Here comes the sun, but are we at risk from solar flares?
Elizabeth Norton, of Hampden, asked: Just lately there was news that a solar flare crossed the orbit of the Earth in recent times, missing the Earth by just five days. I understand that should a flare such as this strike the Earth, electricity supply, electronic appliances and communications would be in jeopardy.
What would be the most likely consequence of such an event and what could happen in a ‘‘worstcase’’ scenario? Ian Whittaker, a physicist at the University of Otago, responded: To answer this excellent question we first have to look at the processes on the Sun. Solar flares are a sudden release of energy made up of visible light, X-rays, radio waves and everything in between. These flares, while interesting from a research perspective, have very little effect on the Earth.
Solar flares are usually linked to a phenomenon we call Coronal Mass Ejections (CME). These are bubbles of solar material (hydrogen and helium particles) that get trapped inside a magnetic field just above the surface of the Sun. It can be imagined like a balloon inflating with the magnetic field acting as the rubber and the solar gas filling it.
The pressure increases and the magnetic field expands until the pressure of the gas is stronger than the magnetic tension. At this point the outer layer of the magnetic field and all the solar material within flies off into space and this is what is dangerous to us.
A solar flare can usually be seen accompanying the CME, but as the flare travels at the speed of light we usually observe it between one and three days before the arrival of the particles.
The emission of events from the Sun is highly dependent on how ‘‘active’’ the Sun is. It takes 11 years to go from quiet to active and back to quiet and you can tell the activity by the number of visible sunspots (historically recorded from 1826, although Galileo also kept track of them, circa 1600).
To answer the first part of your question, we get hit by CMEs fairly regularly. What generally happens is that the sea of highenergy particles hits our magnetic field and shakes it up. This plays an important role in atmospheric chemistry but the most obvious effect is that aurora (Northern and Southern Lights) can be seen further away from the poles. A CME strike is necessary for aurora to be seen in New Zealand.
A recent report in the scientific journal Space Weather stated that there was a 12 per cent chance of a dangerously powerful CME hitting the Earth in any 10-year period. To put this into context, this is approximately one such impact every 80 years.
The first such storm of this kind we are aware of is called the Carrington Event in September 1859, in which the preceding solar flare was visible to the naked eye, with subsequent aurora seen in Cuba! Lesley McDonald, of Sacred Heart School Dunedin, asked: Why is it that some children and teachers get nits constantly but others don’t get them at all? Is it
something to do with blood? Trish Priest, an epidemiologist at the University of Otago, responded: We don’t have anyone who is doing research in this area as far as I know. However, I’ve had a very quick look at PubMed and I can’t find any information about genetic or physiological host factors affecting the risk of infestation – presumably because this hasn’t been widely studied, since the studies I found have not taken blood samples.
Reasonably consistent risk factors seem to be female gender (I expect probably because of hair length, which is also a risk factor where it’s measured), age (children at higher risk, the exact age group at highest risk isn’t completely consistent but possibly early to mid-primary school age), coming from larger/more crowded households, going to schools with higher prevalence of infestation and, in some studies, poor quality housing.
Measures of socioeconomic status are reported as risk factors in some studies and not others, but all except one of the studies in my search were done in developing countries, so their socioeconomic status results may not be relevant to New Zealand.
So most of the risk factors could be conceptualised as relating to ‘‘opportunity to be infested’’ – that is, children whose hair is more likely to be in contact with the hair of other children, some of whom have headlice.
I didn’t see anything about teachers, but in principle I expect that teachers who teach children with headlice and/or whose own children have them, and who have long hair, are likely to be at increased risk.
It’s a condition that causes a lot of angst and which many parents of primary school-aged children are concerned about.
However, I know – from writing an unsuccessful application for a grant to do a pilot study of prevalence in schools here – that it’s quite hard to come up with a really convincing justification for funding research on head lice given all the other more serious health problems out there.
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