Coronal Heating of an Active Region Observed by XRT on May 5, 2010 A Look at Quasi-static vs Alfven...
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Transcript of Coronal Heating of an Active Region Observed by XRT on May 5, 2010 A Look at Quasi-static vs Alfven...
Coronal Heating of an Active Region Observed by XRT on May 5, 2010
A Look at Quasi-static vs Alfven Wave Heating of Coronal Loops
Amanda PersichettiAad Van Ballegooijen
... Meet the CoronaSolar Corona
Plasma: “The 4th State of Matter”
~ An ionized gas consisting of electrons that
have been pulled free of atoms and ions, in which
the temperature is too high for neutral, un-ionized
atoms to exist
Low Densities
High Temperatures
Dominated by
Magnetic FieldsElectrically neutral
Electrically neutral
plasmaplasma
As a result of plasma motion,
magnetic fields are generated in the sun
X-ray Radiation
B-Field Frozen-into Plasma
~Quasi-static~Quasi-static
~Alfven Wave Turbulence~Alfven Wave Turbulence
~Micro/Nano Flares~Micro/Nano Flares
Coronal Heating
it defies expectationsit defies expectations--> hundreds of times --> hundreds of times
hotter than photospherehotter than photosphere
ThermodynamicsThermodynamics
Why do we Study Why do we Study
it?it?
A few studiedA few studiedMechanismsMechanisms
Identify Energy Identify Energy SourceSource
Conversion Conversion MechanismMechanism
HeatingHeating
Plasma ResponsePlasma Response
RadiationRadiation
ObservablesObservables
Klimchuk, SoPh, 2006
Magnetohydrodynamics (MHD)
Equation of Motion
Force Free Condition Ampere’s Law
A function of position that describes the twist of the
field and must be constant along field lines.
Cases= 0 Potential Field
= constant Linear FFF
(r) Non-Linear FFF
Instruments
XRT (Hinode)XRT (Hinode) Solar Dynamics Solar Dynamics Observatory (SDO)Observatory (SDO)
AIAAIA
HMIHMI
Active Region: a region in the Active Region: a region in the solar atmosphere, from the solar atmosphere, from the
photosphere to the corona, that photosphere to the corona, that develops when strong magnetic develops when strong magnetic fields emerge from inside the fields emerge from inside the sun. Magnetized realm in and sun. Magnetized realm in and
around sunspots. around sunspots.
Magnetogram
Magnetogram
from HMIfrom HMI
XRT XRT
ImageImage
Modeling Magnetic Fields
~A software package that ~A software package that allows you to construct allows you to construct
models of the solar models of the solar corona based on corona based on
photospheric photospheric magnetograms from magnetograms from
HMI and coronal images HMI and coronal images from AIAfrom AIA
~Models provide ~Models provide information about the information about the
coronal magnetic field that coronal magnetic field that cannot already be directly cannot already be directly observed from SDO data. observed from SDO data.
Accurately model the magnetic field lines of the Accurately model the magnetic field lines of the active region based on data from SDO. This gives us a better active region based on data from SDO. This gives us a better
idea of the properties of the region in order to make more idea of the properties of the region in order to make more educated conclusions, in our case, about the heating.educated conclusions, in our case, about the heating.
Non-Potential FieldNon-Potential Field
1) Construct potential field1) Construct potential field
2)Insert flux rope in model along manually 2)Insert flux rope in model along manually selected pathselected path
3)Apply magneto-frictional relaxation3)Apply magneto-frictional relaxation
CCMMSS
PurposePurposeMMSS
Program Program ApproachApproach
van Ballegooijen et al. (2010 in prep)
green green contoucontou
rs = rs = neg neg
BfieldBfield
adjust adjust model model
so so field field lines lines
match match loopsloops
Can Can see see
distincdistinct loops t loops in 171 in 171
A A imageimage
red red contourcontours = pos s = pos BfieldBfield
Chromosphere
Waves reflected back down due to Waves reflected back down due to increase in speed with height creates increase in speed with height creates
turbulenceturbulence
Alfven Alfven Wave Wave
TurbulenceTurbulence
New View About Waves New View About Waves
Heating Rates
Quasi-Static Heating Rate per unit volume
Alfven Wave Heating Rate
Quasi-Static heating dependent on Quasi-Static heating dependent on magnetic field, loop length, and magnetic field, loop length, and properties of foot-point motions.properties of foot-point motions.
Alfven Wave heating is based on Alfven Wave heating is based on numerical simulations.numerical simulations.
Heating of Coronal Loops
RadiativeLoses
HeatingRateThermal
Conduction
Compute Temperature Compute Temperature and Density with and Density with
respect to positionrespect to position
Three processes related to Three processes related to heating present in the heating present in the
corona:corona:~Heating rate contribution~Heating rate contribution
~Thermal Conduction~Thermal Conduction~Radiative Loses~Radiative Loses
Alfven velocity = 1.1 km/s Foot-point motion time = 40s
Computed and Observed XRT Count Rates
Alfven Wave Turbulence Quasi-Static Footpoint Motion
Conclusions
Alfven wave turbulence gives off a lot more heating energy than the quasi-static mechanism producing heat rates on orders of 102 greater.
This made it able for us to get a more accurate fit of calculated intensities to actual intensities for reasonable values of the the foot-point motion parameters.
The solar corona is so active and constantly changing. When it comes to modeling active regions, each individual one must be modeled with its own individual parameters. They are not consistent for all active regions on surface.
Continued Study
Apply this analysis to various active regions
New model involving Alfven wave turbulence
Consider interactions between neighboring flux tubes including splitting/merging of flux tubes