formation of coronal large- amplitude waves and the chromospheric response...

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:slulic@vuka.hr, tzic@geof.hr, bvrsnak@geof.hr

Europska UnijaUlaganje u budućnostProjekt je sufinancirala Europska Unija izEuropskog socijalnog fonda

INTRODUCTION• Violentsolareruptionsintheformofcoronalmassejections(CMEs)

andflares,oftencausepulseddisturbancespropagatingthroughthecoronaonaglobalscale

• TheseCME/flareigniteddisturbancescauseavarietyofeffectsinthecorona,transitionregion,andchromosphere,asobservedinEUV-range,X-rays,radio-wavelengthdomain,aswellasInthechromospheric andtransition-regionspectrallines

• Themainobjectiveofthisstudyisquantitativeanalysisofthepropagationofthecoronalwaveandtheeffectsitcausesinthe

transitionregionandchromosphere

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]

THEMODEL• Allquantitiesarenormalized,sothatdistancesareexpressedinunitsofthenumerical-boxlength(L=1)

• velocitiesarenormalizedtotheAlfvén speedvA,andtimeisexpressedintermsoftheAlfvén traveltimeoverthenumerical-boxlength(tA=L/vA )

• Weapplytheapproximationβ=0,whereβistheplasma-to-magneticpressureratio.

• Theoriginofthecoordinatesystemissetatthenumerical-boxcenter

THEMODEL• Wefocusedontheunderstandingofthepropagationwaves/shocks inlowestlayersofthesolarcoronaandtheireffectsinthesolarchromosphere,specialattentionispaidtotheverticalprofileofthedensity

• Toreproducethesolaratmosphere,thenumericalboxisdividedinthreedomains,correspondingtothechromosphere,transitionregion,andlowcorona

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.

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

ACKNOWLEDGMENTS• WeacknowledgethesupportofEuropeanSocialFundunderthe„PoKRet“project.