In May 2024, the skies above Japan’s Honshu and Hokkaido islands had been set alight by a unprecedented auroral show, not like something scientists had noticed earlier than. This occasion, pushed by a strong geomagnetic storm, featured blue-dominant auroras, together with a salmon-pink glow, a phenomenon not often seen at low latitudes. While auroras are historically seen in inexperienced or pink hues, particularly in areas close to the Arctic and Antarctic, the looks of such uncommon blue auroras at these latitudes has left the scientific group with extra questions than solutions.
Captured by newbie photographers and verified by way of scientific information, these auroras have challenged long-established theories about their formation. Researchers from Japan and Sweden, led by Sota Nanjo and Professor Kazuo Shiokawa, examined the phenomenon utilizing public contributions and their very own information, unveiling new particulars concerning the spatial and structural traits of the blue auroras. The examine, printed in December 2024, has opened the door to a brand new chapter in understanding auroral processes.
Blue Auroras and the Unexpected Altitudes
Typically, auroras are produced by charged particles from the solar interacting with Earth’s magnetosphere. The ensuing collisions with atmospheric gases, notably oxygen and nitrogen, emit the intense, colourful glows we affiliate with auroras. However, the blue auroras noticed throughout this occasion had been not like something beforehand documented at such low latitudes.
In a normal aurora, inexperienced and pink colours are generated when oxygen atoms at altitudes between 100 and 200 km are excited by photo voltaic wind particles. But the blue auroras that appeared over Japan defied these expectations, glowing at altitudes between 400 and 900 km, a lot larger than the standard aurora-producing altitudes. This raised questions on what prompted this peculiar phenomenon.
As Professor Kazuo Shiokawa of Nagoya University explains, “Our findings recommend that nitrogen molecular ions could have accelerated upward by some mechanism and had been answerable for the formation of the blue-dominant aurora.” This concept introduces the opportunity of a brand new atmospheric course of at excessive altitudes, one which has not been noticed earlier than. However, there’s nonetheless a lot that scientists don’t perceive about how these nitrogen ions, that are usually heavy and unstable at such heights, can persist within the higher environment.
Challenging Existing Auroral Theories
The most accepted mannequin for aurora formation entails the ring present, a area of charged particles trapped in Earth’s magnetic subject. These particles are thought to supply energetic impartial atoms (ENAs), which then work together with the environment to create auroras. But the blue-dominant auroras noticed over Japan don’t align nicely with this concept.
Shiokawa highlights a key inconsistency: “In this examine, a construction of a number of hundred kilometers was discovered within the blue-dominant aurora within the longitudinal course, which is troublesome to interpret by ENA exercise solely. In addition, ENAs are unlikely to create auroral constructions aligned with magnetic subject strains, as noticed on this examine.” These findings recommend that conventional fashions of aurora formation could not totally clarify this new kind of aurora.
The blue auroras noticed in May 2024 additionally exhibited longitudinal constructions, which means the auroras had been organized alongside Earth’s magnetic subject strains—a function not beforehand recognized in low-latitude auroras. This discovery additional complicates the present understanding of aurora formation and raises questions concerning the presence of unidentified atmospheric processes at these larger altitudes.
The Mystery of Nitrogen Ions at High Altitudes
While the presence of nitrogen molecular ions has been advised as a doable clarification, the researchers admit that their precise conduct stays mysterious. “To date, it’s not nicely understood how nitrogen molecular ions with giant molecular weight can exist at such excessive altitudes,” mentioned Shiokawa. These ions aren’t secure in Earth’s environment at excessive altitudes resulting from their heavy mass and brief dissociative-recombination time intervals, which means they usually can not survive for lengthy in these areas.
The remark of nitrogen ions at altitudes of 400 km or extra defies typical scientific understanding. The course of that enables these ions to exist at such excessive altitudes stays shrouded in thriller. The discovery raises the likelihood {that a} beforehand unknown atmospheric mechanism could possibly be at play, one which accelerates nitrogen ions to those excessive heights.
