GRB 221009A: The BOAT Burns, Eric; Svinkin, Dmitry; Fenimore, Edward ...
Astrophysical journal. Letters,
03/2023, Volume:
946, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract GRB 221009A has been referred to as the brightest of all time (BOAT). We investigate the veracity of this statement by comparing it with a half century of prompt gamma-ray burst ...observations. This burst is the brightest ever detected by the measures of peak flux and fluence. Unexpectedly, GRB 221009A has the highest isotropic-equivalent total energy ever identified, while the peak luminosity is at the ∼99th percentile of the known distribution. We explore how such a burst can be powered and discuss potential implications for ultralong and high-redshift gamma-ray bursts. By geometric extrapolation of the total fluence and peak flux distributions, GRB 221009A appears to be a once-in-10,000-year event. Thus, it is almost certainly not the BOAT over all of cosmic history; it may be the brightest gamma-ray burst since human civilization began.
ABSTRACT Since its launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has triggered and located on average approximately two γ-ray bursts (GRBs) every three days. Here, we present the third of a ...series of catalogs of GRBs detected by GBM, extending the second catalog by two more years through the middle of 2014 July. The resulting list includes 1405 triggers identified as GRBs. The intention of the GBM GRB catalog is to provide information to the community on the most important observables of the GBM-detected GRBs. For each GRB, the location and main characteristics of the prompt emission, the duration, peak flux, and fluence are derived. The latter two quantities are calculated for the 50-300 keV energy band where the maximum energy release of GRBs in the instrument reference system is observed, and also for a broader energy band from 10 to 1000 keV, exploiting the full energy range of GBM's low-energy NaiTl) detectors. Using statistical methods to assess clustering, we find that the hardness and duration of GRBs are better fit by a two-component model with short-hard and long-soft bursts than by a model with three components. Furthermore, information is provided on the settings and modifications of the triggering criteria and exceptional operational conditions during years five and six in the mission. This third catalog is an official product of the Fermi GBM science team, and the data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center.
Do terrestrial gamma‐ray flashes (TGFs) produce their own radio signatures? To explore this question, we analyze TGF data from the Fermi Gamma‐ray Burst Monitor, independent lightning geolocation ...data from the National Lightning Detection Network, and low‐frequency (LF) magnetic field waveforms, to determine the relationship between TGF generation and LF waveforms. LF waveforms associated with six TGFs are found to contain a clear and isolated slow pulse (~80‐μs duration) within a sequence of multiple fast pulses (<10‐μs risetime). We find that the slow LF pulse is produced simultaneously with the observed gamma rays, with an uncertainty as small as 7 μs. Simultaneity implies a consistent TGF source altitude range of approximately 10–15 km, which is consistent with previous estimates. These findings provide important evidence that the slow LF pulse, when observed, is associated with TGF production and perhaps produced by the electron acceleration itself.
Key Points
Approximately 10% of TGFs are simultaneous with a distinct and isolated slow low frequency radio pulse
Simultaneity implies that a TGF source altitude range of 10‐15 km is consistent with the analyzed examples
The consistency of the TGF and radio time scales indicate that the radio pulse is produced directly by the electron acceleration in the TGF production process
In this work, we investigate the effect of the geomagnetic field on terrestrial gamma ray flashes (TGFs). Although this effect should be relatively weak for a single event, for example compared to ...the effect of the electric field orientation in the source region, it must be systematically present. Indeed, we show that a statistically significant excess of TGFs is detected to the east of their presumed lightning source by Fermi‐Gamma‐ray Burst Monitor (GBM). The corresponding eastward deviation is found to be likely greater than 0.1° in longitude, which is consistent with the expected effect of the geomagnetic field on relativistic runaway electron beams producing TGFs. Using analytical and numerical means, we show that the geomagnetic deviation can be used to estimate the magnitude of the electric field in TGF source regions. The electric field magnitudes we obtain are consistent with those necessary to drive relativistic runaway electron avalanches (RREAs).
Key Points
Statistically significant excess of TGFs is detected to the east of their presumed sources by Fermi
This is consistent with the expected geomagnetic field effect on relativistic runaway electron beams
The discovered excess can be used to estimate the E‐field in TGF source regions, which is found close to or larger than the RREA threshold
Strong electric fields inside thunderclouds give rise to enhanced fluxes of high-energy electrons and, consequently, gamma rays and neutrons. During thunderstorms at Mount Aragats, hundreds of ...Thunderstorm Ground Enhancements (TGEs) comprising millions of energetic electrons and gamma rays, as well as neutrons, were detected at Aragats Space Environmental Center (ASEC) on 3200m altitude. Observed large TGE events allow for the first time to measure the energy spectra of electrons and gamma rays well above the cosmic ray background. The energy spectra of the electrons have an exponential shape and extend up to 30–40MeV. Recovered energy spectra of the gamma rays are also exponential in energy range 5–10MeV, then turns to power law and extends up to 100MeV.
