The Sun –Energy for Life
The Sun is the star at the center of the Solar System, the most important source of energy for life on Earth. The sun is a sphere of hot plasma, with internal convection currents that generate a magnetic field. Its diameter is 109 times that of Earth and its mass is 330,000 times bigger than earth’s. Three quarters of the Sun's mass consists of hydrogen (73%), the rest is mostly helium (25%), with smaller quantities of oxygen, carbon, neon, and iron.
The sun’s energy output is created by hydrogen fusion that creates electromagnetic radiation and helium. The Sun has an absolute magnitude of +4.83, estimated to be brighter than about 85% of the stars in our galaxy, most of which are red dwarfs. The sun rotates and releases energy in all frequencies of the electromagnetic spectrum. The surface is turbulent with moving sunspots, solar flares and coronal mass ejections. High-speed streams of solar wind are emitted from coronal holes. Both coronal-mass ejections and high-speed streams of solar wind carry plasma and an interplanetary magnetic field outward into the Solar System. The surface temperature of the photosphere is approximately 6,000 K, but surprisingly the temperature of the surrounding corona reaches 1,000,000–2,000,000 K.
In December 2017, NASA launched an instrument to the International Space Station to continue monitoring the Sun’s energy input to the Earth system. The Total and Spectral solar Irradiance Sensor (TSIS-1) will precisely measure what scientists call “total solar irradiance.” These data will give us a better understanding of Earth’s primary energy supply and help improve models simulating Earth’s climate. The input from the Sun is just one of many factors scientists used to model Earth’s climate. Earth’s climate is also affected by other factors such as greenhouse gases, clouds scattering light and small particles in the atmosphere called aerosols — all of which are taken into account in comprehensive climate models.
Patel wrote:” The Sun’s output energy is not constant. Over the course of about 11 years, our Sun cycles from a relatively quiet state to a peak in intense solar activity — like explosions of light and solar material — called a solar maximum. In subsequent years the Sun returns to a quiet state and the cycle starts over again. The Sun has fewer sunspots — dark areas that are often the source of increased solar activity — and stops producing so many explosions, going through a period called the solar minimum. Over the course of one solar cycle (one 11-year period), the Sun’s emitted energy varies on average at about 0.1 percent. That may not sound like a lot, but the Sun emits a large amount of energy – 1,361 watts per square meter. Even fluctuations at just a tenth of a percent can affect Earth.” (Kasha Patel. Four decades and counting: New NASA instrument continues measuring solar energy input to Earth NASA Goddard Space Flight Center. Nov 28 2017.)
Despite the sun’s obvious turbulence, animals and plants on earth humans have depended on its relative stability. A recent and serious concern is that the sun can produce magnetic storms that would disable or destroy our electric grids and electronics. Most solar disturbances are reflected by our magnetic field or absorbed by the atmosphere. However, infrequent large events can be anticipated. Geomagnetic storms have caused solar energetic Particle (SEP) events, geomagnetically induced currents (GIC), ionospheric disturbances that cause radio and radar scintillation, disruption of navigation by magnetic compass and auroral displays at much lower latitudes than normal. In 1989, a geomagnetic storm energized ground induced currents that disrupted telegraph networks, electric power distribution and caused aurorae as far south as Texas. NASA operates continuous sun observations. Their understanding of solar flares is advancing. NASA described:” Solar flares are intense bursts of light from the sun. They are created when complicated magnetic fields suddenly and explosively rearrange themselves, converting magnetic energy into light. During a December 2013 solar flare, three solar observatories captured the most comprehensive observations of an electromagnetic phenomenon called a current sheet. These eruptions on the sun eject radiation in all directions. The strongest solar flares can impact the ionized part of Earth’s atmosphere – the ionosphere – and interfere with our communications systems, like radio and GPS, and also disrupt onboard satellite electronics. Additionally, high-energy particles – including electrons, protons and heavier ions – are accelerated by solar flares.