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These strange ripples in the heliosphere - BFC space

These strange ripples in the heliosphere – BFC space

Graphical representation of the heliosphere and shock front (NASA)

A group of American researchers has discovered strange ripples at the edge of the heliosphere, the region where the solar wind slows down and does not counteract the pressure of outer interstellar space. Discovery matured from data collected by probes Voyager And theInterstellar Frontier Explorer (IBEX) NASA. IBEX, which has been in orbit around the Earth since 2009, aims to study properties and phenomena at the boundaries of the Solar System.

Schematic representation of structures located on the border with interstellar space. The heliosphere is located in the same region as the Kuiper belt, and therefore is still under the influence of the Sun’s gravity. (NASA)

An area still incomprehensible

Other research has already shown that the heliosphere was anything but calm. In particular, the Vayagers showed their versatility and a certain dependence on solar activity.

Previous analyzes have instead shown how the structure of the heliosphere can be inferred from the interrelationships between the evolution of solar wind pressure and energy emissions from neutral atoms. In the apical direction there is also a shock front which is constantly monitored by IBEX.

Representation of the Interstellar Border Explorer (IBEX) satellite. (NASA)

Analyzing data from the three spacecraft, the researchers recorded a sudden change in pressure exerted by the solar wind at the end of 2014. The dynamic pressure of the solar wind increased by 50% in 6 months which increased the production of energetic neutral atoms whose anisotropy, intensity and direction were measured by IBEX. This relatively short event was used as a marker to map the heliosphere and the shock interface.

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like sonar

To reconstruct the shape of the structures, the proportion of the atom flux was measured and pushed back toward the solar system. In many ways, those atoms were behaving like sonar, so the arrival times of the signals reshaped the heliosphere, close to the Kuiper belt.

An example of measurements made by the IBEX satellite. [Tratto da Zirnstein, EJ, Shrestha, BL, McComas, DJ et al. Nat Astron (2022)]

Surprisingly, the researchers found that clear ripples formed exactly in the boundary region, about one astronomical unit wide (the average distance between the Earth and the Sun). Comparisons of distances obtained with observations Voyager They indicate substantial differences in heliosphere boundaries in the northern versus southern hemispheres and movement over time. According to the study, there are about a dozen such huge ripples.

Ripples were detected in the study, varying in time and space. [Tratto da Zirnstein, EJ, Shrestha, BL, McComas, DJ et al. Nat Astron (2022)]

The heliosphere itself showed insignificant differences in distance, indicating that its shape is not constant over time but is constantly changing for reasons that are not yet understood.