Saturday, July 21, 2012

Space Weather

Hi it's just me again, I talk about the weather on this page and you hear about the weather all the time. weather is all around us and it's a very important part of how we plan our activities, go about our lives, and even how we dress. When talking about weather, usually we think of temperature, rain or snow, the speed and direction of the wind, air pressure, how humid it is. Basically when we say the word weather, we're talking about the day to day atmospheric conditions of a particular place. The earth is not the only place that has weather; most of the other planets in the solar system have it. There's weather of a sort even in deep space. This blog post will touch on what space weather is, the different types of space weather, and how it affects us on the planet Earth.

What is space weather anyway?

Just like earthbound weather space weather is conditions in space that change from time to time. In our Solar System all space weather starts at the Sun. The Sun gives off radiation. The amount of radiation coming off the Sun is not constant, sometimes there a lot and sometimes there's very little. However, there is always some, this flow of particles off the Sun is called the solar wind. Space is filled with magnetic fields in the solar system, The interplanetary magnetic field (IMF) is a part of the Sun's magnetic field that is carried into interplanetary space by the solar wind. Because of the Sun's rotation, the IMF, like the solar wind, travels outward in a spiral pattern that is often compared to the pattern of water sprayed from a rotating lawn sprinkler. Earth's magnetic field (also known as the geomagnetic field) is the magnetic field (MF) that extends from the Earth's inner core to where it meets the solar wind. Earths strong MF is the reason Earth has liquid water.

Magnetic fields and magnetospheres are beyond the scope of this blog post. However, I will give a brief explanation as to what they are, so that we all have the same frame of reference.

Most of the planets in the solar system have a MF. Venus has none and Mars has one that is almost nonexistent. The earth has a strong MF, because it has a core made of solid nickel and iron. This inner core is surrounded by liquid iron and nickel. Because the core is so dense, the magnetic field is very strong. The Earth's MF is formed the same way as an electromagnet. In an electromagnet you wrap some insulated copper wire around a piece of iron (for example an iron nail); the wire is attached to the positive terminal of an battery and the other end of the wire to the negative terminal. Electricity in almost all conductors is just the flow of electrons. When the electric current passes through the wire wound around the nail, it creates a MF. In the case of the earth as electrons flow around the core a MF is created. The Earth's fast rotation causes the electrons to move at very high speeds. As for Venus, in part, it has no magnetic field because Venus has a rotation speed that is extremely slow (243 days). The lack of fast rotation doesn't allow electrons to flow in the numbers that's needed to create an MF.

The Magnetosphere:

The region above the ionosphere is called the magnetosphere. Our magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the magnetic field surrounding Earth. This magnetosphere is what protects the Earth from cosmic rays that would strip away the upper atmosphere, including the ozone layer that protects the earth from harmful ultraviolet radiation.

With the recent X-class solar flare and Northern Lights displays, you may have heard to something called Van Allen Belts. The Earth's Van Allen Belts consists of highly energetic ionized particles trapped in the Earth's MF. On the sunward side of the Earth, the MF is compressed by the solar wind, while on the opposite side of the Earth, the MF extend out much farther. As a result, inside the MF is an area known as the Chapman-Ferraro Cavity, which surrounds the Earth. The Van Allen Radiation Belts sit inside this area. It consists of an inner belt and a outer belt. The radiation belts contain protons, ions, and electrons. When particles from a Solar Flare interact with the belt some of the electrons produce auroras (the northern lights).

                                                     Solar particles interacting with Earth's magnetic field

                           Artist rendering of what solar influence looks like interacting with the magnetic field 

Sunspot Cycle:

The Solar Cycle (Solar Magnetic Activity Cycle). This cycle is what is commonly known as the Sunspot Cycle; it has a period of about 11 years in which the Sun goes from minimal sunspot activity...thru increased sunspot activity...and back to minimal sunspot activity. When the sunspot activity is high it's called the Solar Maximum, while the period of fewer sunspots is called the Solar Minimum. It reverses itself in both hemispheres from one sunspot cycle to the next. Therefore a full cycle takes around 22 years. The Suns magnetic field varies greatly during the cycle, During the solar maximum, the magnetic field is strong, so the Suns surface temperature is higher. On the other hand, during solar minimum, the field is weak, so the surface temperature is lower. Our current solar cycle 24 is forecast to peak in early or mid 2013 with 60 sunspots.

Types of Space Weather:

There are three major types of space weather events that impact technologies we take for granted here on Earth.

1) The first is a radio blackout, which is a disturbance of the ionosphere caused by X-ray emissions of a solar flare. Radio blackouts caused by space weather are measured by the National Oceanic and Atmospheric Administration on a scale that goes from 1 (minor) to 5 (extreme). In this event, the density of the lower region, known as the D-region, is increased, causing radio waves to be misdirected or absorbed. Conditions in the D region of the ionosphere have a dramatic effect on high frequency (3 - 30 MHz) communications and low frequency navigation systems. Examples of low frequency navigation systems would be VOR (VHF Omni-directional Range), Radar, and transponders. The intensity of the X rays determines how long the radio blackout last. It can last from as little as a few minutes up to several hours. Radio blackouts affect communications primarily at middle to low latitudes, but only on the dayside of Earth.

2) The second type of event is a solar radiation storm, which is also sometimes called a solar energetic particle (SEP) event . These happen when an explosion on the sun accelerates solar protons toward where energetic particles from the Sun, primarily protons, elevate the levels of radiation near Earth. Radiation storms cause harmful levels of radiation above the shielding provided by our atmosphere. Solar radiation storms are rated on a scale from S1 (minor) to S5 (extreme), determined by how many very energetic, fast solar particles move through a given space in the atmosphere. At their most extreme, solar radiation storms can cause complete high frequency radio blackouts, severe damage to electronics, effect memory and imaging systems on satellites. These storms potentially have an effect on astronauts and, to a lesser degree, passengers in commercial jets. A solar radiation storm can arrive in as little as 10 minutes and may continue bombarding Earth for a few hours to as long as several days.

3) The third type of event, a geomagnetic storm, is caused by a gust in the solar wind, such as a Coronal Mass Ejection (CME), energizing Earth's magnetic field. These disturbances reach Earth in as little as 18 hours to 4 days and may last for a day or two. Geomagnetic storms can play havoc with power grids damage satellites, but are also responsible for the magnificent auroras we enjoy watching. Geomagnetic storms are measured by ground-based instruments that observe how much the horizontal component of Earth's magnetic field varies. Based on this measurement, the storms are categorized from G1 (minor) to G5 (extreme). In the most extreme cases transformers in power grids may be damaged, spacecraft operation and satellite tracking can be hindered, high frequency radio propagation and global positioning system (GPS) can be blocked, and auroras may appear much further south than normal.

If you're into Ham Radio here is a good site.

A link to the NOAA space weather prediction center that shows the different levels of space weather and their effects can be found here.

Here's is a NASA video that talks about the Sun and the different types and causes of space weather.

Well that's it for this blog installment. The next post will cover the subject of bombogenesis. Rebecca

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