Seminar: Peter Wintoft from the Swedish Institute of Space Physics will present a seminar titled “The Sun and Space Weather”.

14 March, 2019 - 15:15

This seminar is presented in collaboration with Östergötlands Astronomiska Sällskap.

The seminar will be held in “Planck” at Linköping University.


The Sun and Space Weather
Peter Wintoft
Swedish Institute of Space Physics
The Sun is a G-type star on the main sequence with a photospheric (visible surface) temperature of
about 6000 degrees. It is essential for life on Earth providing radiative power of 1400 W/m^2 at the
top of our atmosphere. Although the radiation in the visible spectrum is quite stable over time
(around 0.1% variability in modern time), the radiation at shorter wavelengths (e.g. X-ray and UV)
varies by several orders of magnitude on many different timescales. This variability is caused by
plasma processes that are driven by the ever changing solar magnetic fields. Above the photosphere
the solar atmosphere gets hotter reaching several million degrees and expands out forming the
heliosphere. The Earth orbits the Sun at 150 million km (1 AU) engulfed in the solar plasma and
magnetic fields that permeates the heliosphere out to about 120 AU. The interaction between the
heliospheric plasma and the Earth’s magnetic field creates a magnetosphere which is highly dynamic
with many different processes and phenomena. Magnetic fields are continuously generated in the
Sun and emerges through the photosphere producing active regions (AR) and sunspots. The large
scale solar magnetic fields also cause large scale structures in the heliosphere knows as high-speed
streams. The ARs are regions with complex magnetic structures where energy is built up and released
through solar storms, which are observed as flares and coronal mass ejections (CME). The flares
produce strong radiation in X-ray and UV and has direct effects on the Earth’s upper atmosphere
causing increased ionisation. The CMEs are clouds of plasma that are ejected at high speed and can
reach the Earth within 15 hours to a couple of days. Thus, there is a physical link between the Sun
and Earth via the heliospheric plasma, and the auroras are visible and beautiful manifestations of this
link. However, with the advent and increased use of technologies that are affected by
electromagnetic disturbances it has become more important to understand this link, known as space
weather. Space weather can affect astronauts, satellites, communication, GPS, magnetic sensors,
pipelines, and electrical grids. A fleet of spacecraft that continuously monitors the Sun and the
heliosphere, and networks of ground based observatories, produce real-time data that are fed into
models and algorithms to provide information and predictions of space weather.