Coronal mass ejections (CME) are one of the most important phenomena derived from solar activity that potentially perturb space weather of Earth. In this work we present a semiempirical arrival forecasting tool for Earth‐directed halo CMEs. This tool combines the piston shock model and an empirical relationship to estimate in situ arrivals of halo CMEs. The empirical relationship uses the initial conditions of CMEs to calculate the value of free parameter of the piston shock model, a parameter which is closely related to the initial inertia of CMEs. Such a value will let the model to simultaneously approximate the travel time and arrival speed of CMEs (i.e., CME arrivals). We test the forecasting capabilities of our model and its empirical relationship by calculating the arrivals of 40 halo CMEs detected during the period of 1995–2015. Our results indicate that, together, the piston shock model and its empirical relationship approximate CME arrivals with average errors of 7 h for travel times, and 100 km s−1 for arrival speeds. Our results show that our model is suitable for arrival forecasting of isolated events propagating through quiet interplanetary medium.
In situ observations of interplanetary (IP) coronal mass ejections (ICMEs) and IP shocks are important to study as they are the main components of solar activity. Hundreds of IP shocks have been detected by various space missions at different times and heliocentric distances. Some of these are followed by clearly identified drivers, while some others are not. In this study, we carry out a statistical analysis of the distributions of plasma and magnetic parameters of the IP shocks recorded at various distances to the Sun. We classify the shocks according to the heliocentric distance, namely from 0.29 to 0.99 AU (Helios-1/2); near 1 AU (Wind, ACE, and STEREO-A/B); and from 1.35 to 5.4 AU (Ulysses). We also differentiate the IP shocks into two populations, those with a detected ICME and those without one. As expected, we find that there are no significant differences in the results from spacecraft positioned at 1 AU. Moreover, the distributions of shock parameters, as well as the shock normal, have no significant variations with the heliocentric distance. Additionally, we investigate how the number of shocks associated with stream-interaction regions (SIRs) increases with distance in the proportion to ICME/shocks. From 1 to 5 AU, SIRs/ shock occurrence increases slightly from 21% to 34%; in contrast, ICME/shock occurrence decreases from 47% to 17%. We also find indication of an asymmetry induced by the Parker spiral for SIRs and none for ICMEs.
In situ observations of interplanetary (IP) coronal mass ejections (ICMEs) and IP shocks are important to study as they are the main components of the solar activity. Hundreds of IP shocks have been detected by various space missions at different times and heliocentric distances. Some of these are followed by an ICME while not for others. In this study, we carry out a statistical analysis of the distributions of plasma and magnetic parameters of the IP shocks. We classify the shocks according to the heliocentric distance, namely from 0.29 to 0.99 au (Helios-1/2); near 1 au (Wind, ACE and STEREO-A/B); and from 1.35 to 5.4 au (Ulysses). We also differentiate the IP shocks into two populations, those with a detected ICME and those without it. We find, as expected, that there are no significant difference in the results from spacecraft positioned at 1 au. Moreover, the distributions of shock parameters, as well as the shock normal have no significant variations with the heliocentric distance. Additionally, we investigate how the number of shocks associated to stream interaction regions (SIRs) increases with distance in proportion of ICME/shocks. From 1 to 5 au, SIRs/ shock occurrence increases slight from 21% to 33%, in contrast ICME/shocks occurrence decreases from 47% to 17%. We find also no indication of an asymmetry induced by the Parker spiral.
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