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Plasma Space Physics

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Published in: Physics
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Space physics mainly deals with the study of plasma and their behaviour in solar system. how plasma created in sun and transferred to the solar system and how they interact with planetary magnetic field is the main subject of study.

Govinda B / Cuttack

1 year of teaching experience

Qualification: Pursuing PostGraduation(Physics)

Teaches: Physics, Chemistry

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  1. PLASMA IN SPACE PHYSICS The universe is made up of space plasma. Plasma is the fourth state of matter (solid, liquid, gas and plasma). A plasma is a gas that is so hot that some or all it's constituents are split up into electrons and ions, Which can move independently of each other. Because they made up of charged particle; plasma can be strongly influenced by electrostatic and electromagnetic forces which can led to very complicated and interesting behavior. Space physics is the study of plasma as they occur naturally in earth's upper atmosphere. Today near earth space has become a "laboratory "in which we study plasma physics. It includes both solar and earth physics research which explores a diverse range of plasma physical phenomena encountered at first hand in solar system. We can explain space physical phenomena like, 1) Sunspot 2) Solar flare 3) Coronal mass ejection 4) Solar wind 5) Magnetosphere 6) Radiation belt 7) Auroras 8) Ionosphere of earth Using physical principle of plasma physics. Therefore space physics mainly includes, 1) Solar physics 2) Earth space physics Solar physics Solar physics is the study about sun's composition, structure, sources of energy, how they radiate, how magnetic field created and transported throughout the space .
  2. Composition of sun Sun is a yellow dwarf star which is nothing but a gigantic plasma ball, which is powered by its self-sustaining thermonuclear fusion process (combination of two or more light nuclei to form single heavier nuclei with release of plenty of energy). 1) Its radius is 109 times that of earth. 2) The internal temperature is 1.5*10A7 K 3) In photosphere it is 5772 K 4) Plasma density inside the sun is 150g/cmA3 Creation of magnetic field in sun Because of the broad importance of magnetic field in large scale plasma dynamics, developing a first principle understanding of the physical mechanism that control the generation and dissipation of magnetic field is an essential goal. Magnetic field is generated in sun by a self-sustaining dynamo process. In which convection motion of conducting material (plasma) such as turbulence can temporarily amplify a magnetic field inside the sun driven by heat generated from thermonuclear fusion. Sun spot It is a relatively dark region on photosphere caused by temperature difference due to heavy concentration of magnetic field flux that inhibit convection. It has two parts 1. Umbra (darkest region) Due to vertical magnetic flux 2. Penumbra (lighter dark) Due to inclined flux Solar corona Corona is an aura of plasma which surrounds the sun. It extends millions of kilometer in space and it is most easily seen during solar eclipse. Density of solar corona is very less than photosphere i.e. IOA-12 times dense than photosphere. Coronal mass ejection
  3. This is nothing but the ejection of charged particles from sun's surface at a speed of 20-3200 Km/s during creation of strong magnetic fields but due to that strong gravitational and magnetic field it is bend like a rubber band and again falls on surface. If the erupting magnetic field is so high then the charge particles completely ejected to the space leaving the sun and transported throughout the solar system. Solar wind Solar wind is the stream of plasma that flows radially outwards from the upper atmosphere of the sun carrying with it the solar magnetic field. It consists of mostly electron, protons and alpha particles (1.5-10 Kev). Its particle can escape the sun's gravity because of high energy resulting from the high temperature of corona. Temperature (1.4-1.6*10A6K) Velocity (300-500 Km/s) Slow solar wind is twice more dancer than fast solar wind. Magnetic field of earth Magnetic field of earth created due to conventional motion of conducting material inside the outer core, driven by heat flow from the inner core and Coriolis force create circulating electric current generate the magnetic field. The magnetosphere The magnetic field produced by the earth is surrounds the earth in 3dimensional space and called magneto sphere. Whose magnetic field strength is higher near poles and weaker in equator. This earth magnetosphere mainly controls the motion of plasma( charged particles) near earth. It doesn't allow any outer charged particles to enter, therefore our earth magnetosphere protects us from outer harm full charged particles. Generally earth has a dipole magnetic field which is symmetric about both day side and night side of earth. But actually this symmetric structure doesn't exists. Because there is an interaction between solar magnetic field (solar wind carry solar magnetic field)and earth magnetic field results alteration in shape of the magnetic field lines of earth.
