Earth Struck by Historic Gamma-Ray - Cosmic Flash

ESA’s Integral space telescope has detected a remarkably intense and enduring gamma-ray burst (GRB) at 14:21 BST / 15:21 CEST on October 9, 2022. This event, which was observed by numerous high-energy satellites near Earth, including ESA’s Integral mission, stands out as one of the brightest GRBs ever recorded. The burst, originating from a star that exploded nearly two billion light-years away, caused a significant disruption in Earth's ionosphere. While disturbances in the ionosphere are typically associated with energetic particle events on the Sun, this particular occurrence offers a unique opportunity to study the effects of a distant stellar explosion. By analyzing the impact of this burst, scientists hope to gain valuable insights into the mass extinctions that have occurred throughout Earth's history.

The International Gamma-Ray Astrophysics Laboratory (Integral) has been detecting gamma-ray bursts on a daily basis since its launch in 2002. However, the recent detection of GRB 221009A was exceptional due to its brightness, which is considered the strongest ever measured. Gamma-ray bursts were once a mystery, but now they are known to be the result of energy released from exploding supernovae or the collision of neutron stars. Co-author Pietro Ubertini stated that statistically, a GRB as strong as GRB 221009A only occurs once every 10,000 years.

The burst of gamma rays that impacted Earth for 800 seconds had a significant impact on the planet's ionosphere. Lightning detectors in India were activated by the burst's energy, while instruments in Germany detected disturbances in the ionosphere that lasted for several hours. This unprecedented amount of energy led the team to investigate the effects of the burst on the ionosphere. The ionosphere, which is the upper layer of Earth's atmosphere containing electrically charged gases, extends from 50 km to 950 km in altitude. It is divided into the top-side ionosphere above 350 km and the bottom-side ionosphere below that. Despite its tenuous nature, spacecraft can maintain orbits within most of the ionosphere. The China Seismo-Electromagnetic Satellite (CSES), also known as Zhangheng, is one such spacecraft that monitors the top side of the ionosphere for changes in its electromagnetic behavior. Launched in 2018 as a joint Chinese-Italian mission, its primary objective is to study potential connections between ionospheric changes and seismic events like earthquakes. Additionally, it can investigate the impact of solar activity on the ionosphere. Mirko and Pietro, both members of the CSES science team, recognized that if the gamma-ray burst had caused a disturbance, CSES would have detected it. However, they couldn't be certain as they had not observed this effect from previous gamma-ray bursts.

In the past, it was believed that Gamma-Ray Bursts (GRBs) did not have enough power to affect the top-side ionosphere and produce a variation in the ionospheric conductivity leading to an electric field variation. However, recent observations have shown that this is not the case. Scientists have detected an intense perturbation in the form of a strong electric field variation in the top-side ionosphere caused by a GRB that took place almost 2 billion light-years away. This GRB had enough energy to affect Earth and trigger instruments that are generally used to study solar flares.

The disturbance caused by the GRB impacted the very lowest layers of Earth's ionosphere, leaving an imprint comparable to that of a major solar flare. This imprint came in the form of an increase in ionization in the bottom-side ionosphere, which was detected in very low frequency radio signals that bounce between the ground and Earth's lower ionosphere. The fact that a GRB can have such a far-reaching impact on Earth reinforces the idea that a supernova in our own galaxy might have much more serious consequences.

1. The potential consequences of a burst affecting the ionosphere are dire, as it could lead to damage of the ozone layer and the subsequent penetration of harmful ultraviolet radiation from the Sun to Earth's surface. This phenomenon has been linked to mass extinction events in the past, but further investigation is necessary to confirm this theory.

2. The team responsible for studying this phenomenon has begun analyzing data collected by CSES and comparing it to other gamma-ray bursts observed by Integral. Although they can only examine data from 2018 onwards, a follow-up mission has already been planned to continue this research and gain a deeper understanding of how Earth interacts with the Universe.

Reference: “Evidence of an upper ionospheric electric field perturbation correlated with a gamma ray burst” by Mirko Piersanti, Pietro Ubertini, Roberto Battiston, Angela Bazzano, Giulia D’Angelo, James G. Rodi, Piero Diego, Zhima Zeren, Roberto Ammendola, Davide Badoni, Simona Bartocci, Stefania Beolè, Igor Bertello, William J. Burger, Donatella Campana, Antonio Cicone, Piero Cipollone, Silvia Coli, Livio Conti, Andrea Contin, Marco Cristoforetti, Fabrizio De Angelis, Cinzia De Donato, Cristian De Santis, Andrea Di Luca, Emiliano Fiorenza, Francesco Maria Follega, Giuseppe Gebbia, Roberto Iuppa, Alessandro Lega, Marco Lolli, Bruno Martino, Matteo Martucci, Giuseppe Masciantonio, Matteo Mergè, Marco Mese, Alfredo Morbidini, Coralie Neubüser, Francesco Nozzoli, Fabrizio Nuccilli, Alberto Oliva, Giuseppe Osteria, Francesco Palma, Federico Palmonari, Beatrice Panico, Emanuele Papini, Alexandra Parmentier, Stefania Perciballi, Francesco Perfetto, Alessio Perinelli, Piergiorgio Picozza, Michele Pozzato, Gianmaria Rebustini, Dario Recchiuti, Ester Ricci, Marco Ricci, Sergio B. Ricciarini, Andrea Russi, Zuleika Sahnoun, Umberto Savino, Valentina Scotti, Xuhui Shen, Alessandro Sotgiu, Roberta Sparvoli, Silvia Tofani, Nello Vertolli, Veronica Vilona, Vincenzo Vitale, Ugo Zannoni, Simona Zoffoli and Paolo Zuccon