U. Rajitha M.Sc Space Physics Department of Physics VisakhapatnamANDHRA UNIVERSITY
Organization of the talk Introduction Space weather Sun (Sun spots, Coronal Mass Ejection, Aurora) Magnetosphere Geomagnetic storms Effects of geomagnetic storms
SPACE WEATHERSpace weather refers to conditions on the Sun and in the spaceenvironment that can influence the performance and reliabilityof space-borne and ground-based technological systems, andcan endanger human life or health.
This diagram shows the different zones of the Sun, from itscore out to the corona.
Solar activityThe output of the sun in all forms , light , solar wind , and energetic particles ,is not constant.It varies with both time ( seconds to centuries!) and position on the Sun.These changes are called Solar activity and are probably reflections of changes below the Sun’s surface.The Sun’s energy output takes two main forms: Electromagnetic radiation The emission of charged particles Solar activity produces Space weather that effects the Earth
SUN SPOTSDark spots some as large as 50000 miles diameter moveacross the surface of the sun contracting and expanding asthey go. These strange and powerful phenomena is known assunspot.
Solar flaresSolar flares are tremendous explosions on the surface ofthe Sun. In a matter of just a few minutes they heatmaterial to many millions of degrees and release as muchenergy as a billion megatons of TNT.
Coronal HolesCoronal holes are areas of the Suns surface that are the source of open magnetic field lines that headway out into space. They are also the source regions of the fast solar wind, which is characterized by arelatively steady speed of approximately 800 km/s. As the Sun continues to rotate, the high speed solar windparticles blowing from this hole will likely reach Earth in a few days and may spark some auroral activity.
Coronal Mass EjectionWhat are CMEs?Large-scale magnetized plasma ejected from the Sun (part of the corona is expelledwith its magnetic field)Propagate into the interplanetary medium and impact planets in the solar system
Coronal mass ejection
Aurorae are a luminous glow of the upper atmosphere caused byenergetic particles descending from the Earth’s magnetosphere orcoming directly from the Sun. These energetic particles aremostly electrons, but protons can also be involved, and theirenergetic rain into the atmosphere is greatest during magneticstorms.
The aurora becomes active during geomagnetic storms which occur oftenabout 40 h after an intense solar flare.
Is the earth magnet?The crust of the Earth has some permanent magnetization, and the core of theEarth, the outer part of which is liquid iron and the inner of which is solid iron,generates its own magnetic field, sustaining the main part of the field we measureat the surface. So we could say that the Earth is, therefore, a magnet.
VAN ALLEN BELTSThe earth’s core behaviour is like a very large magnet. The geomagneticfield associated with core is like a magnetic oriented South-North. Like polesof two magnets repel. So a north seeking compass will direct itself towards the south orientedmagnet inside the earth.The Van Allen radiation belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field.
MAGNETOSPHERE The earth resides in a vast magnetic cavity, is called themagnetosphere. The magnetospheric cavity is created by the electrodynamicinteraction between the solar wind (a gas of charged particlescontinuously flowing from sun) and the earths magnetic field. The geomagnetic cavity is formed as the solar wind is swept around. The boundary terminating the magnetosphere is called the magnetopause A shockwave is a discontinuity of the medium ,produced when information about an approaching perturbation is not reached into the medium.
Geomagnetic storm A geomagnetic storm is a temporary disturbance of the earth’s magnetosphere caused by a disturbance in space weather. They are associated with solar mass ejections(CME) or solar flares Geomagnetic storm is caused by a solar wind shock wave which strikes the earths magnetic field 24 to 36 hours after the event. The shock waves should travel towards earth. Geomagnetic storm have a duration of several days, during which the geomagnetic field is severely disturbed from the normal. There is another phenomenon called as a sub storm in which geomagnetic field in the polar region is perturbed by strong electric currents flowing in the upper atmosphere with a time scale of ten of minutes. Bright auroras show intense variations at the time of sub storm.
Geomagnetic storm effects Radiation hazards to humans Biology Disrupted systems o Communications o Navigation systems o Satellites