Flux tubes are an interesting aspect of astrophysics. Flux or more accurately magnetic flux is the amount of magnetic field line flowing through a given 2D surface. A flux tube is therefore infinitely many circular 2D surfaces stuck together to create a long tube which magnetic field lines are imagined to flow through without ever exiting the sides of the tube. As magnetic field lines near the surface of the tube are always perpendicular to the surface they keep moving through and the total magnetic flux within the tube must stay constant even if the tube bends or grows and shrinks in diameter. Flux tubes and a slightly more advanced example that we’ll get onto in a second are found most prominently in the Sun. When large flux tubes are projecting out of the surface of the Sun then large amounts of magnetic field also flow out at this point, stymieing convection and producing a sunspot.
And we’re back. Two days ago I posted Manufacturing Magnetically Frustrated 2D System which contains a good basis for what frustration is. Although that one quickly diverted into the topic of magnetic frustration this post can stay more on the chemical side. If anyone isn’t familiar with the structure of ice it is demonstrated in the diagram on the right.
But is it? Ice can actually take on many different crystalline structures and the one displayed here is not the common one. This is called cubic ice and is the only other kind of ice found naturally on Earth and even then only in small quantities in the upper atmosphere. The common structure of ice is more hexagonal while this structure, relevant for today’s post, is quite similar to diamond with the oxygen being the carbon or for those who’ve seen it silicon dioxide with one of the atoms existing between the main structure points (in the case of SiO2 the atom is oxygen here it’s hydrogen).
Continue reading Perceiving Phase Changes In Water And Ammonia Mixtures
Most people are now very aware of at least the words gravitational waves. A considerable number know that they were discovered because of two black holes spiralling into each other, no other event could be as massively (very literally) catastrophic as to produce such waves. The common wisdom would probably end when asked how big a black hole is. The confused faces that result from question stem from the misleading that you can never escape a black holes gravitational pull. Of course we’re all getting pulled by black holes right now, every piece of mass in the universe attracts every other. If the Sun was to suddenly turn into a black hole with the same mass, the Earth’s orbit wouldn’t change. All the Earth knows is that there is a big mass resulting in a gravitational pull forcing it to go in a circle, the size (as in volume) of the object, whether it is a star or a black hole is quite irrelevant.
The Living With a Star (LSW) program is a project by NASA with the goal of understanding why the Sun varies over time and how this effects the Earth, more specifically, how it effects human life on Earth rather than just general geoastrophysics. The scientific portion of the project began on the 11th of February, 2010, when the Solar Dynamics Observatory (SDO) was launched into a geosynchronous orbit. This spacecraft was given the task of taking incredibly detailed readings from the Sun in regards to its magnetic field, corona and solar radiance. To perform this task three separate modules were integrated onto the satellite: The Helioseismic and Magnetic Imager (HMI); the Extreme Ultraviolet Variability Experiment (EVE); and the Atmospheric Imaging Assembly (AIA). Luckily it is the just the final one that we need to concern ourselves with today. The AIA unit is most similar to traditional photography being able to take pictures containing the whole Sun in eight different ultraviolet wavelengths and with very high resolutions (4096×4096).
Ultra high energy cosmic rays (UHECR) are cosmic rays which are measured to have over 1018 eV of kinetic energy. Many of these particles exist beyond the Greisen–Zatsepin–Kuzmin limit, a theoretical limit based on the interaction of the cosmic rays above a certain energy threshold and the photons of the cosmic microwave background radiation. In essence if the particles were of too high energy they would have interacted and slowed down, but this restriction only applies over a certain distance. UHECRs are believed to be produced locally and so are not restricted by the limit. There is also a possibility that heavier nuclei may circumvent the limit also, but what particles make up UHECRs are still unknown. Despite this the mass compositions have been measured by the Pierre Auger Observatory in Argentina which is believed to show particles of higher mass than helium with an upper limit of about iron.
I would hope that everybody reading would at least have some idea of what a solar flare is. When eruptions on the surface of the Sun are great enough it is possible for a coronal mass ejection to occur. This massive release of plasma (weighing up to 100,000,000,000 kg, and considering it’s gas that’s an incredible volume) and magnetic flux speed away from the Sun at about 1500 km s−1. They can be considered as one of the driving forces for space weather and are also important for understanding the Sun’s magnetic field in the corona. Now at the surface of the Sun, where the magnetic fields permeate, they end up bending back and reconnecting at constantly shifting points. This massive three dimensional structure is known as the magnetic flux ropes.
In recent years there has been increased interest amateur aerospace engineering with more and more individuals thinking it might be fun to give it a try. The CubeSat, originally proposed in 1999, is simply a cubic satellite with each edge only being 10 cm long. They normally contain simple commercial electronics and weigh no more that 1.5 kilo each. Normally they get thrown out of space station or dropped off as part of the payload on a rocket. They can carry a wide variety of scientific equipment (although only one or two at a time) and are perfect both for people wanting to learn about a bit of engineering and also researchers who want to perform simple mass studies in an astrophysical environment.