data at 91.2 GeV*

We present a study of jet substructure using archived ALEPH e⁺e^- data at √s = 91.2 GeV. Jets are reconstructed with the anti-k_T algorithm over R ∈ [0.1, 1.2], providing a clean test of QCD without hadronic initial states. The fixed collision energy enables direct confrontation with perturbative predictions and establishes precision baselines. Beyond inclusive jet spectra and traditional substructure based on jet grooming, we examine further particle distributions inside jets, offering insight into parton shower dynamics. We introduce a new method based on Fourier decomposition of intra-jet particle azimuthal distribution, inspired by effects from flow in QGP in heavy-ion collisions. We study its dependence on jet energy, and jet axis choice. Detector effects are corrected with iterative unfolding, and systematic uncertainties are assessed. This serves as a set of novel substructure observables sensitive to jet evolution in vacuum. Looking forward, jet drift may also be explored in heavy-ion collisions to study possible flow effects. Collectively, these measurements broaden the understanding of jet substructure and inform future electron-ion collider studies.