Interpretation of the Activity due to Flux Emergence in an AR

MANDRINI, C.H.; DÉMOULIN, P.; SCHMIEDER, B.; DENG, Y.Y.; RUDAWY, P.

Florencia

Congreso; Magnetic Fields and Solar Processes. The 9th European Meeting on Solar Physics; 1999

ESA

The  short.-livecl   active  region  (AR)  NOAA  7968  was thoroughly   observed   al!  along  its  disk   transit    (June 3  to  10,  1996)  from  the  space  ancl  from  the  ground. During  it.s  early  st.age  (.June  6) ,  it  presented   a  very clynamical  behaviour.    Flux  emerged   in  between   the two   ma.in   pola.rities,    while   a.rch   filament   systems (AFS)   were   observed   in   Ha.   After   this  continuous ancl  fast  photospheric  changes,  the  total  posit.ive  a.nd negative  flux  increa.sed   at  a.slower  rate.   Some  new bipoles  were  observecl  a.t  the South of  thema.in posi­ tive pola.rity  on .June 9.  The AR presented  a very  low leve!of a.ctivity  cluring its life , only small X-ra.y  (class B) fiares ancl surge like ejections were seen. Using a magnetoh.vdrost .at.ic approach , we have moclelled the magneti<· configuration of AR 7968 a.nd have  a.na­ lyzed in particular its topology in relation toa surge observecl on .June 9. We  have  found  that  magnetic fielcl lines relatecl t.o the event have dips that touch tangentially  the  photosphere  ( the  so  called  "bald patches' ' , BPs). Two intera.cting BPs, defining a sep­ m·a.tor, havebeen iclentifiecl at the South of the new emerging flux  region. We propose that magnetic field reconnect.ion  occurring  at  the  separator  is  the  origin of the observed surge. This result shows  that  current sheets can be  formecl  and  efficiently  dissipated  at  a very  low  leve]  in  the  atmosphere.