Space Weather Tech - The photographic world of Graham Palmer

Most people are unaware of the fact that the planet we live on, is actually inside the outer atmosphere of the sun. The solar-terrestrial environment is a very complex one, and is often difficult to predict accurately. However, in our increasingly technological world of electronics and global communication, it is now essential to understand temper tantrums on the sun.

There are two small tutorials further down that go into a bit of detail about solar activity and how this affects Earth's magnetic field. I recommend you have a look at these if you are interested to join my aurora-alert list. There are some useful 'real-time' data links at the bottom of the page.

Latest News: (21st March 2008)
NASA releases detailed prediction for upcoming solar cycle.

NASA's Marshal Space Flight Centre has just released the latest, and probably most accurate prediction for the next solar cycle. The attached plot shows the situation as it stands in March, 2008, and implies that within the next few months, sunspot numbers will begin a fairly rapid surge. Also, the predicted peak for cycle 24 is roughly 10-15% higher than the previous cycle that peaked around 2000-2001. This next cycle is estimated to peak in 2011.

For more information of how these predictions are made, see: http://solarscience.msfc.nasa.gov/predict.shtml

The good news from all this, is that we can begin to expect a rise in frequency and power of magnetic storms around the Earth. These storms lead to the very beautiful aurora australis and borealis.

Click the thumbnail below to see full size image

E-mail alerts about expected solar and aurora activity are posted as required. To sign up for free, click here for the mailing list. These alerts are also now available online.

Latest alert: 2008-04-27

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The sun is not stable. It is like a teenage kid that is prone to out-bursts of considerable fury. Usually the tantrums come in cycles that last around 11 years from start to finish. During the peak, or solar max, the sun is usually covered in a parade of planet sized sun spots. These are relatively cool areas on the face of the sun, and so appear dark. They are the product of severe magnetic fields within the sun, which can twist up like coiled rubber bands in a toy airplane. These bands can loop far out into space then arc gracefully back to their point of origin. Super heated plasma travels along the magnetic loops and can be seen as beautiful prominences and filaments. If, however, the bands wind to tight... they snap open and release vast quantities of gas into space. In doing so, the already hot gas is heated to unimaginable temperatures, where the gas begins to glow in X-rays. A solar flare is born. Here on earth, the detection of these X-rays is the first sign of excitement.

Solar flares are eruptions on the surface of the sun when magnetic fields become 'tangled' and suddenly snap or unwind. There are five classes of flares. These range from the benign background hum of A-class activity, and the only-just more interesting B-class up to mild C-flares. From there we move up the scale to M-class - Now we are getting interested! Finally we come to the brave new world of X-class flares. These are what we want, the big guns. Within all these classes are increments ranging from 0 - 9.9. For example, a C2 flare releases double the energy of a C1 and a C9 is 9 times as powerful. An M1 flare is 10 times as energetic as a C1. In the case of X flares, there is no 'next level' so we just keep moving higher up the X scale. The fantastic X-17 flare we saw in November 2004 was at least 27 times more powerful than an M-1. Any size flare above C-class can result in a coronal mass ejection (CME).

A coronal mass ejection is the gaseous material that has been thrown out from the sun in a violent solar flare. (hopefully towards the Earth) These events result in the most energetic types of auroral displays, and the biggest storms can be seen from large areas of the earth. The best chance of earth being hit by such am event is when the spot group that produces it is near the solar meridian or centre-line. However, we can still catch glancing hits from events near the limb. In contrast, coronal holes are the quiet movers of solar activity. The corona is the atmosphere of the sun.

A Coronal Hole forms in the Sun's corona when the magnetic field 'opens.' That is, instead of roughly following the curvature of the Sun, the magnetic field lines over parts of the Sun 'break' open allowing solar material to escape through. When this occurs over solar equatorial regions, the escaping material can intercept the Earth - we then see quiet auroral glows, arcs and sometimes rays. When Earth encounters a wind stream from a coronal hole, there may be a prolonged period (2-5 days) of low to moderate auroral activity in the sky.

The sun-earth environment is a broad term used to describe the vast area of space between the sun an earth, and immediately surrounding the earth. It will help to think of this area as being part of the sun’s outer atmosphere. Here, charged particles flowing from the sun can interact with earth’s magnetic field, and find their way into our atmosphere, causing the aurora.

1. Solar wind velocity. This is measured in kilometres per second. The solar wind usually moves along at between 200 - 300 km/s. At these speeds, there is little chance of any auroras, even at the magnetic poles. The wind can be accelerated by either a coronal hole, or a CME. Typical coronal hole winds blow between 300 - 500 km/s but can reach 700 - 800 km/s. I start to pay attention when this gets above 450 - 500 km/s. At these speeds, the potential for auroral activity begins to steadily climb. Wind speeds from a CME can vary hugely. Anything from 400 - 2,000 km/s is possible. The stronger the wind, the greater the potential for auroras.

2. The inter-planetary magnetic field (IMF) is actually the magnetic field of the sun reaching far into space. This field can be either smooth and constant, or turbulent and quickly changing. The key things we are interested in are the Bz and Bt. Now don't ask me exactly what these stand for, because I don't know... However, they are related to the orientation and strength of the IMF.

2a. Bz measurements are either expressed as positive numbers eg. 1, 2, 3... (referred to as 'North') or negative values eg. -1, -2, -3... (referred to as 'South') When the Bz is positive (north) the particles in the solar wind slip quietly over earth's magnetic field, and auroras don’t get started. However, if the charge is negative (south) the solar wind connects with our magnetic field, and charged particles collide with the upper atmosphere, and an electric current causes the sky to glow. (just like a neon light) To make an analogy, imagine you are petting a cat… When you stroke from the shoulders towards the tail, the fur lays flat on the cats back, and a gentle purring sound can be heard. This is the ‘north’ orientation… Now try rubbing it the other way… Fur stands on end, sparks (and claws) fly… This is the ‘south’ orientation. The more the fur is rubbed the wrong way, the better the chance of seeing some red stuff… (aurora, that is) What we want to see is negative Bz. The higher the negative values, the better the show. -12 is better than -1. During the aurora storm of August 2004, the Bz reached about -50 at one stage, and this was the most impressive part of the display.

2b. Bt referrers to the intensity or strength of the IMF. Bt usually sits around 1 - 5 during quiet periods, but can climb to over 50 during a strong storm. The higher this value, the better. This is because if the Bt is low (say 10), then the Bz can't be very strong either, thus reducing the chance of good auroras.

3. Proton density. Usually just called density, this is the number of solar protons (hydrogen ions) to be found in one cubic centimetre of space above the Earth's magnetic field. Commonly, this hangs around 0.5 - 2.0. Strong shows can occur while this low, but higher values are better. Say 15 or higher.

4. Kp index. As I understand it, this is related to the amount of energy available in earth's magnetic field. Kp 1 is low. Kp 4 can result in a faint, but definite glow on the horizon at mid latitudes. (most of New Zealand fits in this area) Whereas Kp 9 is a full blown geomagnetic storm. If you ever see numbers like this, get off the computer and get to a clear sky!!!