formation of coronal large- amplitude waves and the chromospheric response...
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FORMATION OF CORONAL LARGE-AMPLITUDE WAVES AND THE
CHROMOSPHERIC RESPONSE1SlavenLulić,2TomislavŽic,2BojanVršnak
1 KarlovacUniversityofAppliedSciences,TrgJ.J.Strossmayera9,HR-47000Karlovac,Croatia
2 HvarObservatory, FacultyofGeodesy, UniversityofZagreb,Kačićeva26,HR-10000Zagreb,Croatia
e-mail:[email protected], [email protected], [email protected]
Europska UnijaUlaganje u budućnostProjekt je sufinancirala Europska Unija izEuropskog socijalnog fonda
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INTRODUCTION• Violentsolareruptionsintheformofcoronalmassejections(CMEs)
andflares,oftencausepulseddisturbancespropagatingthroughthecoronaonaglobalscale
• TheseCME/flareigniteddisturbancescauseavarietyofeffectsinthecorona,transitionregion,andchromosphere,asobservedinEUV-range,X-rays,radio-wavelengthdomain,aswellasInthechromospheric andtransition-regionspectrallines
• Themainobjectiveofthisstudyisquantitativeanalysisofthepropagationofthecoronalwaveandtheeffectsitcausesinthe
transitionregionandchromosphere
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THEMODEL• Inthefollowing,a2.5-Dmodelisconsidered,meaningthatallquantitiesareinvariantalongthez-coordinate,butthez-componentofthemagneticfieldBz(x,y)̸=0isincludedinthecalculation.
• Ontheotherhand,thez-componentofthevelocityisalwayskeptzero(vz=0)
• the input and the basic output quantities are the density [ρ] the x- and y-component of the velocity [vx, vy] and all three components of the the magnetic field [Bx, By, Bz]
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THEMODEL• Allquantitiesarenormalized,sothatdistancesareexpressedinunitsofthenumerical-boxlength(L=1)
• velocitiesarenormalizedtotheAlfvén speedvA,andtimeisexpressedintermsoftheAlfvén traveltimeoverthenumerical-boxlength(tA=L/vA )
• Weapplytheapproximationβ=0,whereβistheplasma-to-magneticpressureratio.
• Theoriginofthecoordinatesystemissetatthenumerical-boxcenter
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THEMODEL• Wefocusedontheunderstandingofthepropagationwaves/shocks inlowestlayersofthesolarcoronaandtheireffectsinthesolarchromosphere,specialattentionispaidtotheverticalprofileofthedensity
• Toreproducethesolaratmosphere,thenumericalboxisdividedinthreedomains,correspondingtothechromosphere,transitionregion,andlowcorona
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THEMODEL• The density is set to ρ = 1 at the base of the corona, i.e., the top
of the transition region• The lowest layer, representing the chromosphere, extends
from y = 0 to y = 0.1• In the applied model-atmosphere, in this domain the density
decreases for ≈ 5 orders of magnitude, following the exponential law
• The next layer, representing the transition region [TR], extends from y = 0.1 to y = 0.125
• Over this height range, we apply a linear a density decrease of two orders of magnitude
• Above y = 0.125 extends the corona whose density decreases exponentially from ρ = 1, where we apply the scale height 100 times larger than in the chromospheric layer.
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CONCLUSION• Toconclude,thechromospheric perturbation(correspondingtoa
Moreton wave)lagsbehindthetransition-regionandcoronalperturbation(correspondingtoanEUVwave).
• Thisisfullyconsistentwiththeobservationsofthesharp-wavefrontEITwavesassociatedwithHαandHeI Moreton waves
• After thepassageofasharpcoronalEUVwaveassociatedwiththeMoreton wave,onecanexpecttoobserveapassageofasignificantly-slowerperturbation,manifestedmainlyasadensitycompressionthatpropagatesupward/sidewise,andisassociatedwithslowupwardrelaxationofthelowercorona,transitionregionandchromosphere
• Duetotheinclinationandthespatialextent,thisfeatureshouldbeobservedasawide/diffusefeaturepropagatingfromthesourceregion,andbeingmuchslowerthanthesharpcoronalEUVwavefrontassociatedwiththeMoretonwave
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ACKNOWLEDGMENTS• WeacknowledgethesupportofEuropeanSocialFundunderthe„PoKRet“project.