The meeting began with our chairman, Mark Stronge, describing the new additions to the monthly EAAS newsletter which includes the latest astronomy news, a monthly observing guide, the all new Deep Sky Top 10 and the lunar and star charts. Mark also encouraged everyone to get actively involved on the EAAS forum on the website. He then introduced the main speaker, Mr. Ryan Milligan. Ryan has just finished his PhD in Astrophysics at Queens University and the title of his talk was “Solar Flares and Space Weather”
Ryan started his talk by outlining the main topics - the Solar Atmosphere and the Solar Cycle, Solar Flares and Coronal Mass Ejections (CME), Space Weather and Current Space Based Solar Observatories and Future Missions. He first showed two slides which demonstrated the full extent of the electromagnetic spectrum and how the sun can be viewed at different wavelengths along the spectrum. He then described the different regions of the sun. First there is the Photosphere or surface of the sun, its approximate temperature is 6,000 degrees Celsius and is the region where sunspots form. He went on then to the Chromo sphere, which is the region where you can view giant prominences of gas many times larger than the Earth. Its approximate temperature is 10,000 degrees Celsius. The final region of the sun described was the Corona. It can be viewed during a total solar eclipse and is an amazing sight. Its temperature is estimated to be more than 1 million degrees Celsius. This increase of temperature away from the sun’s surface is something which solar astronomers are currently investigating, as it is an unusual phenomenon.
Ryan then went on to describe how the sun is essentially a giant ball of gas with magnetic field lines across its surface. It does not rotate constantly and the equator region of the sun rotates more quickly than the polar regions. He then outlined the active regions of the sun - the Photosphere, the Chromo sphere, the Corona and the Magnetic Fields. He described the different terms used to classify the level of activity on the sun. This went up from alpha to beta to gamma and finally delta being the strongest. Ryan then discussed the Solar Cycle. It is an eleven year cycle where the sun goes from being highly active to very quiet. He outlined how current evidence is showing that the magnetic poles on the sun have begun to flip, a sign of a new cycle beginning. He went on to say that this new cycle, no. 24, was not due to start until next year and he estimated that it will peak around 2009-2010.
Ryan then moved onto the subject of Solar Flares. These are caused when positively charged regions on the sun’s surface clash with negatively charged regions. It is much like two tectonic plates clashing on Earth causing an earthquake. This creates a sudden release of energy. Solar flares are associated with Coronal Mass Ejections. These are massive ejections of material from the sun’s surface into space at a speed of six million miles per hour. Ryan then outlined the classification system for flares. The lowest level is class A, then B, C, M and finally X. There is a tenfold increase between each class, so a class B flare is 1,000 times less intense than a class X flare. Ryan then moved onto describe the solar activity of October/November 2003. This was the most active period ever since recorded history began. There was the largest ever solar flare ever recorded on the 4th November. This flare caused some damage on Earth, with power outages in Sweden and some satellites losing their orbits. However it also produced the wonderful Aurora Borealis (Northern Lights). Ryan then showed images of the same phenomenon occurring on Saturn, Jupiter and Mars because of the same flare. He then noted that six months later in April 2004, the sensors on the Voyager spacecraft picked up evidence of this flare when it was beyond the orbit of Pluto.
Ryan then moved onto the area of Space Weather. He noted that it was important to monitor the weather in space as it can have consequences on Earth. Satellites can lose their orbit when the upper atmosphere becomes ionized and expands. Satellite components can be damaged as can power lines. Also transatlantic flights travelling over the pole sometimes have to be rerouted or even grounded in Greenland whilst the solar storms subside. For astronauts in the International Space Station, they can be exposed to dangerous levels of radiation during solar storms. However as previously noted, such storms can also produce wonderful phenomenon like the Northern Lights. Ryan then highlighted a website www.SolarMonitor.org which he described as a ’one-stop shop’ for monitoring the sun.
Ryan then outlined the current solar missions and the future ones. He first talked about The Solar and Heliospheric Observatory (SOHO), which was launched in December 1995 and was only supposed to be a two year mission, but is still going strong eleven years later. Among other things, it has discovered one thousand comets. He also mentioned the Transition Region and Coronal Explorer (TRACE) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) missions. Ryan then talked about Solar-B which was launched on September 22 of this year. Its purpose is to study the cause of solar flares and CME‘s. He then mentioned the Solar Dynamics Observatory (SDO) which is due for launch in 2008, its purpose to try and understand the solar cycle. Ryan completed his talk by outlining four questions which solar astronomers hope to answer in the future - How is the Corona heated?, What causes Solar Flares?, How are the Solar Flares and CMEs’ related? and What is the origin of the Solar Cycle? He then took questions from the audience who enjoyed an excellent talk.
Until Next Month