astronomy

Solar spicule

Solar spicule is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Solar spicule rather than just read about it. In short: In solar physics, a spicule, also known as a fibril or mottle, is a dynamic jet of plasma in the Sun's chromosphere about 300 km in diameter. They move upwards with speeds between 15 and 110 km/s from the photosphere and last a few minutes each before falling back to the solar atmosphere.

Key takeaways

Solar spicule belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Solar spicule to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Solar spicule from memory before moving on to harder problems.

Reference excerpt

In solar physics, a spicule, also known as a fibril or mottle, is a dynamic jet of plasma in the Sun's chromosphere about 300 km in diameter. They move upwards with speeds between 15 and 110 km/s from the photosphere and last a few minutes each before falling back to the solar atmosphere. They were discovered in 1877 by Angelo Secchi, but the physical mechanism that generates them is still hotly debated.

Description Spicules last for about 15 minutes; at the solar limb they appear elongated (if seen on the disk, they are known as "mottles" or "fibrils"). They are usually associated with regions of high magnetic flux; their mass flux is about 100 times that of the solar wind. They rise at a rate of 20 km/s (or 72,000 km/h) and can reach several thousand kilometers in height before collapsing and fading away.

Prevalence There are about 3,000,000 active spicules at any one time on the Sun's chromosphere. An individual spicule typically reaches 3,000–10,000 km altitude above the photosphere.

Motion Spicules are generally found to move in a parabolic fashion, eg <Pereira et al, 2012>. This means that after their ejection from the solar surface at high speed they decelerate at a constant rate until they reach their maximum height (or length, as most are inclined to the vertical). They then descend back down towards the surface, accelerating at the same rate, until reaching their starting point with the same speed downwards as they originally had in the upward direction.

Causes

Bart De Pontieu (Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, California, United States), Robert Erdélyi and Stewart James (both from the University of Sheffield, United Kingdom) hypothesised in 2004 that spicules form as a result of P-mode oscillations in the Sun's surface, sound waves with a period of about five minutes that causes the Sun's surface to rise and fall at several hundred meters per second (see helioseismology). Magnetic flux tubes that are tilted away from the vertical can focus and guide the rising material up into the solar atmosphere to form a spicule. However, there is still some controversy about the issue in the solar physics community.

Notes

References

External links NASA Astronomy Picture of the Day: Spicules: Jets on the Sun (2 November 2008)

Illustrations

Worked examples

Example 1 — a first encounter with Solar spicule

Start with the simplest possible case. Write down what Solar spicule claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Solar spicule before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Solar spicule ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Solar spicule

In research: Solar spicule appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Solar spicule in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Solar spicule is common in secondary-school and first-year university syllabi. It links to neighbouring topics Solar phenomena, so understanding it makes those chapters shorter.
In everyday life: Look for Solar spicule outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Solar spicule in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Solar spicule means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Solar spicule out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Solar spicule in simple terms?

Why does Solar spicule matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Solar spicule?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Solar spicule.