physics

Hiss (electromagnetic)

Hiss (electromagnetic) is a physics 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 Hiss (electromagnetic) rather than just read about it. In short: Electromagnetic hiss is a naturally occurring Extremely Low Frequency/Very Low Frequency electromagnetic wave (i.e., 300 Hz – 10 kHz) that is generated in the plasma of either the Earth's ionosphere or magnetosphere. Its name is derived from its incoherent, structureless spectral properties which, when played through an audio system, sound like white noise (hence the onomatopoetic name, "hiss").

Key takeaways

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

Reference excerpt

Electromagnetic hiss is a naturally occurring Extremely Low Frequency/Very Low Frequency electromagnetic wave (i.e., 300 Hz – 10 kHz) that is generated in the plasma of either the Earth's ionosphere or magnetosphere. Its name is derived from its incoherent, structureless spectral properties which, when played through an audio system, sound like white noise (hence the onomatopoetic name, "hiss").

Varieties Hiss may be observed in any of several varieties depending on local time and L-shell of the observer:

Plasmaspheric hiss is generally observed within the plasmasphere, peaking in frequency slightly below ~1 kHz and rarely exceeding 3 kHz. Exo-hiss and ELF hiss are two varieties of hiss observed outside of the plasmasphere, both having a spectrum similar to that of plasmaspheric hiss. Midlatitude hiss is generally observed outside of the plasmasphere and tends to have frequencies between 2 and 10 kHz. Auroral hiss is observed in the auroral zones of the Earth and can extend up to several hundred kHz.

Generation mechanisms There are several proposed generation mechanisms for plasmaspheric hiss in particular, including:

Generation from discrete chorus emissions Generation via electromagnetic impulses from terrestrial lightning, specifically via lightning-generated whistlers Generation through coherent nonlinear interaction with energetic electrons near the equatorial plasmasphere

See also Dawn chorus (electromagnetic) Whistler (radio)

References

Illustrations

Worked examples

Example 1 — a first encounter with Hiss (electromagnetic)

Start with the simplest possible case. Write down what Hiss (electromagnetic) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, 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 Hiss (electromagnetic) 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 Hiss (electromagnetic) 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 Hiss (electromagnetic)

In research: Hiss (electromagnetic) appears in physics 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 Hiss (electromagnetic) 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: Hiss (electromagnetic) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electrical phenomena, Geomagnetism, so understanding it makes those chapters shorter.
In everyday life: Look for Hiss (electromagnetic) 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 Hiss (electromagnetic) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hiss (electromagnetic) 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 Hiss (electromagnetic) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hiss (electromagnetic) in simple terms?

Why does Hiss (electromagnetic) matter?

Because it connects several physics 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 Hiss (electromagnetic)?

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 Hiss (electromagnetic).