Methods for estimating total open heliospheric magnetic flux

Tuesday, 16 December 2014: 2:32 PM
Samantha DeMarco, Embry-Riddle Aeronautical University, Daytona Beach, FL, United States, Charles Nickolos Arge, AFRL/RVBXS, Kirtland Afb, NM, United States, Marios Pattichis, University of New Mexico Main Campus, Department of Electrical and Computer Engineering, Albuquerque, NM, United States, Rachel A Hock, USAF/AFRL, Albuquerque, NM, United States and Carl J Henney, Air Force Research Laboratory Kirtland AFB, Kirtland AFB, NM, United States
There are extended periods over the solar cycle where significant discrepancies occur between the observed open magnetic flux (i.e., those based on spacecraft observations) and that determined from coronal models. One explanation for the source of these discrepancies is that the magnetic fields in CMEs, which have yet to disconnect from the Sun and are thus “closed,” are nonetheless included in open flux estimates because open and closed magnetic field lines are not easily distinguished in spacecraft data. Another possibility is that a portion of the open flux measured by in-situ spacecraft originates from the time-dependent evolution of solar magnetic fields that is not captured by static or steady state coronal model solutions. In this paper, we compute total open heliospheric magnetic flux using three different methods and compare these results with those obtained using in-situ interplanetary magnetic field observations. The first two methods make use of the Potential Field Source Surface (PFSS) model to calculate the total open magnetic flux using as its input: 1) traditional Carrington or diachronic maps and 2) Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model synchronic maps. The diachronic and synchronic photospheric magnetic field maps are derived from identical sets of magnetograms taken with the National Solar Observatory (NSO) KPVT and VSM magnetographs. The third method makes use of observationally derived Helium and EUV coronal hole maps overlain on the above mentioned magnetic field maps to compute total open magnetic flux. Key questions to be addressed in this paper are: 1) do diachronic versus synchronic PFSS open flux estimates differ significant from one another and 2) how do open flux estimates based on observationally derived coronal holes compare with model and in-situ values?