euronews’ web team asks a European Space Agency expert about the risks and basic information on the solar storm that’s currently making headlines.
We are pleased to have joined solar physicist Dr. Bernhard Fleck, SOHO Project Scientist.
(ESA Website: SOHO overview )
Dr. Fleck, what exactly is a solar storm?
The term “solar storm” is relatively new. It was introduced about 10 years ago when colleagues from the public education & outreach side tried to explain “space weather” to the public and the main stream media. It suggests something dynamic and potentially dangerous.
A major solar storm (as the one we’ve been observing over the last couple of days) has three major components:
A) X-ray flare
Flares are observed best in soft X-rays or the extreme ultraviolet light (e.g. with SDO/AIA or the soft X-ray telescope on Hinode)
They are the result of a sudden and dramatic heating of a small, localized volume in the solar corona to over 10 million degrees. The enhanced X-ray and EUV emission causes increased ionization in our ionosphere. Possible effects of the increased ionization are radio blackouts and a degradation of the accuracy of GPS signals, as the wave travel time of the GPS signal depends on the ionization degree of the medium in which the signal travels. The X-ray flash arrives with the speed of light, i.e. about 8 min after the event happened on the Sun.
B) Coronal Mass Ejection (CME)
Practically all large flares are associated with coronal mass ejections, in which up to 10 billion tons of hot coronal plasma are ejected at speeds of up to 10 million km/h. Flares and CMEs are two very different things (but often mixed). A “flare” is the sudden brightening of a relatively small region on the Sun, mainly in X-rays and EUV, i.e. electromagnetic radiation; a CME is the ejection of real matter into the heliosphere (interplanetary space). CMEs are best observed with white light coronagraphs, such as the LASCO instrument on SOHO.
If the magnetic plasma cloud of a CME hits Earth’s magnetosphere, it can create geomagnetic disturbances (geomagnetic storms). Important parameters determining the severity of a geomagnetic storm are the speed and density of the CME, and – most importantly – the magnetic field configuration of that plasma cloud. If it is northward directed, it cannot couple into Earth’s magnetic field and is therefore deflected.
For a CME to be “geo-effective”, the magnetic field of the plasma cloud needs to have a significant southward component. Among the effects of a geomagnetic storm are voltage control problems of power systems (including damage to transformers), spacecraft surface charging that could damage electronic circuits, and increased spacecraft drag. Geomagnetic storms have one very beautiful side effect: polar lights.
The typical travel time of a CME to Earth is 1 1/2 to 3 days.
C) Solar Energetic Protons (SEP)
Both the flare as well as the shock front of the CME plowing through the heliosphere can accelerate protons to very high energies. The speed of these energetic protons can reach a significant fraction of the speed of light. They start to arrive at Earth about half an hour to an hour after the event on the Sun. If you look at SOHO/LASCO images from the last couple of days, you notice lots of white specks and streaks. These are caused by energetic protons bombarding the detector (CCD) of the instrument.
It is these SEPs that pose a radiation hazard to astronauts outside a shielded environment and to passengers and crew in high-flying aircraft in polar regions. Other potential effects include damage to satellites (memory impacts, impacts on the star trackers, permanent damage to solar panels) and HF radio communication blackouts.
Should we be worried? Why?
Solar storms are nothing I’m worried about personally. This does not mean that they are unimportant. We need to monitor them and where possible take appropriate action to mitigate their effects. But I don’t see any reason to scare people.