Magnetic explosions in space

2001/03/29 Carton Virto, Eider - Elhuyar Zientzia

• Klima
• Astrofisika

At the end of the atmosphere is the magnetosphere, the natural magnetic shield that protects the Earth. The magnetosphere obstructs and diverts particles charged by the Sun and makes the Earth habitable, but it is not a very quiet place and often magnetic storms occur. Then, magnetic energy is emitted at full speed.

Storms can last a few minutes or a few days and, in addition to generating spectacular auroras, they can interrupt satellite communications. Researchers have been trying to understand how magnetic energy can be emitted so quickly for forty years. There is a theory that has emerged and has been reinforced in recent years and today in the journal Nature have been published experimental data that coincide with this theory.

The magnetic energy of space is produced by moving plasma. The plasma is formed by ions and when it meets a magnetic field, it takes characteristic motion patterns that reinforce this field. The process is called dynamo and is similar to what happens at the core of all planets. The opposite is the mystery of how magnetic energy is transformed into kinetic energy of plasma. Clarifying it is critical to answer scientific questions such as why star crowns are warmer than skin or why plasma escapes in fusion experiments.

One of the great mysteries is to discover why and how magnetic energy comes off as soon as possible. To explain this, a magnetic reconnection has been proposed in recent years. In regions where the magnetic field is inverted, magnetic field lines act as if they were pieces of rubber and release energy by their spring movement (see figure). In this process, the magnetic energy of the field and plasma are thrown on both sides, while in half the field lines the plasma pressure is increased inward.

The theoretical model of magnetic reconnection is endorsed by satellite data, but has had a big problem to date. That two models were proposed for the representation of the field lines, with data defending one and the other defending the other. Model 2a of the figure is perfectly related to the output velocities measured for plasma, but computer models rely mainly on model 2b proposed in the 50s. However, the 2b model cannot explain why the phenomenon is explosive.

A few years ago a new behavior for plasma was defined that would unite model 2b with explosiveness, and that has been observed for the first time today. In the region where the magnetic field is inverted, it was postulated that electrons and protons should not move together and a new plasma wave, the whispering plasma, was defined. The whispering plasma is capable of greatly accelerating electrons, creating a special magnetic field and causing explosions in model 2b.

The whispering plasma was detected a few years ago and now a special magnetic field created by them has been detected. The observations coincide with the theoretical forecasts and have aroused great interest among scientists, although all are to be confirmed. The Cluster II mission already underway by ESA and the Magnetospheric Multiscale mission led by NASA can contribute to this.