► Particle acceleration in thundercloud electrical fields ► Detector location is close to thunderclouds, which enables to detect electrons before their attenuation. ► The spectra of electrons and gamma rays accelerated in the atmospheric electrical fields are obtained.
We report measurements of a terrestrial gamma ray flash (TGF) detected by the Fermi Gamma‐ray Burst Monitor that was produced during a negative cloud‐to‐ground (CG) lightning leader. This is the ...first report of a downward directed TGF occurring during a CG flash but detected by a space‐based instrument. The gamma ray photons are produced 3 ms preceding a return stroke (−146 kA) and are essentially simultaneous with an isolated low frequency radio pulse. Based on timing, the pulse is estimated to initiate at approximately 6 km altitude, and its polarity indicates downward moving negative charge, the opposite of regular satellite‐detected upward TGFs. A likely scenario is that the runaway electrons accelerate into the upper, positively charged end of the leader in a high field region, with the reverse positron beam generating upward gamma rays detectable from space. A search for similar waveform features indicates that this type of downward CG‐TGF may occur prior to 1% of high peak current CG strokes. Extrapolating gives a global rate of 5–10% of previously known TGFs and potentially a significant fraction of global TGFs.
Key Points
A TGF detected by Fermi GBM occurred 3 ms before a −CG stroke during the descending negative leader, coincident with a 120 μs radio pulse
The radio pulse polarity indicates that it is likely a downward TGF produced at ~6 km altitude with a reverse positron beam detected by Fermi GBM
This type of downward CG‐TGF may occur prior to 1% of high‐intensity CG strokes, constituting 5–10% of the previously known TGF population
Terrestrial gamma ray flashes (TGFs) are brief bursts of energetic gammy‐ray photons generated during thunderstorms, which have been detected almost exclusively by satellite‐based instruments. Here ...we present three lines of evidence which includes the three out of three simultaneously observed pairs, the same occurrence contexts, and the consistent estimated occurrence rate, which indicate a direct relationship between a subset of TGFs and a class of energetic radio signal easily detectable by ground‐based sensors. This connection indicates that these gamma ray and radio emissions are two views of the same phenomenon and further enable detection of these TGFs from ground distant radio signals alone. Besides dramatically increasing the detection rate of TGFs, this ground detection approach can identify TGFs in continental and coastal areas that are at latitudes too high for present TGF‐detecting satellites and will provide more insights into the mechanism of TGF production.
Key Points
+EIPs and a subset of TGFs are intrinsically linked, and they are the two views of the same phenomenon
+EIPs can serve as a proxy for the ground detection of TGFs from distant electromagnetic radio signals
More measurements can be done on +EIP‐TGFs on land and thus deepen the insight into TGFs
The electric field change (E‐change) data presented herein provide a complementary view of a known terrestrial gamma ray flash (TGF), namely, TGF1 from Cummer et al. (). The main E‐change pulse ...coincident with TGF1 was likely an initial breakdown (IB) pulse of an intracloud (IC) flash since it had the typical characteristics of such an IC IB pulse: a bipolar shape with a positive leading peak and a duration of 47 μs. The IB pulse was especially energetic, with an estimated zero‐to‐peak amplitude between 36 and 47 V/m range normalized to 100 km (compared to an average IC IB pulse amplitude of ~1.5 V/m). The positive peak of the IB pulse occurred 19 μs after the beginning of the pulse. The first and most energetic gamma ray (7.6 MeV) detected in TGF1 occurred at 9 ± 10 μs after the beginning of the IB pulse. Thus, at the earliest the first detected gamma ray may have been produced just before or at the beginning of the IB pulse; at the latest, it may have been produced at the peak of the IB pulse.
