No abstract

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.

We present a physical methodology to reconstruct the trajectory of interplanetary shocks using type II radio emission data. This technique calculates the shock trajectory assuming that the disturbance propagates as a blast wave in the interplanetary medium. We applied this Blast Wave Reconstruction (BWR) technique to analyze eight fast Earth-directed ICMEs/shocks associated with type II emissions. The technique deduces a shock trajectory that reproduces the type II frequency drifts, and calculates shock onset speed, shock transit time and shock speed at 1 AU. There were good agreements comparing the BWR results with the type II spectra, with data from coronagraph images, in situ measurements, and interplanetary scintillation (IPS) observations. Perturbations on the type II data affect the accuracy of the BWR technique. This methodology could be applied to track interplanetary shocks causing TII emissions in realtime, to predict the shock arrival time and shock speed at 1 AU.

In the interval of 4–10 September 2017, the Sun presented multiple solar flares from active region AR 2673. There were also coronal mass ejections that interacted with the Earth's magnetosphere. This solar activity produced several space weather events. These events were observed with ground‐based instruments of the Mexican Space Weather Service. The Mexican Array RadioTelescope detected highly perturbed solar transits associated with Type I radio emissions from active regions. The Compact Astronomical Low‐frequency, Low‐cost Instrument for Spectroscopy in Transportable Observatories‐Mexican Array RadioTelescope station detected several radio bursts including a Type III associated with the X8.2 flare on 10 September. The magnetometer detected variations reaching a regional K index of 8.3 during the geomagnetic storm. The ionosphere over Mexico was disturbed by different space weather phenomena with the dominant effects of the geomagnetic storm. We used total electron content data to study latitudinal and longitudinal ionospheric effects in this interval. The cosmic rays monitor detected a Forbush decrease associated also with the geomagnetic storm. This low‐latitude instrumental network in Mexico allowed estimating the regional response to space weather events. Coincidentally with the space weather events referred above, there were also two other types of natural hazards affecting the country at that moment, the hurricane Katia category 2 in the Gulf of Mexico, and two major earthquakes (7 and 19 September 2018). The conjunction of these natural phenomena were close to creating a worst‐case scenario in terms of civil protection reaction.