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astronomy

Solar energetic particles

Solar energetic particles 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 energetic particles rather than just read about it. In short: Solar energetic particles (SEP), formerly known as solar cosmic rays, are high-energy, charged particles originating in the solar atmosphere and solar wind. They consist of protons, electrons and heavy ions with energies ranging from a few tens of keV to many GeV.

Solar energetic particles — main illustration
Solar energetic particles — illustration

Key takeaways

  • Solar energetic particles 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 energetic particles to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Solar energetic particles from memory before moving on to harder problems.

Reference excerpt

Solar energetic particles (SEP), formerly known as solar cosmic rays, are high-energy, charged particles originating in the solar atmosphere and solar wind. They consist of protons, electrons and heavy ions with energies ranging from a few tens of keV to many GeV. The exact processes involved in transferring energy to SEPs is a subject of ongoing study. SEPs are relevant to the field of space weather, as they are responsible for SEP events and ground level enhancements.

History SEPs were first detected in February and March 1942 by Scott Forbush indirectly as ground level enhancements.

Solar particle events

SEPs are accelerated during solar particle events. These can originate either from a solar flare site or by shock waves associated with coronal mass ejections (CMEs). However, only about 1% of CMEs produce strong SEP events. Two main mechanisms of acceleration are possible: diffusive shock acceleration (DSA, an example of second-order Fermi acceleration) or the shock-drift mechanism. SEPs can be accelerated to energies of several tens of MeV within 5–10 solar radii (5% of the Sun–Earth distance) and can reach Earth in a few minutes in extreme cases. This makes prediction and warning of SEP events quite challenging. In March 2021, NASA reported that scientists had located the source of several SEP events, potentially leading to improved predictions in the future.

Research SEPs are of interest to scientists because they provide a good sample of solar material. Despite the nuclear fusion occurring in the core, the majority of solar material is representative of the material that formed the Solar System. By studying SEP's isotopic composition, scientists can indirectly measure the material that formed the Solar System.

See also Solar wind

References

Reames, Donald V. (2013). "The Two Sources of Solar Energetic Particles". Space Science Reviews. 175 (1–4): 53–92. arXiv:1306.3608. Bibcode:2013SSRv..175...53R. doi:10.1007/s11214-013-9958-9. ISSN 0038-6308. S2CID 255072537. Reames D.V., Solar Energetic Particles, Springer, Berlin, (2017a) ISBN 978-3-319-50870-2, doi: 10.1007/978-3-319-50871-9.

External links Solar Energetic Particles (Rainer Schwenn) NASA The Isotopic Composition of Solar Energetic Particles

Illustrations

Solar energetic particles: Animation of NASA's STEREO coronagraph during a coronal mass ejection followed by solar energetic particles
Animation of NASA's STEREO coronagraph during a coronal mass ejection followed by solar energetic particles

Worked examples

Example 1 — a first encounter with Solar energetic particles

Start with the simplest possible case. Write down what Solar energetic particles 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 energetic particles 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 energetic particles 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 energetic particles

In research
Solar energetic particles 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 energetic particles 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 energetic particles is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cosmic rays, Solar phenomena, so understanding it makes those chapters shorter.
In everyday life
Look for Solar energetic particles 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.

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How to study Solar energetic particles in 20 minutes

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

Frequently asked questions

What is Solar energetic particles in simple terms?

Solar energetic particles (SEP), formerly known as solar cosmic rays, are high-energy, charged particles originating in the solar atmosphere and solar wind. They consist of protons, electrons and heavy ions with energies ranging from a few tens of keV to many GeV.

Why does Solar energetic particles 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 energetic particles?

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 energetic particles.

Tags

  • Cosmic rays
  • Solar phenomena

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