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Zhang Y.,CAS Institute of Geology and Geophysics | Du A.M.,CAS Institute of Geology and Geophysics | Feng X.S.,Chinese Academy of Sciences | Sun W.,University of Alaska Fairbanks | And 7 more authors.
Solar Physics | Year: 2014

Images observed by the twin spacecraft Solar TErrestrial RElations Observatory (STEREO) A and B appear as complex structures for two coronal mass ejections (CMEs) on 1 August 2010. Therefore, a series of sky maps of Thomson-scattered white light by interplanetary coronal mass ejections (ICMEs) on 1 August 2010 are simulated using the Hakamada-Akasofu-Fry (HAF) three-dimensional solar-wind model. A comparison between the simulated images and observations of STEREO-A and -B clarifies the structure and evolution of ICMEs (including shocks) in the observed images. The results demonstrate that the simulated images from the HAF model are very useful in the interpretation of the observed images when the ICMEs overlap within the fields of view of the instruments onboard STEREO-A and -B. © 2013 Springer Science+Business Media Dordrecht. Source

Wu C.-C.,U.S. Navy | Liou K.,Applied Physics Laboratory | Wu S.T.,Applied Physics Laboratory | Dryer M.,University of Alabama in Huntsville | And 3 more authors.
AIP Conference Proceedings | Year: 2012

There were nineteen flare associated coronal mass ejection (CME) events that were reported during the Halloween 2003 epoch from 19 October to 20 November [1]. Ten of these CMEs were associated with class X flares, 8 CMEs were associated with class M flares, and one CME was associated with a class C flare. Using a well-developed hybrid code, HAFv2+3DMHD, the evolution and interactions of 16 out of 19 interplanetary CMEs from 21 October to 17 November 2003 were simulated and investigated. The HAFv2+3DMHD model combines two physical base simulation codes: the Hakamada-Akasofu-Fry code (HAFv2) and a fully three-dimensional, time-dependent magnetohydrodynamic code. We compared simulated solar wind velocity, number density, temperature, and magnetic fields with those observed by the ACE spacecraft. We have demonstrated that our global three-dimensional (3-D) simulation model is capable of simulating the evolution and interaction of multiple CMEs in a realistic and continually changing complicated solar wind structure during uniquely severe space weather conditions at Earth. This study clearly demonstrates that the HAFv2+3DMHD model can be a useful tool for space weather operations. © 2012 American Institute of Physics. Source

Wu C.-C.,U.S. Navy | Liou K.,Johns Hopkins University | Plunkett S.,U.S. Navy | Fry C.D.,Exploration Physics International Inc. | Wu S.-T.,University of Alabama in Huntsville
Terrestrial, Atmospheric and Oceanic Sciences | Year: 2013

The unusually long-extended solar minimum between cycles 23 and 24 (from 2007 to 2008) yielded a number of anomalies with regard to solar/heliospheric phenomena wherein the solar wind magnetic field is 36% weaker than that for the previous solar cycle minimum (from 1996 to 1997) at 1 AU, the solar wind dynamic pressure is the lowest observed since the beginning of the space age, the unusually high tilted angle of the solar dipole, and the absence of a classical quiescent equatorial streamer belt. To understand the cause of the anomalies, we perform numerical simulation of a realistic inner heliosphere using a global three-dimensional, time-dependent, numerical model with observed solar inputs. It is suggested that these solar extremes are associated with (1) an inflated heliospheric current/plasma sheet (HCS/HPS) and (2) a decrease in the integrated fluxes of mass and magnetic field ejected from the Sun, which was manipulated by some unknown internal solar dynamics. Source

McKenna-Lawlor S.M.P.,National University of Ireland, Maynooth | Fry C.D.,Exploration Physics International Inc. | Dryer M.,Exploration Physics International Inc. | Dryer M.,National Oceanic and Atmospheric Administration | And 5 more authors.
Annales Geophysicae | Year: 2012

The performance of the Hakamada Akasofu-Fry, version 2 (HAFv.2) numerical model, which provides predictions of solar shock arrival times at Earth, was subjected to a statistical study to investigate those solar/interplanetary circumstances under which the model performed well/poorly during key phases (rise/maximum/decay) of solar cycle 23. In addition to analyzing elements of the overall data set (584 selected events) associated with particular cycle phases, subsets were formed such that those events making up a particular sub-set showed common characteristics. The statistical significance of the results obtained using the various sets/subsets was generally very low and these results were not significant as compared with the hit by chance rate (50%). This implies a low level of confidence in the predictions of the model with no compelling result encouraging its use. However, the data suggested that the success rates of HAFv.2 were higher when the background solar wind speed at the time of shock initiation was relatively fast. Thus, in scenarios where the background solar wind speed is elevated and the calculated success rate significantly exceeds the rate by chance, the forecasts could provide potential value to the customer. With the composite statistics available for solar cycle 23, the calculated success rate at high solar wind speed, although clearly above 50%, was indicative rather than conclusive. The RMS error estimated for shock arrival times for every cycle phase and for the composite sample was in each case significantly better than would be expected for a random data set. Also, the parameter "Probability of Detection, yes" (PODy) which presents the Proportion of Yes observations that were correctly forecast (i.e. the ratio between the shocks correctly predicted and all the shocks observed), yielded values for the rise/maximum/decay phases of the cycle and using the composite sample of 0.85, 0.64, 0.79 and 0.77, respectively. The statistical results obtained through detailed analysis of the available data provided insights into how changing circumstances on the Sun and in interplanetary space can affect the performance of the model. Since shock arrival predictions are widely utilized in making commercially significant decisions re. protecting space assets, the present detailed archival studies can be useful in future operational decision making during solar cycle 24. It would be of added value in this context to use Briggs-Rupert methodology to estimate the cost to an operator of acting on an incorrect forecast. © Author(s) 2012. Source

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