Catalog of Large-Amplitude Oscillations
in Solar Prominences
Europs k a Unija
Ulaganje u budućnos t
Projek t je s ufinancirala Europska Unija
Iz Europs k og s oc ijalnog fonda
Dumbović, Mateja, Luna, M., Ballester, J. L., Chen, P-F., Čalogović, J., Gilbert, H., Karpen, J., Knizhnik, K., Magyar, N., Ruderman, M., Schuck, P., Terradas, J., Vršnak, B., Zhang, Q.
Correspondence: [email protected]; [email protected]
The s olar dy nam o generates magnetic fi elds storing ener gy in 3D m agneti c confi gurations w here promi nence m as s can form. Pr ominenc es ar e therefor e rel ated to res erv oirs of fr ee m agneti c energy i n the s olar
atm os pher e that is often r eleas ed abruptl y, pr oduci ng eruptiv e phenom ena ( flar es, CMEs). Large-am plitude oscillations (LAOs) in pr omi nenc es inv olv e m oti ons with v elocities abov e 20 km/s and l arge porti ons of the
filam ent that move in phas e and are easily obs erv ed by ground- and spac e-bas ed i nstr um ents. T he LAO properties ( e.g. period, dam ping tim e) are dir ectly rel ated to the mor phol ogy of promi nenc es and the pr oc ess
of formation. Understandi ng the prominence evolution is therefore key to our understanding of the evolution of magnetic fields on the Sun and their relationship to eruptive phenomena.
A catal og of Lar ge- Ampli tude Os cillati ons ( LAOs) in sol ar promi nenc es is com pil ed i n the sc ope of the Inter national Spac e Scienc e Ins titute (ISSI) Inter national team “ Large-Am plitude Oscill ati ons in Solar
Promi nenc es”, l ed by M anuel Luna. The catal og is based on the H-al pha observ ati ons performed by the Global Oscill ati on N etw ork Group ( GON G) i n 2011 and 2014 to c ov er l ower and hi gher sol ar-activity peri ods,
respec tiv ely. We list and classify all w ell-defi ned LAOs in these tw o tim e periods. In an ongoi ng r es earc h we are par ametrizing the oscillations and identifyi ng the triggering agents/ev ents. T he c atal og is fores een to
be a s tar ting point for case studies, and i n addi tion, will s erv e for a c om prehensiv e statis tic al s tudy of LAO pr operti es to adv ance our unders tanding of the nature and ex citati on mechanisms of LAOs , and the nature
of prominences in general.
BUILDING THE LAO CATALOG
Step 1: detecting a LAO
start
21:15
Big Bear Hα 20:57
1st min
1st max
21:25
21:45
21:35
2nd max
21:55
Step 3: Identifying triggering agents
Step 2: Time-distance diagrams
2nd min
22:05
The GON G networ k telesc opes ar e plac ed around the w orld
at Learm onth ( Aus trali a), U daipur (India) , El Teide ( Spai n),
Cerro Tolol o (Chil e), Big Bear (Califor nia, U SA) and M auna
Loa (Haw aii, U SA). T he GONG Hα images all ow to i dentify
filam ents easily and to foll ow LAO m otions, w hich ar e
detected by eye by visualizi ng the data (usi ng Solar data
view er av ailable at gong2.ns o.edu). LAOs ar e s een as
peri odic m oti ons of parts of fil aments (or whol e fil am ents),
where we only s elec t ev ents where the peri odic m oti on is
clear and disc ard apparent c ounter str eaming flows or
oscill ations w hich ar e not clear. We foc us on two tim e peri ods:
(1) near s olar minim um – si nc e August 2010 (w hen the
netw ork s tar ted to oper ate) to J uly 2011, and ( 2) near s olar
maximum – since January 2014 to December 2014.
It s houl d be noted that vis ual identific ati on of LAOs i s only
step 1 i n buil di ng the catal og, i .e. not all vis ually detec ted
LAOs are s uitable for further analysis (s tep 2) becaus e
ampli tudes ar e too small or the m oti on is too c om plex to tr ack
it with a slit. After the step 2 (tim e-dis tanc e di agr ams) the
oscillation is either confirmed as an actual LAO or discarded.
22:15
22:25
To analy ze the oscill atory m ov ement and deriv e its param eters
time-di stance diagr ams ar e pr oduc ed usi ng slits along the path of
moti on. The slits from c onsecutive im ages ar e then folded next to
each other i n a m anner that the x- axis c orr esponds to the tim eline,
whereas the y- axis c orres ponds to the s pati al ex tent i n the
direc tion of the m ov em ent and the intensi ty profil e outlines the
oscillatory movement (see e.g. Luna et al., 2014, ApJ).
In order to enc om pass the entir e motion i n the filam ent it is
necessar y to follow the m oti on of the lar ge-am plitude
dis plac em ents with c urv ed paths. F or that pur pose w e us e a
proc edure involvi ng curv ed slits . Firs t the path of m oti on is
sel ected by clicki ng on the im age to pr oduc e points w hic h are
fitted with a curv e. T he curv e is then divided into s egments whic h
are used instead of pix els when fol ding slits next to each other,
where a pr oc edur e has been dev el oped to account for the fact
that the c oor dinates are not c ontinuous ( Luna et al ., in
preparation).
The param eters of the oscillatory m oti on ( am plitude, peri od and
dam pi ng tim e) are deriv ed from tim e-dis tanc e di agr ams by fitting a
damped harmonic function (exponentially decreasing sinusoid).
We analyz e w hether or not LAO w as triggered by an er uptiv e ev ent and to eac h
LAO w e try to ass oci ate a fl ar e, CM E or EUV w ave. F or that purpos e w e first
determi ne visually w hether a flar e or eruptiv e promi nence is observ ed in the
corres pondi ng GON G Hα im age prior to the start of the oscill ati on. T he
times pan in whic h w e woul d expec t to obs erve the trigger is limited by the
distance of the triggeri ng fl are/CME/EUV wave s ourc e r egion to the fil ament and
ex pected speed range of the disturbanc e (400-1200 km/s), w hic h is estim ated
based on the ”realisti c” ex pec ted v alues for Alfv en speed. W e use the online
SOH O LASC O CME catal og (avail abl e at c daw.gsfc .nas a.gov), w hic h provi des
CME obs ervations in LASCO c oronagr aph, as well as fl are observ ati ons i n EU V
imager and GOES X-ray fl ux. CM E is ass oci ated to a flar e/eruptiv e filam ent
usi ng tempor al and s pati al criteria (see Vrš nak et al., 2005, A&A). F or bac ksided
ev ents w e us e ST EREO observ ations (i n 2014 w hen i ts fi el d of vi ew captur es
the bac k si de of the Sun, ST EREO C OR CM E c atalog av ailabl e at
cdaw.gsfc.nas a.gov).In addi tion, we s ear ch an online l arge-sc al e c oronal
propagati ng fr onts ( LC PFs) c atal og by N. Nitta ( av ailabl e at aia.lms al.c om) for
possible associated EUV wave.
It s houl d be noted that not all LAOs c an be as sociated wi th a pos sibl e
flare/CM E/EUV w av e tri gger. H ow ev er, when possi bl e, this allows s peed
estimation of the disturbance that triggered LAO.