A study published July 31, 2026, reports that NASA’s Juno spacecraft detected several kinds of plasma waves during two crossings of Jupiter’s bow shock on December 10 and 11, 2024. The inbound crossing also showed magnetic structures recurring about every 8.3 seconds. The study’s authors consider shock self-reformation the most likely explanation for that pattern.
What Juno crossed at Jupiter
Juno crossed Jupiter’s bow shock outbound at about 17:25 UT on December 10, 2024, then crossed back inbound at about 03:05 UT on December 11. A bow shock is the boundary where the solar wind—a flow of charged particles from the Sun—slows as it encounters Jupiter’s magnetic environment. The incoming flow’s bulk kinetic energy is converted primarily into heat through collisionless processes, including interactions between particles and waves.
The two crossings had different shock geometries. The reported angle between the magnetic field and the shock normal was 16.5° ± 14.3° outbound and 53.5° ± 7.9° inbound.
Ion-acoustic harmonics and an 8.3-second magnetic pattern
In the December 11 crossing, Juno’s Waves instrument recorded ion-acoustic waves at the shock foot. These plasma oscillations had harmonic components at 5,610, 11,130, and 16,680 Hz, with a maximum electric-field amplitude of about ±0.015 V/m. The study describes this harmonic structure as the first direct observation of its kind at a planetary bow shock.
The inbound crossing also contained magnetic structures that recurred about every 8.3 seconds. Other plasma waves reported in or around the crossings included electron cyclotron drift instability waves, electrostatic solitary waves, Langmuir waves, and electron Bernstein waves.
| Observed phenomenon | Reported measurement | Observation context |
| Ion-acoustic harmonics | 5,610, 11,130, and 16,680 Hz; maximum amplitude about ±0.015 V/m | Shock foot, December 11 crossing |
| Magnetic structures | Recurrence about every 8.3 seconds | Inbound crossing, December 11 |
| Electron cyclotron drift instability waves | About 18 spectral peaks spaced roughly 300 Hz; peak amplitude about 0.06 V/m | Shock ramp near 03:06:06.780 UT, December 11 |
| Electrostatic solitary waves | Lifetimes about 0.2 ms; amplitudes of several tens of mV/m | Reported around the crossings |
What the magnetic pattern may mean
The study’s authors consider shock self-reformation the most likely explanation for the 8.3-second magnetic recurrence. In this process, reflected ions may help rebuild the shock front. The recurrence itself was observed; the proposed mechanism was not directly confirmed through ion reflection.
Juno’s instruments sampled different signals at different rates. The Waves instrument recorded electric-field waveforms at 50 kHz in burst mode, intermittently at a 12.5% duty cycle. MAG measured magnetic fields near the shock at up to 8 Hz, typically 1 Hz. JADE’s ion measurements came at a two-minute cadence—far slower than the observed 8.3-second recurrence—so they could not directly confirm ion reflection on that timescale.
How Jupiter’s bow shock interacts with the solar wind
The waves offer a view of how energy moves through the boundary where the solar wind meets Jupiter’s magnetic environment. But the study’s estimates of wave-power dissipation are qualitative: Juno’s instruments were not designed to quantify that energy loss. Its single-probe electric-field configuration also prevented determination of wave polarization and phase velocity.
