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Flare Dynamics in the Lower Solar Atmosphere
H. S. HudsonSpace Sciences Laboratory, University of California, Berkeley, USA
Astronomy & Astrophysics Group, Glasgow
St. Andrews Feb. 9, 2011
Outline
St. Andrews Feb. 9, 2011
1) Some background on the lower atmosphere2) Some background on flares3) My current passion: EVE and spectroscopy - three small discoveries
Motivation: the chromosphere
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Wedemeyer-Bohm(ex cartoon archive)
Extrapolation of photospheric field
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De Rosa et al. 2009
Modeling the chromosphere
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• 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 athttp://sprg.ssl.berkeley.edu/~stephchow/plasma/webpage/plasma.html
VAL-C
Motivation: the flares
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Cartoon archive home pagehttp://sprg.ssl.berkeley.edu/~stephchow/cartoons.html
(cartoon archive random samples)
Motivation: the flares
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Fletcher-Hudson 2008F
Motivation: the flares
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Fletcher-Hudson 2008FWhat is the tensor conductivity?
How is momentum conserved?
How are the particles accelerated?
Part III: studying the flare EUV
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• Motivation for studying the EUV
• The EVE spectrographs on SDO
• Three discoveries
Motivation: flare global spectrum
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Hudson et al. 2009
THz
WLF
EUV
nfn= lflQuiet Sun
Flare Excesses
Motivation: flare global spectrum
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Hudson et al. 2009
THz
WLF
EUV
nfn= lflQuiet Sun
Flare Excesses
More motivation - motions
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Milligan & Dennis 2009
Still more motivation – lines
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Kowalski et al. 2010
…and yet more motivation
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Peter et al.1990
Charge-exchange continuum from a-particles 0.1-1 MeV
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
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Sun-as-a-star EUV tools
• SOHO/SEM: broad EUV band at 30.4+-4 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)
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Vicinity of He II “Ly-a” at 30.4 nm
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EVE 304A for SOL2010-06-12
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RHESSI 100 keV
EVE 30.4 nm
EVE 304A for SOL2010-06-12
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Line detail, total and subtracted
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Flare vs preflare
Impulsive vs gradual
Doppler shift?
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EVE 304A for SOL2010-06-12
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EVE 304A for SOL2010-06-12
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• 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
EUV compared with White Light
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WLF
EUV flare
QS
Woods et al. 2004
Flare bolometric signature
EVE 304A for SOL2010-06-12
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…and yet more motivation
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Peter et al.1990
Charge-exchange continuum from alpha particles 0.1-1 MeV
EVE 304A for SOL2010-06-12
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??
Evaporation flow
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Milligan & Dennis 2009
Sun-as-a-star EUV irradiance
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• The EVE instrument on board SDO gives us solar people something really new: stellar spectroscopy
• The MEGS component gives 1Å resolution over 6.5-105 nm, at 10 s cadence
• The ESP component gives five broad bands, at 0.25 s cadence
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 Doppler shifts useful
for flare dynamics in the lower atmosphere• In the first example, EVE spectra do not show the
charge-exchange signature expected from “solar cosmic rays”
St. Andrews Feb. 9, 2011
Comments on EVE• There are lots of lines to work with• He II spectrum in the impulsive phase (Ly-a excellent;
can see Ly-b and a hint of Ly- g in SOL2010-06-12)• Need bigger flares• Looking forward to near UV (MEGS-B) as a part of
WLF characterization
St. Andrews Feb. 9, 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)
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Other slides
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304 time series, one day
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Flux and Doppler, one day
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ESP 304A for SOL2010-11-06
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EVE ESP and SOL2010-06-12
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EVE 304 narrow vs SEM
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EVE 304 narrow vs SEM
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EVE 304, SEM, EVE broad
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EVE 304 vs SEM, broad
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Fla
re S
OL2
010-
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Martinez-O
liveros et al. 2011
Fla
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010-
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Martinez-O
liveros et al. 2011
Eve 304A
