emission measure distribution in loops impulsively heated at the footpoints paola testa, giovanni...
TRANSCRIPT
Emission measure Emission measure distribution in loops distribution in loops
impulsively heated at impulsively heated at the footpointsthe footpoints
Paola Testa, Giovanni Peres, Fabio Paola Testa, Giovanni Peres, Fabio RealeReale
Universita’ di PalermoUniversita’ di PalermoSolar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo
9/3/20049/3/2004
RationaleRationale
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
GENERAL PROBLEMSGENERAL PROBLEMS
OBSERVATIONAL EVIDENCEOBSERVATIONAL EVIDENCE
CORONAL LOOPS MODELSCORONAL LOOPS MODELS::
standard hydrostatic models vs. standard hydrostatic models vs. observations observations
need for improved need for improved modelsmodels
hydrodynamic model with hydrodynamic model with footpoint footpoint heatingheating
GENERAL PROBLEMSGENERAL PROBLEMS:: spatial and thermal structuring, spatial and thermal structuring,
heating, heating, dynamic properties of dynamic properties of solar and stellar solar and stellar coronae coronae
DIAGNOSTIC TOOLSDIAGNOSTIC TOOLS::
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
SOLAR CORONASOLAR CORONA:: high spatial and temporal resolution, high spatial and temporal resolution,
spectral informationspectral information
STELLAR CORONAESTELLAR CORONAE:: X-ray spectral coverage with high X-ray spectral coverage with high
spectral spectral resolutionresolution
Coronal LoopsCoronal Loops Loops are basic Loops are basic components of components of the solar corona the solar corona
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
development of loop modelsdevelopment of loop models::
e.g. e.g. Rosner et al. 1978, Vesecky et al. Rosner et al. 1978, Vesecky et al. 1979, 1979, Serio et al. 1981Serio et al. 1981
TRACE 171TRACE 171ÅÅ
Yohkoh/SXTYohkoh/SXT
Coronal LoopsCoronal Loops Loops are basic Loops are basic components of components of the solar corona the solar corona
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
apparent disagreement mostly with apparent disagreement mostly with EUV EUV observations (TRACE, SoHO) observations (TRACE, SoHO) ::
e.g. e.g. Aschwanden et al. 2000,2001, Aschwanden et al. 2000,2001, Winebarger Winebarger et al. 2002, Warren et et al. 2002, Warren et al. 2003al. 2003
location of heating? location of heating? ::e.g. e.g. Priest et al. 2000, Aschwanden 2001, Priest et al. 2000, Aschwanden 2001,
Reale 2002Reale 2002
Coronal LoopsCoronal Loops Loops are basic Loops are basic components of components of the solar corona the solar corona
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
how are active stars how are active stars structured?structured?
can simple loop modelscan simple loop models explainexplain thethe
emission from active stars? emission from active stars? solar analogy for interpreting solar analogy for interpreting stellar coronaestellar coronae??
Coronal Loops in Stellar Coronae?Coronal Loops in Stellar Coronae?
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Lack of spatial resolution Lack of spatial resolution we must we must resort to resort to indirect means for comparing indirect means for comparing properties of stellar properties of stellar coronal structures with coronal structures with
solar loopssolar loops
spectral observations spectral observations ::high resolution EUV (high resolution EUV (EUVEEUVE) and X-ray ) and X-ray
spectra spectra ((ChandraChandra, , XMM-NewtonXMM-Newton))
Emission Measure DistributionEmission Measure Distribution
EM(T) = T ne2(T) dV
Coronal Loops in Stellar Coronae?Coronal Loops in Stellar Coronae?
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
EM(T) expected for hydrostatic loop EM(T) expected for hydrostatic loop models models TT3/23/2 howeverhowever
EM(T) derived from observations are EM(T) derived from observations are steepersteeper and with and with bumpsbumps, i.e. large , i.e. large amounts of almost isothermal plasma amounts of almost isothermal plasma
Scelsi et al. (2004)
31 Com
e.g.e.g.EM(T) of EM(T) of 31Com 31Com from XMM from XMM spectra spectra
New Loop Models?New Loop Models?
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
can footpoint heating yield loops can footpoint heating yield loops with with characteristics compatible characteristics compatible with with observations?observations?
Problem:Problem: INSTABILITY (INSTABILITY (e.g.e.g. Serio et Serio et
al.1981al.1981))
dynamic loops since static dynamic loops since static solutions do not exist for heating solutions do not exist for heating concentrated at the footpointsconcentrated at the footpoints
how do EM(T) change with how do EM(T) change with characteristics characteristics of heating? of heating?
Loop ModelLoop Model
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
1-D hydrodynamic loop model symmetric equations solved for half loop uniform cross-section footpoint heated by periodic heat pulses Palermo-Harvard code (Peres et al.,1982; Betta et
al.,1997)
consistently solves the consistently solves the time-time-dependent density, momentum and dependent density, momentum and energy equationsenergy equations for the plasma for the plasma confined by the magnetic fieldconfined by the magnetic field
Loop ModelLoop Model
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
INITIAL CONDITIONS:INITIAL CONDITIONS:
solutions of hydrostatic loop modelsolutions of hydrostatic loop model (Serio et (Serio et al. 1981)al. 1981)
HEATING FUNCTION:HEATING FUNCTION:satisfy the scaling satisfy the scaling lawslaws p0 ~ (Tmax/1.4·103 )3·1/L
E0 ~ 105 p07/6·L-5/6
EH (s,t) = EH (s)·EH (t) EH (s) = H0·e-(s-s0)2/22
spatial distribution :spatial distribution :
temporal distribution : periodic temporal distribution : periodic pulses with pulses with duty cycle 10%duty cycle 10% intensity of heating scaled from the static intensity of heating scaled from the static modelmodel
= L/3, L/5, = L/3, L/5, L/10L/10
Set of simulationsSet of simulations
[MK] [dyn/cm2] [erg cm-3s-1] [s]
Tmax p0 E0 cool
Initial ConditionsInitial Conditions
0.4513 ~ 2200
303610 ~ 1200
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Set of simulationsSet of simulations
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Heat PulsesHeat Pulses
cool/4, cool /2E0,4E0L/3,L/5,L/10 10000
5000
H trun [s]
cool/4, cool /2E0,4E0L/3,L/5,L/10
Evolution of footpoint heated Evolution of footpoint heated loopsloopsConstant heatingConstant heating
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Evolution of footpoint heated Evolution of footpoint heated loopsloopsImpulsive heatingImpulsive heating
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Evolution of footpoint heated Evolution of footpoint heated loopsloops
TemperatureTemperature and and DensityDensity at loop at loop apexapex
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Emission measure distributionEmission measure distribution
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Emission measure Emission measure distributiondistribution::
models models vs. vs. observations observations
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
ConclusionsConclusions
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
Loop ModelLoop Model
Solar Coronal Loop Workshop — Palermo Solar Coronal Loop Workshop — Palermo 9/3/20049/3/2004
adaptive grid initial model atmosphere uses Vernazza, Avrett and
Loeser (1980) to extend the S81 static model to chromospheric temperatures
effective plasma viscosity fractional ionization ne/nH
hydrogen ionization potential