Arrival times of Flare/Halo CME associated shocks at the Earth: comparison of the predictions of three numerical models with these observations

Abstract

Abstract. The arrival times at L1 of eleven travelling shocks associated both with X-ray flaring and with halo CMEs recorded aboard SOHO/LASCO have been considered. Close to the Sun the velocities of these events were estimated using either Type II radio records or CME speeds. Close to the Earth the shocks were detected in the data of various solar wind plasma, interplanetary magnetic field (IMF) and energetic particle experiments aboard SOHO, ACE, WIND, INTERBALL-1 and IMP-8. The real-time shock arrival predictions of three numerical models, namely the Shock Time of Arrival Model (STOA), the Interplanetary Shock Propagation Model (ISPM) and the Hakamada-Akasofu-Fry Solar Wind Model (HAFv.2) were tested against these observations. This is the first time that energetic protons (tens of keV to a few MeV) have been used to complement plasma and IMF data in validating shock propagation models. The models were all generally successful in predicting shock arrivals. STOA provided the smallest values of the "predicted minus measured" arrival times and displayed a typical predictive precision better than about 8 h. The ratio of the calculated standard deviation of the transit times to Earth to the standard deviation of the measurements was estimated for each model (treating interacting events as composite shocks) and these ratios turned out to be 0.60, 1.15 and 1.02 for STOA, ISPM and HAFv.2, respectively. If an event in the sample for which the shock velocity was not well known is omitted from consideration, these ratios become 0.36, 0.76 and 0.81, respectively. LargerCorrespondence to: S. M. P. McKenna-Lawlor (stil@may.ie)statistical samples should now be tested. The ratio of the in situ shock velocity and the "Sun to L1" transit velocity (V sh /V tr ) was in the range of 0.7-0.9 for individual, noninteracting, shock events. HAFv.2 uniquely provided information on those changes in the COBpoint (the moving Connection point on the shock along the IMF to the OBserver) which directly influenced energetic particle rise times. This model also illustrated the non-uniform upstream conditions through which the various shocks propagated; furthermore it simulated shock deformation on a scale of fractions of an AU. On the spatial scale (300 R E ), where near-Earth spacecraft are located, the passing shocks, in conformity with the models, were found to be locally planar. The shocks also showed tilting relative to the Sun-Earth line, probably reflecting the inherent directionality associated with their solar origin.

The “Same Side – Opposite Side Effect” of the Heliospheric Current Sheet in Ionospheric Negative Storms

“…They are characterized by enhanced [N 2 ]/[O] and they propagate to lower latitudes carried by the horizontal neutral winds that arise from the pressure gradient force in the auroral oval and by ion drag in the polar cap. Then they cause negative storms by increasing the loss rate and decreasing the ionospheric electron density (see, e.g., Prölss, 1981Prölss, , 1993Buonsanto, 1999;Burns, Killeen, and Roble, 1991;Fuller-Rowell, Codrescu, and Araujo-Pradere, 2001). Feng and Zhao (2006) and Xie et al (2006) investigated the effect of HCS on propagation and geoeffectiveness of CME-ICME events and CME-IP shock events, respectively.…”

“…Ionospheric storms are often described as positive storms when foF2 is increased and as negative storms when foF2 is significantly reduced. The negative storm is caused by changes in the atmospheric composition, and this explanation has been fully supported by analyzer measurements (Prölss, 1980). At the main phase of a magnetic storm, the enhanced energy input from the magnetosphere causes considerable heating of the ionized and neutral gases in the auroral zone, leading to the "composition bulges".…”

“…The heliospheric current sheet (HCS), frozen in the solar wind and spread to the interplanetary space, is the boundary encircling the Sun that separates oppositely directed magnetic fields originating from the Sun, and it also represents the magnetic equator of the global heliosphere (Ness and Wilcox, 1964;Wilcox and Ness, 1965;. Since the HCS is a characteristic reference surface for the organization of the solar wind plasma, the influence of the HCS on the propagation and geoeffectiveness of solar disturbances in the interplanetary space have been studied in many papers (Burlaga, Hundhausen, and Zhao, 1981;Wei, Zhang, and Huang, 1990;Wei, Liu, and Zhang, 1991;Wei and Dryer, 1991;Zhao and Feng, 2005).…”

A statistical study of the performance of the Hakamada-Akasofu-Fry version 2 numerical model in predicting solar shock arrival times at Earth during different phases of solar cycle 23

“…, and references therein). These models include the "Shock Time of Arrival"/STOA Model (Dryer and Smart, 1984;Shea, 1984, 1985); the "Interplanetary Shock Propagation"/ISPM Model (Smith and Dryer, 1990); and the "Hakamada-Akasofu-Fry version 2"/modified HAFv.2 model Fry et al, 2001Fry et al, , 2003Fry et al, , 2004Fry et al, , 2005Fry et al, , 2007McKenna-Lawlor et al, 2002Sun et al, 2002aSun et al, , b, 2003. Overviews of the characteristics of these three models are provided in Sect.…”

A New Prediction Method for the Arrival Time of Interplanetary Shocks

“…The performances of the above three models have been tested and the comparative study revealed that the performances of these three models were practically identical in forecasting the shock arrival time (McKenna-Lawlor et al, 2002;Fry et al, 2003;Cho et al, 2003;McKenna-Lawlor et al, 2006).…”