Decoding the Origins of Lightning’s Violent Currents

science & techanalysisEos

Decoding the Origins of Lightning’s Violent Currents

the gist

The return stroke is the surge of current that races upward through a lightning channel once a leader from the cloud connects to the ground. It carries tens of thousands of amperes at a sizable fraction of the speed of light, producing the flash, the thunder and the radio pulse that detection networks use to locate strikes. A review by researchers at New Mexico Tech shows that the Telegrapher's Equations, the same framework used for signals on power cables, can explain its shape. The current rises quickly when the leader connects and decays more slowly because of the channel's resistance. The same model explains why the wave travels slower than light, weakens with height and spreads out as it climbs.

how it works

The lightning channel is modelled as a long conductor with resistance, inductance and capacitance spread along its length. Charge stored in the sheath around the core is neutralised as the wave moves, and the balance between these effects sets the current's rise, decay and speed.

so what

Return strokes cause much of lightning's damage, including billions of dollars a year to power and communication lines and many wildfire ignitions. They are also the atmosphere's main natural source of nitrogen oxides, so understanding them matters for both safety and atmospheric chemistry.

Eos (AGU) · CC BY-NC-ND 3.0

Illustrative photo · Mathias Krumbholz, CC BY-SA 3.0, via Wikimedia Commons

source: Eos ↗

historyWikipediaclassic1336–1565 · Karnataka, India

Hampi was once one of the world's largest cities, until its Vijayanagara capital was destroyed in 1565

the gist

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.

how it works

The city was built around a fortified core with temples, markets and water structures along the river, supplied by an extensive network of roads and waterworks. When the empire fell, the city was not rebuilt, so its stone monuments were left standing.

so what

Hampi shows how quickly a great city can vanish after a military defeat, and how a ruined capital can remain sacred. Its ruins give historians a view of medieval South Asia that few other sites can match.

fun fact

The name Hampi comes from Pampa, an old name for the Tungabhadra River.

From Wikipedia, the free encyclopedia · text CC BY-SA 4.0

Image: Wikimedia Commons

source: Wikipedia ↗

2 min

politicsshortCNA2:01

False allegations about Singapore’s hand in Indonesia’s markets and a made-up meeting

from CNA

CNA Verify has found close to 400 posts pushing falsehoods tying Singapore to Indonesia’s stock market rout and to a secret meeting that never took place. Together, they drew nearly 12 million views, and some were circulated by accounts that appeared to be working in concert, across multiple social media platforms.

Here’s how the disinformation campaign targeting Singapore was uncovered.

on YouTube: CNA ↗