Key Points
The electric field pulse associated with a TGF is identified as an initial breakdown (IB) pulse of an intracloud flash with 47 microseconds duration
The IB pulse had an exceptionally large zero‐to‐peak amplitude that was a factor of 25–30 larger than typical of IB pulses
The first TGF gamma ray detected was the most energetic (7.6 MeV) and occurred at 9 ± 10 microseconds after the beginning of the IB pulse
A transpolar arc (TPA), which extended from postmidnight to prenoon, was seen on 16 September 2001 in the Northern Hemisphere under northward interplanetary magnetic field (IMF)‐Bz and weakly ...dawnward IMF‐By conditions. Super Dual Auroral Radar Network detected significant westward plasma flows just equatorward of the poleward edge of the midnight sector auroral oval. These plasma flows were confined to closed field lines and are identified as the ionospheric plasma flow signature of tail reconnection during IMF northward nonsubstorm intervals (TRINNIs). These TRINNI flows persisted for 53 min from prior to the TPA appearance to the cessation of TPA growth. They are usually observed before (and during) intervals when TPAs are present, but in this case, subsided after the TPA was completely connected to the dayside. Additional slower flows across the open/closed polar cap boundary were seen at the TPA onset time in the same magnetic local time sector as the nightside end of the TPA. These ionospheric flows suggest that magnetotail reconnection significantly contributed to the TPA formation, as proposed by Milan et al. (, https://doi.org/10.1029/2004JA010835). We propose a possible scenario for an absence of the TRINNI flows during the TPA brightening by considering the relation between the extent of the magnetotail reconnection line mapped onto nightside auroral oval and the TPA width; TRINNI flows would subside when the extent of X‐line is comparable to the TPA width. Therefore, our results suggest that the fate (absence or presence) of TRINNI flows on closed field lines during the TPA formation would be closely related with magnetotail reconnection extent.
Plain Language Summary
Magnetotail magnetic reconnection is considered as one of the most possible mechanisms to form transpolar arc (TPA), frequently seen under the northward interplanetary magnetic field conditions. The closed flux tube formed by nightside reconnection is considered as a source of the TPA. When magnetotail reconnection occurred, reconnection‐accelerated westward plasma flows can be observed on the midnight sector of the main auroral oval. These flows are identified as the ionospheric plasma flow signature of tail reconnection during interplanetary magnetic field northward nonsubstorm intervals (TRINNIs), which is an indispensable phenomenon to physically explain the growth and brightening of TPA based on nightside magnetic reconnection as proposed by Milan et al. (, https://doi.org/10.1029/2004JA010835). We find the case where the ionospheric TRINNI flows were seen just before and during the TPA growth from the nightside main auroral oval, but subsided during the TPA brightening, when the TPA completely connected to the dayside region. There was clear evidence where magnetotail reconnection had persisted even during the TPA brightening in our case. In this study, based on the ionospheric plasma flow patterns just before and during the TPA formation, we discuss plausible cause why the ionospheric TRINNI flows subsided during the TPA brightening; nevertheless, magnetotail reconnection process persisted.
Key Points
We present a case where ionospheric fast flows in the midnight sector main auroral oval subsided during a transpolar arc brightening
We suggest that subsidence of these flows during the transpolar arc brightening is closely related to the extent of nightside reconnection
The static nature of the arc is explained by its proximity to the cusp, where lobe reconnection signatures are observed by Cluster
Many of the details of how terrestrial gamma‐ray flashes (TGFs) are produced, including their association with upward‐propagating in‐cloud lightning leader channels, remain poorly understood. ...Measurements of the low‐frequency radio emissions associated with TGF production continue to provide unique views and key insights into the electrodynamics of this process. Here we report further details on the connection between energetic in‐cloud pulses (EIPs) and TGFs. With coordinated measurements from both ground‐based radio sensors and space‐based gamma‐ray detectors on the Fermi and Reuven Ramaty High Energy Solar Spectroscopic Imager spacecraft, we find that all ten +EIPs that occurred within the searched space‐and‐time window are associated with simultaneous TGFs, including two new TGFs that were not previously identified by the gamma‐ray measurements alone. The results in this study not only solidify the tight connection between +EIPs and TGFs, but also demonstrate the practicability of detecting a subpopulation of TGFs with ground‐based radio sensors alone.
Plain Language Summary
Terrestrial gamma‐ray flashes (TGFs) are kinds of high‐energy emissions produced during thunderstorms and are almost exclusively detected with spacecraft‐based gamma‐ray detectors. Because of the strong atmospheric gamma‐ray attenuation from the low‐altitude atmosphere and the geometry‐driven short horizontal detection range, the ground detection of TGFs with gamma‐ray detectors is challenging. Recently a class of distinct radio emissions during thunderstorms, called energetic in‐cloud pulses (EIPs), was found to be closely linked to the production of some TGFs. In this study, we present several additional lines of strong evidence that strengthen the connection between a subpopulation of TGFs and EIPs. Importantly, by identifying EIPs from radio signals, we found two new TGFs that were previously unreported from space‐based detection. This demonstrates that some TGFs can be detected from the radio measurements alone when the spacecraft‐based detectors are unavailable.
Key Points
Positive polarity energetic in‐cloud pulses (+EIPs) produce terrestrial gamma‐ray flashes (TGFs) with high‐to‐certain probability (74%–100%)
New TGFs previously missed by space‐based detectors were found by ground detection of +EIPs
Demonstrated that a subset of TGFs can be found from remote ground‐based radio detection alone
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