Flare Dynamics in the Lower Solar Atmosphere H. S. Hudson Space Sciences Laboratory, University of California, Berkeley, USA Astronomy & Astrophysics Group, Glasgow Orleans Feb. 22, 2011

Outline Orleans Feb. 22, )Some background on the lower atmosphere 2) Some background on flares 3)My current passion: EVE and spectroscopy - three small discoveries

General background Orleans Feb. 22, ) Photosphere, chromosphere, corona 2) Flare occurrence 3)The chromosphere as an interface between domains: - collisional / noncollisionless - weakly / strongly ionized - high beta / low beta - optically thick / thin

What is a flare? Orleans Feb. 22, 2011

What is a flare? Orleans Feb. 22, 2011 Flare >

Flare Dynamics Orleans Feb. 22, 2011 TRACE “white light” Pixel size 0.5 arc s Courtesy N. V. Nitta

Motivation: the chromosphere Orleans Feb. 22, 2011 Wedemeyer-Bohm et al. (2008)

Motivation: the chromosphere Orleans Feb. 22, 2011 Wedemeyer-Bohm et al. (2008)

Comment: MHD vs Plasma Physics Orleans Feb. 22,

Extrapolation of photospheric field Orleans Feb. 22, 2011 De Rosa et al. 2009

Modeling the chromosphere Orleans Feb. 22, 2011 Semi-empirical 1D models (VAL-C type) 1D radiation hydro models (e.g. Fisher, McClymont) of flares 3D (MHD) models (Asplund triumph; Abbett) Plasma physics; see pages at how/plasma/webpage/plasma.html Vernazza et al (VAL-C)

Motivation: the flares Orleans Feb. 22, 2011 Cartoon archive home page how/cartoons.html (cartoon archive random samples)

Motivation: the flares Orleans Feb. 22, 2011 Fletcher-Hudson 2008F

Motivation: the flares Orleans Feb. 22, 2011 Fletcher-Hudson 2008F What is the tensor conductivity? How is momentum conserved? How are the particles accelerated?

Part III: studying the flare EUV Orleans Feb. 22, 2011 Motivation for studying the EUV The EVE spectrographs on SDO Three discoveries

Motivation: flare global spectrum Orleans Feb. 22, 2011 Hudson et al THz WLF EUV f = f Quiet Sun Flare Excesses

Motivation: flare global spectrum Orleans Feb. 22, 2011 Hudson et al THz WLF EUV f = f Quiet Sun Flare Excesses

More motivation - motions Orleans Feb. 22, 2011 Milligan & Dennis 2009

Still more motivation – lines Orleans Feb. 22, 2011 Kowalski et al. 2010

…and yet more motivation Orleans Feb. 22, 2011 Peter et al.1990 Charge-exchange continuum from  - particles MeV/nuc

Introductory conclusions The chromosphere is complicated but has rich physics (e.g. coupling to interior) Flares provide excellent test cases for the dynamics: we can use energy and momentum conservation There has been a paucity of useful data, but that is changing now Orleans Feb. 22, 2011

Sun-as-a-star EUV tools SOHO/SEM: broad EUV band at nm SDO/EVE MEGS-A: far-UV, 1 A resolution, 10 s cadence (data available) SDO/EVE MEGS-B: near-UV, 1 A resolution, 10 s cadence (some problems?) SDO/EVE ESP (broad EUV bands, 0.25 s cadence) Orleans Feb. 22, 2011

Vicinity of He II “Ly-  ” at 30.4 nm Orleans Feb. 22, 2011 MEGS spectrum ESP channel

EVE 304A for SOL Orleans Feb. 22, 2011 RHESSI 100 keV EVE 30.4 nm

Line detail, total and subtracted Orleans Feb. 22, 2011 Flare vs preflare Impulsive vs gradual

EVE 304A for SOL Orleans Feb. 22, 2011

EVE 304A for SOL Orleans Feb. 22, 2011 Fits via gaussfit in IDL Note the high precision (six sig. figures) Uncertainty comparable with the best solar work Can almost begin to search for unknown solar planets

EVE 304A for SOL Orleans Feb. 22, 2011 Fits via gaussfit in IDL Note the high precision (six sig. figures) Uncertainty comparable with the best solar work Can almost begin to search for unknown solar planets “Hi Hugh, No, no, no. You’re not understanding the issue with MEGS-A optical design.” – Tom Woods, EVE PI

EVE 304A for SOL Orleans Feb. 22, 2011

EUV compared with White Light Orleans Feb. 22, 2011 WLF EUV flare QS Woods et al Flare bolometric signature

EVE 304A for SOL Orleans Feb. 22, 2011

Where the continuum should be Orleans Feb. 22, 2011 Peter et al.1990 Charge-exchange continuum from alpha particles MeV

EVE 304A for SOL Orleans Feb. 22, 2011 ??

Evaporation flow Orleans Feb. 22, 2011 Milligan & Dennis 2009

Sun-as-a-star EUV irradiance Orleans Feb. 22, 2011

Three discoveries The EUV does not have the bulk of the flare energy; only the UV is left as a viable candidate. EVE is good enough to measure redshifts useful for flare dynamics in the lower atmosphere (if Doppler, then 33.7 ± 6.7 km/s in SOL ). In the first example, EVE spectra do not show the charge-exchange signature expected from “solar cosmic rays”. What is wrong with the model? Orleans Feb. 22, 2011

Comments on EVE There are lots of lines to work with He II spectrum in the impulsive phase (Ly-  excellent; can see Ly-  and a hint of Ly-  in SOL ) Need bigger flares Looking forward to near UV (MEGS-B) as a part of WLF characterization Orleans Feb. 22, 2011

Conclusions The SDO data for the Sun “as a star” are rather fine There are many applications of these data - Global flare spectra - Doppler shifts / flare dynamics - Charge-exchange components - Seismology (classical) - Seismology (coronal) How do we convert this excellent new information (RHESSI and SDO) into constraints on the plasma physics? Orleans Feb. 22, 2011

Other slides Orleans Feb. 22, 2011

304 time series, one day Orleans Feb. 22, 2011

Flux and Doppler, one day Orleans Feb. 22, 2011

ESP 304A for SOL Orleans Feb. 22, 2011

EVE ESP and SOL Orleans Feb. 22, 2011

EVE 304 narrow vs SEM Orleans Feb. 22, 2011

EVE 304 narrow vs SEM Orleans Feb. 22, 2011

EVE 304, SEM, EVE broad Orleans Feb. 22, 2011

EVE 304 vs SEM, broad Orleans Feb. 22, 2011

Flare SOL T00:57 Orleans Feb. 22, 2011 Martinez-Oliveros et al. 2011

Flare SOL T00:57 Orleans Feb. 22, 2011 Martinez-Oliveros et al Eve 304A