What are sunspots, what is the solar wind, and how does the Earth shield us from it?
The structure, origin and evolution of sunspots, using sunspot data to find the solar rotation period and the solar cycle, the solar wind and its effects, and the Earth's magnetosphere.
A focused answer to Edexcel GCSE Astronomy statements 10.6 to 10.8 and 10.10 to 10.12, covering the structure, origin and evolution of sunspots, using sunspot data to find the mean solar rotation period and the solar cycle, the nature and origin of the solar wind and its effects, and the shape and position of the Earth's magnetosphere and Van Allen Belts.
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What this dot point is asking
Edexcel statements 10.6 to 10.8 and 10.10 to 10.12 want you to understand the structure, origin and evolution of sunspots, to use sunspot data to find the mean solar rotation period and to study the solar cycle, the nature, composition and origin of the solar wind and its principal effects, and the shape and position of the Earth's magnetosphere including the Van Allen Belts.
Sunspots
The key point is that sunspots are dark only relative to the hotter photosphere around them; in absolute terms they are still extremely hot and bright. Their magnetic origin explains why they come and go and why they are linked to other solar activity. Observing them safely (by projection, Topic 10) lets you track the Sun's rotation and monitor the solar cycle.
The solar rotation period and the solar cycle
This is the topic's calculation: from sunspot positions over time, deduce the rotation period (and note the Sun rotates differentially, faster at the equator than the poles). Plotting sunspot numbers against time reveals the 11 year cycle, a graph-reading skill (statement 10.8). Solar maximum brings more flares, more solar wind and more aurorae.
The solar wind and its effects
The solar wind is a flow of matter, not light, escaping the Sun's outer atmosphere. Its interaction with the Earth produces the aurorae and can damage technology during strong storms, which is why "space weather" is monitored. That it shapes comet tails (always pointing anti-sunward) links directly to comet structure (Topic 11). Effects on satellites, aircraft and crewed missions are explicitly named in statement 10.11.
The magnetosphere and Van Allen Belts
The magnetosphere acts as a protective shield: without it the solar wind would strip the atmosphere and irradiate the surface. Its asymmetric shape (compressed sunward, stretched anti-sunward) comes from the pressure of the solar wind. The Van Allen Belts trap energetic particles and are a hazard for spacecraft and astronauts. This links back to the Earth's liquid iron core generating the field (Topic 1).
How Edexcel examines this
This is telescopic Paper 2 content with calculation, graph and explanation marks. The sunspot question rewards explaining them as cooler magnetic regions that look dark by contrast, and reading the mean solar rotation period (about 25 to 27 days) from sunspot data. The solar cycle is tested by recall (about 11 years) and by reading a sunspot-number graph. The solar wind question rewards defining it as a stream of charged particles from the corona and giving two effects (aurorae, geomagnetic storms, satellite or power disruption, comet tails). The magnetosphere is tested by its shape (compressed sunward, tail anti-sunward), its protective deflection, and the Van Allen Belts. Synoptic links run to comet tails (Topic 11) and the Earth's magnetic field from its core (Topic 1). The commonest errors are treating sunspots as cold holes and the solar wind as radiation, so keep sunspots as cooler magnetic regions and the solar wind as charged particles.
Try this
Q1. State why sunspots appear darker than the rest of the Sun's surface. [1 mark]
- Cue. They are cooler than the surrounding photosphere, so they emit less light (dark by contrast).
Q2. State what the solar wind is. [1 mark]
- Cue. A stream of charged particles (mainly protons and electrons) flowing out from the Sun's corona.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 1AS0 20224 marksA sunspot is observed to return to the same position on the Sun's disc after 27 days. Use this to find the mean solar rotation period, and explain what sunspots are and why they appear darker than the surrounding surface.Show worked answer →
If a sunspot returns to the same apparent position after 27 days, the Sun's mean rotation period (relative to the Earth) is about 27 days (1 mark). Sunspots are regions of the photosphere where strong magnetic fields suppress the convection that brings up heat, so the gas there is cooler (1 mark). Because they are cooler than the surrounding photosphere, sunspots emit less light and so appear darker by contrast (1 mark), even though they are still very hot and bright in absolute terms (1 mark). Markers reward reading the rotation period of about 27 days from the data, explaining sunspots as cooler magnetic regions, and that they look dark only by contrast with the hotter surroundings.
Edexcel 1AS0 20214 marksExplain what the solar wind is, and describe two effects it has when it reaches the Earth.Show worked answer →
The solar wind is a stream of charged particles (mainly protons and electrons) that flows out from the Sun's corona in all directions through the Solar System (2 marks). When it reaches the Earth, one effect is the aurorae (the Northern and Southern Lights), produced when charged particles are funnelled towards the poles and excite gases in the upper atmosphere to glow (1 mark). A second effect is geomagnetic storms, which can disrupt satellites, power grids, radio communications and aircraft navigation, and the solar wind also blows comet tails away from the Sun (1 mark). Markers reward the solar wind as a stream of charged particles from the corona and two valid effects such as aurorae, geomagnetic storms, satellite or power disruption, or shaping comet tails.
Related dot points
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Sources & how we know this
- Pearson Edexcel Level 1/Level 2 GCSE (9-1) in Astronomy (1AS0) specification — Pearson (2017)