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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
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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
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Motivation: the chromosphere
St. Andrews Feb. 9, 2011
Wedemeyer-Bohm(ex cartoon archive)
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Extrapolation of photospheric field
St. Andrews Feb. 9, 2011
De Rosa et al. 2009
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Modeling the chromosphere
St. Andrews Feb. 9, 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 athttp://sprg.ssl.berkeley.edu/~stephchow/plasma/webpage/plasma.html
VAL-C
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Motivation: the flares
St. Andrews Feb. 9, 2011
Cartoon archive home pagehttp://sprg.ssl.berkeley.edu/~stephchow/cartoons.html
(cartoon archive random samples)
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Motivation: the flares
St. Andrews Feb. 9, 2011
Fletcher-Hudson 2008F
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Motivation: the flares
St. Andrews Feb. 9, 2011
Fletcher-Hudson 2008FWhat is the tensor conductivity?
How is momentum conserved?
How are the particles accelerated?
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Part III: studying the flare EUV
St. Andrews Feb. 9, 2011
• Motivation for studying the EUV
• The EVE spectrographs on SDO
• Three discoveries
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Motivation: flare global spectrum
St. Andrews Feb. 9, 2011
Hudson et al. 2009
THz
WLF
EUV
nfn= lflQuiet Sun
Flare Excesses
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Motivation: flare global spectrum
St. Andrews Feb. 9, 2011
Hudson et al. 2009
THz
WLF
EUV
nfn= lflQuiet Sun
Flare Excesses
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More motivation - motions
St. Andrews Feb. 9, 2011
Milligan & Dennis 2009
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Still more motivation – lines
St. Andrews Feb. 9, 2011
Kowalski et al. 2010
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…and yet more motivation
St. Andrews Feb. 9, 2011
Peter et al.1990
Charge-exchange continuum from a-particles 0.1-1 MeV
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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
St. Andrews Feb. 9, 2011
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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)
St. Andrews Feb. 9, 2011
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Vicinity of He II “Ly-a” at 30.4 nm
St. Andrews Feb. 9, 2011
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EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
RHESSI 100 keV
EVE 30.4 nm
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EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
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Line detail, total and subtracted
St. Andrews Feb. 9, 2011
Flare vs preflare
Impulsive vs gradual
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Doppler shift?
St. Andrews Feb. 9, 2011
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EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
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EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 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
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EUV compared with White Light
St. Andrews Feb. 9, 2011
WLF
EUV flare
QS
Woods et al. 2004
Flare bolometric signature
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EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
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…and yet more motivation
St. Andrews Feb. 9, 2011
Peter et al.1990
Charge-exchange continuum from alpha particles 0.1-1 MeV
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EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
??
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Evaporation flow
St. Andrews Feb. 9, 2011
Milligan & Dennis 2009
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Sun-as-a-star EUV irradiance
St. Andrews Feb. 9, 2011
• 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
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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
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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
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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)
St. Andrews Feb. 9, 2011
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Other slides
St. Andrews Feb. 9, 2011
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304 time series, one day
St. Andrews Feb. 9, 2011
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Flux and Doppler, one day
St. Andrews Feb. 9, 2011
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ESP 304A for SOL2010-11-06
St. Andrews Feb. 9, 2011
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EVE ESP and SOL2010-06-12
St. Andrews Feb. 9, 2011
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EVE 304 narrow vs SEM
St. Andrews Feb. 9, 2011
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EVE 304 narrow vs SEM
St. Andrews Feb. 9, 2011
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EVE 304, SEM, EVE broad
St. Andrews Feb. 9, 2011
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EVE 304 vs SEM, broad
St. Andrews Feb. 9, 2011
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Fla
re S
OL2
010-
06-1
2T00
:57
St. Andrews Feb. 9, 2011
Martinez-O
liveros et al. 2011
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Fla
re S
OL2
010-
06-1
2T00
:57
St. Andrews Feb. 9, 2011
Martinez-O
liveros et al. 2011
Eve 304A