Joint Physics Dept.–Inst. for Space Weather Sci. Colloquium

April 10, Thursday (** SPECIAL DAY**)

Flux Cancellation in Solar Photosphere:

What do we mean by that? And what are the consequences for the upper atmosphere?

Dr. Viggo Hansteen

SETI Institute

(Solar Physics, Host: Jeongwoo Lee)

Room: ECE 202

Time: 11:45 am - 12:45 pm with 11:30 am teatime

*ZOOM Meeting ID for those who cannot attend in-person: 917 2169 7568

(APPROVAL by Prof Ahn REQUIRED for APPH/MTSE PhD Students to attend online)

*Password: check email or request from kenahn@njit.edu

Fluxcancellation, like flux emergence, is one of the basic processes that determinethe change of magnetic flux at the solar surface on a large range of spatialand time scales, from small granular-sized events to large active regions. Theexistence of a small scale dynamo also implies that flux will emergecontinuously over the entire solar surface. This emergence will result inmultiple cancellations - in addition to those that result from the random walkof already emerged flux - but also in the injection of cool photosphericmaterial into the upper chromosphere and even lower corona with observationalconsequences for lines formed there. Widely studied from an observational pointof view in the low atmospheric layers (photosphere and chromosphere), there arestill many open questions regarding the overall 3D structure and evolution ofthe cancellation process, especially concerning the links of the lowatmospheric layers to the overlying transition region and corona. In this talkwe will concentrate on the cancellation process itself and its observationalconsequences as well as impact on the heating of the surrounding regions of theatmosphere. We will attempt to clearly define what is meant by cancellation,where we expect reconnection to occur and on what timeline as well asconcentrate on the evolution of the magnetic field to isolate emergence andsubmergence processes.