Other Space Activities

Solar Activity

Last updated:Sep 27, 2024

Science

Astronomy and Telescopes

Solar activity refers to phenomena associated with the Sun driven by its magnetic field. The Sun is made up of ionised plasma, and its motion drives a powerful magnetic field. The differential motion of the Sun’s plasma distorts its magnetic field, which results in enhanced solar activity and space weather. Solar activity evolves according to an 11-year cycle that resets when the Sun’s magnetic field flips in polarity. At the start and end of each solar cycle, we observe a ‘solar minimum’, where solar activity is much lower compared to the middle of the cycle at the ‘solar maximum’. The solar maximum is a result of the magnetic field winding up into its most disordered state. 1) 2) 3)

The primary types of solar activity are sunspots, flares, coronal mass ejections (CMEs), prominences, and solar wind.

Sunspots are regions on the Sun’s surface with a high magnetic field strength. Material on the Sun’s surface convects as cool plasma sinks and hot plasma rises - but material in these sites of high magnetic field strength are locked in place, preventing it from falling as it cools. This process gives sunspots their characteristic darkened colour. 4) 5)

Figure 1: Large sunspot captured in September 2011 (Image credit: NASA)

Solar flares are a dense and localised emission of electromagnetic radiation from the Sun’s corona, generated by intense regions of magnetic field strength. 6) 8)

Figure 2: Animation of a solar flare captured on February 16, 2024, across three different ultraviolet wavelengths (Image credit: NASA)

CMEs are intense plasma emissions from the corona that occur when unstable magnetic field lines snap and reconnect in a process called ‘magnetic reconnection’. 9)

Figure 3: CME observed on October 18, 2021 (Image credit: ESA)

Solar prominences are loops of plasma and magnetic field lines that are anchored at both ends to the Sun’s surface. It consists of cooler plasma compared to the coronal plasma it stretches into. A prominence when viewed straight on against the solar disk is called a filament.

Figure 4: Solar prominence (Image credit: NASA)

The solar wind is a continuous stream of plasma that is released from the Sun’s corona. It is made up of energetic protons and electrons, and a small percentage of ionised helium (alpha particles), heavy atomic ions.

Figure 5: Plot of solar wind velocity against radial position (Image credit: NASA)

Solar activity is important to monitor as it can impact our activities on Earth. The Earth’s magnetic field is strong enough to deflect charged particles from solar wind and CMEs, yet events like radio blackout storms, solar radiation storms, and geomagnetic storms can still occur.

Radio blackout storms perturb the ionosphere, preventing long-distance radio communication. Electromagnetic radiation emitted by solar flares creates a higher concentration of ionised particles in the ionosphere which absorb high-frequency (HF) radio waves used for long-distance communication, which results in signal blackouts.

Meanwhile, solar radiation storms consist of energetic charged particles emitted from CMEs that can harm astronauts, spacecraft, and occasionally Earth-based technology. To mitigate the effects of solar radiation storms, spacecraft may be powered off and astronauts instructed to move to a better-shielded section of their spacecraft.

Finally, Geomagnetic storms alter Earth’s magnetic field. They are caused by heavier high-energy particles of CMEs and the solar wind travelling through our magnetic field. These particles can induce electric current in power lines creating power outages, alter satellite trajectories, disrupt high-frequency communications, and produce auroras.

Example Products

ESA Space Weather Service Network

Space Weather is the physical and phenomenological state of natural space environments. ESA’s Space Weather Service Network contains several data products concerning different aspects of space weather and solar activity. Examples products from the network include: 1) 7) 10)

The SIDC Solarmap, provided by the Solar Influences Data analysis Centre (SIDC). It is a map of the solar disc that identifies sunspots, flares, CMEs, and filaments throughout the solar cycle.

Figure 6: Solarmap (Image credit: ESA SIDC)

A time series of Hα provided by the Kanzelhöhe Observatory for Solar and Environmental Research. When a solar flare occurs in the chromosphere (the thin region between the corona and photosphere) a spike in Hα is detected and observed on the graph in near real-time.

Figure 7: Full disk flare forecast (Image credit: SIDC)

The European Heliospheric Forecasting Information Asset (EUHFORIA), which computes near-Sun solar wind properties. The asset is updated every 24 hours and is managed by RAL (Rutherford Appleton Laboratory) Space of the United Kingdom’s Science and Technology Facilities Council (STFC).

