1. Locarno, 8 June 2005Peter Gallagher (UCD) Chromospheric Evaporation Peter Gallagher University College Dublin Ryan Milligan Queens University Belfast

2. Locarno, 8 June 2005Peter Gallagher (UCD) Chromospheric Evaporation oNon-thermal electrons supply the necessary energy to heat the plasma and cause flows. E nonthermal -> E thermal + E kinetic

3. Locarno, 8 June 2005Peter Gallagher (UCD) Chromospheric Response oHow does the chromosphere respond to nonthermal electrons? oAssume power-law electron spectrum: oF(E) ~ (E/E c ) -  electrons cm -2 s -1 oChromospheric response depends on properties of accelerated electrons: 1.Low-energy cut-off (E c ). 2.Power-law index (  ). 3.Total flux. T 1 : Nonthermal Electrons T 2 : Impulsive Heating T 3 : V up <1000 km/s T 3 : V DOWN <100 km/s Density Loop leg

4. Locarno, 8 June 2005Peter Gallagher (UCD) oGentle oChromosphere heated directly by non-thermal electrons oVelocities < 300 km/s oFlux < 10 10 ergs cm -2 s -1 oExplosive oChromosphere unable to radiate energy deposited by non-thermal electrons oVelocities > 400 km/s oFlux > 10 10 ergs cm -2 s -1 Gentle Explosive Threshold? v/2.35c s Log F (ergs s -1 cm -2 )

5. Locarno, 8 June 2005Peter Gallagher (UCD) CDS and TRACE: 26 March 2002 Flare oSOHO/CDS oHe I (0.03 MK) oO V (0.25 MK) oMg X (1.1 MK) oFe XVI (2.5 MK) oFe XIX (8 MK) oTRACE 17.1 nm oFe IX/X (1.0 MK)

6. Locarno, 8 June 2005Peter Gallagher (UCD) Footpoint Downflows oLoops are not static oMaximum downflow ~110 km/sec oLoops cool via conduction, radiation, and flows. (SHOW MOVIE)

7. Locarno, 8 June 2005Peter Gallagher (UCD) RHESSI Integrated Spectrum

8. Locarno, 8 June 2005Peter Gallagher (UCD) M2.2 Flare – CDS/EIT/GOES

9. Locarno, 8 June 2005Peter Gallagher (UCD) 6 - 12 keV (dashed line) Thermal 25 – 50 keV (solid line) Non-thermal

10. Locarno, 8 June 2005Peter Gallagher (UCD) RHESSI Lightcurve

11. Locarno, 8 June 2005Peter Gallagher (UCD) RHESSI Spectrum Thermal: T ~ 20 MK EM ~ 10 49 cm -3 Nonthermal: E c ~ 24 keV  ~ 7.3 HXR Area ~ 10 18 cm 2 => Nonthermal Electron Flux ~2x10 10 ergs cm -2 s -1

12. Locarno, 8 June 2005Peter Gallagher (UCD) Evidence for Upflows Stationary Fe XIX Component Blueshifted Fe XIX Component Doppler shifts measured relative to a stationary component: v/c = ( - 0 )/ 0 In Fe XIX v = 260 km s -1

13. Locarno, 8 June 2005Peter Gallagher (UCD) Flow velocity vs. Temperature Downflows Upflows

14. Locarno, 8 June 2005Peter Gallagher (UCD) M2.2 flare In context …

15. Locarno, 8 June 2005Peter Gallagher (UCD) Future Work oHow does the chromospheric response depend on the nonthermal electron properties? oWe now have one event! oNonthermal electrons:  ~7.3, E c ~ 24 keV, F~2x10 10 ergs cm -2 s -1 oResponse: ~260 km s -1 o=> need large number of CDS/RHESSI flares oIs there a threshold for explosive evaporation? o=> need large number of CDS/RHESSI flares