Fig. 2: Minute-scale flare as a diagnostic tool for the jet geometry.

a Shows the 3-min (circle) and ten-minute (square) binned light curves measured during the orbit wherein a strong rapid variability of the order of a few minutes with high significance (4.7 σ) was observed. During this orbit, 3C 279 was found to be highly inconsistent with the constant flux having p-values 0.002 (χ²-test) and 10⁻⁵ (χ²-test) for the three-minute and 10-min binned light curves, respectively. Hence, the best-fit function to the 3-min binned light curve is deduced using the sum of two exponentials represented by the dashed cyan-blue line. Notably, the error bars in the light curve represent 1 σ uncertainty and the significance of each 3-min bin is colour-coded. b Shows a proposed sketch of the inner jet of a blazar, explaining the peak-in-peak light curve with reference to the jet-in-jet magnetic reconnection model. In this scenario, the magnetic field fragments into small plasmoids that interact and grow into monster plasmoids within the reconnection region. Subsequently, these massive plasmoids lead to the formation of mini-jets, which produce optically thin minute-scale gamma-ray flares. These mini-jets are represented in the sketch in magenta. Moreover, the emission from the reconnection region, as a whole, accounts for the observed envelope emission.