Figure 8: EUHFORIA (Image credit: STFC | RAL Space)

Related Missions

Dedicated Solar Missions

Parker Solar Probe

Launched in 2018, the Parker Solar Probe is a pioneering NASA mission that aims to "touch the Sun" by flying closer to it than any other spacecraft in history. The mission's primary goal is to study the Sun's outer corona and understand the processes that heat it and accelerate the solar wind. In 2021, it became the first spacecraft to fly through the Sun's corona. By making direct measurements of the Sun’s outer atmosphere, Parker Solar Probe helps scientists understand solar activity and its impact on the Earth.

SOHO (Solar and Heliospheric Observatory)

The SOHO mission, launched in 1995 as a collaboration between ESA and NASA, represents the most comprehensive space mission devoted to the study of the sun and of the heliosphere. SOHO provides near-continuous observations of the Sun, focusing on its internal structure, outer atmosphere, and solar wind. The spacecraft has contributed significantly to our understanding of solar flares, coronal mass ejections, and other phenomena that can affect Earth’s space environment. SOHO worked in coordination with Cluster (launched in 2000), a constellation of four identical spacecraft, to study the interaction between the solar wind and Earth's magnetosphere in three dimensions.

Earth-Observing with Solar Activity Auxiliary

GOES (Geostationary Operational Environmental Satellites)

The GOES Constellation of National Oceanic and Atmospheric Administration (NOAA) is a series of Geostationary satellites dedicated to providing continuous observations on atmospheric, land, and space conditions. The missions, launching from 1974, carry the Space Environment Monitor (SEM) instrument, which has the objective to provide daily measurements of solar wind particle flux. The SEM package was upgraded with the introduction of the Solar X-ray imager (SXI) from GOES-12 (launched July 2001) onwards. In addition, the third generation GOES satellites, GOES-R, carry the Solar Ultraviolet Imager (SUVI) and the Space Environmental in Situ Suite (SEISS). SUVI is a soft X-ray imager that measures solar activity and its effects on Earth and the near-Earth space environment, and SEISS monitors the near-Earth particle and electromagnetic environment in real-time.

Read more: GOES 2nd Generation | GOES-N, O, P | GOES-R

DSCOVR (Deep Space Climate Observatory)

Launched in 2015, DSCOVR is a satellite operated by NOAA to monitor space weather and capture deep space imagery of the Earth’s surface. DSCOVR carries four instruments, EPIC (Earth Polychromatic Imaging Camera), NISTAR (National Institute of Standards and Technology Advanced Radiometer), PHA (Pulse Height Analyser) and the PlasMag (Plasma Magnetometer) Instrument suite. PlasMag contains a Faraday Cup that measures solar wind bulk properties in 3D and magnetic fields at very high time resolution. The instrument aims to provide continuity to solar wind measurements made by IMP-8, SOHO, and ACE. DSCOVR operates in a Lissajous orbit about L1 (Lagrangian Point 1).

MetOp (Meteorological Operational Satellite Program of Europe)

The MetOp series, operated by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), is primarily designed for meteorological monitoring, but it also contributes to space weather forecasting. The polar-orbiting satellites began launching in 2006, and carry the Space Environment Monitor-2 (SEM-2), which measures charged particles from solar wind and other space weather phenomena. MetOp’s observations of energetic particle environments help in understanding how solar activity interacts with the Earth's geomagnetic field, aiding in space weather prediction and mitigation efforts.

References

1) ESA Space Weather Service Network. (n.d.). What is Space Weather?. Space Weather. https://swe.ssa.esa.int/what-is-space-weather

2) Gold, A. (2023, July 26). Five Questions About Space Weather And Its Effects On Earth, Answered. NASA. https://www.nasa.gov/technology/five-questions-about-space-weather-and-its-effects-on-earth-answered/

3) Hathaway D. H. (2015). The Solar Cycle. Living reviews in solar physics, 12, 4. https://doi.org/10.1007/lrsp-2015-4

4) NOAA’s National Weather Service. (n.d.). The Sun and Sunspots. https://www.weather.gov/fsd/sunspots

5) Pastor, A. (n.d.). How do Sunspots Form? European Solar Telescope. https://est-east.eu/?option=com_content&view=article&id=924&Itemid=622&lang=en

6) NASA/Marshall Solar Physics. (n.d.). https://solarscience.msfc.nasa.gov/flares.shtml

7) Current Space Weather - Space Weather. (n.d.). Space Weather. https://swe.ssa.esa.int/

8) Solar Flares. (n.d.). NASA/Marshall Solar Physics. https://solarscience.msfc.nasa.gov/flares.shtml

9) Coronal Mass Ejections. (n.d.). NOAA | NWS Space Weather Prediction Center. https://www.swpc.noaa.gov/phenomena/coronal-mass-ejections