flare dynamics in the lower solar atmosphere h. s. hudson space sciences laboratory, university of...
Post on 19-Dec-2015
218 views
TRANSCRIPT
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
St. Andrews Feb. 9, 2011
Wedemeyer-Bohm(ex cartoon archive)
Extrapolation of photospheric field
St. Andrews Feb. 9, 2011
De Rosa et al. 2009
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
Motivation: the flares
St. Andrews Feb. 9, 2011
Cartoon archive home pagehttp://sprg.ssl.berkeley.edu/~stephchow/cartoons.html
(cartoon archive random samples)
Motivation: the flares
St. Andrews Feb. 9, 2011
Fletcher-Hudson 2008F
Motivation: the flares
St. Andrews Feb. 9, 2011
Fletcher-Hudson 2008FWhat is the tensor conductivity?
How is momentum conserved?
How are the particles accelerated?
Part III: studying the flare EUV
St. Andrews Feb. 9, 2011
• Motivation for studying the EUV
• The EVE spectrographs on SDO
• Three discoveries
Motivation: flare global spectrum
St. Andrews Feb. 9, 2011
Hudson et al. 2009
THz
WLF
EUV
nfn= lflQuiet Sun
Flare Excesses
Motivation: flare global spectrum
St. Andrews Feb. 9, 2011
Hudson et al. 2009
THz
WLF
EUV
nfn= lflQuiet Sun
Flare Excesses
More motivation - motions
St. Andrews Feb. 9, 2011
Milligan & Dennis 2009
Still more motivation – lines
St. Andrews Feb. 9, 2011
Kowalski et al. 2010
…and yet more motivation
St. Andrews Feb. 9, 2011
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
St. Andrews Feb. 9, 2011
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
Vicinity of He II “Ly-a” at 30.4 nm
St. Andrews Feb. 9, 2011
EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
RHESSI 100 keV
EVE 30.4 nm
EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
Line detail, total and subtracted
St. Andrews Feb. 9, 2011
Flare vs preflare
Impulsive vs gradual
Doppler shift?
St. Andrews Feb. 9, 2011
EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
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
EUV compared with White Light
St. Andrews Feb. 9, 2011
WLF
EUV flare
QS
Woods et al. 2004
Flare bolometric signature
EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
…and yet more motivation
St. Andrews Feb. 9, 2011
Peter et al.1990
Charge-exchange continuum from alpha particles 0.1-1 MeV
EVE 304A for SOL2010-06-12
St. Andrews Feb. 9, 2011
??
Evaporation flow
St. Andrews Feb. 9, 2011
Milligan & Dennis 2009
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
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)
St. Andrews Feb. 9, 2011
Other slides
St. Andrews Feb. 9, 2011
304 time series, one day
St. Andrews Feb. 9, 2011
Flux and Doppler, one day
St. Andrews Feb. 9, 2011
ESP 304A for SOL2010-11-06
St. Andrews Feb. 9, 2011
EVE ESP and SOL2010-06-12
St. Andrews Feb. 9, 2011
EVE 304 narrow vs SEM
St. Andrews Feb. 9, 2011
EVE 304 narrow vs SEM
St. Andrews Feb. 9, 2011
EVE 304, SEM, EVE broad
St. Andrews Feb. 9, 2011
EVE 304 vs SEM, broad
St. Andrews Feb. 9, 2011
Fla
re S
OL2
010-
06-1
2T00
:57
St. Andrews Feb. 9, 2011
Martinez-O
liveros et al. 2011
Fla
re S
OL2
010-
06-1
2T00
:57
St. Andrews Feb. 9, 2011
Martinez-O
liveros et al. 2011
Eve 304A