginning of CME eruption • Simultaneous within 3 minutes. • Do we need to do this better? Temmer et al (2008) Rubio da Costa et al (2009) – TRACE Lya Imaging – but what kind? Lyman alpha? Strong line but not hugely enhanced in a flare (no saturation issues). Shows ribbons and filament lift-off – study link between filament lift-off and flare

6. Faint coronal HXR sources With RHESSI, we are just scratching the surface of the ways in which a magnetised plasma can accelerate electrons! Need higher dynamic range From radio - there are far more subtle changes that accelerate electrons – e.g. decimetric spike bursts possibly caused by compression of corona With RHESSI, we have seen a great variety of faint looptop X-ray sources, thermal and non-thermal; e.g. merging of downward propagating plasmoid and looptop. Milligan et al. 2010 Khan & Aurass 2006

7. Summary • Desirable observations for a multi-wavelength view of flares: • UV and EUV spectroscopy for density, velocity, temperature, turbulence of chromospheric, TR and coronal flare plasmas • Broad-band optical spectroscopy, as well as narrow band focussing on some lines with capacity to diagnose beam properties (e.g. H-a, Ca 8542) and Stark broadening (high order Balmer series) • High time cadence (seconds) and high resolution (0.1-1”) optical and UV imaging – for footpoints and early phase of CME liftoff (also WL for co-alignment with ground-based) • High dynamic range HXR imaging – at least to a few 10s of keV to probe link between coronal field restructuring and particle acceleration