The Extensive Air Showers (EAS) with delayed particles have been detected by the Horizon-10T experiment, located at the elevation of 3346 m above sea level near the city of Almaty, Republic of Kazakhstan. Among these EAS with delayed particles there were events that had signals with two distinct pulses (maximums or modes). Such pulses we call bimodal, and showers-bimodal events. This article presents the study of the properties of only bimodal events and comparison of these properties with the EAS that were simulated using the CORSIKA software package. This thorough comparison has shown that bimodal events cannot be explained only by known physical processes taking place in electron-hadron showers.

A total of 23500 Extensive Air Showers (EAS) with energies above ∼ 10 16 eV have been detected during the ∼3500 hours of the Horizon-T (HT) detectors system operations before Aug. 2016. Among these EAS, more than a thousand had an unusual spatial and temporary structure that showed pulses with several maxima (modals or modes) from several detection points of the HT at the same time. These modes are separated in time from each other starting from tens to thousands of ns. These EAS have been called multimodal. Analysis shows that the multi-modal EAS that have been detected by Horizon-T have the following properties:1. Multi-modal EAS have energy above ∼10 17 eV. 2. Pulses with several modes are located at large distances from the EAS axis.An overview of the collected data will be provided. General comments about the unusual structure of the multi-modal EAS will be presented.

The Extensive Air Shower (EAS) data collected by the Horizon-10T detector system has numerous events exhibiting the unusual spatial and temporal structure. These are events typically with two to four pulses of tens of ns wide that are present at distances above 300 m from the EAS axis, with these pulses being delayed by hundreds of ns. Each of such pulse groups were registered simultaneously by several detectors separated by up to a km from each other. The detectors brief overview and the analysis of simulated EAS by the CORSIKA software package are given in this article. The analysis indicates that such events with unusual structure cannot be formed by showers with EM and hadronic components only. This indicates a possibility for a new process observation beyond the standard model description in the energy range above ~1018 eV.

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An innovative detector system called Horizon-T is constructed to study Extensive Air Showers (EAS) in the energy range above 10 16 eV coming from a wide range of zenith angles (0 o -85 o ). The system is located at Tien Shan high-altitude Science Station of Lebedev Physical Institute of the Russian Academy of Sciences at approximately 3340 meters above the sea level.The detector consists of eight charged particle detection points separated by the distance up to one kilometer as well as optical detector to view the Vavilov-Cherenkov light from the EAS. Each detector connects to the Data Acquisition system via cables. The calibration of the time delay for each cable and the signal attenuation is provided in this article. 1 dmitriy.beznosko@nu.edu.kz (also dima@dozory.us) a P. N. Lebedev Physical Institute of the Russian Academy of Sciences,