  4. This phenomena results a variety of plasma region in magneto sphere. These are described as follows The bow shock A supersonic shock wave created when a solar wind collides with another medium, such as a planets magnetosphere. Magnetopause The outer thin boundary separating the solar wind plasma from plasma of magneto sphere is called magnetopause. Inside magnetopause motion of all plasma is dominated by earth's magnetic field. It is mainly a region where the pressure from the planetary magnetic field is balanced with the pressure from solar wind. Magnetosheath The region of space between bowshock and magnetopause, caused by the solar wind,its particles are denser than those of magnetosphere, also known as heliosheath. The particle in magnetosheath come from the shocked solar wind and have a density that typically decreases from bow shock to magnetopause. The magnetosheath plasma is primarily hot, dense, slow plasma with Te . Magnetospheric Cusp The point of intersection of two arcs; where two section of magnetosphere meets. It is a funnel like shaped in between two types of magnetic fields i) one is sunward ii)other is tail ward The magnetospheric cusp plays an important role by acting a most direct connection between ionosphere and interplanetary medium through magnetic reconnection.
  5. The magnetic reconnection Reconnection is the heart of many spectacular events in our solar system. E.g solar player, coronal mass ejection which occurs near sun spot are believed to be powered by magnetic reconnection. Magnetic reconnection refers to the breaking and reconnecting of oppositely directed magnetic field lines in a plasma. In this process magnetic field energy is converted to plasma kinetic and thermal energy. Energy conversion and topological rearrangement are the key properties. Neutral sheet A sheet of plasma that extend down the magnetotail dividing two lobes of magnetotail is known as plasma sheet. The Magnetotail The standing shock wave developed in-front of the magnetopause breaks the magnetic field lines in the reconnection process and stretched in anti-sunward direction forming a long magnetotail in the night side of the earth. The region of magnetotail between magnetopause and the neutral sheet is called tail lobe . The lobes has nearly parallel and opposite magnetic field lines in bundles. Trapping region The part of the magnetosphere that traps electrically charged particle or radiations also known as radiation belt(Van-allen radiation belt). It is generally understood that the Van Allen belts are a result of the collision of Earth's magnetic field with the solar wind. Radiation from the solar wind then becomes trapped within the magnetosphere. The trapped particles are repelled from regions of stronger magnetic field, where field lines converge. This causes the particle to bounce back and forth between the earth's poles, where the magnetic field increases. The outer belt consists mainly of high energy (0.1-10 MeV) electrons trapped by the Earth's magnetosphere The trapped particle population of the outer belt is varied, containing electrons and various ions. Most of the ions are in the form of energetic protons, but a certain percentage are alpha particles and 0+ oxygen ions, similar to those in the ionosphere but much more energetic The Aurora The light over the northen and southern pole sky is called Auroras.
  6. Aurora borealis (northen light) Aurora Australis (southern light) These are produced due to two reason, i) due to polar cusp region (day side) ii) due to magnetic burst in tail region (night side) as the cusp region has very less magnetic field , charged particles from magnetosheath region enters direcly towards pole which interacts with oxygen, nitrogen atom making them excited and emission of visible light . similarly in tail region , two tail lobes of opposite field lines reconnect to burst out a huge amount of charged particles towards earth causing these to move towards earth pole forming night side Aurora. Ionosphere It is the upper atmosphere of earth. This ionosphere is caused by photoionization. Hence when solar ultraviolet radiation incident on the upper layer of atmosphere it causes ionization of constituent gases i.e. this ionosphere is in plasma state. This ionospheric plasma plays an important role in the propagation of round the curved sphere of the earth and allow us in long distance radio communication. In Ionosphere electron density gradually increases with height hence the velocity of wave gradually increases with height. From the figure here the wavefront AB is incident on ionosphere ,A of the wavefront move the region of higher density so the velocity of this part is more than that of region B. This means the upper portion moves more than the lower portion toward the ground. The radio signal will naver come back by absence of this plasma.

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